the professional constructor - october 2012

ThePROFESSIONALCONSTRUCTORJOURNAL OF THE AMERICAN INSTITUTE OF CONSTRUCTORSOCTOBER 2012 | VOLUME 36 | NUMBER 02

in this issueRisk Identification, Allocation, and Management in Sustainable Projects

Research of Concrete Containing Scrap-Tire Rubber for Pavement Construction

Shallow Flat Soffit Precast Floor System: A Construction Comparative Analysis

Reinforced Concrete Deterioration Due to Corrosion

Quality Management: The philosophy and approach utilized by top performing US contractors

AIC 2012/2013 Officers & Directors

PRESIDENT Tanya C Matthews, FAIC DBIA TMG Construction Corporation PO Box 2099 Purcellville, VA 20134 Work Phone: 540-751-4465 Fax: 540-338-9518 [email protected]

VICE PRESIDENT Saeed Goodman, CPC, PMP United States Navy – NAVAIR 3626 Weymouth Road Brown Mills, NJ 08015 Phone: 757-462-9121 [email protected]

SECRETARY Matthew A Conrad, CPC The Christman Company 3011 N. Cambridge Rd. Lansing, MI 48911 Work Phone: (517) 482-1488 [email protected]

TREASURER Paul W Mattingly, CPC 2116 Plantside Dr. Louisville, KY 40299-1924 Work Phone: (502) 671-0995 [email protected]

Journal of the American Institute of Constructors

PURPOSEThe purpose of the American Institute of Constructors is to promote individual

excellence throughout the related fields of construction.

MISSIONOur mission is to provide:

A qualifying body to serve the individual in construction, the Constructor, who has achieved a recognized level of professional competence; Opportunities for the individual constructor to participate in the process of developing quality standards of practice and to exchange ideas; Leadership in establishing and maintaining high ethical standards; Support for construction education and research; Encouragement of equitable and professional relationships between the professional constructor and other entities in the construction process; and An environment to enhance the overall standing of the construction profession.

AIC PAST PRESIDENTS 1971-74 Walter Nashert, Sr., FAIC

1975 Francis R. Dugan, FAIC

1976 William Lathrop, FAIC

1977 James A. Jackson, FAIC

1978 William M. Kuhne, FAIC

1979 E. Grant Hesser, FAIC

1980 Clarke E. Redlinger, FAIC

1981 Robert D. Nabholz, FAIC

1982 Bruce C. Gilbert, FAIC

1983 Ralph. J. Hubert, FAIC

1984 Herbert L. McCaskill Jr.,FAIC

1985 Albert L Culberson, FAIC

1986 Richard H. Frantz, FAIC

1987 L.A. (Jack) Kinnaman, FAIC

1988 Robert W. Dorsey, FAIC

1989 T.R. Benning Jr., FAIC

1990 O.L. Pfaffmann, FAIC

1991 David Wahl, FAIC

1992 Richard Kafonek, FAIC

1993 Roger Baldwin, FAIC

1994 Roger Liska, FAIC

1995 Allen Crowley, FAIC

1996 Martin R. Griek, AIC

1997 C.J. Tiesen, AIC

1998-99 Gary Thurston, AIC

2000 William R. Edwards, AIC

2001-02 James C. Redlinger, FAIC

2003-04 Stephen DeSalvo, FAIC

2005-06 David R. Mattson, FAIC

2007-09 Stephen P. Byrne, FAIC, CPC

2009-11 Mark E. Giorgi, AIC

2011-12 Andrew Wasiniak, CPC

AIC 2012/2013Board of Directors

Bernard J. Ashyk, Jr.National Director (Appointed)Shook Inc. Northern Division10245 Brecksville Rd.P.O. Box 41020Brecksville, OH 44141-0020Work Phone: (440) 838-5400 x8005Email: [email protected]

Dennis C. Bausman, FAIC CPC PhDNational Director (Elected 2011-2014)126 Lee HallClemson, SC 29634-0001Work Phone: (864) 656-3919Email: [email protected]

David J. Bierlein, CPCNational Director (Elected 2011-2014)TMG Construction Group10245 Brecksville Rd.P.O. Box 2099Purcellville, VA 20134Work Phone: (800) 610-9005 x4499Email: [email protected]

Greg Carender, PMP AIC CPCNational Director (Elected 2012-2015)Denmark Consulting Inc.4814 M Ave. NWCedar Rapids, IA 52405Work Phone: (303) 896-9901Email: [email protected]

Matthew A. Conrad, CPCAIC SecretaryThe Christman Company3011 N. Cambridge Rd.Lansing, MI 48911Work Phone: (517) 482-1488Email: [email protected]

Allen L. Crowley, Jr., FAICNational Director (Elected 2010-2013)COR Services16781 Chagrin Blvd., Suite 225Cleveland, OH 44122Work Phone: (216) 406-2364Email: [email protected]

Joseph DiGeronimoNational Director (Elected 2011-2014)Precision Environmental Co.5500 Old Brecksville Rd.Independence, OH 44131-1508Work Phone: (216) 642-6040Email: [email protected]

Edward Terence Foster, CPC PhD PE FAICNational Director (Elected 2009-2012)University of Nebraska1014 N 67th CircleOmaha, NE 68132-1110Work Phone: (402) 554-3273Email: [email protected]

Mark E. GiorgiNational Director (Elected 2010-2013)Past-PresidentErie Affiliates, Inc.29017 Chardon Rd., Ste. 200Willoughby Hills, OH 44092-1405Work Phone: (440) 943-5995Email: [email protected]

Saeed A. Goodman, PMP CPC CMITNational Director (Elected 2012-2015)Construction SpecialistUnited States Army Corps of Engineers3626 Weymouth RoadBrowns Mills, NJ 08015Work Phone: (757) 462-9121Email: [email protected]

Mike W. Golden, AIC CPC National Director (Elected 2011-2014)MW Golden ConstructorsPO Box 338Castle Rock, CO 80104-0338Work Phone: (303) 688-9848Email: [email protected]

Mark D. Hall, CPCNational Director (Elected 2009-2012)Hall Construction Co., IncPO Box 770Howell, NJ 07731-0770Work Phone: (732) 938-4255Email: [email protected]

Larry C. Hiegel, CPCNational Director (Elected 2010-2013)10914 Panther Mountain Rd.Maumelle, AR 72113Work Phone: (501) 851-7484Email: [email protected]

John R. Kiker, III, CPCNational Director (Appointed - Tampa)Kiker Services Corp.1501 Missouir Ave.Palm Harbor, FL 34683-3642 Work Phone: (727) 787-8877Email: [email protected]

Tanya C. Matthews, FAIC, DBIAAIC PresidentTMG Construction CorpPO Box 2099Purcellville, VA 20134-2099Work Phone: (540) 751-4465Fax: (540) 338-9518Email: [email protected]

Paul W. Mattingly, CPCAIC TreasurerBosseMattingly Constructors, Inc.2116 Plantside Dr.Louisville, KY 40299-1924Work Phone: (502) 671-0995Email: [email protected]

Hoyt Monroe, FAICNational Director (Elected 2010-2013)Vice President Clark Power CorporationPO Box 45188Little Rock, AR 72214-5188Work Phone: (501) 558-4901Email: [email protected]

Bradley T. Monson, CPCNational Director (Elected 2010-2013)Tierra Group, LLC182B Girard St.Durango, CO 81303Work Phone: (970) 375-6416Email: [email protected]

Wayne Joseph Reiter, CPC CPANational Director (Elected 2011-2014)Reiter Companies110 E. Polk St.Richardson, TX 75081-4131Work Phone: (972) 238-1300Email: [email protected]

Bradford L. Sims, PhDNational Director (Elected 2010-2013)The Kimmel School of Constr. Mgmt. & Tec211 Belk BuildingCullowhee, NC 28723 Work Phone: (828) 227-2175Email: [email protected]

Andrew J. Wasiniak, CPCAIC Past PresidentWalbridge777 Woodward Ave., Suite 300Detroit, MI 48226Work Phone: (313) 221-1013Email: [email protected]

THEPROFESSIONALCONSTRUCTORVolume 36, Number 02 OCTOBER 2012

Articles

Risk Identification, Allocation, and Management in Sustainable Projects .....................5 Ihab M. H. Saad, Ph.D., P.Eng. PMP

Research of Concrete Containing Scrap-Tire Rubber for Pavement Construction ......13 Adel ElSafty, PhD., PE, Maged Malek, PhD., PE, Matthew Graeff

Shallow Flat Soffit Precast Floor System: A Construction Comparative Analysis ........18 Eliya Henin, James Goedert, Ph.D., P.E, George Morcous, Ph.D., P.E.

Reinforced Concrete Deterioration Due to Corrosion ...................................................26 Dr. M. Malek, University of North Florida

Quality Management: The philosophy and approach utilized by top performing US contractors ....................................................................................31 Dennis C. Bausman, PhD, FAIC, CPC & Daniel R. Mattox, MCSM Clemson University

The Professional Constructor (ISSN 0146-7557) is the official publication of the American Institute of Constructors (AIC), 700 N. Fairfax St. Suite 510 Alexandria, VA 22314. Telephone 703.683.4999, Fax 703.683.5480, www.professionalconstructor.org.

Subscription rates: This subscription includes 2 copies of The American Professional Journal in digital PDF copy for the year for $112.00 USD.

This publication or any part thereof may not be reproduced in any form without written permission from AIC. AIC assumes no responsibility for statements or opinions advanced by the contributors to its publications. Views expressed by them or the editor do not represent the official position of the The American Professional Constructor, its staff, or the AIC.

The Professional Constructor is a refereed journal. All papers must be written and submitted in accordance with AIC journal guidelines available from AIC. All papers are reviewed by at least three experts in the field.

OCTOBER 2012 — Volume 36, Number 02The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalcostructor.org

5

Risk Identification, Allocation, and Management in Sustainable Projects

Ihab M. H. Saad, Ph.D., P.Eng. PMP Associate Professor of Construction Management,

Northern Kentucky [email protected]

Keywords: Sustainability, Project Management, Risk Management.

INTRODUCTION Risk has been defined as “an uncertain event or condition that, if it occurs, has a positive or negative effect on a project objective” (PMI, 2004) and as “an uncertain event or set of circumstances that, should it occur, will have an effect on the achievement of the project’s objectives” (APM, 1997). Uncertainty can be due to known unknowns, unknown unknowns, and bias (Chapman and Ward, 2003). Negative risks are identified as threats to be eliminated or minimized,

whereas positive risks are defined as opportunities to be exploited and maximized.

Risk can result from several sources related to the natural project development cycle and the interaction of the parties involved therein. Figure 1 displays a simplified fishbone diagram of the sources of risk related to the project. Some of these risks arise during project formulation and definition, others are related to the selection of the project design features and deliverables, and a third group manifests during the project execution ending with its completion, commissioning, and operation and maintenance, up till the disposal.

ABSTRACT: The volume of green construction is on the rise both in the United States and worldwide. The US Green Building Council (USGBC) (2008) estimate the projected market value of the Green building industry in 2010 in the United States alone to reach $30 to $60 Billion in new construction, and another $240 Billion in renovation. These projections have been since revised downwards in response to the global financial crisis. To encourage serial owners to spread the green culture, USGBC has adopted a new program called “LEED Volume”, streamlining the certification process (2012). The exponential growth in green and sustainable projects will be contingent upon positive feedback from existing projects, reporting on the achievement of the sustainability objectives including reduction in operating costs, increase in building resale/lease value, improved occupancy ratio and a healthy return on investment. In order to achieve these objectives however, there are many risks to overcome and manage. These risks can be classified under several categories including economic (initial cost, life cycle cost, payback period, etc), technical and design (obsolescence, incompatibility, descriptive versus performance specifications, etc), social (awareness, participation and buy-in, etc), and regulatory (incentives versus disincentives, legislation and codes, etc).

This paper presents a general framework for managing the risks of a sustainable project through a systematic approach, starting with the scoping and identification of the risk, and ending with monitoring and reviewing the decision taken to manage that risk.

Dr. Ihab M. H. Saad is the Chairperson of the Department of Construction Management at Northern Kentucky University. He has more than 27 years of experience in Construction Project Management practice and education. He lectures internationally in the areas of project scheduling, construction contracts, construction safety, project management systems, project risk management, and sustainable development.


6Risk Identification, Allocation, and Management in Sustainable Projects

Figure 1. Sources of risk during project development 1.1 Structured Risk Management1.1.1 Elements of Risk Management

The Project Management Institute (PMI, 2003) identifies risk management as “the process of identifying, allocating, quantifying, analyzing, and responding to the risk (opportunity or threat) in order to maximize or minimize its probability and impact”. Project risks can be identified by three attributes determining the severity of the risk and pointing toward the most appropriate risk response strategy. These attributes are:

• The perception that something could happen (Risk identification)

• The likelihood or probability of something happening (Risk Probability)

• The consequences if it happens (Impact)

The risk evaluation is the product of the probability of occurrence x the impact if it occurs. The process of risk analysis or evaluation is generally performed under one or both of two types of analysis; qualitative and quantitative (Flanagan and Norman 1993).

Qualitative risk analysis is performed by using the probability and impact matrix (PIM) to prioritize and rank risks for subsequent further analysis or action. This is an iterative process that helps rank and prioritize the risks so that the right emphasis can be put on the right risks.

Quantitative risk analysis calculates numerically the probability and impact of risks and helps estimate contingencies as well as their implication for project objectives. Tools used for quantitative analysis include Monte Carlo simulations, Expected Monetary Value (EMV) analysis, and Decision Trees. The combination of qualitative and quantitative risk analysis techniques results in the development of a risk register including,

among other information, the type of risk, its triggers, its likelihood, impact, and monetary evaluation, in addition to its status (Active, Dormant, Expired) and response strategy. Figure 2 represents a sample risk register.

Figure 2. Risk Register

1.1.2 Risk response strategies

In response to or anticipation of risk occurrence, an organization can design its risk response strategy to follow one or a combination of several paths including:• For Negative risks (threats): Avoidance (Change method, location, design, or abort project if risk is excessive) Transfer (Contractual, insurance) Mitigation (Use less risky approach, provide safeguards, pay attention to trade-offs)• For Positive risks (opportunities): Exploitation (Increase likelihood and benefits, utilize synergies) Sharing (Partnering, joint ventures, incentive plans for partners) Enhancement (improve features and deliverables)• For both types: Acceptance (Assess residual risk and determine required contingencies) Ignoring (Not desirable)

The formulation of the risk response strategy therefore becomes part of the comprehensive framework of risk management as displayed in figure 3.


7 Risk Identification, Allocation, and Management in Sustainable Projects

Figure 3. Risk Management Framework

2 Research Methodology2.1 Literature Review

A literature search was performed to identify previous research in managing risk in construction projects, risk response strategies, and applications of these strategies to sustainable projects. Several efforts were undertaken in the analysis and quantification of the sources of risk in construction projects, together with proposed measures to manage these risks. However, most of the performed research focused on certain aspects of the project risk, or addressed certain project phases or project team members. Dawood (1998) addressed risks to the project schedule during construction and how to manage those risks through proper network management. Akintoye and MacLeod (1997) limited their focus to the construction phase and particularly to financial risks. Ahmad et al (2001) investigated risk allocation and reported on the proper selection of risk response strategies. Al-Bahar and Crandall (1990) have identified sources of risk to the construction project including physical, environmental, financial, legal, political, and technical including design, construction, and operation. Kangari (1995) reported on the current and perceived risk allocation among contractors and owners, based on an investigation of 100 large construction contractors and recommended further research be performed investigating non-technical risks. Mansfield (2009) limited the risk investigation to design consultants on conservation projects, whereas Lew and Overholt (2006) only addressed contractors’ risk management through insurance and sureties. Del Cano and De La Cruz (2002) focused primarily on risk management in the earlier project phases, particularly among owners and their consultants. No

comprehensive research was conducted addressing the project risk from the complete project life cycle perspective rather than from the point of view of one of the project parties during one or more of the project phases. There is not enough literature investigating unique risks to sustainable projects as a separate and identified segment of projects.

