347.3r-13 guide to formed concrete surfaces...the german concrete association (dbv) (merkblatt...

ACI 347.3R-13

Guide to Formed Concrete

Surfaces

Reported by ACI Committee 347

Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=qrtr, tety4

Not for Resale, 01/26/2015 01:46:12 MSTNo reproduction or networking permitted without license from IHS

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First PrintingJanuary 2014

Guide to Formed Concrete Surfaces

Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.

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ISBN: 978-0-87031-863-4

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Advancing concrete knowledge



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The primary goal of the construction team is to produce as-cast concrete surfaces that meet project specifications and expectations. Although various descriptions, interpretations, and methods exist to achieve an as-cast concrete surface, no unified definitions of different concrete surfaces exist.

This document defines four quality levels of formed concrete surfaces and provides methods to achieve and evaluate them. These quality levels are identified by three surface finish categories: 1) form facing; 2) concrete surface void ratio; and 3) characteris-tics of form-facing materials. The basic procedures for classifi-cation are defined using tables derived from recommendations of the German Concrete Association (DBV) (Merkblatt Sichtbeton Deutscher Beton- und Bautechnik-Verein e.V. 2004).

This guide assists the project owner, design team, contractor, formwork and concrete suppliers, and all other parties in reaching a more specific understanding of how to produce a more clearly defined as-cast concrete surface. All other parties should under-stand the procedures, processes, and costs for producing defined surfaces of formed concrete. The guide also discusses all phases of construction relating to concrete surfaces from planning, descrip-tion of work, and construction through acceptance of a concrete surface.

This guide can be used by both specifier (architect/licensed design professional) and contractor as a supplemental tool for defining, specifying, and evaluating concrete surfaces and offers guidance to the development of concrete surface specifications and expecta-

tions. Please refer to ACI 303R-12 for information regarding post-construction treatment of formed concrete surfaces.

This guide also describes an entire process for comprehensive use, including the creation of a concrete surface team and its defined roles and responsibilities in the construction process.

Keywords: color uniformity; exposed to view; form facing; job-built form-work; mockup; offsets; panelized formwork; reference area; surface finish; surface void ratio; texture; tolerances.

CONTENTS

CHAPTER 1—INTRODUCTION, p. 2

CHAPTER 2—DEFINITIONS, p. 2

CHAPTER 3—FORMED CONCRETE SURFACE DESCRIPTIONS, p. 2

3.1—General, p. 23.2—Examples and determination of surface void ratio,

p. 5

CHAPTER 4—BASICS OF LAYOUT AND DESIGN, p. 7

4.1—General, p. 74.2—Design and construction recommendations, p. 74.3—Planning and detailing, p. 84.4—Formwork and facing selection, p. 94.5—Premanufactured panelized formwork, p. 114.6—Job-built formwork, p. 114.7—Design with form liners, p. 144.8—Post-construction treated concrete surfaces, p. 14

Kenneth L. Berndt, Chair

ACI 347.3R-13


Reported by ACI Committee 347

Rodney D. AdamsMary Bordner-Tanck

George CharitouJames N. Cornell II

Jack L. DavidWilliam A. Dortch Jr.

Jeffrey C. ErsonNoel J. Gardner

William A. GiorgiTimothy P. HayesGardner P. Horst

David W. JohnstonRoger S. Johnston

Robert G. KentKevin R. Koogle

H. S. Lew

Robert G. McCrackenEric S. Peterson

William R. PhillipsDouglas J. Schoonover

Aviad ShapiraJohn M. Simpson

Rolf A. Spahr*

Pericles C. Stivaros

Daniel B. ToonRalph H. Tulis

Consulting membersSamuel A. Greenberg

R. Kirk GregoryDonald M. Marks

————————————*Principal author

ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

ACI 347.3R-13 was adopted and published January 2014.Copyright © 2014, American Concrete InstituteAll rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

1Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=qrtr, tety4


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CHAPTER 5—SPECIFICATIONS, p. 145.1—General description, p. 145.2—Design features, p. 145.3—Surface finish limitations, p. 14

CHAPTER 6—CONSTRUCTION, p. 156.1—Formwork, p. 156.2—Reinforcement and inserts, p. 156.3—Concrete mixture, p. 156.4—Concrete placement, p. 166.5—Concrete surface team, p. 16

CHAPTER 7—EVALUATION OF FORMED CONCRETE SURFACES, p. 16

7.1—Basics, p. 167.2—Overall impression, p. 167.3—Procedure in case of deviations, p. 16

CHAPTER 8—REFERENCES, p. 17Authored references, p. 17

CHAPTER 1—INTRODUCTIONThe scope of this guide is to solve a lack of uniformity in

the appearance criteria of concrete surfaces, provide defini-tions for the various levels of formed concrete surfaces, and give objective evaluations of them.

Although there are various reference sources for constructing and evaluating concrete surfaces, none exist that offer a comprehensive guidance and understanding to its production and evaluation. Several ACI and ASCC docu-ments, however, do provide partial guidance:

1) ACI 347-04 provides terms for classes of formed concrete surfaces, discusses irregularities in formed surfaces, and gives general guidance for the use of formwork for concrete;

2) ACI 309R-05 provides terms about visible effects of consolidation on formed concrete surfaces, why they occur, and how to avoid them;

3) ACI 303R-12 discusses architectural concrete, applica-tions, and details of production including formwork, release agents, repair, and economics;

4) ACI 301-10 specifies concrete surfaces (Section 5.3.3.3);

5) The ASCC Education and Training Committee (1999) guide uses samples of concrete surfaces to illustrate appear-ance expectations.

These references, which exclude uniform appearance criteria or a process for evaluating formed concrete surfaces, make it difficult to achieve a wide range of expectations.

The ultimate authority on a project is the contract docu-ment. The contract document is a guide for the:

a) Designer to specify the desired surface finish;b) Owner to understand what the final product will approx-

imately look like;c) Contractor to select facing materials, concrete mixture,

release agents, and construction methods to achieve the specified surface finish.

CHAPTER 2—DEFINITIONSACI provides a comprehensive list of definitions through

an online resource, “ACI Concrete Terminology,” http://www.concrete.org/Tools/ConcreteTerminology.aspx. Defi-nitions provided herein complement that source.

area exposed to view—portion of structure that can be observed by the public during normal use.

blushing—slight pink or rose color on concrete surface.flatness—deviation of a surface from a plane.form facing—the form material that comes in direct

contact with the concrete.gap—space between abutting edges of the form-facing

materials measured on the plane of the form surface.mockup—a sample of a component of the building as

specified in the contract documents that is used to establish the expected surface finish.

reference area—a significantly large area of a completed concrete surface serving as a basis of comparison for the acceptance of a surface category of work at a specified loca-tion of a given project.

surface void ratio—the ratio of the total surface void area to the total concrete surface area after stripping with no subsequent surface treatment.

CHAPTER 3—FORMED CONCRETE SURFACE DESCRIPTIONS

3.1—GeneralTables 3.1a through 3.1d define the various measurable

properties pertaining to formed concrete surface texture, surface void ratio, color, flatness, and joints. Four concrete surface categories (CSCs) are defined in Table 3.1a. CSC1 has the lowest classifications and CSC4 the highest for a finished surface. The individual constituents used to define each CSC are further described in Table 3.1b. The classifica-tion for form-facing materials is described in Table 3.1c. The surface void ratio is defined and categorized according to net pore area in Table 3.1d.

