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Precast Concrete: TheArchitects Solution
Outline
Introduction
Manufacturing Process of Precast
Benefits to Architects
Benefits to Owners
Benefits to Contractors
Design and Use
Summary
Introduction
Precast Concrete concrete cast
elsewhere than its final position (ACI)
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Introduction
Architectural Precast - Precast concrete
that will remain visible when in its finalposition, thereby contributing to theaesthetics of the structure or site.
Structural Precast - Precast concrete thatsupports or transfers loads other than itsown weight (e.g. floor & roof loads).
Above Ground Applications
Buildings and structures
Site amenities/accessories
Retaining & sound walls
Bridges
Traffic and security barriers
Road repairs
Fencing
Buildings - Commercial
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Buildings - Residential
Foundations & Walls
Buildings - Residential
Buildings Floor and Roof
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Buildings - Trim
Buildings Modular
Buildings StructuralElements
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Buildings StructuralElements
Site Amenities &Accessories
Site Amenities&Accessories
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SoundWalls
RetainingWalls
Bridges
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Bridges
Traffic Barriers
Security Barriers
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Road Repair
Fencing
Underground Applications
Water and wastewater
Stormwater
Sanitary
Utilities
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Water &
Wastewater
Stormwater
Sanitary
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Utilities
Manufacturing
Forms
Types of Concrete
Materials
Mix Design
Properties
Stripping
Curing
Storage and Shipping
Manufacturing - Forms
Wood most common for architectural,good details, limited number of uses perform
Metal Most common for underground,
durable, reusable for years Fiberglass great detail and finish,
expensive
Formliners resin, elastomeric, plastic,wood, steel, plaster
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Forms - Wood
Forms - Wood
Forms - Metal
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Forms - Metal
Forms
What to watch for:
Forms require drafts and chamfersfor ease of removal
Proper form preparation, seal joints
Proper cleaning and maintenance
Types of Concrete
What is Concrete?
Different types: Conventional wet-cast
Dry-cast
Lightweight
High-performance
Self-Consolidating Concrete (SCC)
Architectural
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Types of Concrete - SCC
Types of Concrete - SCC
Types of Concrete Architectural
Face mix
Minimum thickness after consolidation
one-inch or 1.5 x max. agg. size Similar thermal and shrinkage
coefficients
Similar w/cm ratios and proportions
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Manufacturing - Materials
Coarse and fine aggregate (stone
and sand) 60-70% by volume, 70-85% by mass
Properly Graded
Gap Graded
Note: natural materials will vary
Manufacturing - Materials
Cement
Grey - color may vary
White - more stable for colors
Water - must be potable or meetASTM C 1602
Admixtures
Air
Manufacturing Mix Design
Water-cementitious ratio, lower thebetter (0.40 0.45)
Type IType IType I
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Manufacturing Mix Design
Water-cementitious ratio by volume
300 lbs600 lbs
= 0.504.81 ft3
3.05 ft3
240 lbs600 lbs
= 0.403.85 ft3
3.05 ft3
Hardened Properties
Appearance
Strength
Durability
Moisture penetration
Abrasion resistance
Dimensional stability
Appearance
Precast concrete can be made inmany: Shapes or designs
Colors Textures
Finishes
Combinations of the above
*Repeatable due to quality control
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Strength
Maximum stress concrete can
withstand before failure
Concrete is good in compression,but weak in tension
Durability
A products ability to survive in its
exposure environment for its intended
service life.
Ability to resist internal and external
attack Corrosion of reinforcement
Freeze/Thaw resistance
ASR
Moisture Penetration
Porosity - a ratio of the total voids in amass to the total mass itself
Permeability is a measure of the flowof a liquid or a gas through a substance
Water resistant reduces wetting, butpermits passage of moisture underhydrostatic pressure
Water proof impervious to water ineither liquid or vapor state
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Abrasion Resistance
Ability to resist damage caused by
rubbing Important for:
Floors
Hydraulic Structures
Bridges
Parking Garages
Dimensional Stability
Concrete experiences volumetricchange due to:
Temperature
Moisture
Chemical
External forces
What Effects Concretes
Hardened Properties?
Water-Cementitious ratio
Quality materials and mix design
Good production practices Proper curing procedures
*All of which you get with precast concrete.These are more difficult to ensure in fieldconditions.
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Stripping/Form Removal
Must have appropriate stripping
strength Forms must be removed properly
and completely
Always lift pieces level and asdesigned
Curing
Why cure?