2.2 The SurveyA survey was developed investigating different project parties’ experience and perceptions on risk management in sustainable project. The survey was sent to 310 participants in sustainable projects, ranging from project owners, developers, designers, contractors, commissioning agents and public officials. 169 responses were received, at a response rate of 54.5%.

The survey consisted of the following sections:• Role of the participant in the sustainable project and level of involvement in the Green industry

• Drivers and Obstacles to further participation in sustainable projects

• Risk factors associated with the sustainable project Types of contracts and project delivery method currently used on the sustainable project

Respondents were asked to give relative weights to drivers, obstacles, and risks associated with their projects and the identified elements scoring 5 or above on a 10 point scale were considered relevant factors to be addressed as displayed in figure 4.

Figure 4. Sustainability Drivers



3 Research Findings

Participants were asked to identify major risk sources in the sustainable project, which resulted in the development of a Risk Breakdown Structure (RBS), as shown in figure 5. The presence of many of these factors represented threats to be minimized, whereas the introduction of established risk management measures including proper allocation and monitoring with preventive and corrective actions has the potential of converting it to an opportunity to be exploited.

Figure 5. Risk Breakdown Structure

Examples on risks and threats in sustainable projects based on the participants’ responses and their prioritization of identified risks based on the survey tally, and recommendations for mitigation and transformation into opportunities are displayed in figure 6 and include:

Utilization of new materials / methods / and techniques: which according to the majority of respondents was one of the major risks. Thorough investigation of these sources of risk, together with earlier participation of the contractors, suppliers, and manufacturers in the design process and in the

preparation of specifications can lead to the proper selection thus reducing the threat and using the familiarity with these material/methods/techniques as an opportunity improving the project deliverables including its time, cost, and quality.

Design innovation / Creativity: Which was primarily perceived by owners and designers as an opportunity, and by contractors as a threat, can be transformed to a mutual opportunity by including the contractor’s input, particularly in issues related to constructability and value management, in the early phases of design development. Seeking the contractor’s input can be achieved through the traditional project delivery methods by hiring a “construction consultant”, or by adopting other project delivery methods such as Design/Build or the more progressive approach of Early Contractor Participation (ECP) in the form of Integrated Project Delivery (IPD)

Project Performance and Operation: Many sustainability rating systems (LEED, BREEAM, Green Star, HQE, etc) focus primarily on the design for sustainability, with less emphasis on prescribed construction and operation guidelines to achieve the life cycle energy reduction. This may pose a threat for the owner of the project not performing up to expectations, and not being certified as designed. Such a problem can be mitigated by the inclusion of the commissioning agents as an integral part of the project team as early as possible, so that design decisions and criteria can be viewed from an operational perspective, thus eliminating the threat of non-certification.

Figure 6. Perceived risks and suggested response based on survey tally


9 Risk Identification, Allocation, and Management in Sustainable Projects

Initial and Life Cycle Costs: While it is well established that there is a higher likelihood of the existence of a initial cost “premium”, estimated by McGraw-Hill (2007, 2008) as 3 to 5%, the report perceives better marketability and value reflected in 7.5% value increase, 3.5% occupancy ratio increase, and an offset of the cost premium by a 3% rent ratio increase. The same report cites initial results on operating cost showing a decrease of 8 to 9% compared with traditional non-sustainable buildings.

Capitalizing on synergies and reducing impact of Trade-offs: Some sustainable design and construction criteria in a certain area tend to add value to other elements in another area, thus creating a synergy to be exploited and maximized. Examples of such synergies include development density and community connectivity, which work well with reducing required parking capacity, which in turn leads to reduced heat island effect and improved surface runoff control through better storm water management. Another example for opportunities to be maximized is the synergy between Brownfield development and removal of hazardous material resulting in better health and performance levels and leading to such intangible benefits as the social and economic revitalization of surrounding environment. On the other hand, some criteria tend to set-off the benefits of other criteria, creating new threats to be minimized. Examples of such conflicts include the negative effect of development density and community connectivity on the indoor air quality and the limiting of daylighting. Awareness with such positive and negative effects and optimizing the design to build on the synergies and minimize the threats leads to better risk management.

Incentives: State and Federal governments offer incentives for the development of sustainable projects in the form of tax breaks, financial packages, material and equipment rebates, and an expedited project review and approval process. Failure to meet the requirements for receiving these incentives in the form of non-improvement in project energy performance can result in a threat manifested in the discontinuity of these incentives, with its negative impact on the project life-cycle cost.

Figure 7. Project Management Practices to Reduce Risk Exposure

Figure 7 provides some additional project management practices that would help offset/mitigate/reduce sustainable project risks if properly implemented along the project life-cycle. These measures include technical (performance specifications, BIM , and Value Engineering, M&V), logistical (Lean principles), budgetary and costing (Life-cycle costing), as well as contractual and regulatory measures (Equitable risk association and relational contracts).

CONCLUSION

With the increasing growth in sustainable projects, new areas of risk arise, presenting both opportunities and threats. A comprehensive risk management system addresses the project in its different phases and covers the risks of different team members. Equitable allocation of risks through progressive contract forms and innovative project delivery systems allows for project team members to better address the threats in order to minimize their probability and impact, while capitalizing on synergies improving project performance and maximizing the benefits from opportunities. Better data collection about long term project performance will help validate the assumptions made during the project initiation and design phases. Contractors, suppliers, and commissioning agents have to be brought on board as early in the project development as practically possible. A structured project risk management has to be introduced to allow for the early identification, quantification, allocation, and response to different identified risks.



Risk registers have to be updated regularly reflecting the risk status and reporting on the implemented corrective and preventive actions. Results from risk management have to be communicated for further reference in similar projects. The implementation of proper project management practices during different project development phases can lead to a considerable reduction in the project risk exposure.

REFERENCES US Green Building Council (2008), Why Build Green, USGBC PMI (2004), A Guide to the Project Management Book of Knowledge: PMBOK Guide (3rd edition), Upper Darby, PA, Project Management Institute

APM (1997), PRAM Project Risk Analysis and Management Guide, Association for Project Management, Norwich, UK

Chapman, C., Ward, S. (2003), Project Risk Management; Processes, Techniques and Insights (2nd Edition), Chichester, UK: John Wiley & Sons.

Flanagan, R, Norman, G. (1993), Risk management and construction, Cambridge: Backwell Scientific.

Dawood, N. (1998), Estimating project and activity duration: a risk management approach using network analysis, journal of Construction Management and Economics, Volume 16.

Akintoye, A., Macloed, M. (1997), Risk Analysis and Management in Construction, International Journal of Project Management, Vol.15, No.1

Ahmed, S., Azhar, S.& Roldan, J. (2001), Development of a Risk Management Model for Florida Contractors. Technical Report Prepared for Building Construction Industry Advisory Committee (BCIAC), Department of Community Affairs, Florida.

Al-Bahar, J., and Crandall, K. C. (1990), Systematic risk management approach for construction projects, Journal of Construction Engineering and Management, ASCE

Kangari, R. (1995), Risk management perceptions and trends of U.S. construction, Journal of Construction Engineering and Management, ASCE

Mansfield, J. (2009), The use of formalized risk management approaches by UK design consultants in conservation refurbishment projects, Engineering Construction and Architectural Management, Vol. 16 No. 3

Lew, J., Overholt, M. (2006), Construction Project Risks: How to Estimate Insurance Costs, ASC Proceedings of the 42nd Annual Conference, Colorado State University Fort Collins, Colorado

Del Cano, A., De La Cruz, P. (2002), Integrated Methodology for Project Risk Management, Journal of Construction Engineering and Management, ASCE November/December 2002

McGraw-Hill Construction (2008), Key Trends in the European and U.S. Construction Marketplace, Smart Market Report

McGraw-Hill Construction (2007), Greening of Corporate America, Smart Market Report


11 Research of Concrete Containing Scrap-Tire Rubber for Pavement Construction

INTRODUCTIONThe state of Florida’s Waste Tire Management Program reports in “Waste Tires in Florida: State of the State 2008” that approximately 16,000,000 car and light truck tires, and 900,000 medium and large truck tires accumulated in 2007 (Department of Environmental Protection, 2008). Using a weight adjustment referred to as the Passenger Tire Equivalent (PTE), where 1 PTE is equal to a 20 pound passenger tire, a total of 20,500,000 PTE weighing 205,000 tons accumulated in Florida in 2007. Since the establishment of the Waste Tire Management

Program, the Department of Environmental Protection (DEP) has been exploring methods to encourage and accelerate market developments to achieve a full utilization of wasted tires as a resource. Successfully, several markets have been established for civil engineering applications, energy usages, and several other crumb rubber applications in order to utilize the states wasted tires.

Raw Materials and Binders: Tires are a complex mixture of various types of rubber, carbon black, inorganic materials, organic compounds, and reinforcing wire/

Research of Concrete Containing Scrap-Tire Rubber for Pavement Construction

Adel ElSafty, PhD., PE, Associate Professor

Maged Malek, PhD., PE, Department Chair

Matthew Graeff, Graduate Student

ABSTRACT: One of the major environmental challenges facing municipalities is the disposal of worn out automobile tires. To address this global problem, several studies have been conducted to examine various applications of recycled tire rubber (fine crumb rubber and coarse tire chips). The following research presents an experimental program conducted to develop a Portland concrete mixture that includes rubber as a replacement for some aggregates and that meets the low traffic pavements specifications of Florida’s Department of Transportation (FDOT). Several previously published articles document the change in concrete properties due to the inclusion of rubber. These changes include a lower density, enhanced ductility, better sound and thermal insulation, improved toughness, higher cracking/fracture and impact resistance, more traction, superior durability, lower compressive strength, and a lower flexural strength. The losses in strength are attributed to issues with the bonding between the rubber and the cement paste. Therefore our efforts were directed to designing a successful mix that contains the maximum amount of rubber and increases the bonding capabilities to regain lost strengths. Experiments were conducted using two different sizes of rubber aggregate, one small (approximately 0.25-inch diameter) and the other large (approximately 1-inch diameter). Several different admixtures and surface treatment techniques for the rubber aggregate were investigated with the attempt to recover the lost strength. A total of 70 concrete samples were tested in either compression or flexure. The engineered mix design which was found to best meet the desired and required specifications includes: 36.48% coarse aggregate, 25.07% fine aggregate, 6.44% epoxy/sand coated rubber, 11.30% cement, 17.82% water, and 2.89% air.

Dr Malek, Chair of the Construction Department, College of Computing Sciences, Engineering and Construction at the University of North Florida. He was conferred a Ph.D in Engineering from the University of Central Florida in 1996. Dr Malek is the graduate degree coordinator for the department and the director of the research center at UNF.

Dr. Adel ElSafty, PE, P.Eng is an Associate Professor at the University of North Florida (UNF). Dr. ElSafty earned his PhD in Civil Engineering from North Carolina State University. He holds P.E. registration/license in Florida and in Ontario, Canada. Dr. ElSafty worked in the industry at a Bridge Design firm “Lochner” in Orlando and as a Specification Manager at FOSROC (British Construction Chemical Company).

Matthew K. Graeff is a recent graduate of the University of North Florida where he has received a Master’s degree in Civil Engineering. His focus of study was related to the rehabilitation and strengthening of damaged concrete bridge girders repaired with carbon fiber reinforced polymers.


12Research of Concrete Containing Scrap-Tire Rubber for Pavement Construction

fabric. Tires are processed into shredded products or crumb rubber to turn them into useful products. Also binders are used to bind tire chips and crumb rubber together into a cohesive mass under simple contact mixing or compression molding. Examples include the use of polyurethane binders with crumb rubber to form “pour-in-place” (contact) and rubber tile (compression) cushioning surfaces in playgrounds. Polyurethane, latex, and epoxy binders have been used with crumb rubber, but latex binders have historically experienced some long-term failures in running track applications.

The Florida Department of Transportation (FDOT) has made efforts to include wasted tire in state road construction and repair consuming 5000 tons annually as part of the interlayer, friction coarse, and crack sealants (FDOT, 2007). However, there are high costs associated with manufacturing the

small crumb rubber and the time- and effort- consuming process of producing the modified rubberized asphalt. The development of a suitable rubberized Portland cement concrete (RPCC) for pavement design could increase the environmentally safe usage of millions of wasted tires, lower costs for future green construction, and supply a means to further deplete all stock piles of wasted tires in the state of Florida and could contribute to having a more flexible concrete pavement to mitigate the adverse effects of high stresses and possible cracks.

Previous Studies: Several published studies have already completed preliminary investigations into the usage of wasted rubber in a Portland cement concrete and have established classifications of waste tire products and their properties, environmental management options, and research findings from integrating wasted tire rubber in concrete (Ganjian et al., 2008, Hammer and Gray, 2004, Hossian et al., 1995, Kumaron et al., 2008, Li et al., 2004, Huang et al., 2004, Zheng et al., 2008, Siddique and Naik, 2004, FDOT 2007, ASCE/ASTM 2005). The research findings have addressed several variables when preparing various

mixtures of rubberized Portland concrete. Efforts have included using different shapes, sizes, and amounts of recycled rubber aggregate. Other investigations into admixtures and pretreatment of the rubber aggregate were also analyzed. The research findings included values for slump, air content, unit weight, compressive and tensile strength properties, shrinkage, toughness and impact resistance, freezing and thawing resistance, and sound insulation.

The reviewed research makes conclusions pertaining to the usage of rubber strips vs. rubber chips, large rubber pieces vs. small, the amount of rubber used and its corresponding effect, and the improvements from treatments and admixtures. The conclusions were summarized as follows:

(1) Rubber strips perform better than chips at retaining the strength and stiffness of the concrete. Although thinner strips perform better than thick strips, the effect was not very significant. (2) Longer strips entangle. It is suggested that strip length be restricted to less than 50 mm. (3) The optimum size and shape without admixtures is 48mm long by 7mm high and 7mm wide. (4) Steel belt wires in waste tires have a positive effect on increasing the strength of rubberized concrete. Truck tires perform better than car tires at retaining strength and stiffness. (5) The compressive strength of the rubberized concrete is affected by the portions and surface texture of the rubber. For example, when 100% of the coarse aggregate is replaced by rubber the compressive strength and tensile strength are 85% and 50% lower. Likewise, when the fine aggregate is completely replaced by rubber the reduction in compressive strength and tensile strength are 65% and 50% respectively. (6) More than 15% of rubber replacement severely decreases the strength of the concrete. (7) A NaOH surface treatment improves bonding of smaller rubber; however, it does not seem to enhance bonding for larger size tire chips. (8) Lack of proper bonding between the rubber and the cementitious material of the concrete is the primary factor for the strength reductions. (9) Hybrid polypropylene fiber reinforcement has a potential to produce higher strength and higher toughness concrete.

FIGURE 1: Stock Pile of Wasted Tires



(10) The inclusion of superplasticizers increases the strength and improves workability. (11) Rubberized concrete has many desirable characteristics such as lower density, enhanced ductility, better sound and thermal insulation, improved toughness, higher cracking, fracture, and impact resistance, more traction, and durability.