Concrete surface levels are specified for individual parts of the structure to reflect the owner’s needs, desires, and budget. Possible examples include:

a) Basement walls: CSC1;b) Industrial structures: CSC1 or CSC2;c) Electrical and mechanical rooms: CSC1 or CSC2;d) Stairwells: CSC1, CSC2, or CSC3;e) Commercial building exteriors: CSC3;f) High-end commercial building exteriors: CSC3 or

CSC4;g) Religious structures or museums: CSC3 or CSC4;h) Monumental or landmark structures: CSC4.These examples are only provided to illustrate the various

classifications of concrete surfaces and are not recommenda-tions of the committee.

Concrete surface finish schedules should be designated as part of the contract documents in drawings or by designa-tions on exterior/interior views of the structure.

American Concrete Institute Copyrighted Material—www.concrete.org

2 GUIDE TO FORMED CONCRETE SURFACES (ACI 347.3R-13)



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Table 3.1a—Description of formed concrete surface categories (CSC)

Formed concrete surface category* Description

CSC requirements†‡ Additional requirements

Relative costsTexture

Surface void ratio§

Color uniformity||

Surface irregu-larities

Construc-tion and

facing-joint Mockup#Form-facing category**a na a na

Con

cret

e su

rfac

e fin

ish

with

Bas

ic re

quire

men

ts

CSC1

Concrete surfaces in areas with low visibility or of limited impor-tance with regard to formed concrete surface requirements, used or covered with subse-quent finish materials.

T1 SVR1 SVR1 CU1 CU1 SI1 CJ1 Optional FC1 Low

Nor

mal

re

quire

-m

ents

CSC2

Concrete surfaces where visual appear-ance is of moderate importance.

T2 SVR2 SVR1 CU1 CU1 SI2 CJ2 Optional FC1 Average

Spec

ial r

equi

rem

ents CSC3

Concrete surfaces that are in public view or where appearance is important, such as exte-rior or interior exposed building elements.

T3 SVR3 SVR2 CU2 CU2 SI3 CJ3Highlyrecom-mended

FC2 High

CSC4

Concrete surfaces where the exposed concrete is a prominent feature of the completed structure or visual appearance is important.

T4 SVR4 SVR3 CU2 CU3 SI4 CJ4 Should be required FC3 Very

high

*For matching requirements of formed concrete surface categories, please refer to the following notes and tables.†The appearance of the formed concrete surface should only be judged in its entirety, not by looking at separate criteria only. The failure of one agreed criterion according to this guide should not result in the obligation to repair deviations if the overall positive image of the structure or the building is not disturbed.‡These requirements/features are described in detail in Table 3.1b.§Void area of pores of surface. Refer to Table 3.1d; legend: a = absorbent form facing; and na = nonabsorbent form facing.||The general impression of existing or not existing discolorations can usually be seen only after a longer period of time and for at least 8 weeks. The uniformity of coloring should be judged from the common viewing distance (Chapter 7).#If required, additional mockups should be prepared.

**Refer to Table 3.1c.


GUIDE TO FORMED CONCRETE SURFACES (ACI 347.3R-13) 3



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Table 3.1b—Description of visible effects on as-cast formed surfaceCriterion Classification Characteristics

Texture,panel-joint*

T1(Table 4.6.4)

- Acceptable gaps in adjacent formwork components ≤ 3/4 in. (19 mm) (6.1 h).- Acceptable depth of mortar loss ≤ 1/2 in. (13 mm).- Acceptable surface offsets of panel joints up to 1 in. (25 mm). (ACI 117-10, Section 4.8.3, Class D).- Allowable projections 1 in. (25 mm) from adjacent surface. (ACI 301-10, Section 5.3.3.3.a).- Form-facing material examples: Rough sawn lumber, CDX plywood, and particle board.- Imprints of modular panel frames are acceptable.

T2(Table 4.6.4)

- Acceptable gaps in adjacent formwork components ≤ 1/2 in. (13 mm) (6.1 j).- Acceptable depth of mortar loss ≤ 3/8 in. (10 mm).- Acceptable surface offsets of panel joints up to 1/2 in. (13 mm) (ACI 117-10, Section 4.8.3, Class C).- Allowable projections 1/2 in. (13 mm) from adjacent surface.- Form-facing material examples: Class BBOES plywood, MDO plywood.- Imprints of modular panel frames are acceptable.

T3(Table 4.6.4)

- Acceptable gaps in adjacent formwork components ≤ 1/4 in. (6 mm) (6.1 j).- Acceptable depth of mortar loss ≤ 1/4 in. (6 mm).- Acceptable surface offsets of panel joints up to 1/4 in. (6 mm) (ACI 117-10, Section 4.8.3, Class B).- Allowable projections 1/4 in. (6 mm) from adjacent surface (ACI 301-10, Section 5.3.3.3.b).- Form-facing material examples: HDO plywood, phenolic surface film, plastic, or steel.- Imprints of modular panel frames are acceptable.

T4(Table 4.6.4)

- Formwork should be grout tight. Avoid grout/mortar leakage and correct where occurs.- Permissible surface offsets of panel joints up to 1/8 in. (3 mm) (ACI 117-10, Section 4.8.3, Class A).- Form-facing material examples: HDO plywood, PSF plywood, full plastic, steel, and fiberglass.-Imprints of modular panel frames are unacceptable unless demonstrated and approved in the mockup.

Surface void ratio (SVR) SVR1-SVR4 - Refer to Table 3.1d.

Color uniformity†

CU1- Light and dark color variations are acceptable.- Color variations between adjacent placements and layer lines are acceptable.- Rust and dirt stains are acceptable.

CU2

- Gradual light and dark discolorations are acceptable.- Color consistency between adjacent placements and layer lines should be mostly uniform.‡- Concrete source materials and form-facing material should be of consistent type, grade, and source to avoid causing deviations in appearance.- Rust and dirt stains are unacceptable.

CU3- Discolorations caused by concrete source material of different type and origin; different types or treatments of facing materials; or inconsistent treatment of concrete surfaces are unacceptable.§- Rust stains, dirt stains and visible pouring layers are unacceptable.

Surface irregularities||

SI1

- ACI 117-10, Section 4.8.3, Class D-Surface.- Maximum gradual deviation over a distance of 5 ft (152 cm), or abrupt deviation is 1 in. (25 mm).- Limit deflection of formwork structure to L/240.- ACI 117-10, Section 4.8.2 does not apply.

SI2

- ACI 117-10, Section 4.8.3, Class C-Surface.- Maximum gradual deviation over a distance of 5 ft (152 cm), or abrupt deviation is 1/2 in. (13 mm).- Limit deflection of formwork structure to L/360.- ACI 117-10, Section 4.8.2 does not apply.

SI3

- ACI 117-10, Section 4.8.3, Class B-Surface.- Maximum gradual deviation over a distance of 5 ft (152 cm), or abrupt deviation is 1/4 in. (6 mm).- Limit deflection of formwork structure to L/360.- ACI 117-10, Section 4.8.2 does not apply.

SI4

- ACI 117-10, Section 4.8.3, Class A-Surface.- Maximum gradual deviation over a distance of 5 ft. (152 cm), or abrupt deviation is 1/8 in. (3 mm).- Limit deflection of formwork structure to L/400.- ACI 117-10, Section 4.8.2 does apply.