Tests Standards in literature - ASTM Standards: Many of these American Standards for Testing Materials (ASTM) provide clear definitions of technology, applications, and testing methods for products made from waste tires (ASCE/ASTM 2005). Examples related to waste tire products include the following tests:

• D6270-98 Standard Practice for Use of Scrap Tires in Civil Engineering Applications• D5603-01 Standard Classification for Rubber Compounding Materials—Recycled Vulcanizate Particulate Rubber• D5644-01 Standard Test Method for Rubber Compounding Materials—Determination of Particle Size Distribution of Vulcanized Particulate Rubber• D6814-02 Standard Test Method for Determination of Percent Devulcanization of Crumb Rubber Based on Crosslink Density

Other studies involving the concrete mix design were also investigated (Kett, 2000, Kosmatka and Panarese, 1988).

MATERIALS AND EXPERIMENTAL RESEARCHThe aim of this experimental research was to achieve a workable and adequate rubberized concrete mixture that could be used for Florida’s roadway and pavement construction. Intentions are to create the mix design which contains the maximum amount of rubber and still meets the FDOT specifications for construction. The previous research suggested that the problem that arises with the inclusion of rubber is the large loss of strength due to the lack of adhesion between the rubber and the cementitious material. Efforts to overcome or compensate for these factors were performed. The final product that meets strength specifications should have improved ductility, toughness, cracking/fracture resistance, impact resistance, traction, durability, and sound insulation.

Investigations to achieve the desired mix design were carried out in this study using two different sizes of rubber. First a small sized crumb rubber product that is readily available at multiple home good stores (approximately 0.25-inch diameter) without tire fibers or steel wire was sold as playground material. The second product used was a large chunk rubber product from a relatively local recycling plant which still contains the fibers and steel wire from the tire (approximately 1-inch diameter). For each size, the crumb and chunk, ASTM standards were used to test and design control batches of the concrete for strength comparisons. Table 1 lists all the ASTM standards followed in the process of executing this research experiment.

TABLE 1: ASTM Tests and Procedures.

Materials Used: Portland cement Type I/II were used. Coarse Aggregate with 1-inch max aggregate size and fine aggregate of standard light colored sand were used. Rubber aggregate of 1-inch max size with fibers and steel was also used in this research. Epoxy and acrylic were used in this study. Water-based acrylic bonding and modifying admixture was used. This acrylic-polymer emulsion was mixed with Portland cement mortars and concrete mixes to enhance their physical properties and adhesion to rubber aggregate.

The Superplasticizer used was from Grace Concrete Products (ADVA® 140M). It is a high-range water-reducing admixture based on polycarboxylate technology specifically formulated to meet the needs of the concrete industry. ADVA 140M meets the requirements of ASTM C494 as a Type A and F, and ASTM C1017 Type I. Also, the used fly ash was “Class F fly ash”.

Procedure Tests to Perform ASTM Designation

Procedure Tests to Perform ASTM Designation

1 Rodded unit weight of coarse aggregate C 29 7

Compressive strength of cylindrical concrete specimens

C 39

2 Specific gravity and absorption of coarse aggregate

C 127 8

Flexural strength of concrete using simple beam w/third-point loading

C 78

3 Specific gravity and absorption of fine aggregate C 128 9 Unit weight C 138

4 Sieve analysis of fine aggregate C 136 10 Slump of hydraulic

cement concrete C 143

5 Sieve analysis of coarse aggregate C 117 11

Static modulus of elasticity & Poisson's ratio of concrete in compression

C 469

6 Mix Design for Control Batch



The acrylic polymer used (Acryl 60® by BASF) is an acrylic-polymer emulsion mixed with Portland cement mortars and concrete mixes to enhance their physical properties, adhesion to substrates, and durability. The epoxy used (PRO-POXY 200) was a solvent-free, moisture insensitive, 100% solids, medium viscosity, two component epoxy bonding agent. It meets ASTM-C-881 Types I, II, Grade 2, Classes B & C. It is an excellent epoxy adhesive for making epoxy mortars and grouts.

Research Experiments: From previous researches, it is known that more than 15% of rubber replacement severely decreases the strength of the concrete and the adhesion between the cement and rubber is a primary factor in recovering some of the lost benefits. In order to achieve the most economical design, a constant 15% of coarse aggregate was replaced with rubber aggregate and several methods to improve the bonding were examined in order to recover the lost strengths. Methods to improve the bonding included the use of several admixtures, treatments, or application techniques as listed in Table 2.

TABLE 2: Batch Description and Technique Applied.

The parameters required by the FDOT for low traffic road pavements are listed below in Table 3. As listed, the minimum compressive strength requirement is 3,000 psi. However, since there is a certain amount of expected losses, the control mix was designed to be 3,500 psi with 100% rock aggregate. Then the subsequent mixes used either the chunk or crumb rubber to replace 15% of the coarse aggregate.

TABLE 3: FDOT Type I Concrete Specifications

All the rubber used in the concrete mixtures was cleaned and treated with a NaOH solution, rinsed with water, and drained prior to being used in order to enhance the bonding capabilities of the rubber to any of the other materials. After cleaning the rubber and including the various admixtures, as depicted previously in Table 2, the batches of rubberized concrete were used to cast (6 in x 12 in) cylinders, (4 in x 8 in) cylinders, and (6 in x 6 in x 21 in) flexural beams. Those specimens were then tested using procedures 7-11 as listed in Table 1. The following figures (Figures 2 - 4) show the procedure for mixing the polymer with rubber aggregate, preparing the concrete cylinders and beams, and testing them.

Batch Rubber Admixture Technique control None None N/A

2 Crumb None N/A 3 Crumb Superplasticizer Mixed in 4 Crumb Fly ash mortar Rubber surface treatment 5 Chunk None N/A 6 Chunk Acrylic Mixed in 7 Chunk Epoxy Rubber surface treatment & mixed when tacky

8 Chunk Epoxy & Sand Rubber surface treatment & mixed when hardened

Type I (pavement) Concrete Requirements

Minimum Strength 28-day (psi) 3,000 Target Slump (in) 2 Air Content (%) 1 to 6 Minimum Cementitious Material Content (lb/yd3) 508 Maximum Water/Cementitious Materials (w/c) Ratio (lb/lb) 0.5

(a) Mix materials

(b) Mixing the polymer

(c) Preparing rubber aggregate and mixing with polymer

(d) Prepared rubberized aggregate

(e) Treatments for rubber chunks

(f) Preparing concrete beams (g) Testing the beams in flexure

(h) Tested beams (i) Tested cylinders

FIGURE 2: The procedure for aggregate and specimen preparation: (e), (f) the tested beams, (g) tested concrete cylinders having rubber aggregate



FIGURE 3: The testing of rubberized concrete cylinder

FIGURE 4: The testing of rubberized concrete Beams/prisms

RESULTSThis research was conducted in two consecutive phases, first with the crumb rubber and then again with the chunk rubber. The first phase of testing yielded a compressive strength in the control that exceeded the targeted strength. The second phase produced more moderate compressive strengths in the control design and yet meeting the requirements. An analysis of the comparisons of these controls was performed to attain conclusions about the rubberized concrete and the performance of the admixtures used in the controls.

Prior to establishing these mentioned mix designs, all of the aggregate was tested for its basic properties. The properties of the rubber were extracted from “Development of Waste Tire Modified Concrete” (Guoqiang et al., 2004). The test values for the rodded unit weight, specific gravity, and absorption of the fine and coarse aggregate are listed in Table 4. The sieve analysis for each material is presented in Tables 5 through 7.

TABLE 4: Aggregate Test Results

TABLE 5: Sieve Analysis of Fine Aggregates

TABLE 6: Sieve Analysis of Coarse Aggregate

TABLE 7: Sieve Analysis of Chunk Rubber Aggregate

Using the properties of the aggregates, a control mix design was established as shown in Table 8. Then, by replacing 15% of the coarse aggregate, samples for the crumb rubber specimens were made. That included a total of 16 (6 in x12 in) cylinders, 16 (4 in x 8 in) cyl-inders, and 6 (6 in x 6 in x 21 in) flexural beams. The average results for compressive tests of these samples are also shown in Table 9.

TABLE 8: Control Mix Design for Crumb Rubber Specimens

Procedure Tests to Perform ASTM

Designation Results

1 Rodded unit weight of coarse aggregate C 29 95.3 lb/ft3

2 Specific gravity and absorption of coarse aggregate C 127 2.49

3.18%

3 Specific gravity and absorption of fine aggregate C 128 2.37

0.27%

##44 00..001144 00..3344%% 9999..6666%% 00..3344%% ##88 00..005588 11..4400%% 9988..2277%% 11..7733%%

##1166 00..229999 77..2200%% 9911..0077%% 88..9933%% ##3300 11..000099 2244..2288%% 6666..7799%% 3333..2211%% ##5500 22..116633 5522..0055%% 1144..7744%% 8855..2266%%

##110000 00..55666655 1133..6633%% 11..1111%% 9988..8899%% ##220000 00..004433 11..0033%% 00..0077%% 9999..9933%% PPaann 00..00002255 00..0066%% 00..0011%% 9999..9999%%

TToottaall 44..115555 FFMM 22..2288

Sieve Size

Weight Retained (g) % Retained % Passing

Cumul. % Passing

11 1/2 iinn 00 00..0000%% 10000..0000%% 00..0000%% 11 iinn 00..006655 00..6699%% 9999..3311%% 00..6699%%

33//44 iinn 11..99443355 2200..6633%% 7788..6688%% 2211..3322%% 11//22 iinn 33..9911 4411..5500%% 3377..1199%% 6622..8811%% 33//88 iinn 11..552222 1166..1155%% 2211..0033%% 7788..9977%%

##44 11..33007755 1133..8888%% 77..1166%% 9922..8844%% PPaann 00..66774455 77..1166%% 00..0000%% 110000..0000%%

TToottaall 99..44222255

Sieve Size


Cumul. % Passing

Sieve Size


Cumul. % Passing

1 in 0.0165 0.95% 99.05% 0.95% 3/4 in 0.3935 22.69% 76.36% 23.64% 1/2 in 0.8395 48.41% 27.94% 72.06% 3/8 in 0.2535 14.62% 13.32% 86.68%

#4 0.207 11.94% 1.38% 98.62% Pan 0.024 1.38% 0.00% 100.00% Total 1.734

By Volume By Weight

Coarse 12.26 ft3/yd3 Coarse 1675 lb/yd3

Fines 5.97 ft3/yd3 Fines 882.9 lb/yd3

Cement 3.18 ft3/yd3 Cement 625 lb/yd3

Water 4.00 ft3/yd3 Water 249.6 lb/yd3

Air 1.59 ft3/yd3 Air 0 lb/yd3



TABLE 9: Compression Test Results for Crumb Rubber Specimens

Flexural testing was also completed to determine if the inclusion of rubber in the concrete could enhance the flexural strength of the concrete. The average values for the flexural strength of the crumb rubber speci-mens are listed in Table 10. It can be seen that, as ex-pected, the first round of testing showed a loss of flex-ural strength in all samples.

TABLE 10: Results for Flexural Testing of Crumb Rubber Specimens

The results reported for the crumb rubber concrete mixtures show that the desired strengths were reached. By analyzing the reduction in strength from the control, it is shown that the additives used were not effective in significantly recovering the lost strength associated with using the rubber; which led us to the second part of the testing that used the chunk rubber pieces.

Again using the properties of the aggregates, a new mix design was established for the chunk rubber specimens as shown in Table 11. Then, samples for the chunk rubber specimens were made including a total of 16 (6 in x12 in) cylinders, 16 (4 in x 8 in) cylinders, and 6 (6 in x 6 in x 21 in) flexural beams. The average results for compressive tests of these samples are also shown in Table 12.

TABLE 11: Mix Design for Chunk Rubber Specimens

TABLE 12: Compression Test Results for Chunk Rubber Specimens

Flexural testing was again completed with the chunk rubber specimen to determine if the inclusion of larger rubber pieces could enhance the flexural strength of the concrete. The average values for the flexural strength of the chunk rubber specimens are listed in Table 13. It can be seen that the second round of testing developed a technique in which the flexural strength is actually maintained or slightly increased.

TABLE 13: Results for Flexural Testing of Chunk Rubber Specimens

From the results reported for the chunk rubber concrete mixtures, it is shown that one of the admixture batches has the potential to increase flexural strength while maintaining the other desired properties which are associated with the inclusion of the rubber.

The following table shows the optimum mix design by volume used in the final stages of this research study that resulted in good flexural strength and acceptable compressive strength.

Table 14: The Optimum Mix Design by Volume

Specimen ID Stress (psi) Strain (in/in) % Strength Loss

Control 6197.5 0.030235 ---

Rubber 4323.4 0.022254 27.11%

Rubber with Fly Ash Mortar 4405.5 0.022134 25.72%

Rubber and Superplasticizer 4039.0 0.026769 31.90%

Specimen ID Flexural Stress (psi) % Strength Loss

Control 702 --- Rubber 652.5 7.05%

Fly Ash Mortar Additive and Rubber 534 23.93%

Superplasticizer and Rubber 527 24.93%

By Volume By Weight

Coarse 11.59 ft3/yd3 Coarse 1857.78 lb/yd3

Fines 6.77 ft3/yd3 Fines 1001.16 lb/yd3

Cement 3.05 ft3/yd3 Cement 600 lb/yd3

Water 4.81 ft3/yd3 Water 300 lb/yd3

Air .78 ft3/yd3 Air 0 lb/yd3

Specimen ID Compressive Stress (psi) % Strength Loss

Control 5574 -----

Rubber 3004 46%

Rubber w/ Acrylic 2778 50%

Rubber w/ Epoxy 1 2691 52%

Rubber w/ Epoxy 2 3064 45%

Specimen ID Flexural Stress (psi) % Strength Loss

Control 680 -----

Rubber 618 9.1% Rubber w/ Acrylic 429 36.9%

Rubber w/ Epoxy 1 491 27.8%

Rubber w/ Epoxy 2 709 -4.3%

By VOLUME (ft3/yd3) % by Volume Coarse 9.85 36.48% Rubber 1.74 6.44% Fines 6.77 25.07% Cement 3.05 11.30% Water 4.81 17.82% Air .78 2.89%



OUTCOMES & CONCLUSIONS

• The smaller pieces of rubber (approximately 0.25- inch diameter) result in a smaller loss of compressive strength when compared to the larger pieces (approximately 1-inch diameter).• The addition of superplasticizers and acrylics did not recover in any significant way the strength lost by including rubber aggregates.• The fly ash mortar surface treatment application did improve the strengths when compared to the inclusion of rubber without fly ash. • The samples that utilized the rubber aggregate coated with epoxy and sand provided the best results. These samples demonstrated a very slight gain in both flexural strength of about 14% compared to the samples containing rubber alone. Also, the compressive strength of the samples utilizing rubber aggregate coated with epoxy and sand was comparable to that of samples with rubber alone.• The inclusion of the epoxy and sand coated rubber aggregate slightly increased the flexural strength of the specimen by about 4% when compared to the controls.• At failure in flexure, the inclusion of the rubber deterred the samples from a sudden failure confirming the assumption of creating a more ductile concrete. • The engineered mix design which best meets specifications includes: 36.48% coarse aggregate, 25.07 fine aggregate, 6.44% epoxy/sand coated rubber, 11.30% cement, 17.82% water, and 2.89% air. It should also be noted that the minimum compressive strength requirement of 3,000 psi was achieved using this mix design.• It is recommended to expand the study in future work to further investigate the performance of larger test samples including concrete slabs under traffic loading.