Construction and facing

joints#

CJ1 - Acceptable offset of surfaces between two adjacent placements ≤ 1 in. (25 mm).

CJ2 - Acceptable offset of surfaces between two adjacent placements ≤ 1/2 in. (13 mm).- The use of chamfer strips or similar reveals are recommended at construction joints.

CJ3- Acceptable offset of surfaces between two adjacent placements ≤ 1/4 in. (6 mm).- The use of chamfer strips or similar reveals are recommended at construction joints.- Construction joint locations should be coordinated with architectural design.

CJ4

- Acceptable offset of surfaces between two adjacent placements ≤ 1/8 in. (3 mm). Offsets less than 1/8 in. (3 mm) should be specified in design documents.- The use of chamfer strips or similar reveals are recommended at construction joints.- Construction joint locations should be coordinated with architectural design and approved by architect or engineer.- The mockup should contain all features representative to the finished product.

*Refer also to Chapters 5 and 7.†Color uniformity is subjective and expectations for uniformity should be addressed before construction.‡Concrete color deviations and discolorations cannot be completely eliminated, even using the best practices. If this is a concern, in addition to a mockup use a reference structure of similar size and finish.§An approved mockup of the surface is required; even the best practices and quality control may result in minor color deviations and discolorations.||Surface irregularities do not apply for worked or textured areas.# Construction joints that remain visible.





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3.2—Examples and determination of surface void ratio

Figures 3.2a(a),(b), and (c) through 3.2e provide views of concrete surfaces to aid in the understanding of the concrete surface void ratio determined in accordance with Tables 3.1a and 3.1d. These images are only provided as examples. Refer to 5.2.1, 5.2.2, and Chapter 7 for detailed descriptions for evaluating single criteria and the overall impression of a given concrete surface.

The surface void ratio is only required to be determined if the entire impression of the surface does not meet the contract expectation.

Wall views from distance Fig. 3.2a(a) and at measurement areas Fig. 3.2a(b) and Fig. 3.2a(c) with void area as single criterion.

The images in Fig. 3.2a(a), (b), and (c) through 3.2c only show examples of surfaces with void areas, also called “bugholes,” that conform to SVR1 to SVR4 (Table 3.1d). They are not intended to show all aspects of CSC categories as noted in Table 3.1a.

1) Framed area with void count of 215 and maximum D = 1/4 in. (6.3 mm).

The method of measurement of void dimensions is shown in Fig. 3.2d. Using this method for the framed area in Fig. 3.2d, the total void area sums up to 2 in.2 (1300 mm2).

Table 3.1c—Form-facing categories

Criterion

Form-facing category

FC1 FC2 FC3

Holes, greater than 3/16 in. (5 mm) Plug or disk covers are acceptable

Acceptable if patched sanded and sealed or ground to match adjacent form surface Visible filling is unacceptable

Holes, 3/16 in. (5 mm) or less Acceptable Acceptable without patching, provided form surface is not damaged or torn around hole(s)

Acceptable if patched, sanded, and sealed or grounded to match adjacent form surface

Vibrator burns Acceptable Unacceptable Unacceptable

Scratches/dents Acceptable Acceptable if patched, sanded, and sealed or grounded to match adjacent form surface Unacceptable unless otherwise approved

Concrete remnants* Acceptable Unacceptable Unacceptable

Cement residue† Acceptable Acceptable Should not affect finished concrete surface

Swelling of facing at fastener or tie holes Acceptable Unacceptable Unacceptable

Patching‡ Acceptable Acceptable Should not affect finished concrete surface*Concrete remnant is hardened concrete on the form face.†Cement residue is a thin film remaining on the form face.‡Perform and inspect repairs of form facing and make acceptable for the intended formed concrete surface.

Table 3.1d—Concrete surface void ratio (SVR) on as-cast formed surfacesSurface void ratio SVR1 SVR2 SVR3 SVR4

Void area of pores of surface* occurring

within a24 in. x 24 in. square

(610 x 610 mm)*

6.9 in.2 (4452 mm2); Dmax = 3/4 in. (19 mm)

5.8 in.2 (3742 mm2); Dmax = 5/8 in. (16 mm)

3.5 in.2 (2258 mm2); Dmax = 3/8 in. (9.5 mm)

1.7 in.2 (1095 mm2); Dmax = 1/4 in. (6 mm)

Suggested concrete placement practices to yield desired results

- Void area not to exceed 1.2 percent of the test area.

- Void area not to exceed 1 percent of the test area.



- Standard formwork and placement practices should yield these results without any special effort.- This surface void ratio category limitation should not apply to permanently concealed concrete surfaces.

- Release agent should be compatible with the form-facing material.- Formwork should be cleaned before the application of release agent.- Apply release agent thinly and uniformly.- A mockup might be beneficial.

In addition to the efforts described for the SVR2 category:- Adequate vibration should be provided especially at features, openings, and embeds.- Concrete mixture consis-tency is important in achieving reproducible results.- Use revibration method at top lift.- Mockups are recommended.

- In addition to the efforts described for the SVR2 and SVR3 categories:- Concrete design and form-work should eliminate surfaces that inhibit the upward move-ment of entrapped air.- Placement rate should consider vertical ascent rate of entrapped air during consolidation.- Use methods of deposition that minimize agitation at the surface that introduces entrapped air.- Mockups are required.

*Void area is the summation of the areas of all voids within the sample space of 24 in. x 24 in. (610 x 610 mm). Voids with an average diameter of d < 3/32 in. (2.4 mm) are excluded from the calculation of the void area.

Note: If these criteria are made applicable to the project, then the mockup should demonstrate the ability of the contractor to meet the surface void ratio expected for these surfaces. The general appearance of the final structure should be compared with the general visual appearance of the mockup.





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According to Table 3.1d, the determination would be surface void ratio category = SVR3. Measuring of surface voids is expected to be done manually as shown until opto-photo-graphical methods become available.

2) Measurement of void length l and width w by interpola-tion to find approximate areas.

In arriving at the length and width, the objective for sizing the rectangle is to have about as much void area falling outside as non-void area falling within the rectangle.

Fig. 3.2b—(a) Single area and (b) where summation of small surface voids viewed from distance indicate no sign of imperfection.

Fig. 3.2a(c)—Close-up view of wall Fig. 3.2a(a) at a different location.

Fig. 3.2a(a)—Large area viewed from a distance of 150 ft (46 m).

Fig. 3.2a(b)—Close-up view of wall Fig. 3.2a(a) with 24 x 24 in. (610 x 610 mm) measuring frame.





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CHAPTER 4—BASICS OF LAYOUT AND DESIGN

4.1—GeneralAfter stripping formwork, the concrete surface will reflect

the texture and other properties of the formwork. Based on the formed concrete surface category selected from Table 3.1a, the following features are considered for the formwork design:

a) Form-facing material;b) Form face joint locations;c) Form tie locations;d) Reveals, such as size, shape, and patterns;e) Properties of the concrete mixture design.A formed surface appearance drawing describes the

intended surface appearance of a specifically referenced, formed concrete surface. The use of formed surface appear-ance drawings help convey the desired features and appear-ance of formed concrete surfaces by showing all applicable

features, such as: tie hole treatments; textured surfaces; reveals; fluting; fractured fins; sandblasted surfaces; geometric patterns; wood grain; exposed aggregates; reveals and rustications; construction joint appearances; integral color; form joint appearances, and modularity or other surface characteristics that affect the intended visual appear-ance of the finished work.