REFERENCES[1] American Society of Civil Engineers, 2005. “Annual Book of ASTM Standards 2005: Section Four-Construction”, ASTM International, West Conshohocken, Pennsylvania.

[2] Department of Environmental Protection, 2008. “Waste Tires in Florida: State of the State”. Waste Tire Management Program. Tallahassee, Florida.

[3] Florida Department of Transportation. 2007. “Section 346: Portland Cement Concrete”. Materials Manual-Concrete Production Facilities Guidelines. Tallahassee, Florida.

[4] Ganjian, Eshmaiel; Khorami, Morteza; and Maghsoudi, Ali Akbar, 2008. “Scrap-Tyre-Rubber Replacement for Aggregate and Filler Concrete”, Construction and Building Materials, Vol. 23, 2009, pp. 1828-1836.

[5] Hammer, Chris; and Gray, Terry A., 2004. “Designing Building Products Made with Recycled Tires”. Integrated Waste Management Board, California.

[6] Hossian, M.; Sadeq, M.; Funk, L.; and Muag, R., 1995. “A Study of Chunk Rubber from Recycled Tires as a Road Construction Material”, Department of Transportation. Topeka, Kansas.

[7] Huang B, Li G, Pang S-S, Eggers J. Investigation into waste tire rubber-filled concrete. Journal of Materials in Civil Engineering. 2004; 16(3):187-194.

[8] Kett, Irving. 2000. “Engineered Concrete: Mix Design and Test Methods”, Boca Raton, Florida. CRC Press LLC.

[9] Kosmatka, Steven H.; and Panarese, William C., 1988. “Design and Control of Concrete Mixtures: 13th Edition”, Stokes, Illinois. Portland Cement Association.

[10] Kumaron, Senthil G.; Mushule, Nurdin; and Lakshmipathy, M., 2008. “A Review on Construction Technologies that Enables Environmental Protection: Rubberized Concrete”, American Journal of Engineering and Applied Sciences, Vol. 1 No. 1 2008, pp. 41-45.

[11] Li, Guoqiang; Stubblefield, Michael A.; Garrick, Gregory; Eggers, John; Abadie, Christopher; and Huang, Baoshan. “Development of waste tire modified Concrete”, Cement and Concrete Research Vol. 34, 2004, pp. 2283-2289. Elsevier Ltd.

[12] Siddique, Rafat; and Naik, Tarun R., “Properties of concrete containing scrap-tire rubber – an overview”, Waste Management, Vol. 24, 2004, pp. 563-569. Elsevier Ltd.

[13] L. Zheng, X. Sharon Huo, and Y. Yuan, 2008, “Strength, Modulus of Elasticity, and Brittleness Index of Rubberized Concrete”, ASCE, Journal of Materials in Civil Engineering, Vol. 20, Issue 11, (Nov. 2008), pp. 692-699


18Shallow Flat Soffit Precast Floor System: A Construction Comparative Analysis

Shallow Flat Soffit Precast Floor System: A Construction Comparative Analysis

Eliya Henin, James Goedert, Ph.D., P.E, George Morcous, Ph.D., P.E.

Keywords: Precast Concrete, Floor System, Beam Ledges, Column Corbels, Hollow-Cores INTRODUCTION

Conventional hollow-core floor systems consist of hollow-core planks supported by inverted-tee precast prestressed concrete beams, which are, in turn, supported on column corbels or wall ledges. These floor systems provide a rapid construction solution to multi-story buildings that is economical and fire-resistant with excellent deflection and vibration characteristics. The top surface of hollow-core floor systems is usually a thin non-structural cementitious topping, at least 2 in. (5.1 cm) thick that provides a level surface. Despite the advantages of conventional precast hollow-core floor systems, they have two main limitations: a) low span-to-depth ratio and b) floor projections, such as column

corbels and beam ledges. A 30 ft (0.76 m) conventional precast hollow-core floor bay would require a 28 in. (71 cm) deep inverted-tee plus a 2 in. (5.1 cm) topping, for a total floor depth of 30 in. (76 cm). This leads to a span-to-depth ratio equals to 12 (See design tables in section 3.11 of the 7th edition of PCI design handbook, PCI, 2010). In addition, this floor would have a 12 in. (31 cm) deep ledge below the hollow-core soffit and 16 in. (41 cm) deep column corbel below the beam soffit. While column corbels and beam ledges are common in parking structures and commercial buildings, they are not favourable in residential and office buildings due to aesthetics and increase building volume. False ceiling are used in these applications to hide the unattractive floor projections, resulting in reduced vertical clearance. Elimination of floor projections combined with shallow structural depth will improve the building aesthetics and overall economics.

ABSTRACT: This paper compares the constructability, cost and schedule of a new shallow flat soffit precast floor system with a typical precast floor system. The new system consists of continuous precast columns without corbels, partially continuous rectangular beams without ledges, partially continuous hollow-core planks (HC), and cast-in-place composite topping. The main criteria in the design of the new system includes: span-to-depth ratio of 30, flat soffit floor system, economy, and consistency with prevailing erection techniques. The new shallow flat soffit precast floor system has a depth and flat soffit comparable to cast in place systems. It has no constructability issues and costs $23.60/square foot as compared to $21.90/square foot for a typical precast system. Although the new system takes 20% longer erection duration than typical precast system, the flat soffit and shallowness of the proposed system outweighs the cost and duration disadvantages. The continuous beam connections also have the added benefit of eliminating shear walls in moderate wind load conditions. This investigation uses a typical six story hotel or office building with 16 bays 30 ft (9.14 m) x 30 ft (9.14 m) for construction costs and schedule comparisons.

Dr. Eliya Henin is a Structural Design Engineer at Ebmeier Engineering LLC since May 2012, Also, he is an assistant lecturer at Civil Engineering Department at the Assiut University-Egypt since April 2006. He has a B.S. and M.S. degrees in Civil Engineering from Assiut University-Egypt. He earned his doctorate degree from University of Nebraska – Lincoln in May 2012. His research interests include design and construction of reinforced and prestressed concrete structures.

Dr. James Goedert is an Associate Professor at the Durham School of Architectural Engineering and Construction at the University of Nebraska-Lincoln. He has a B.S. in Construction Engineering Technology, an MBA from the University of Indiana, and a Ph.D. in the Interdisciplinary Area of Business Administration from the University of Nebraska-Lincoln. His research interests include construction modelling and simulation and energy efficient residential construction.

Dr. George Morcous is an associate professor at Durham School of Architectural Engineering and Construction at the University of Nebraska-Lincoln since January 2005. He has a B.S. and M.S. degrees in Civil Engineering from Cairo University-Egypt. He earned his doctorate degree from Concordia University – Canada in 2000. His research and teaching interests include design and construction of reinforced and prestressed concrete structures.


19 Shallow Flat Soffit Precast Floor System: A Construction Comparative Analysis

Post-tensioned cast-in-place concrete slab floor systems can be built with a span-to-depth ratio of 45 with a flat soffit, resulting in a structural depth of 8 in. (20.3 cm) for the 30 ft (76 cm) bay size (PTI, 2006). The major drawbacks of cast-in-place construction, in general, are the cost and duration required for shoring, forming, pouring, and stripping operations. In addition, post-tensioning operations increase the construction cost, duration, and complexity because of the involvement of specialty contractors (PCI, 2004).

If the structural depth of precast floor systems can come close to that of post-tensioned cast-in-place concrete slab system, then precast concrete would be very favourable due to rapid construction and high product quality. Reducing the depth of structural floor leads to reduced floor height, which leads to savings in architectural, mechanical and electrical systems and may allow for additional floors for the same building height. The cost of operation and maintenance of office buildings is about 80% of the initial cost of construction (Snodgrass, 2008), so any small savings in these systems would have a significant impact on the building life cycle cost.

The main objective of this paper is to present a shallow flat soffit precast floor system and compares its construction sequence, cost, and duration against a typical precast system. The shallow flat soffit precast floor system is an innovative system with no ledges or corbels, similar to cast-in-place floors, and shallow structural depth when compared to conventional precast floor systems. The new system has continuity in both directions that is adequate to resist lateral loads that reduces the need for shear walls. The new system is a total precast floor system that consists of precast concrete columns, precast/prestressed concrete rectangular beams, precast/prestressed concrete hollow-core planks, and cast-in-place composite topping. The system is ideal for six story buildings with 30 ft (9.14 m) x 30 ft (9.14 m) bays, which are typical for hotels and office buildings. This system was developed by researchers at the University of Nebraska-Lincoln and was funded by two precasters: Concrete Industries (CI) Inc., Lincoln, NE; and EnCon Precast, Denver, CO.

The next section is a review of the existing precast concrete floor systems followed by a description of the

new system and its construction sequence. The new system is then compared on the basis of construction cost and duration against a typical precast operation

CURRENT PRECAST FLOOR SYSTEMS Low, et al. (1991 and 1996) developed a shallow floor system for multi-story office buildings. The system consists of HC planks, 8 ft (2.4 m) wide and 16 in. (40.6 cm) deep prestressed beams, and single-story precast columns fabricated with full concrete cavities at the floor level. The column reinforcement in this patented system is mechanically spliced at the job site to achieve the continuity (Tadros and Low, 1996). The beam weight and the complexity of the system design and detailing were discouraging to producers. Thompson and Pessiki, (2004) developed a floor system of inverted tees and double tees with openings in their stems to pass utility ducts. This floor system is appropriate and economical for parking structures as it does not provide either a shallow floor or flat soffit required for residential and office buildings

Simanjuntak (1998) developed a shallow ribbed slab configuration without corbels. This is accomplished by threading high tensile steel wire rope through pipes imbedded in the floor system and holes in the columns. The limitations of this system include the distance between columns, the time required to make connections, unattractive slab ribs, and weak lateral load resistance. Compton (1990) designed a system with a retractable hangar at the upper end of the beams that extends into a recess in the column. The system has low resistance to lateral loads and requires highly skilled labour.

Wise (1973) used composite flexural concrete construction to build two way and flat slabs with little to no formwork. The precast panels bear on temporary or permanent supports. They have one or more lattice trusses firmly embedded in the panel to provide longitudinal reinforcement. The disadvantages of this system include the shoring requirement and the size of the panels. Hanlon (1990) used modular precast components with a series of columns with wide integral capitals. Wide beams are supported by the capitals on hangars. This system works well with long span column grids. The disadvantage of the system is the requirement for heavy construction equipment



to handle the heavy components. Composite Dycore Office Structures (1992) developed the Dycore floor system for office buildings, schools, and parking garages. This system consists of shallow soffit beam, high strength Dycore floor slabs. This is attached to cast-in-place/precast columns with block outs at the beam level. The precast beams and floor slab act as a form for the CIP operations.

Filigree Wideslab System was originally developed in Great Britain and is presently used there under the name of OMNIDEC (Mid-State Filigree Systems, Inc. 1992). It consists of reinforced precast floor panels that serve as permanent formwork. The panels are composite with cast-in-place concrete and contain the reinforcement required in the bottom portion of the slab. They also contain a steel lattice truss, which projects from the top of the precast unit. One of the main advantages of this system is a flat soffit floor that does not require a false ceiling. However, this system has poor thermal insulation and requires advanced techniques to produce due to the fabrication difficulties in lattice truss fabrication and installation (Pessiki et al., 1995)

Several efforts have been made to minimize the depth of flooring systems by combing steel and precast concrete products. Steel beams are used in Europe to support hollow core planks by their bottom flanges and the composite topping by their top flanges. The steel beams are plate girder (built up) sections, and rolled steel section (Board of Federation International Du Beton (fib) steering committee, 1999). These systems provide a high span-to-depth ratio, however, they are limited to about 20 ft (6.1 m) spans, which is reasonable for apartment/hotel buildings, but considerably less than the spans generally required for office building applications. These systems may merit further investigation if the fire protection issues of the underside of the beam can be satisfactorily resolved and if the cost of fabrication is comparable to the equivalent prestressed concrete beam.

In the United States, steel beams have been developed by Girder-Slab Technologies LLC of Cherry Hill, NJ, (2002). Similar to the European practices, the precast planks are supported on the bottom flange of the steel beams. The D-BEAMTM steel girder is a proprietary shallow beam that usually spans 16 ft (4.9 m), which

would not suit typical office framing spans. Longer spans require extra manufacturing and shipping costs due to the 16 ft (4.9 m) span limit in the beam production.

The Deltabeam (Peikko Group, 2010), is a hollow steel-concrete composite beam made from welded steel plates with holes in the sides. It is completely filled with concrete after installation. Deltabeam acts as a composite beam with hollow-core, thin shell slabs, and in-situ casting. Deltabeam can have a fire class rating as high as R120 without additional fire protection. The Deltabeam height varies based on the required span. For a 32 ft (9.75 m) span, the Deltabeam can be as shallow as 23 in. (58 cm) including the 2 in. (5.1 cm) topping. Although this is 5 in. (12.7 cm) less than the precast/prestressed concrete inverted tee, it requires shoring for erection, adding shims to raise hollow cores up to match the level of the top plate, and additional fire protection operations if higher ratings are required. Bellmunt and Pons (2010) developed a new flooring system which consists of a structural grid of concrete beams with expanded polystyrene foam in between. The grid has beams in two directions every 32 in. (81 cm). The floor is finished with a light paving system on top and a light ceiling system underneath. This system has many advantages, such as lightweight, flat soffit, and thermal insulation. However, some of its disadvantages include the floor thickness, unique fabrication process of forms due to the special connections required

PROPOSED SYSTEMThe shallow flat soffit precast floor system is proposed for hotel or office buildings in low-moderate seismicity zones. Figure 1 shows a plan view of a 16 bay office building with 30 ft (9.14 m) by 30 ft (9.14 m) bays. The shallow flat soffit precast floor system supports standard hollow core planks with 10 in. (25.4 cm) thick precast/prestressed rectangular beams supported by precast concrete columns. The 10 in. (25.4 cm) thick and 48 in. (122 cm) wide hollow core planks is the most affordable precast product due to simple fabrication, ease of handling and reduced shipping cost due to their light weight (CI, 2012). The connections are simple for precasters to produce and quick for contractors to erect. The entire system is topped with a cast-in-place composite topping.



Figure 1. Building Precast Plan View (ft = 0.3048m)

The precast columns are continuous to the full height of the building. They include an opening at each floor level with a profile as shown in Figure 2.

The beams are made continuous on site during the construction process before the topping is installed. The beam continuity is created by placing reinforcing in pockets at the beam ends. Figure 3 is the top plan view of the beam end that goes through column openings shown in Figure 2 to the opposing beam. Figure 4a and 4b show sections A-A and B-B of the beam, respectively.

Figure 3. Top Plan View of the End of the Sallow Flat Soffit Precast Floor Beam (ft = 0.3048 m)

Figure 4a. Cross Section of Sallow Flat Soffit Precast Floor Beam at A-A (ft = 0.3048 m)

Figure 4b. Cross Section of Sallow Flat Soffit Precast Floor Beam at B-B (ft = 0.3048m)

The shear connection between the hollow core planks (Figure 5a) and the beam is provided by hat bars running from the core in one hollow core plank over the beam and into the core of the opposing plank. In addition, rectangular reinforcement loops are inserted into the core through a sleeve cut into the end of the hollow core (see Figure 5b). The pockets are filled with grout when the hollow core keyways are grouted. The top of the reinforcement loops are later cast into the concrete topping.