Figures 4.1a and 4.1b show the elevation of a finished wall and a plan view of a wall formwork layout done with panel-ized formwork. Figures 4.1c and 4.1d show the elevation of a finished wall and a plan view of a wall formwork layout done with job-built formwork. Both elevations show tie and form joint patterns. These elevations are sample figures and should be used for reference in 4.2 through 4.6.4.

4.2—Design and construction recommendationsRequirements for the formed concrete surface can only be

met if it is possible to place and consolidate the concrete properly. The following are design and construction recom-mendations (Refer to Table 3.1a):

a) Evenly arrange pouring windows and make sure they are of sufficient size to permit concrete placement. Pouring windows are openings in the formwork for placing concrete when placement from the top is not possible. Consider other compaction methods or mixture design modification—for example, SCC or high-flowable concrete—if pouring windows cannot be installed in the formwork without affecting areas exposed to view. Consider the locations and forming details of pouring windows in CSC2 and CSC3. Pouring windows are not recommended for CSC4. The use

Fig. 3.2c—(a) Single area with high ratio of surface voids; and (b) single size measurement of surface voids.

Fig. 3.2d—Example for measuring surface voids (refer to 1) and 2) as follows).





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of filling nozzles may be required for placing highly flow-able concrete or SCC.

b) When installing reinforcement, observe minimum clearances in accordance with contract documents. Verify that spacers will not affect the appearance of the finished surface by corroding, protruding, or being recognizable at the surface of the formed concrete surface, especially in CSC3 and CSC4.

c) In CSC3 and CSC4, give careful consideration to the method of installation and aesthetic layout of inserts and embedments.

d) Building elements should be dimensioned and designed so the concrete can be placed and consolidated without difficulty. When using SCC, observe the recommendations of ACI 237R-07. If the shape and the dimensions of the building elements, openings, or both, result in difficulties in placement and consolidation, consider the possibility of a reduced surface quality. Consider the previously mentioned

possibility when choosing the formed CSC and when evalu-ating the resulting surface.

e) At recesses, reveals, flutes, rebates or other locations where the nominal concrete section is reduced, or when the section may be reduced by subsequent mechanical texturing, provide adequate concrete cover to comply with contract documents

4.3—Planning and detailingIf required, or when the appearance of a concrete surface

is important to the appearance of the finished structure, generate a formed surface appearance drawing in accor-dance with the requirements of the contract documents. This formed surface appearance drawing helps to match expecta-tions with the final appearance of the formed concrete surface. The drawing should provide locations for joints in the form-facing material, tie holes, and any architectural features such as reveals or faux tie holes. This drawing is generated by

Fig. 3.2e—(a) through (d) Example images of surfaces with void areas ranging from CSC1 to CSC4. Images do not provide any sense of scale or distance from surface.





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the contractor and reviewed for compliance with the contract documents by the licensed design professional.

In planning and detailing formwork for acute-angled walls, sharp corners, edges, and other abrupt or unusual shapes, it is possible for edges to be damaged.

When designing the formwork, anticipate conditions that can result in air becoming trapped during placement and make provisions for venting the air or for modifications to the concrete placement method to avoid surface voids or bug holes.

For surfaces subjected to weathering, the concrete surface design should allow for rainwater shedding to avoid staining the concrete surface.

4.4—Formwork and facing selection4.4.1 General considerations—Consider commonly

available formwork systems and how the selected system will affect project cost, design, and level of craftsmanship required. Both job-built formwork (Fig. 4.1c and 4.1d) and premanufactured formwork systems are used to construct structures. The formwork designer should consider the avail-able form system properties and coordinate the structure’s features with the characteristics of the specific systems being considered for use. The form-facing material that depends on the form-facing category (Table 3.1c) may also have limita-tions of available dimensional sizes. Facing made of plastic composites, steel, and aluminum sheets that can be welded together are available for large seamless form faces. Form panels may create differences in the concrete surface appear-ance when reused over the course of the project (Table 4.6.4).

Fig. 4.1a—Panelized formwork, plan view example. Elevation A: Use of panels 8 x 8 ft (2.4 x 2.4 m), and form face appearance elevation.

Fig. 4.1b—Panelized formwork, plan view example.





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Nonabsorbent facings produce lighter concrete surfaces, and color differences, such as mottling, become more apparent.

During the design phase, coordinate the design concept and formwork construction systems, such as the modular frames or job-built systems and their dimensions. For curved formwork and complicated geometrical shapes, consider the construction process, methods, and systems that may be used.

4.4.2 System-related considerations—Consider the following when designing a system:

a) The projected number of reuses when specifying a form-face material; the number of reuses and condition of the plywood or panels have an effect on the surface quality;

b) The age of the plywood influences the color uniformity of the concrete due to different storage conditions, number of uses, panel sealing, and the form release agent and its application;

c) The untreated edges of the plywood are susceptible to swelling when there is no edge sealing;

d) Joints in premanufactured panelized formwork can be more visible than joints between gang forms, depending on panel and facing material type, and method used for joining panels. Dimensional instability of plywood should be consid-ered, as initial manufacturing tolerances and dimensional changes with use may impact form concrete surface. When using plywood in modular formwork, it is initially recessed from the steel or aluminum side protection. With use and exposure, plywood thickness may change. Full plastic facing remains even with side protection over the entire time of use. Steel facing remains even over the entire time of use;

e) Color and surface void formation depend on form-facing material and release agent, as well as on concrete mixture, concrete placing method, curing and environmental conditions. The proper release agent and most reasonable

Fig. 4.1c—Job-built formwork, use of gangs 4 x 8 ft (1.2 x 2.4 m), and form face appearance elevation.

Fig. 4.1d—Job-built formwork, form plan and similar.





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concrete mixture for the intended result should be discussed in advance with the concrete team and chosen based on advanced testing;

f) If an absorbent form facing is used, the absorbency decreases with an increasing number of reuses, resulting in an increasingly lighter concrete surface;

g) Nonabsorbent form facing produces a higher quality surface that tends to focus the viewer’s attention on slight imperfections, such as color deviations and surface voids. Attention should be given to selection and application of release agents based on form facing-type;

h) Use a thin layer of release agent on form-facing mate-rials with guidance from manufacturer’s instructions.

4.5—Premanufactured panelized formwork4.5.1 General description—Panelized formwork systems

(Fig. 4.1a and 4.1b) consist of premanufactured frames with cross stiffeners in a given panel size, with plywood, steel, or plastic form-facing material.

4.5.2 Dimensions—Panel sizes vary by manufacturer. Common sizes for wall formwork are:

a) Height: 2 to 12 ft (0.61 to 3.66 m);b) Width: 1 to 20 ft (0.31 to 6.10 m).Fillers and corner sizes vary by manufacturer.Depending on the quality of the facing material and on

how the formwork is assembled, only form-facing seams could be visible at most. If steel or full plastic facing is used in a panel, there will be less joint visibility because the steel or plastic sheets could be welded.

4.5.3 Formwork panel quality—The surface quality of formwork depends, as it does with all reusable formwork systems, on the quality and condition of the material used, and panel maintenance and design. Some panels have recessed plywood for side protection around each panel, which is visible in the concrete surface. Steel faced forms do not have this property, nor do some panels with full plastic facing. To accommodate the structure’s dimensions, the available panel sizes may necessitate the use of fillers that could adversely affect the appearance of the structure if they cannot be made to look like the rest of the formwork system.

4.5.4 System-related considerations—System-related considerations for panelized formwork include:

a) Panel frame imprint visibility;b) Panel and facing sheet condition influence the quality

of the surface within the panel and at panel joints;c) The age of plywood facings influence the color unifor-

mity because of different usage numbers. Panels not in compliance should be repaired or removed;

d) Tie locations and panel layout are determined by panel design;

e) Plastic and steel facings provide a smoother and more consistent concrete surface;

f) Filler panels are required and visible. Fillers and corners may not have the same form-facing material as the main form panels.

4.5.5 Advantages—Advantages of panelized formwork include:

a) Durable with high reuse factor;b) Flexible use either vertically, horizontally, or both;c) Panels are simply combinable with assembly locks or a

similar device;d) Quickly adaptable to different structure shapes when tie

and form joint line locations are flexible;e) Produces a more consistent surface over a longer period

of time;f) Pre-engineered and readily available;g) User friendly;h) Easy to transport and store;i) Weather-resistant metal frames;j) Low waste factor.

4.6—Job-built formwork4.6.1 General description—Job-built formwork (Fig. 4.1c

and 4.1d) is made of wood or metal beams and walers. It is possible to assemble formwork panels in specific sizes. The job-built panels can use any commercially available form-facing material. Job-assembled panel size depends on specific handling considerations for each project. Depending on the quality of facing material and on formwork assembly, only form-facing seams could be visible at most.

The form facing is usually directly fastened to supporting members. As a result, the fasteners are visible on the concrete surface. To avoid visibility, the form-facing material can be back fastened; however, this should be stated as a require-ment in the contract documents.

Before each use, check the facing panels to ensure compli-ance with the requirements of the facing category according to Table 3.1a. Panels out of compliance should be removed.

4.6.2 Dimensions and standard sheet sizes—Standard plywood sizes, with or without overlays, are 4 x 8 ft (1.22 x 2.44 m) / 4 x 9 ft (1.22 x 2.75 m) / 4 x 10 ft (1.22 x 3.05 m); other sizes are available on special order.

4.6.3 Surface quality at formwork joints—The surface quality at formwork joints depends, as with all multiple use formwork systems, on quality and condition of formwork, craftsmanship, connection details, care in removal, and cleaning the panels. Seal all edges of plywood, including tie holes or any other cuts, to reduce swelling due to moisture absorption. Follow the manufacturer’s technical data for maintenance and installation requirements.

4.6.4 Advantages—Advantages of job-built formwork include:

a) Tie locations can be designed to symmetrically fit the structure, become a feature of the formed surface appear-ance, or both;

b) The panel arrangement can be designed to fit the dimen-sional requirements of the structure and also be a feature in and of itself;

c) The type of form facing can be chosen independent of the facing support structure.

Table 4.6.4 serves as an overview of form-facing materials. This table is not intended to replace the research necessary for proper selection and handling of form-facing materials.





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Table 4.6.4—Characteristics of various form-facing materials

Type of facingTexture of formed concrete surface Advantages Other considerations

Approxi-mate

number of reuses*

Moi

sure

resi

stan

ce

Abs

orba

nt

Unsanded plywood (CDX) or plywood with similar properties

Rough, wood grain, and defects visible

-Easy to work with including cutting, trim-ming, nails, and screws-High availability

-Saccharide from wood may cause dusting and sanding, non-uniform color†

-Sensitive to moisture, resulting in strength loss, swelling and warping, edges swelling quickly-Coarse wood grain and defects visible-Bleeding at seams unless tongue and groove-Declining absorbency with reuse

2-3

Rough sawn lumber

Rough, wood grain and defects visible

-Easy to work with including cutting, trim-ming, nails, and screws-High availability


-Very sensitive to moisture; loss in strength; swelling and warping-Coarse wood grain and defects visible-Bleeding at seams, unless tongue and groove-Declining absorbency with reuse

Up to 3

Surfaced lumber Grain and defects visible

-Easy to work with including cutting, trim-ming, nails, and screws.-High availability-Can be milled for creating formwork features


-Very sensitive to moisture; loss in strength; swelling and warping-Wood grain and defects visible-Bleeding at seams, unless tongue and groove-Declining absorbency with reuse

Up to 5

Sem

i-abs

orba

nt

Sanded and oiled plywood (BBOES or plywood with similar proper-ties); pre-oiled for initial release and moisture resistance

Wood grain and defects visible, smoother release than other raw wood surfaces

-Easy to work with including cutting, trim-ming, nails, and screws.-High availability-Can produce reasonably good surface for civil and commercial structures


-Sensitive to moisture, loss in strength, swelling and warping-Repair plugs cause discoloration-Wood grain and defects visible-Certified sustainable options available-Not commonly used for architectural purposes-Declining absorbency with reuse

5 to 10

Painted or liquid coated plywood (non-overlay coatings)

Wood grain and defects slightly visible

-Easy to work with including cutting, trim-ming, nails, and screws.-High availability

-Sensitive to moisture, loss in strength, swelling and warping depending on type and thickness of coating-Repair plugs cause discoloration-Wood grain may be visible depending on type and thickness of coating-Certified sustainable options available-Declining absorbency with reuse

10 to 20

Medium density overlay (MDO) plywood; pre-oiled for initial release and moisture resistance uses

Matte surface, wood grain and defects slightly visible

-Easy to work with including cutting, trim-ming, nails, and screws-High availability-Imparts matte finish-Consistent concrete surface possible

-Prone to irregularities in color and texture‡

-Sensitive to moisture, loss in strength, swelling and warping-Repair inserts could create imprints on concrete surface-Certified sustainable options available-Surface appearance changes with number of uses-As overlay degrades absorbency will increase

10to 20

Non

abso

rban

t

High density overlay plywood (HDO)‡

No texture to slight wood grain visible, depending on overlay weight and substrate panel construction

-Easy to work with including cutting, trim-ming, nails, and screws.-High availability-Imparts semi-glossy finish-HDO describes a wide variety of productsa) Selection of grade, overlay, surface veneer, number of steps in sanding, overlay weight, and other properties can have a significant effect on concrete surface propertiesb) Proper selection, therefore, does not end with the specification of just ‘HDO’c) With proper selection and care HDO produces uniform concrete surfaces suited for exposed concrete

-Performance varies significantly depending on substrate panel and overlay combinations-Loss in strength, swelling, and warping under influence of moisture-Repair inserts could create imprints on concrete surface-As overlay degrades, absorbency increases-Certified sustainable options available-Surface appearance changes with number of uses-Blushing or pinking could occur with first use when using Type III cement§

-Panels from different manufactures should not be mixed on architectural project-Sensitive to type, amount and application of release agent-Fasteners at surface could cause circular shadows as water is absorbed at a different rate around the fasteners; the same may happen with nail holes

10 to 50, depending

on construc-tion of panel and overlay

weight





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Table 4.6.4—Characteristics of various form-facing materials (cont.)M

oits

ture

resi

stan

ce

Non

abso

rban

t

Phenolic surface film (PSF) overlaid plywood and other proprietary overlays||

No texture -Easy to work with including cutting, trim-ming, nails, and screws-High availability-Imparts semi-glossy to glossy finish-High alkaline-resistant overlays available-Surface hardness is greater than HDO, producing more consistent surfaces including color and texture, and suited for exposed concrete