Figure 5a. Cross Section of Typical Hollow Core (ft = 0.3048m)

Figure 5b. Cross Section of Hollow Core End with Slots (ft = 0.3048m)

The cast-in-place composite topping is reinforced in the hollow core direction to provide partial continuity in the direction of the hollow core planks for lateral load resistance. Figure 6 shows the beam-column connection and hollow core-beam connection and the reinforcement detail. With the exception of the beams all components are typical and are easy to produce, handle, and erect.

Figure 6. Column, Beam, and Hollow Core Connection (ft = 0.3048m)

10"

1'-6"

3"

314"

1012"

434"

8"9"

7"

Figure 2. Precast Column Elevation (in. = 2.54 cm)

A

A

B

B

7'-6" 4'

2'

3'-10"

10"

3"

1"1"

12"

4"

4'

2"

34" Coil Insert

7" 10"

8"

6"

4"512"

11" 2'-2" 11"

912"

10"

358" 13

8"

112"

4'

4'

112"

112"

338"

138"

738"

214"35

8"

112"11

2"

10"

3" 9#8

HSS 10x8x12

3x38" plate

4x38" plate

6"

3x2x38"

4'

1'-8"

19-0.6"

6#42"

3"

7"4"

2"

30'

120'

30'

30'

30' 30' 30' 30' 30'

30'Beam

Coulmn

HC



The construction sequence of the proposed system includes the following ten steps: Step 1) The precast columns are bolted to the foundation and temporary corbels are installed beneath the beam lines. The temporary corbels are 6 in. (15.4 cm) x 4 in. (10.2 cm) x ½ in. (1.3 cm) angles bolted to each side of the column. The 1 in. (2.5 cm) bolts go through two 1-1/16 in. (2.7 cm) diameter sleeves in the column (Figure 7). These angles are temporary, low cost supports for the precast beam during construction and can be reused several times.

Step 2) Precast/prestressed rectangular beams are placed on each side of the column so that the beams align with each other and the beam pockets align with the column opening. The beams are placed at a distance of 1 in. (2.5 cm) from the column face in addition to the 1 in. (2.5 cm) recess in column sides, resulting in a 2 in. (5.1 cm) wide gap between the recessed column section and the beam end to be grouted later. Two 38 in. (97 cm) long angles 3 in. (7.6 cm) x 2.5 in. (6.4 cm) x 3/8 in. (1 cm) are welded to the beam end plates and column side plates as shown in Figure 8 to stabilize the beams during HC erection.

Step 3) Hollow tube steel sections are installed as temporary ledges to support the hollow core planks. The tubes are connected to the bottom of the precast beam using coil inserts and threaded rods as shown in Figure 9.

Figure 9. Temporary Beam Ledges

Step 4) HC planks are placed on the temporary beam ledges on each side of the beam as shown in Figure 10.

Figure 10. Hollow Core Planks on Temporary Beam Ledges

Step 5) Continuity reinforcement is placed in the beam pockets and through the column opening as shown in Figure 11. This reinforcement includes the hidden corbel reinforcement needed for the beam-column connection and the hat bars connecting the HC planks to the beam placed over the beam at the HC keyways.

Figure 11. Continuity Reinforcement and Hat Bars

Step 6) The hollow core keyways, beam pockets, column opening, and shear key between HC planks and beam sides are all grouted using high slump 4 ksi (27.6 MPa) grout as shown in Figure 12.

Figure 12: Grouting shear keys and beam pocket

Figure 7. Temporary Corbels

Figure 8. Installation of Beam Angles



Step 7) Second layer of continuity reinforcement is placed over the beam, as shown in Figure 13

Figure 13. Beam Continuity Reinforcement

Step 8) Welded wire fabric is placed over the HC planks to reinforce the composite topping.Step 9) Topping concrete is poured using medium slump 3.5 ksi (24 MPa) concrete.Step 10) Finally, the temporary corbels and ledges are removed after topping concrete reaches the required compressive strength to provide a flat soffit.

CONSTRUCTABILITY, COST, AND SCHEDULE ANALYSIS

This section compares the constructability, cost and schedule of the proposed system with a typical precast floor system. The cost and schedule analysis refers to a single 120 ft x 120 ft (36.6 m x 36.6 m) elevated floor slab as shown in Figure 2.

CONSTRUCTABILITY ANALYSISThe shallow flat soffit precast floor system appears to have no major constructability issues. The temporary corbels, Step 1, are easy to install as are the temporary beam ledges, Step 3. A rolling scaffold provides easy access to both. Welding the two 38 in. (97 cm) long angles to the beam end plates and column side plates, Step 2, take slightly longer than welding a typical inverted T beam to the column but requires no exceptional skill or equipment. Placing the beams, Step 2, and the HC planks, Step 4, are no more and no less complex than standard precast floor systems. Placing continuity reinforcement, Step 5 and 7, while not complex, are additional steps required for the shallow flat soffit precast floor system that requires more steel reinforcement. The grouting operation, Step 6, is comparable to other precast floor systems with the exception of the need for slightly more grout

for the beam pocket and column opening. Placing the welded wire fabric, Step 8, and the concrete topping, Step 9, are identical operations for both the shallow flat soffit precast floor system and the typical precast floor system. Removing the temporary supports at the column and the hollow core planks is a simple, albeit additional operation.

COST ANALYSISTable 1 shows a cost analysis comparing the shallow flat soffit precast floor system to a typical precast floor system. All cost data was developed using RSMeans Building Construction Cost Data 2011 unless specified otherwise. For clarity, the estimate line items in this section coincide with the construction steps described in the proposed system section of this paper.

Table 1. A Cost ($US) Comparison between shallow flat soffit and typical precast floor systems per floor

There are 25 precast concrete columns on each floor. Since the depth of the inverted-tee beams in the typical precast system are 28 in. (71 cm) compared to 10 in.(25.4 cm) in the shallow flat soffit precast floor system, the typical precast columns are 12.5 ft (3.8 m) per floor compared to 11 ft (3.4 m) per floor for the shallow flat soffit precast floor system to provide 10 ft (3.05 m) equivalent clearance. Columns of the shallow flat soffit precast floor are assumed to be have the same cross section and reinforcement as those of the typical precast floor systems .

Temporary corbels are attached to each shallow flat soffit precast floor system column. Installation productivity is listed at five per hour with two structural steel workers and two rolling scaffold while removal rates are estimated at 10 per hour. This is based on actual field measurements from two full scale

Item Shallow Flat Soffit Floor System Typical Precast Floor System Materials Labour Equipment Total Materials Labour Equipment Total

Step 1-Column 29,150 7,838 4,373 41,361 33,125 8,906 4,969 47,000 Temporary Corbel 322 777 160 1,259 Step 2-Beam placement 111,901 4004 2226 118,131 95,360 4,004 2,226 101,590 -angles vs. corbels* 750 305 122 1177 777 312 1089 Step 3-HC Supports 3000 1457 300 4,757 Step 4-HC Plank Install 93,600 11,856 6,614 112,070 103,500 13,110 7,314 123,924 Step 5-Continuity Reinf. 2,961 1,659 0 4,620 Step 6-Grout 7,725 1,260 420 9,405 5,974 974 325 7,273 Step 7-2nd Continuity Reinf. 6,642 3,526 0 10,168 Step 8-WWF Installation 2,995 3,960 0 6,955 2,995 4,514 0 6,954 Step 9-Concrete Topping 12,240 11,376 4,032 27,648 12,240 11,376 4,032 27,648 Step 10-Remove Supports 1846 380 2,226 Total cost 339,777 315,478 Cost per square foot (m2) $23.6

($254.0) $21.9

($235.8) *There are two corbel welds per column approximately 6 in. (15.24 cm) long in the overhead position from a scaffold vs. the two 36 in. (0.91 m) long angle welds in the horizontal position from the deck. It was determined that it would take approximately 15 minutes per column for the former and twice as long per column for the later at $58.05/hour for welder and equipment.



installations. The angles are 6 in. x 4 in. x 0.5 in. (15.2 cm x 10.2 cm x 1.3 cm) and are 2 ft (0.61 m) long with a weight of 16 pounds per lineal foot (23.81 kg per meter). There are 40 reusable angles per floor at a cost of $32 each resulting in angle material cost of $1,280. Two, 1 in. (2.5 cm) diameter and 2 ft (0.61 m) long all thread rods fasten the angles to the columns through 1-1/16 in. (2.7 cm) diameter holes precast into the 25 column. The cost for 50 rods is $650 for a total material cost including angles of $1,930. Assuming a reuse rate of six give a total material cost of $322 per floor.

Twenty beams are installed in either system and installation costs are similar because of the similar weights between the two systems (RSMeans Building Construction Cost Data 2011, section (03 41 05.10 1400) There are eight spandrel beams that are the same for either system since they are concealed within the exterior wall. The cost of the eight spandrel beams is $3,425 each. The beam material costs for the shallow flat soffit beam system and the inverted-tee were priced from the manufacturer at $150 and $120 per lineal foot, respectively. Inserts are cast into the beam for field installation of the temporary plank supports.

Installation of the temporary plank supports is estimated at 20 supports per hour with two structural steel workers and two rolling scaffold units while removal rates are estimated also at 20 per hour. This is based on measurements from full scale field installation. The 5 ft (1.52 m) long temporary supports are 4 in. x 4 in. x 0.25 in. (12.3 cm x 12.3 cm x 0.64 cm) tubes that weigh 12 pounds per lineal foot (17.86 kg per meter). There are four supports per plank and 120 planks. Each support is estimated to cost $50 plus $5 for bolt and washer resulting in total material cost of $18,000. With six reuses material cost per use is $3,000 per floor.

Continuity reinforcement is only required with the shallow flat soffit precast floor system. There are two layers as indicated in Steps 5 and 7 in the construction sequence. There is 3.1 tons (2,722 kg) of reinforcement required in the first layer and 8.2 tons (7,439 kg) in the second.

There are 16 bays, 30 ft x 30 ft (9.14 m x 9.14 m), that require approximately 4 yd3 (3.06 m3) of grout for each bay regardless of operation. The shallow flat soffit floor system requires an additional 0.5 yd3 (0.38 m3) per column to fill the beam and column pocket.

Welded wire fabric is identical for both operations as is the concrete topping. There was 15,840 ft2 1,445 m2) of welded wire fabric and 14,400 ft2 (1,338 m2) of 2.5 in. (6.4 cm) concrete topping.

SCHEDULE ANALYSISThe schedule results are shown in the table below. Durations were determined from the daily output in Table 2. One crew was assumed for each activity in order to develop a consistent comparison. Other durations were taken from the estimated productivity described in the previous section. Since the focus of this analysis is on the difference between shallow flat soffit precast floor system and a typical precast operation, it was determined unnecessary to incorporate factors like learning curve, mobilization, equipment delays, weather, etc. since these would have a similar effect on either floor system.

Table 2. A Schedule Comparison between shallow flat soffit and typical precast floor systems

SUMMARY AND CONCLUSIONS The shallow flat soffit precast floor system has a flat soffit and shallow depth comparable to cast-in-place floor systems. The constructability comparison of the shallow flat soffit precast floor system against a typical precast floor system using inverted-tees revealed no constructability issues. The additional operations were accomplished with crews typically mobilized for a precast operation. The cost of the shallow flat soffit precast floor system including columns for a 10 ft (3.05 m) clear height is 23.6 per square foot ($254 per square meter) compared to $21.9 per square foot ($235.80 per square meter) for the typical precast floor system which is only 7.7% increase. The schedule indicates that one floor of the shallow flat soffit precast floor system would take 18 days compared to 15 days for the typical

Item Shallow Flat Soffit Precast Floor System

(Days)

Typical Precast Floor System (Days)

Step 1-Column 2.5 2.5 -Temporary Corbel 0.5 N/A Step 2-Beam placement 1.5 1.5 -Weld angles 1 1 Step3-Temporary HC Supports 1.0 N/A Step 4-HC Plank Installation 3 3 Step 5-Continuity Reinforcement 0.5 N/A Step 6-Grout 0.5 0.5 Step 7-2nd Continuity Reinforcement 0.5 N/A Step 8-WWF Installation 3 3 Step 9-Concrete Topping 3.5 3.5 Step 10-Remove Supports 0.5 N/A Total durations in days 18 15



precast assuming single crew for either operation, which is 20% higher. The advantages of the flat soffit and shallowness of the proposed system outweighs this slight increase in its cost and construction duration. In addition, the continuity of the shallow flat soffit precast floor system minimizes the need for shear walls commonly used in multi-story residential and commercial buildings. The constructability and cost of the proposed system compares favourably with a typical precast floor system at it follows standard construction practices with no need for specialized labour or equipment.

ACKNOWLEDGMENTS The authors wish to acknowledge the support of Concrete Industries (CI) Inc., and EnCon (Colorado) for material and specimen donations and their technical input in developing the proposed system.

REFERENCESBellmunt, R., and Pons, O., (2010) “NEW Precast Light Flooring System” 3rd fib International Congress, May Washington, DC.

Board of Federation International Du Beton (fib) Steering Committee, (1999) “Special Design consideration for Precast Prestressed Hollow Core floors”, No. 6, October.

Composite Dycore Office Structures, (1992) “Company literature ”, Finforck Industries, Inc., Orlando, Florida.

Compton, L. A. (1990). “Retractable Hangers for Mounting Precast Concrete Beams and the Like in Buildings” United States Patent, Patent number: US 2002/0062616 A1

Concrete Industries, Inc. (CI) (2012) “Hollow Core Floor and Roof Systems: Load Tables and Recommended Connection Details”, Lincoln, NE.

Girder-Slab Technologies, (2002) “Composite Steel and Precast System: Design Guide V.1.4”, LLC of Cherry Hill, NJ, http://www.girder-slab.com/designguide.asp

Hanlon, J.W. (1990). “Building System Using Modular precast Concrete Components” United States Patent, Patent number 4,903,448

Low, S., Tadros, M. K., and Nijhawan, J. C., (1991) “A New Framing System for Multi-story Buildings,” Concrete International, Vol. 13, No. 9, September, pp. 54-57.

Low, S., Tadros, M. K., Einea, A., and Magana, R., (1996) “Seismic Behaviour of a Six Story Precast Concrete Office Building,” PCI Journal, Vol. 41, No. 6, November/December, p.56-75.

Mid-State Filigree Systems, Inc. (1992) “The Filigree Wideslab Method of concrete Deck Construction: Company Literature”, Cranbury, NJ

Peikko Group, (2010) “Delta Beam Composite Beams” Peikko News, http://www.peikko.com/

Pessiki, S., Prior, R., Sause, R., and Slaughter, S., (1995) “Review of Existing precast concrete gravity load floor framing systems”, PCI Journal, Vol. 40, March-April, pp.70-83

Post-Tensioning Institute (PTI), (2006) “Post-tensioning Manual 6th Edition”, Phoenix, AZ.

Prestressed Concrete Institute (PCI), (2004) “PCI Bridge Design Manual”, Chicago, IL.

Prestressed Concrete Institute (PCI), (2010) “PCI Design Handbook, 7th Edition”, Chicago, IL.

RSMeans Construction publishers & Consultants, 2011. “RSMeans Building Construction Cost Data” Kingston, MA

Simanjuntak, J. H. (1998). “System for Joining Precast Concrete Columns and Slabs” United States Patent, Patent number 5,809,712

Snodgrass K., (2008) “Life-cycle cost analysis for buildings is easier than you thought” Tech. Rep. 0873– 2839, MTDC. Missoula, MT: U.S. Department of Agriculture Forest Service, Missoula Technology and Development Center.

Tadros, k. M., and Low, S. (1996). “Concrete Framing System” United States Patent, Patent number: 5,507,124

Thompson, J. M., and Pessiki, S., (2004) “Behaviour and Design of Precast/Prestressed Inverted Tee Girders with Multiple Web Openings for Service Systems,” ATLSS Report 04-07, Lehigh University, pp. 156

Wise, H. H. (1973). “Composite Concrete Construction of Two-Way Slabs and Flat Slabs” United States Patent, Patent number: 3,763,613


26Reinforced Concrete Deterioration Due to Corrosion

Keywords: concrete repair, deterioration, corrosion, electro-chemical, chloride

DETERIORATION MECHANISMSPortland cement is made by burning and grinding its constituents and the obtained fine powder is highly alkaline. It reacts with water and hardens. When it is added to coarse and fine aggregate and mixed with water, the cement combines with the aggregate and hardens to form concrete. The hardening process that is usually referred to as hydration continues over an extended period of time, up to several years, depending on the amount of water in the mix. There must be excess water for workability. Excess calcium hydroxide and other alkaline hydroxides are present in the pores and a solution of pH 12.0 to 14.0 develops (pH 7.0 is neutral; values below indicate acidity, and above alkalinity)2.

DETERIORATION THROUGH CARBONATIONCarbon dioxide is present in the air in proportions of around 0.3 per cent by volume. It dissolves in water and forms an acidic solution. This acid now present within the pores of the concrete reacts with the

alkaline calcium hydroxide forming insoluble calcium carbonate. The pH value then drops from an average of 12.5 to about 8.5. The carbonation process moves as a front through the concrete, with a pH drop across the front. The passive alkaline layer, protecting the steel, decays with time2. When it reaches the reinforcing steel and the decaying passive layer’s pH value drops below 10.5, the steel becomes exposed to moisture and oxygen and is susceptible to corrosion. Concrete inside the building frequently carbonates totally without any sign of deterioration as the concrete dries out, leaving the steel exposed to air but not moisture. Problems are seen externally where concrete is exposed to moisture and in certain situations internally, such as kitchens and bathrooms, where the concrete is susceptible to condensation or water-leakage. External facades are particularly vulnerable. Carbonation does not have to penetrate far for the reinforcing steel to rust especially when the concrete quality is poor.

DETERIORATION DUE TO CHLORIDESalt causes corrosion by a different mechanism. When dissolved in water sodium chloride forms a highly corrosive solution of sodium ions (Na+) and chloride ions (Cl-). Salt is used for de-icing roads

Reinforced Concrete Deterioration Due to Corrosion

Dr. M. Malek, University of North Florida

ABSTRACT: Remedial repairs to concrete structures represent an increasingly large proportion of the total expenditure on civil engineering works. A great deal of effort must be directed towards understanding the mechanisms controlling concrete durability and, in particular, corrosion of reinforcement, to ensure that past mistakes are not repeated. The two main causes of reinforcement corrosion are thought to be chlorides, normally derived from the service environment, and the passivation of the steel: by carbonation of the surrounding concrete. Corrosion of steel in concrete when progressing would be considered as a significant problem for many reinforced concrete structures whenever moisture is present. Salt is a main cause of corrosion in the short term. Over an extended period of time, carbonation will affect most structures. In situations where the structure cannot be kept dry, several techniques can be used to mitigate the extent of the problem. This paper analyses the causes of the concrete deterioration and suggests generic steps to be undertaken to increase the life span of the structure.

Dr Malek, Chair of the Construction Department, College of Computing Sciences, Engineering and Construction at the University of North Florida. He was conferred a Ph.D in Engineering from the University of Central Florida in 1996. He has been teaching in academia for 16 years. He established the graduate degree program for the department. Dr Malek is also the graduate degree coordinator for the department and the director of the research center at UNF.


27 Reinforced Concrete Deterioration Due to Corrosion

and its presence in sea water is a major problem for reinforced concrete structures1. The chloride ions disperse through concrete pores in solution and where they come into contact with the reinforcing steel they attack the passive layer. Steel oxidizes in the presence of air and water to form rust, which has a volume, far exceeding that of the steel consumed2. As concrete has a low tensile strength it will crack when as little as a tenth of a millimeter of steel has been consumed fig. (1). Horizontal cracks form, causing corners to ‘spall’ and surfaces to ‘delaminate’ as the reinforcement’s concrete cover becomes detached and falls away in sheets. The consequence can be seen on the underside of road bridges and many buildings and structures beside the sea figs. (2, 3).

THE ELECTRO-CHEMICAL REACTION

By far, the most important factor in corrosion is the permeability of concrete. In impermeable concrete, the electrical conductivity is lower (since there is little moisture inside). This slows down the diffusion of reactants, thus nearly stopping the corrosion. In poor quality concrete, there is rapid diffusion of the reactants and steel corrosion takes place. The type of steel has not been shown to have an effect on corrosion. The theory is that differences in electro-chemical potential are essential for corrosion to take place. The actual electro-chemical process is as follows. Because of the difference in potential between anode and cathode, positively charged metal ions at the anode pass into solution as Fe++ and the free electrons e- pass along the steel into the cathode. They are absorbed by the constituents of the eletro1yte and combine with water and oxygen to form (OH)- (hydroxide ions)1. These combine with the ferrous ions to form ferric hydroxide and this is converted to rust. Thus an important conclusion is to be extracted from this mechanism that should have an important impact on the maintenance techniques adopted: There is no corrosion in a completely dry atmosphere. The cracks occur because corrosion products occupy 2.2 times as much space as the metal and may develop mechanical pressures up to 4,700 psi. For 3000 psi compressive strength concrete the true tensile strength is estimated from 164 psi to 274 psi. Once the corrosion begins, it continues as long as oxygen and moisture can reach the reinforcing steel5.

STRUCTURAL IMPLICATIONS

In cases of reinforcement corrosion, cracking and spalling of the concrete cover usually occurs long before there is any significant loss of cross-section of the reinforcing steel, and the cracking and spalling are usually considered to be an early warning sign rather than an indication that the structure is in danger of imminent collapse. In extreme cases, e.g. where there is very extensive spalling of concrete or where the reinforcement is particularly badly corroded, the structural implications of the reduction in cross-section of the concrete and steel have to be investigated and considered and this will require the involvement of a structural engineer. The process of carrying out a repair, e.g. hacking away of concrete, can temporarily weaken structural elements and the possibility of overload should always be borne in mind. Many repair specifications limit the hammer size to 30 lbs.

Figure 1. Example of Severe Cracking and Spalling of Concrete, Exposing Corroded Reinforcing Steel

Figure 2. Example of an initiation of the Cracking process of Concrete Observed at Typical a structure.

Figure 3. Severe Surface Delamination



REPAIR

WORD OF CAUTIONThe generally accepted approach to repairing concrete is to carry out patch repairs on areas of the structure, which are showing signs of distress. It should be understood and accepted that further deterioration is to be expected and that, necessitates a continuing commitment to repair and maintenance8.

Based on the recommended concrete repair details that are presented in the Standard Specifications “For Repair of Concrete, M-47”, and in the subsequent revisions the documents (Bureau of Reclamation, 1975 and 1996), chapter 7 of the Concrete Manual, have formed the basis for the concrete repair procedures explained here below. These standards have been used for the concrete repair for the last 25 years.

THE REPAIR STEPS

1. The principle of repair is as follows: firstly all concrete showing signs of distress is removed and replaced with fresh cementations material in a manner explained here below. This deals with areas where corrosion has already reached the reinforcement. In other areas corrosion will be approaching the reinforcement and unless action is taken, damage will continue to occur in the future. To avoid further deterioration it is necessary to arrest corrosion and this can be done by applying to the surface of all concrete which is at risk, an impermeable coating thereby arresting penetration of the concrete layer. If this is done, then experience suggests that little further deterioration will occur while the coating remains intact. Periodic renewal of the coating will of course be required.

2. It is generally agreed that the first step is to remove all cracked or spalling concrete, where the cracking or spalling is due to reinforcement corrosion. This can be done by inserting a chisel into the crack and striking it with a hammer. The concrete cover should come away easily to reveal corroded reinforcement. If in places, the concrete strongly resists the blows on the chisel or corroding reinforcement is not found, then some of the cracking may be due to causes other than reinforcement corrosion. Where this is the case, the cause of the cracking must be determined in order to choose an appropriate repair method. It is worth

pointing out that reinforced concrete is designed to crack and in some cases fine cracking or crazing, not associated with reinforcement corrosion, may not be detrimental and may best be left alone.

3. The next step according to The Cement and Concrete Association, they recommend the removal of further concrete, both beyond the spalled area for as far as corrosion of the reinforcement extends, and also from behind the reinforcing bar to expose the full perimeter of the bar along its corroded length. This involves considerable extra work since although the cracked and spalling concrete can be knocked off very easily, removing sound concrete, particularly from behind the reinforcement, involves much more effort. Some repair specialists consider this extra work unnecessary despite the fact that if carbonated concrete or chloride ions remain behind the reinforcing bar, the potential for continuing corrosion is not totally removed. Also the steel should be exposed beyond its corroded length to facilitate removal of all corrosion products. In cases of severe corrosion of the reinforcement it may be necessary to replace the bars or to supplement the defective bars by drilling the concrete and tying on additional reinforcement.

4. After removal of concrete, the exposed reinforced bars should be cleaned from rust. All scale and loose rust must be removed and patches of shiny steel should be evident on the bars. Grit blasting is one of the most effective methods of cleaning the steel. Wire brushing is not a very effective method and tends to polish the steel rather than remove the scale. Protection to reinforcing steel: Generally it is recommended to sand or grit blast the rusty reinforcement to a bright steel condition.

5. Thereafter, some form of protection must be applied to prevent further corrosion, either by restoring an alkaline environment around the steel or by encapsulating the reinforcement and providing a barrier to air and moisture around the steel. So, it is recommended that the bars should be treated with a sealing or anti-corrosive coating.

6. Next after all loose debris has been removed from the repair area; repair material should be used like a cement-based repair material, which will have similar properties to the parent material10. Epoxies and polymer products are also commonly used.


29 Reinforced Concrete Deterioration Due to Corrosion

Bonding coats:For hand-applied mortars it is advisable first to use a bonding coat to increase workability, reduce shrinkage, promote bond, enhance flexural and tensile strength, and reduce the permeability of the repair mortar. It is recommended that premixed packs of the bonding coats are used to avoid problems of poor quality control, substandard sands, inadequate mixing, etc. The priming coat must achieve complete coverage and not have the opportunity to dry out before the repair concrete is placed. The priming is applied as follows: Thoroughly damp the repair area with water, but ensure that no surface water remains. Then prime the area and coat all exposed reinforcement by brushing in a grout made up by mixing together equal volumes of ordinary Portland cement and SBR latex. Complete cover is essential.

7. Next, the mortar should be applied using a hand-trowel in layers up to 20mm thick (less than ~1 inch) until the repair area is filled with thoroughly compacted material. Additional bonding coats between successive layers may be required.

8. Curing should be controlled by the use of sprayed curing membranes, provided these are compatible with any proposed surface coating. Alternatively conventional curing methods of damp burlaps and polythene could be used. Generally, surface sealers on their own have limited use in retarding deterioration by carbonation and it is recommended that they be used in conjunction with surface coatings. For all types of coatings the surface must be cleaned of all loose powdery material and dirt, especially any oil or grease.

REPAIR MATERIALS

Without specifying or advertising any of the materials in the market, a generic description of the type of materials to be used is as follows: The patching material would be a 2-component, room temperature curing, solvent less, epoxy sand and mortar. The mortar is to be job-mixed and hand trowelled smooth. Since ordinary sand-cement mortars do not always adhere successfully to old concrete, a polymer modified sand-cement mortar should be used. The most common polymer-modifier is styrene butadiene rubber (SBR), which is milky liquid and is used to replace approximately half the mixing water. It generally

increases the adhesion of the repair mortar to the parent concrete and also reduces it permeability. To increase further the adhesion, a bond coat of SBR and cement should be applied to the concrete just before application of the repair mortar.

The patching mortar constituents will be as follows:

50 kg of ordinary Portland cement

125 kg of clean, zone 2 (ie sharp) sand (by volume, 2 parts sand and one part cement)

10 liters SBR latex

Sufficient water to give a workable mix ( about 10 liters).

Generally the last step protecting the sealed and cured patch is to apply a thick coating of epoxy. The epoxy would be a 2-component, rigid, moisture insensitive, primarily designed to protect cement concrete from moisture intrusion.

CONCLUSION

These described corrosion mechanisms are significantly affected by factors such as mix designs of the concrete, the applied casting practices, with or without cracks in the concrete, the kinds of reinforcing steel, and the lining and environmental conditions of the site.

The deterioration is also influenced by factors, such as the mix proportion of the concrete the depth of cover and the environmental conditions, results from physiochemical processes, such as ion transportation and carbonation. Transport phenomena through the pores of concrete may occur by the penetration and diffusion of substances such as chloride ions, carbon dioxide and sulfate. Hence, the protection of the concrete from moisture is crucial.

Although the useful life of the building would be extended, periodic inspections are required to observe the formation of new cracks. These cracks are expected until the corroding chemical reactions are completed. As cracks occur additional repair should be carried out in the above-described manner.



REFERENCES

1. http://www.azom.com/details.asp?articleID=1318

2. http://www.corrosioncost.com/infrastructure/highway/

3. http://www.civil.auc.dk/i6/publ/srpaper199.PDF

4. http://www.nrc.ca/irc/fulltext/apwa/apwadeterioration.pdf

5. http://www.rist.kindai.ac.jp/no.13/kawah.pdf

6. http://weewave.mer.utexas.edu/MED_files/MED_research/strctl_sensors/TATP_01.htm

7. http://www.bm.chalmers.se/research/publika/p013e.htm

8. “Guide for repair of concrete bridge superstructures” by ACI Committee 546

9. A.H. Anderson, Jr “Investigation, rehabilitation, and maintenance to prevent deterioration of a concrete building” ACI compilation No. 5 V.2, No.9

10. http://www.usbr.gov/pmts/materials_lab/repairs/guide.pdf


31 QUALITY MANAGEMENT | The philosophy and approach utilized by top performing US contractors

Quality Management: The philosophy and approach utilized

by top performing US contractors

Dennis C. Bausman, PhD, FAIC, CPC & Daniel R. Mattox, MCSM Clemson University

ABSTRACT: Over the past several decades construction industry professionals have attempted to integrate quality management programs and philosophies originally developed for the manufacturing industry. These programs, or philosophies, include Total Quality Management (TQM), Lean Construction, and Six Sigma, among others. While all of these programs are different from one another in terms of detailed approach, they share similar quality management principles. Guiding principles that form the foundation of these quality management programs typically include customer focus, continuous improvement, and company-wide involvement. Theoretically, successful implementation of a quality program embodying these principles leads to a higher quality product and enhanced financial performance; ultimately culminating in a better overall value for external (clients) and internal (employees, suppliers, vendors, etc.) customers. While quality management programs have experienced success in the manufacturing sector, acceptance and implementation within the United States (U.S.) construction industry has been sporadic.This research effort investigates the quality management program(s), organizational philosophy, and operational approach utilized by top performing contractors in the United States (U.S.). This study assesses the current state of quality management in the U.S. construction industry and identifies the key drivers for successful execution of a quality management program as exhibited by top performing firms. The research methodology adopted for this study solicits input from the organizational leaders of the nation’s largest general and specialty contractors to determine the extent of implementation, organizational focus, and the key drivers for successful execution of their program(s). The findings of this study provide the foundation for development of a best practice guide for establishing a successful quality management program within a construction contracting firm.