-Performance varies significantly depending on substrate panel and overlay combinations-Loss in strength, swelling and warping under influence of moisture-Repair inserts could create imprints on concrete surface-Certified sustainable options available-Surface appearance changes with number of uses-As overlay degrades, absorbency increases-Panels from different manufactures should not be mixed on architectural project-Sensitive to type, amount and application of release agent-Overlay can be brittle and may chip when drilled or cut-Surface repairs require considerable skill and still may be visible at the surface of the concrete

20 to 75, depending

on construc-tion of panel and overlay

weight

Full plastic form sheets#

No texture -Easy to work with—including cutting, trim-ming, nails, and screws-Fully recyclable-No discoloration from repair plugs and patches-Sheet joints can be sealed by welding-Consistent strength under influence of moisture-No swelling, warping under influence of moisture-Easy to repair (even on site), repairs not visible on concrete surface-Uniform and constant concrete surface possible**

-Sensitive to type, amount and application of release agent

100+

Fiberglass forms Slight texture, depending on used material

Uniform concrete surface possible -Sensitive to type, amount and application of release agent-Less available than plywood-Surface appearance changes with number of uses-High thermal expansion resulting in dimensional changes-Difficult to repair

Multiple

Laminated paper tubes

Spiral pattern from tube construction visible without liner

-High availability -Limited application-Tendency for color variation and surface irregularities-Spiral pattern may not be accepted-Loss in strength and swelling under influence of moisture-Difficult to brace-Sensitive to damages-Reinforcing bar may constrict the use of tubes

1

Metal faced forms

No texture -Fully recyclable-High resistance to scratching,gouging, and denting-Eliminates vibrator burns-No swelling due to water absorption-Repairs can be made completely incon-spicuous and uniform and constant concrete surface possible

-Sensitive to type, amount and application of release agent-Less available than plywood-Rust stains possible-Repair needs welding skills-Difficult adjustment to size(cutting, trimming)

100+

Spec

ial f

acin

gs Drainage fleece: used to convey excess water from concrete surface

Refer to manufac-turer’s data

-Darker surface without surface voids -In general not suitable for architectural concrete surfaces-Risk of wrinkling

1 to 2, depending on material

type

*Number of reuses depends on several factors including desired quality of construction, care and storage on the jobsite, and concrete mixture design.†Scratches can occur and there are no imprints visible after repair. Refer to form-facing category (Table 3.1c) for acceptable defects and repairs for corresponding CSC.‡Plywood manufacturing processes vary significantly, which may affect concrete surface quality and number of reuses; refer to manufacturer’s data for more information.§To prevent blushing with Type III cement, HDO plywood may be pretreated before first use with mason’s lime slurry until panel turns rose-colored.||Phenolic surface film (PSF) and other proprietary overlay manufacturing processes vary significantly; refer to manufacturer’s data for more information.#Mostly used in panel formwork systems and job-built forms when high reuse is desired.**Uniform and constant concrete surface possible.





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4.7—Design with form linersForm liners may be attached to the panelized or job-built

formwork. It is possible to produce a variety of patterns or textures on the exposed concrete surface by using form liners. ACI 303R-12 provides additional information.

4.8—Post-construction treated concrete surfacesSurface features provided to concrete other than those

imparted by the formwork are beyond the scope of this guide. Refer to ACI 303R-12 for additional information.

CHAPTER 5—SPECIFICATIONS

5.1—General descriptionBefore writing specifications, the licensed design profes-

sional should determine the desired appearance of the concrete surfaces and which design features the contract documents should describe. In the contract documents, the licensed design professional chooses the desired CSC from Table 3.1a and specifies the expected appearance and features for each specific area. The contractor, therefore, can determine the means and methods, material type and quanti-ties, and associated costs to achieve the specified concrete surface finish.

5.2—Design featuresSpecifications should consider constructibility, cost, and

achievable expectations, and describe the desired look of the formed concrete surface, which include surface features such as:

a) The CSC according to Table 3.1a;b) Project-specific requirements or criteria related to form-

facing category as shown in Table 3.1c;c) Other visible effects on the concrete surface such as:

formwork joints, tie holes, panel size and panel arrange-ment, texture, color, chamfer rustications, reveals, reglets, drip strips, contraction joints, expansion joints, and rein-forcing bar spacer form contacts.

If additional design features are required, consider their feasibility and include them in the contract documents.

5.2.1 Mockups—Mockups should be constructed under site conditions and meet minimum goals to:

a) Validate the means and methods to be used by the contractor;

b) Providing a sample of the specified concrete surface for the licensed design professional and owner.

Incorporate into the mockup building geometries the: reinforcing bar cover, reinforcing bar finish and layout, inserts and concrete mixture design requirements, sample tie hole patching, and other likely required repair procedures. The licensed design professional should review and accept the results demonstrated by the completed mockup(s). The contractor should confirm in writing that the mockup quality represents work that can be accomplished in the actual struc-ture. Refer to ACI 303R-12 for further information about mockups of architectural concrete.

If the contract requires a CSC3 or CSC4, there should be a mockup for each category specified (Table 3.1a). The

mockups may be considered as a separate contractual reim-bursement item. Additional mockups may be required until all parties involved are in agreement that they represent the work that can be accomplished. Before work begins on the actual structure, the licensed design professional should approve in writing a mockup for that portion. Keep and maintain mockups until the structure has been completed and the concrete surface finishes have been accepted by the owner or licensed design professional.

5.2.2 Reference area—The use of an area in an existing building may be used as a reference only and not as a mockup; it is close to impossible to reproduce an area in exact detail. Create a mockup to illustrate the contractor’s ability to reproduce the appearance of the existing structure used as a reference. Construction should conform to the selected reference surfaces and fulfill contract requirements.

5.3—Surface finish limitationsThis section describes surface characteristics considered

unacceptable or objectionable, and distinguishes those that are preventable. Some surface characteristics are difficult to control, yet considered inherent to concrete construction. When specifications require a concrete surface quality that is greater than the characteristics described in Table 3.1a, the specifier should be aware of what is realistically achievable in as-cast concrete.

Several characteristics cannot be controlled and are diffi-cult to impossible to achieve:

a) Uniform color of all areas of the building;b) Complete elimination of surface voids or bug holes;c) Concrete surface free of mortar leakage defects;d) Sharp corners;e) Consistent concrete texture.For the following characteristics, there is some control,

and therefore they can sometimes be avoided:a) Slight color differences between sequenced pours on

either side of a construction joint;b) Accumulation of surface voids in the upper part of

vertical surfaces;c) Imprint of the reinforcement or aggregate;d) Minor leakage at joints between plywood sheets or

panels, tie holes, and other form penetrations;e) Mottling patterns;f) Alkali streaks and rust stripes on vertical surfaces;g) Rust traces on form surfaces, which can only can be

avoided with enormous efforts to apply immediately before placement.

The following characteristics can be significantly mini-mized if work is executed properly:

a) Rock pockets and cold joints;b) Mortar remnants caused by construction joint leaks of

the vertical components;c) Non-uniform arrangement of formwork ties;d) Sloppy edges caused by damaged, displaced, or inap-

propriate chamfer or reveal strips;e) Varying surface qualities in color and texture as a result

of improperly stored formwork;f) Sloppy or inconsistent sealing of tie holes.