Dr. Dennis C. Bausman serves as Professor and Endowed Faculty Chair in the Construction Science and Management (CSM) Department at Clemson University. He is an AIC Fellow, a member on AIC’s Board and the Constructor Certification Commission, and serves as Editor of AIC’s Journal The American Professional Constructor.

Daniel Mattox is a recent graduate of the Masters of Construction Science and Management program at Clemson University.

This paper originally presented at the CC2012 Creative Construction Conference, Budapest, Hungary, June 2012

Keywords: construction industry, quality management, total quality management.

INTRODUCTIONOver the past several decades there has been an increasing demand for viable quality management options in the United States construction industry. Attempts to meet this increasing demand are evidenced by the construction industry’s adaptation of quality management programs and/or philosophies from the manufacturing industry. The most popular of which include Total Quality Management (TQM), Lean

Construction, and Six Sigma. While these programs have been utilized successfully by many contractors, widespread success of any one program has not been realized in the construction industry (Sullivan 2011). Though different in terms of detailed approach, quality management efforts such as TQM, Six Sigma, and Lean Construction strive for the same objective (Anderson et al. 2006). The objective is to increase customer satisfaction and improve financial performance through the systematic improvement of operational efficiency and building quality. Satisfying this objective, regardless of which quality management effort is being utilized, typically requires


32QUALITY MANAGEMENT | The philosophy and approach utilized by top performing US contractors

a company’s long-term commitment to customer focus, continuous improvement, and company-wide involvement (Dahlgaard & Dahlgaard 2006). These are the foundational principles around which most quality management initiatives are based.

Review of existing literature on the subject of quality management and the construction industry allows a further breakdown of each foundational principle. The following framework is derived from past studies on quality management, and is designed to allow further investigation and understanding of quality management in the construction industry.

Programs and/or philosophies such as TQM, Six Sigma, and Lean Construction rely on customer focus, continuous improvement, and company-wide involvement as keys for success (Emison 2004). Theoretically, customer focus is achieved when companies concentrate on the following: customer feedback (seek, share, react), customer satisfaction (emphasis), and customer value (Pheng & Hui 2004). These are the “drivers” of customer focus. The next foundational principle of quality management, continuous improvement, is comprised of a separate set of drivers: subcontractor selection, operational improvement, performance metrics, and external assessment (Emison 2004; Strickland and Kirkendall 2010). The final foundational principle of quality management, company-wide involvement, requires an emphasis on yet another set of drivers: employee satisfaction, employee participation, and employee empowerment (Sui Pheng & Teo 2004; Salem et al. 2006).

In theory, emphasizing each driver will support achieving the respective foundational principle, which in turn increases the probability of success for a firm’s quality management initiative. Successful implementation of a quality management program is believed to result in operational and building quality improvements leading to greater profit margins and increased customer satisfaction (Anderson et al. 2006).

The purpose of this research effort was to investigate the approach and organizational focus regarding quality management of the nation’s largest general building and specialty contractors. This investigation concentrated on the foundational principles, and the respective drivers, of quality management programs. A primary objective of this study was to determine the

key actions and initiatives of the top performing firms and how their organizational approach differentiates them from poorer performers. It was intended that the findings of this study would provide the foundation for development of a best practice guide to aid a construction contracting firm’s development and implementation of a quality management program.

METHODOLOGY

QUESTIONNAIRE DESIGN

A self-administered questionnaire was developed to solicit input from general and specialty contractors. The first section of the questionnaire addressed general company information such as contractor type, building type(s), company size, and operating area.

The next section was concerned with organizational focus and approach. Questions in this section were framed to assess the contractor’s foundational principles and identify the drivers of their quality management program. Response options for each question were established using a 7-point Likert scale to assess either: 1) the respondent’s extent of agreement with the statement, or 2) the firm’s degree of implementation of the quality management concept or approach on their projects.

The third section of the questionnaire solicited information concerning the firm’s actual quality management program(s). Questions were developed to provide insight regarding implementation, training, participation, and company motivation for investment in quality management initiatives. Additionally, questions were incorporated to assess the perceived impact and benefits that their quality management program(s) had on building quality, customer satisfaction, profitability, and employee satisfaction.

The final section of the questionnaire asked respondents to rank their firm’s performance over the past 5 years compared to the industry. Performance metrics included percentage of pretax profit (based on revenue), return on investment (ROI), and overall firm performance/success. Each performance measure was associated with a 5-point Likert scale permitting the respondent to rate their firm’s performance from the top 20% to the lowest 20%. Data regarding the firm’s revenue trend was also requested.



SAMPLING FRAME

The targeted population for this study was large contracting firms in the United States (US). Listings of the largest U.S. contractors collected and published by Engineering News Record, a well respected industry periodical, were used to identify the sample for this study.

The sampling frame for selection of general contractors was Engineering News Record’s (ENR) 2011 Top 400 Contractors. All 250 general contractors in the Top 400 recognizing ‘general building’ as their largest revenue segment, were included in the sample. Annual volume for general contractors in the sample ranged from 106m to 7,580m.

The sampling frame for specialty contractors was ENR’s 2011 Top 600 Specialty Contractors. Annual volume for the firms in this listing ranged from 12m to 1,135m. One hundred fifty-four specialty contractors were randomly selected from the 377 firms in the Top 600 listing that identified ‘general building’ as their largest revenue segment.

A hardcopy of the questionnaire was mailed to the principle head (Chairman, President, CEO, etc.) of each selected general and specialty contractor, accompanied by a cover letter which also provided a link for online completion of the questionnaire, if the respondent preferred that response option.

RESPONSE

Fifty-one (51) of the 250 general contractors in the sample participated which equates to a response rate of 20.4%. The response rate for specialty contractors was 15.6%. Combined, seventy-four (74) firms, or 17.9% of the 414 contractors in the targeted sample, participated in the study. Geographically, the responses were reasonably distributed across the southern, northeastern, mid-western, and western regions of the U.S.

FINDINGS

GENERAL FINDINGS The average age of the firms participating in the study was sixty (60) years. Combined, 72% of the respondents’ revenue was contracted at risk and approximately two-thirds (64%) of their revenue was from repeat clients (specialty contractors 56%, general contractors 67%).

Eleven percent (11%) of the respondents competed globally, 26% nationally, 40% regionally, and 23% on a state or local basis.

Figure 1. Quality Programs

Approximately 75% of the general contractors, and 66% of specialty firms, had a quality program(s), most following the principles of Total Quality Management (TQM), Lean Construction, and/or Six Sigma. Combined, 73% of the firms had a quality program whereas 27% indicated that they did not have a program. Figure 1: Quality Programs, shows the application of the various quality management programs. Interestingly, 44% of the contractors with quality management programs claimed they utilized, or incorporated the philosophy, of more than one of the programs identified in Figure 1. The age of the respondents’ quality programs ranged from 2 to 40 years with an average maturity of 13 to 14 years.

Figure 2: Participation & Training summarizes the extent of participation and the degree of training in the firm’s quality management program. Over 90% of the firms with a quality program involve project management and project supervision and 80% or more of these companies train these personnel. Conversely, less than 50% of the firms with quality programs involve or train craft-workers. Senior management and department heads are often involved in the program, but only approximately 50% of the firms provide training for these personnel. Involvement and training for quality programs primarily focuses on project management and supervision.



Figure 2. Participation and Training

Firms that did not have a quality management program (27% of respondents) were asked to indicate why they had not developed one for their firm. Figure 3: Reasons for Not Initiating a Program shows the distribution of the responses. The most commonly cited deterrent was training and 25% of the respondents without a program indicated that cost was the reason that their firm did not have a quality management program. Lack of effectiveness and capable personnel were both cited by 20% of the firms. Only 15% of the firms indicated lack of familiarity with quality management as the reason for failing to implement a program.

Figure 3. Reasons for Not Initiating a Program

TOP PERFORMERS

Classification: Respondents ranked their firm’s performance relative to the industry based upon three metrics: percentage of pretax profit based on revenue, return on investment (ROI), and overall firm performance/success. Performance for each metric was rated on a 5-point Likert scale permitting the respondent to classify the firm’s performance anywhere from the top 20% to the lowest 20%. Approximately half of the respondents (52%) ranked

their firm’s performance in the top 20% for at least one of the performance measures. Considering the sampling frame for this study, the ENR Top 400 Contractors and the ENR Top 600 Specialty Contractors, this distribution is not unexpected. For this study these firms are hereafter considered the ‘Top Performers’.An analysis of the data reveals that 90% of the top performers (88% of contractors and 93% of specialty firms) have a well defined quality management program. The vast majority of top performers have a quality management program.

General Contractor vs. Specialty Contractors: A primary thrust of this research effort was to identify quality management best practices for large building contractors (both building contractors and specialty firms). To achieve that objective, the goal of data collection and analysis was to identify the quality management focus and approach of the top performers and how it differed, if at all, from the poorer performers.

Prior to analyzing the top performing general contractors and specialty contractors as a group it was necessary to investigate the consistency of the grouping. To accomplish that objective, a statistical analysis was completed comparing the responses of general contractors and specialty contractors. A statistical comparison of both: a) the total samples, and b) the top performers of each, consistently yielded a statistically significant variance on five responses. These five survey questions all dealt primarily with general contractor issues or actions about which specialty firms may have limited knowledge or a different perspective. These five questions are identified with an asterisk (*) in the following tables and the statistical analysis of these questions/concepts involved only general contractors.

Data and Testing: The following sections investigate the foundational principles of a quality program (customer focus, continuous improvement, and company-wide involvement) and their key drivers for the top performing contractors. The findings are summarized in tables with each table dedicated to a different driver of quality management. Response options for most statements/questions were established using a 7-point Lickert scale to assess the level of agreement or the firm’s degree of implementation. The question/statement response scale is noted in each table as ‘agree’ or ‘project’ respectively. Several questions on the survey had a 5-point Lickert response scale



assessing ‘benefit’ and are labeled such in the response scale for the table. Tables are formatted to provide the mean response for each question/statement for the top performers and indicate if there was a statistically significant difference between the top performers (top 20%) and the poorer performers (lower 80%) on one or more of the performance metrics of profit, ROI, or overall firm performance/success. The mean and 95% confident interval was calculated for each question/statement and all statistical comparative testing was performed to a level of significance of 0.05.

CUSTOMER FOCUS

Customer Feedback: Customer focus is one of the three foundational principles of quality management, and is driven by customer feedback (seek, share, react), customer satisfaction (emphasis), and customer value. Table 1: Customer Feedback (Seek, Share, React), summarizes the results of the survey questions concerned with assessing a contractor’s approach to customer feedback.Top performers regularly utilize customer feedback to enhance their performance and exhibited stronger support for this approach than poorer performers. On almost all their projects top performers shared customer feedback with operational personnel and were more likely to share customer feedback than poorer performers. Lastly, top performers initiated a preconstruction meeting with the Owner & A/E on almost all their projects. On all three statements assessing Customer Feedback, top performers placed a high level of significance (focus) on seeking, sharing, and reacting to customer feedback.

Table 1: Customer Feedback (Seek, Share, React)

Customer Satisfaction (Emphasis): Six statements on the survey questionnaire were structured to provide input regarding the respondents’ emphasis, or approach, regarding customer satisfaction. Table 2: Customer Satisfaction (Emphasis) summarizes the findings concerning this second driver of customer focus.

On most projects the top performers initiated structured client satisfaction surveys both during project delivery and after project completion and were statistically more likely to collect this feedback than the poorer performers. Both top performers and poorer performers submit that: 1) quality takes precedence over profitability, and 2) increased client satisfaction yields improved financial results. Interestingly, poorer performers believe more strongly that customer satisfaction takes precedence over project profitability. Lastly, compared to poorer performers, top performers submit that quality management programs have a more significant beneficial impact on customer satisfaction.

Table 2: Customer Satisfaction (Emphasis)

Customer Value: Statements or questions developed for this portion of the questionnaire addressed variables that could be considered of value to the customer. A summary of the response analysis for this third and final driver of customer focus is presented in Table 3: Customer Value.

There was no statistically significant difference between top and poorer performers. Both groups indicated that they were flexible in accommodating the changing objectives and needs of their clients and both tracked callbacks and warranty issues on most projects. In addition, the time required for project closeout was tracked inconsistently by both groups.

Table 3: Customer Value

CONTINUOUS IMPROVEMENT

The key drivers for the second foundational principle of quality management, continuous improvement, are subcontractor selection, operational improvement, performance metrics, and external assessment.

Statement Response Scale

Top Mean

Significance

Profit ROI Overall

Customer feedback is shared with operational personnel Project 6.05 yes

We initiate a preconstruction meeting with the Owner & A/E* Project 6.60*

We regularly utilize customer feedback to enhance our performance Agree 6.18 yes yes



Top Mean

Significance Profit ROI Overall Customer satisfaction takes precedence over project profitability Agree 5.62 yes We perform structured client satisfaction surveys during project delivery Project 4.71 yes yes We perform structured post-‐project client satisfaction surveys Project 4.84 yes yes Quality Management programs impact on Customer Satisfaction Benefit 4.67 yes Increasing client satisfaction results in improved profitability* Agree 6.56* Quality takes precedence over profitability Agree 5.56



Top Mean

Significance Profit ROI Overall We are flexible in accommodating the changing objectives and needs of

our owners Agree 6.18

We track ‘call backs’ and warranty issues Project 5.47 We track the time required for project closeout Project 4.58



Top Mean

Significance Profit ROI Overall Price is the primary factor when selecting subcontractors Agree 3.92 yes yes We pre-‐qualify subcontractors and suppliers* Project 6.12* We have a structured & comprehensive sub pre-‐qualification system* Agree 5.92*

Table 4: Subcontractor Selection


Top Mean

Significance

Profit ROI Overall






Top Mean




Top Mean






Top Mean




Top Mean

Significance

Profit ROI Overall






Top Mean




Top Mean






Top Mean





Subcontractor Selection: The findings regarding contractor approach to subcontractor selection are summarized in Table 4: Subcontractor Selection.

Table 4: Subcontractor Section

Both top performers and poorer performers have a structured and comprehensive subcontractor prequalification system that they utilize to prequalify subcontractors and suppliers on most of their projects. Top performers neither agree nor disagree with the statement price is the primary factor when selecting subcontractors whereas poorer performers are more likely to disagree with this statement.

Operational Improvement: The findings for the statements/questions formulated to evaluate a firm’s approach to operational improvement are summarized in Table 5: Operational Improvement. Both top and poor performers aggressively implement technological advances to enhance performance, proactively meet with subs to establish quality expectations, and pursue a goal of zero defects on most of their projects. However, top performers are more likely to identify operational improvement as a primary organizational objective and have a stronger commitment to continuous evaluation of operational performance to identify areas for improvement. Top performers are more committed to the training of construction personnel to enhance performance and believe more strongly that quality management programs have a beneficial impact on building quality.

Table 5: Operational Improvement

Performance Metrics: Contractor response to the third driver of continuous improvement is summarized in Table 6: Performance Metrics.

Both top and poor performers have a systematic process to evaluate subcontractor performance and upon project completion perform a formal assessment of each subcontractor’s performance on most of their projects. They both believe that quality management programs have a beneficial impact on profitability. Additionally, both groups develop their own safety plan and require subcontractors to develop and submit theirs on most projects. However, top performers more aggressively track the cost of rework and are more likely to have a systematic process to identify improvements needed in each department. Top performers are also more likely to have metrics to assess performance and isolate areas for company improvement.