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CHAPTER 6—CONSTRUCTION

6.1—FormworkChapter 6 discusses the various steps the contractor should

follow in formwork selection and installation to achieve the specified concrete.

Choose and assemble formwork, facing, and fasteners in conformance with contract documents, including the facing surface that will produce the specified concrete surfaces. Formwork includes materials composing the form structure and facing material. The following recommendations help achieve the concrete surface:

a) Before each use, examine the condition of formwork and facing for imperfections or damage that may produce an unacceptable surface; repair or replace as necessary and properly store the formwork;

b) Ensure that the tolerances and characteristics of the formwork materials used provide the required appearance within specified tolerances;

c) Evenly tighten ties and seal if necessary; over-tightened ties can result in depressions around the tie hole;

d) Depending on the CSC, the edges of cut-to-size plywood may need to be sealed and factory sealed edges may need to be checked and resealed to achieve the required concrete surface at the panel joints;

e) Seals, using silicone or compressible closed-cell joint tapes, can reduce the likelihood of leakage at the facing, form panel joints, or both, including construction joints. The use of foam tape, caulking, or both can become problematic after the initial form use. Residual release agents remaining on the forms may affect the tape or caulk adhesion. If joint sealing or taping is required, it should be specified in the contract documents;

f) Keep porous plywood or other porous facing materials moist to minimize swelling and shrinking;

g) Avoid using new and old plywood sheets or sheets from different manufacturers adjacent to one another, or both, as different sheets could have an effect on the final appearance of the concrete surface;

h) Carefully choose release agents and use in accordance with manufacturer’s instructions and spray, spread, or spray and spread the release agents in even, thin layers unless otherwise directed. Wipe off excess release agents;

i) When locating concrete placement windows or other temporary openings in formwork, avoid areas of congested reinforcement. Consider the concrete’s finished appearance when selecting the location of temporary openings because such openings will most likely leave a form imprint on the finished surface. Make temporary openings large enough to allow the use of internal vibrators with minimal contact with reinforcement and form-facing material;

j) It is difficult to attain completely tight forms unless joint sealing strips are installed between each panel. This docu-ment attempts to address these issues and provides limita-tions to the form gap and mortar leakage. The language of Table 3.1b, Classification T1-T4, is intended to be consistent with ACI 301-10, which states that mortar loss should be

controlled and minimized. If mortar loss causes reinforcing bar cover issues, patching may be required.

6.2—Reinforcement and insertsSecure reinforcement and inserts in a manner to prevent

displacement and deformation when setting the formwork and damage to the facing material. Using a sufficient number of suitable spacers properly placed within the form is impor-tant. When selecting reinforcement spacers, consider the following:

a) The locations of the spacers are usually visible at the surface of the concrete. If there is concern, make a sample and consult with the licensed design professional and client before final selection of the spacers;

b) Spacers could leave imprints on a soft formwork face;c) The type and quantity of spacers depend on the arrange-

ment, spacing, or both of the reinforcement, the type of spacer, and its material properties;

d) With extended duration between reinforcement delivery or installation and concrete placement, there is a risk of stains on the concrete surface due to mill scale, rust, or both—particles on the concrete surface that cannot be removed. Staining may be more pronounced on horizontal surfaces. If rust stains on the underside of horizontal surfaces need to be avoided, use noncorrosive reinforcement as determined in the specifications;

e) Depending on the form-facing category, special care may be required during placement of reinforcement to protect the form-facing material and inserts from damage. Discuss any special care needed with the formwork contractor, general contractor, and all impacted trades during a preconstruction meeting.

6.3—Concrete mixtureVariation in concrete mixture can impact the surface

appearance of the completed structure. The concrete mixture should be selected for appropriate workability and aggre-gate sizes based on geometry and reinforcement spacing. Do not allow the concrete to segregate or have excessive bleed water during placement and consolidation. Batch and deliver concrete with uniform proportions and consistency. Imple-ment quality assurance procedures to provide for consistent mixture production, delivery, and placement. Make provi-sions for a backup batch plant.

a) Consider concrete mixture design when selecting form-facing material; specifically, the cement type, cementitious materials, w/cm, admixtures, and the use of SCC;

b) The use of Type III cement can cause blushing or pinking of the concrete surface when using HDO plywood for the first pours. Blushing is caused by a reaction of the alkalinity in the concrete with free phenols in the overlay. Blushing can be avoided by pretreating the HDO plywood with a mason’s lime slurry;

c) Mixture designs that produce high alkaline concrete will wear out form-facing materials faster, especially for overlaid plywood. This could result in fewer reuses. Low w/cm, Class C fly ash, and mixture characteristics can create concrete with high alkalinity.





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6.4—Concrete placementWhen placing concrete, consider the following items:a) Keep the time between setting the formwork and placing

short to minimize effects of weathering, release agent degra-dation, and dust and debris accumulation;

b) Place concrete to the full height or in equal lifts and consolidated as required to avoid segregation;

c) Minimize mortar leakage. If there is leakage on the completed concrete surface, removed with fresh water as quickly as possible;

d) Provide a uniform and consistent cure. Select curing methods so they do not affect the desired appearance of the concrete surface;

e) Protect appropriate exposure types as required for completed concrete surfaces of Categories CSC3 and CSC4;

f) Protect vertical concrete surfaces from rust, wood tannins, and other stains.

6.5—Concrete surface teamEstablish a concrete surface team for CSC3 and CSC4

to ensure coordination of the construction progress and management of information flow among the parties involved before and during construction. The team will discuss and resolve open questions concerning surface details. Members of the team can include, but not be limited to, the:

a) Owner, licensed design professionals;b) General contractor/construction manager;c) Concrete contractor, special consultants, or both, who

have expertise in formwork;d) Formwork supplier, concrete producer, reinforcement

and concrete placing and testing lab.The roles of the team members should be clearly defined.The contractor, with input from the team and consis-

tent with the contract documents, should develop written processes for the successful execution of the project.

These processes may include:a) Execution of mockup requirements;b) Development, coordination, and review and acceptance

of procedures for the formed surface appearance drawing;c) Concerns to address that will assure the required quality;d) How to complete surface evaluations;e) How to make decisions when corrective work will be

necessary.Although some parties may not be contractu-

ally obligated to other parties within this team, issues may arise—ones that affect the scope and cost to an individual member—that require resolution. The purpose of the concrete surface team is to identify and resolve issues preemptively to avoid contractual disagreements, additional cost, delays, and to bring them in alignment with project expectations.

CHAPTER 7—EVALUATION OF FORMED CONCRETE SURFACES

7.1—BasicsThe overall impression of surface appearance is the basic

acceptance criteria for the agreed upon CSC. Variations in

texture and color are characteristic for all concrete surface categories. Mockups (Chapter 3 and Section 5.2.1), if they were used, should be the basis for the evaluation process. The mockup’s surface conditions are not reproducible without variations. Differences in raw materials, permis-sible variations in concrete mixture, aging effects of form facings, release agents, and weather conditions do not allow for completely identical surface results.

When evaluating exposed concrete surfaces, the overall impression viewed from an appropriate viewing distance is the main method of evaluation (ACI 303R-12, Section 7.2). Individual criteria should only be judged by the overall appearance of the concrete surface, even if one criterion of the overall grade does not achieve the minimum surface agreed on.