Table 6: Performance Metrics

External Assessment: The final driver of continuous improvement is external assessment. The findings are summarized in Table 7: External Assessment. Both top and poor performers solicit subcontractor assessment of operational performance and utilize a structured system to solicit constructive feedback from the design team only on some of their projects. However, top performers solicit design team feedback on a larger portion of their projects.

Table 7: External Assessment

COMPANY-WIDE INVOLVEMENT

Respondent input collected on the key drivers of company-wide involvement, the final foundational principle of quality management, is presented in this section. The key drivers analyzed include employee satisfaction, employee participation, and employee empowerment.


Top Mean

Significance

Profit ROI Overall






Top Mean




Top Mean






Top Mean




Top Mean

Significance Profit ROI Overall Quality Management programs impact on Building Quality Benefit 4.64 yes yes Continuous operational improvement is a primary organizational objective Agree 6.41 yes yes yes We aggressively implement technological advances to enhance performance Project 5.66 Prior to major work activities, we meet with subs to establish quality

expectations* Project 6.24*

The pursuit of zero-‐defects (zero-‐punch list) is a stated goal Project 5.74 We continuously evaluate operational performance to identify areas for

improvement Agree 6.23 yes

Construction personnel regularly receive structured training to enhance performance

Agree 5.85 yes yes



Top Mean

Significance Profit ROI Overall Quality Management programs impact on Profitability Benefit 4.42 We have a systematic process to evaluate subcontractor performance Project 4.81 We track the cost of rework Project 4.92 yes Upon completion, we do a formal assessment of each sub’s performance Project 4.82 Each dept. has a systematic process to identify needed improvement Agree 4.62 yes We have metrics to assess performance and isolate areas for company


We require subcontractors to submit a project specific safety plan Project 5.84 We develop a project specific safety plan Project 6.37



Top Mean

Significance Profit ROI Overall Quality Management programs impact on Building Quality Benefit 4.64 yes yes Continuous operational improvement is a primary organizational objective Agree 6.41 yes yes yes We aggressively implement technological advances to enhance performance Project 5.66 Prior to major work activities, we meet with subs to establish quality

expectations* Project 6.24*

The pursuit of zero-‐defects (zero-‐punch list) is a stated goal Project 5.74 We continuously evaluate operational performance to identify areas for


Construction personnel regularly receive structured training to enhance performance

Agree 5.85 yes yes



Top Mean

Significance Profit ROI Overall Quality Management programs impact on Profitability Benefit 4.42 We have a systematic process to evaluate subcontractor performance Project 4.81 We track the cost of rework Project 4.92 yes Upon completion, we do a formal assessment of each sub’s performance Project 4.82 Each dept. has a systematic process to identify needed improvement Agree 4.62 yes We have metrics to assess performance and isolate areas for company


We require subcontractors to submit a project specific safety plan Project 5.84 We develop a project specific safety plan Project 6.37



Top Mean

Significance Profit ROI Overall We ask our subcontractors to assess our firm’s operational performance Project 3.71 We utilize a structured system to solicit constructive feedback from the design

Project 4.22 yes



Top Mean

Significance Profit ROI Overall Quality Management programs impact on Employee Job Satisfaction Benefit 4.33 yes yes Retention of our supervisor/management personnel is a continuing concern Agree 5.41 We develop employee rewards and incentives to encourage improvement Agree 5.62

Table 8: Employee Satisfaction


Top Mean

Significance Profit ROI Overall We have a well-‐defined process to solicit improvement ideas from employees Agree 4.82 yes We regularly utilize cross-‐functional teams to improve organizational processes Agree 5.10 yes Most improvement suggestions are generated by operational personnel Agree 5.13 Management encourages suggestions for improvement from all employee levels Agree 6.23

Table 9: Employee Participation


Top Mean

Significance Profit ROI Overall Our employees feel empowered to improve their work processes Agree 5.79 Our employees are emotionally invested in the company’s success Agree 5.92 yes Our employees believe it’s their responsibility to continuously improve

performance Agree 5.74 yes

Table 10: Employee Empowerment

teamteam



Employee Satisfaction: A summary of the findings for the first driver of company-wide involvement is presented in Table 8: Employee Satisfaction. Both top and poorer performers submit that retention of supervisor and management personnel is a continuing concern and both indicate that they develop employee rewards and incentives to encourage improvement. In addition, it is the view of both groups that quality management programs have a beneficial impact on employee job satisfaction. However, top performers believe the beneficial impact to be more significant.


Employee Participation: Table 9 presents a summary of the findings regarding employee participation. Both top performers and poorer performers encourage suggestions for improvement from all employee levels in part because they believe that most improvement suggestions are generated by operational personnel. However, top performers are more inclined to have a well-defined process to solicit improvement ideas from employees and utilize cross-functional teams to improve organizational processes.


Employee Empowerment: A summary of the findings for the final driver of company-wide involvement, employee empowerment, is presented in Table 10: Employee Empowerment. Both top and poorer performers submit that their employees feel empowered to improve their work processes. However, the employees of top performers are more emotionally invested in the company’s success and they more strongly believe that it is their responsibility to continuously improve performance.


CONCLUSION

A majority (73%) of large contracting firms have quality management programs. However the implementation rate (90%) is greater for the top performing contractors. Firms that did not have a quality management program (27% of respondents) cited cost, lack of program effectiveness, and the lack of capable personnel as the primary deterrents. Over 90% of the firms with a quality program involve project management and project supervision and 80% or more of these companies train these personnel. Conversely, less than 50% of the firms with quality programs involve or train craft-workers.

Customer Focus: In contrast with poorer performers, top performing contractors more aggressively seek customer and team member feedback. They are more inclined to initiate client satisfaction surveys both during and post construction and are more likely to share this information with operational personnel to enhance performance. Top performers believe that a quality management program has a more significant impact on customer satisfaction and they maintain that it leads to improved profitability. Top performers consider customer satisfaction to be important, but they are less inclined to believe that profitability needs to be sacrificed in order to achieve client satisfaction.

Continuous Improvement: Top performers more strongly support continuous operational improvement as a primary organizational objective and they aggressively implement technological advances to enhance performance. They believe that quality management programs have a significant impact on building quality and profitability. Top performers place greater emphasis on establishing metrics to evaluate departmental, operational, and subcontractor performance. In addition, they solicit feedback from subcontractors and other team members. They utilize this feedback and the insight gained from the performance metrics to identify areas for improvement.


Top Mean


Project 4.22 yes



Top Mean




Top Mean




Top Mean




teamteam


Top Mean


Project 4.22 yes



Top Mean




Top Mean




Top Mean




teamteam


Top Mean


Project 4.22 yes



Top Mean




Top Mean




Top Mean




teamteam



Top performers have a stronger commitment toward quality management training. They proactively establish quality expectations, systematically evaluate subcontractor performance, and pursue a zero-defect strategy.

Company-wide Involvement: Top performers believe that quality management programs have a more significant impact on employee satisfaction. They assert that most improvement suggestions are generated by operational personnel and are more inclined to have a well-defined process to aggressively solicit improvement ideas from employees at all levels of the organization. Top firms develop employee incentives to encourage improvement and more often than poorer performers utilize cross-functional teams to improve organizational processes. As a result of the firm’s focus on company-wide involvement the employees of the top performers feel empowered to improve their work processes and are more emotionally invested in the company’s success. They have a stronger belief that it is their responsibility to continuously improve performance.

REFERENCES

Andersson, R., Eriksson, H., and Torstensson, H., 2006. Similarities and differences between TQM, six sigma and lean. TQM Mag., Vol. 18, No. 3., pp. 282–296.

Dahlgaard, J. J., and Dahlgaard, S. M. P., 2006. Lean production, six sigma quality, TQM and company culture. TQM Mag., Vol. 18, No. 3., pp. 263–281.

Emison, G., 2004. Pragmatism, Adaptation, and Total Quality Management: Philosophy and Science in the Service of Managing Continuous Improvement, Journal of Management in Engineering, Vol. 20, No. 2., pp. 56-61.

Pheng, L., & Hui, M., 2004. Implementing and Applying Six Sigma in Construction. Journal Of Construction Engineering & Management, Vol. 130, No. 4., pp. 482-489.

Salem, O. O., Solomon, J. J., Genaidy, A. A., & Minkarah, I. I., 2006. Lean Construction: From Theory to Implementation. Journal of Management in Engineering, Vol. 22, No. 4., pp. 168-175.

Strickland, John and Kirkendall, Bob. “Applying Lean Production Principles to the Construction Industry”. 16 Oct. 2010. <http://www.idc-ch2m.com/Papers/ IDC2001%20leanproduction.pdf>.

Sui Pheng, L., & Teo, J., 2004. Implementing Total Quality Management in Construction Firms. Journal Of Management In Engineering, Vol. 20, No. 1., pp. 8-15.

Sullivan, K. T., 2011. Quality Management Programs in the Construction Industry: Best Value Compared with Other Methodologies. Journal Of Management In Engineering, Vol. 27, No. 4., pp. 210-219.


39

40

The American Institute of Constructors

Reviewer/Publication Interest SurveyThe Professional Constructor is a refereed journal published two times a year by the American Institute of Constructors (AIC). Each author’s manuscript submission is given a blind review by three AIC members. to evaluate the content and style, and appropriateness as either a general interest or scholarly publication. Based upon the decision of the reviewers, each article is accepted or rejected for publication. Acceptance can be predicated upon incorporation of reviewer comments.

Approximately 10-15 articles are published annually in The Professional Constructor. To maintain our high standards of publication, AIC requires the support of competent and committed reviewers. We would like to express our deep gratitude to the following reviewers of the articles published in the Journal’s Spring and Fall 2012 Issues:

Tariq Abdelhamid, Adam Alexander, Robert Aniol, Heber Arch, Bernard Ashyk, Conrad Benitez, David Bierlein, S. Narayan Bodapati, Richard Boser, Curtis Bradford, Stephen Byrne, James Caldwell, Matthew Conrad, Bruce Demeter, Mark Federle, Mike Golden, Frederick Gould, Thomas Hullen, Roger Liska, Tanya Matthews, David Mattson, Hoyt Monroe, George Morcous, Jens Pohl, Kyle Potts, Randy Rapp, Wayne Reiter, Ihab Saad, M.G. Syal, Kenneth Tiss, James Tramel, Andy Wasiniak, Mike Whittaker, Tony Wintz and Ronald Worth.

We are always looking for additional industry professionals that are interested in serving on our review board. To help ensure reviewers continue to be selected based upon competency and interest, we ask that prospective reviewers take a few minutes to complete the survey below. The reviewer survey and manuscripts for publication consideration should be submitted to: Dennis C Bausman, FAIC, CPC, PhD Editor, The Professional Constructor Clemson University 133 Lee Hall Clemson, SC 29634-0001 Work Phone: (864) 656-3919 Email: [email protected] Fax (864) 656-7542

Please place a mark beside each keyword that is a topic area indicating your expertise or interest. Thank you, in advance, for serving as a reviewer for The Professional Constructor.

Name: ______________________________________________________ Member No.: __________________________________

E-Mail: ______________________________________________________ Phone No.: ___________________________________

Address: __________________________________________________________________________________________________

___________________________________________________________________________________________________________

___________________________________________________________________________________________________________

Topic Areasq Computer Applicationsq Construction Safetyq Estimatingq Financial Managementq Personnel/Human Resource

Managementq Contract Law and Legal Applicationsq Materials and Methodsq Project Managementq Steel Constructionq Concrete Constructionq Design-Build Constructionq Mechanical Constructionq Contract Documentsq Strategic Planningq Planning and Scheduling

q Site Managementq Marketing and Salesq Community Planningq Labor Relationsq Quality Managementq Productivityq Cost Controlq Undergraduate Educationq Graduate Educationq Wood Constructionq Masonry Constructionq Heavy/Highway Constructionq Electrical Constructionq Residential Constructionq International Constructionq Architectureq Real Estate and Factors Affecting

Contractors

q Housing and Related Issuesq Procurementq Bondingq Biddingq Ethicsq Commercial Constructionq Industrial Constructionq Utilities Constructionq Institutional Construction

Other ____________________________________________________________________________________________________


4141

American institute of Constructors

Constructor Code of Ethics

The Construction Profession is based upon a system of technical competence, management excellence and fair dealing in undertaking complex works to serve the public safety, efficiency, and economy. The members of the American Institute of Constructor are committed to the following standards of professional conduct:

I. A Constructor shall have full regard to the public interest in fulfilling his or her responsibilities to the employer or client.

II. A Constructor shall not engage in any deceptive practice, or in any practice which creates an unfair advantage for the Constructor or another.

III. A Constructor shall not maliciously or recklessly injure or attempt to injure, whether directly or indirectly, the professional reputation of others.

IV. A Constructor shall ensure that when providing a service which includes advice, such advice shall be fair and unbiased.

V. A Constructor shall not divulge to any person, firm, or company, information of a confidential nature acquired during the course of professional activities.

VI. A Constructor shall carry out responsibilities in accordance with current professional practice, so far as it lies within his or her power.

VII. A Constructor shall keep informed of new thought and development in the construction process appropriate to the type and level of his or her responsibilities and shall support research and the educational processes associated with the construction

Overview of Emerging Technological Innovations in Construction Management 42

Why Become Certified?

Benefits to the Constructor

• Provides an internationally recognized certification of construction management skills and knowledge. • Provides an analysis of individual strengths and weaknesses in the subject areas tested. • Enhances the Constructor image as a professional to their employer, their clients, and the public. • Provides a marketable credential that sets you apart.

Benefits to the Employer

• Provides an independent assessment of an employee’s skills and knowledge, based on a comprehensive national standard. • Provides a recognized credentialing within your company that improves marketability to clients. • Provides assurance that employee will continue to hone their skills, through the required Continuing Professional Development

program.

Benefits to Owners:

• An increased level of assurance that their projects will be managed more effectively. • Could use the qualification as a means to prequalify contractors • Knowledge that their contractor management team will be more professional.

Click to view our nationwide testing locations: http://goo.gl/ztnLC

Visit www.professionalconstructor.org or email [email protected] for more information.

The Constructor Certification Commission

“Building the Professional Constructor”

Take the next step in your career, become a Certified Professional Constructor!

Join the over 12,000 professionals who have sought the Certified Professional Constructor (CPC) and Associate Constructor (AC) designations.

Mark your calendars for our next examination on November 5, 2011. Online registration will open on July 15th, more information regarding registration and certification can be found at www.professionalconstructor.org.

Candidate handbooks are available upon request, email [email protected] to request yours. Upon registration candidates can download the digital PDF study guide.

Examination Fees

• Level 1 (AC) Applications $155.00

• Level 2 (CPC) Applications: AC Upgrade (Current AC's applying for the CPC exam) $405.00

• Level 2 (CPC) Applications: AC Exemption (For Level 2 applicants not AC certified) $535.00 Applicants receive a PDF study guide via email after registration is completed

Project2_Layout 1 9/26/12 1:28 PM Page 1

42



Upcoming Exams:November 3, 2012

April 6, 2013

Candidate handbooks are available upon request, email [email protected] to request yours.

Upon registration candidates can download the digital PDF study guide.

42






program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees









program.

Benefits to Owners:










Examination Fees





43

For more information contact us at [email protected]

The PROFESSIONALCONSTRUCTOR

JOURNAL OF THE AMERICAN INSTITUTE OF CONSTRUCTORS

TO SUBMIT AN ARTICLE FOR CONSIDERATION

PLEASE REVIEW THE AUTHOR’S GUIDE

43

the professional constructor - october 2012

Documents

faic cpc phdnational

construction process

work phone

construction education

related fields of construction

professional constructor

individual constructor

professional relationships