7.2—Overall impressionMake the evaluation under normal lighting conditions

from a minimum distance of 20 ft (6 m) or greater, that is perpendicular to the concrete surface to be viewed. This viewing distance allows one to evaluate of the overall appearance of the structure has been achieved.

Sunlight striking a concrete surface at an acute angle will amplify the appearance of irregularities, so evalua-tions under these conditions should be avoided. The appro-priate viewing distance is equal to the distance that allows the entire building, the building’s essential parts, or both, to be viewed in their entirety. The individual design features should be recognizable. For architectural concrete, refer to ACI 303R-12.

7.3—Procedure in case of deviations7.3.1 General items—When producing exposed concrete

surfaces, it is possible that deviations from the specified quality in the contract documents could arise, despite the level of care employed during construction. A deviation can be a surface category nonconformance identified during an evaluation according to 7.2, or caused by other factors, including weather, finishes, or other building features.

The failing of a single criterion will only obligate the repair of the defect. The entire surface impression depends on the size of the viewed area, which was agreed upon at the beginning of the project. For example, should the surface void ratio in some areas be higher in the finished work than specified, this alone is not sufficient reason for rejection of the entire work if the overall appearance is still achieved.

7.3.2 Removal of defects—When removing defects of formed concrete surfaces, provide the greatest possible match with the overall impression of the CSC specified in the contract documents, or match or blend into the appear-ance of adjacent concrete surfaces using the materials and methods accepted in the field mockup (ACI 301-10).

The removal of defects requires great care. Even with the best craftsmanship, these areas can remain recognizable as repairs. For this reason, carefully consider for each case, if the proposed repair will result in an improvement over the existing condition. Consider the following procedures:





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a) The parties agree on the techniques for removing defects after production and evaluation of the mockups for each concrete surface

b) Develop a step-by-step work plan;c) Evaluate repair materials:

- Bond strength;- Color;- Serviceability under exposure conditions;- Application method;- Compatibility with subsequent treatments or concrete surfaces;- A mockup repair may be required to validate the mate-rial and method.

7.3.3 Evaluation of repair procedure—The following three steps outline a process for repairing concrete surface deviations:

Step 1—Identify the defecta) Determine causes of defects as material, design, work-

manship, or any combination of these.Step 2—Determine the correct repair processa) Create repair procedures and curing methods;b) Clarify expectations for the visible and cured appear-

ance of the repair by comparison with the mockup repair;c) Consider climatic conditions, which should be main-

tained during implementation and curing of the repair;

d) Question if the repair would result in a condition better than the existing defect. Refer to given repair samples at the surface finish of the mockup;

e) Determine what is to be repaired (7.3.2a).Step 3—Construction at the jobsitea) Implement repair;b) Complete repair procedure;c) Supervise construction with responsible parties such

as engineer/architect, contractor, and others who may be involved in the repair process;

d) Oversee repair process to ensure reliability;e) Perform final inspection.Table 7.3.3 provides an example for common defects and

repair methods.After completing the repair, conduct a second evaluation

of the concrete as noted in 7.2. If the repair does not result in conformance of the concrete surface, the licensed design professional/owner and contractor should negotiate options for further corrective actions. Immediately execute the repair process after the agreement is made. If repair of the deviations does not lead to an improved concrete surface, the resulting surface should be negotiated between the licensed design professional/owner and the contractor.

CHAPTER 8—REFERENCESACI committee documents and documents published by

other organizations are listed first by document number and year of publication followed by authored documents listed alphabetically.

American Concrete Institute (ACI)ACI 117-10—Specifications for Tolerances for Concrete

Construction and Materials and CommentaryACI 237R-07—Self-Consolidating ConcreteACI 301-10—Specifications for Structural ConcreteACI 303R-12—Guide to Cast-in-Place Architectural

Concrete PracticeACI 347-04—Guide to Formwork for ConcreteACI 309R-05—Guide for Consolidation of Concrete

Authored referencesASCC Education and Training Committee, 1999, “Guide

for Surface Finish of Formed Concrete: As-Cast Structural Concrete,” second edition, Aberdeen Group, St. Louis, MO, Apr. 1, 17 pp.

Merkblatt Sichtbeton Deutscher Beton- und Bautechnik-Verein e.V., 2004, Bundesverband der Deutschen Zementin-dustrie E.V., Berlin, Germany, DBV und BDZ, Aug., 5 pp.

Table 7.3.3—Examples of common concrete surfaces deviations and common repair techniques

Deviation Suggested repair techniquesJoints bleeding and sanding/dusting

1. Cleaning 2. Masking 3. Patching 4. Hardening 5. Curing 6. Grinding 7. Fine grinding or sanding

Edges damaged—broken out, no sharp edges)

1. Cleaning 2. Patching 3. Cure 4. Grinding or sanding

Uneven surface that is less than 1/2 in. (13 mm)

1. Patching 2. Cure 3. Grinding or sanding

Cleaning including rust and lime 1. Cleaning with rust remover and cleansing material for concrete2. Fine grinding or sanding

Various layers of different pours are visible

1. Fine grinding or sanding





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As ACI begins its second century of advancing concrete knowledge, its original chartered purpose remains “to provide a comradeship in finding the best ways to do concrete work of all kinds and in spreading knowledge.” In keeping with this purpose, ACI supports the following activities:

· Technical committees that produce consensus reports, guides, specifications, and codes.

· Spring and fall conventions to facilitate the work of its committees.

· Educational seminars that disseminate reliable information on concrete.

· Certification programs for personnel employed within the concrete industry.

· Student programs such as scholarships, internships, and competitions.

· Sponsoring and co-sponsoring international conferences and symposia.

· Formal coordination with several international concrete related societies.

· Periodicals: the ACI Structural Journal and the ACI Materials Journal, and Concrete International.

Benefits of membership include a subscription to Concrete International and to an ACI Journal. ACI members receive discounts of up to 40% on all ACI products and services, including documents, seminars and convention registration fees.

As a member of ACI, you join thousands of practitioners and professionals worldwide who share a commitment to maintain the highest industry standards for concrete technology, construction, and practices. In addition, ACI chapters provide opportunities for interaction of professionals and practitioners at a local level.

American Concrete Institute38800 Country Club DriveFarmington Hills, MI 48331U.S.A.Phone: 248-848-3700Fax: 248-848-3701

www.concrete.org





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The AMERICAN CONCRETE INSTITUTE

was founded in 1904 as a nonprofit membership organization dedicated to public service and representing the user interest in the field of concrete. ACI gathers and distributes information on the improvement of design, construction and maintenance of concrete products and structures. The work of ACI is conducted by individual ACI members and through volunteer committees composed of both members and non-members.

The committees, as well as ACI as a whole, operate under a consensus format, which assures all participants the right to have their views considered. Committee activities include the development of building codes and specifications; analysis of research and development results; presentation of construction and repair techniques; and education.

Individuals interested in the activities of ACI are encouraged to become a member. There are no educational or employment requirements. ACI’s membership is composed of engineers, architects, scientists, contractors, educators, and representatives from a variety of companies and organizations.

Members are encouraged to participate in committee activities that relate to their specific areas of interest. For more information, contact ACI.

www.concrete.org





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347.3r-13 guide to formed concrete surfaces...the german concrete association (dbv) (merkblatt...

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