Proper curing temps, procedures
Concrete is the only material thatgains strength over time
Curing affects color
Curing affects strength
Why precast is cured better thanconcrete cast on site
Storage and Shipping
Storage yards
Shipping time
Erection of products
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Storage and Shipping
Storage &Shipping
Storage and Shipping
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Benefits to Architects
Design flexibility Aesthetic versatility
Quality control
Superior strength
Green - sustainability
Readily available
Saves time and money
DesignFlexibility
Concrete can bemade into anyshape that canbe formed
Modular
High level ofdetail
Finishes are ableto simulate
almost anymaterial
Aesthetic VersatilityWide variety of colors
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Aesthetic Versatility
Exposures:None skin, paste only as cast
Light matrix predominant (Acid, AB)
Medium 50/50 matrix and courseaggregate (Acid, AB)
Deep coarse aggregate predominant(AB, EA)
Aesthetic Versatility
Wide variety textures and finishes:
As cast- form finish
Abrasive blast
Acid etched
Exposed aggregate surface retarder
Grinding/tooling
Veneers
Cast stone
Formliners
As-Cast
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Abrasive Blast / Acid Etch
Exposed Aggregate
Exposed Aggregate
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Polished Finish
Veneer
Veneer
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Cast Stone
Formliners
Quality Control
Controlled and monitoredenvironment
Shelter from weather
Consistent quality materials &trained labor
Quality control personnel
Documentation of production foreach piece
Certified plants
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Superior Strength
Precast concrete has superiorstrength over many other claddingmaterials such as:
EIFS, masonry, metals, wood, glass, etc.
Precast concrete can bemultipurpose i.e. used as a primarystructural material, shear walls, etc.
Green and LEED
Precast concrete can relate directly
to four LEED credits and a total ofeight points
Site credit 6 Stormwater management
Site credit 7 Heat Island reduction
Materials & Resources credit 4 Recycled content
Material & Resources credit 5
Regional Materials
Saves Time and Money
Speed of Erection
Rapid enclosure
High level of detail
Able to duplicate almost any material
Excellent to match older materials orexisting architecture
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Benefits to Owner
Durability/extended service life Low maintenance - life cycle costs Fire resistant non combustible - passive
resistance Noise deadening Thermal benefits Security Speed of construction quicker
occupancy Reduced construction costs
Durability/Extended Service Life
100 year service life is possible
Durability/Extended ServiceLife
Low permeability/porosity
High strength
Resistance to storms, hurricanes,UV, rot, mold, pests
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Low Maintenance
No painting No warping
No rusting
No breakage
No moisture infiltration or mold
Reduced joints
Low Maintenance
Fire Resistant
Non-combustible
Reduces insurance
Saves lives
Fire ratings easily achieved
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Noise Deadening
Reduces sound transmission fromboth outside and inside sources
Concrete is a good sound insulator
Thermal Benefits
Reduced air infiltration
Reduced utility costs
Acts as thermal mass
Security
Extremelydifficult to break
into Pest entry no
vermin, termites
Terrorist threats
Hard to steal
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Speed of Construction
Reduce building enclosure time andoverall construction time
Quicker Occupancy = making moneyfaster
Speed of Construction
Speed of Construction
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Saves Time and Money
Can reduce overall project costs Precast can be less expensive than
traditional materials
Less site labor reduces costs
Benefits to Contractor
Low site impact
Reduced weather dependency
Speed of enclosure
Saves time and money
Low Site Impact
Site Impact a combination ofstorage space required, site access
and duration of that access,limitations on other trades duringthat access
Precast can be delivered to the siteas needed
Other trades can start sooner
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Low SiteImpact
Reduced Weather Impact
Precast can be erected in all temperaturesand in most conditions
Reduced Weather Impact
Site weather conditions do not effect
the manufacturing process
Rain only helps curing
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Speed of Enclosure
Buildings can be erected and dried-infaster than conventionalconstruction
Saves Time and Money
Precast products can be made whilethe excavation and foundations arebeing performed on site.
Design and Use
Design & cost reduction
Total precast construction
Mock-ups and samples
Colors and finishes
Piece design and componentizing
When not to use precast
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Design and Use Design &Cost Reduction
Start with the overall geometry of thestructure, not the panel
Use repetition Master moldconcept, forms are expensive, allowenough time not to need extra molds
Design and Use Design &Cost Reduction
Big pieces are better then small ones reduce handling and erection time
Multiple finishes can increase cost
Must be constructible
Consider site conditions
Involve precaster early in theprocess initial design phase
Design and Use Total PrecastConstruction
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Design and Use Total PrecastConstruction
Design and Use Total Precast
Construction
Design and Use Mock Ups
Build a full scale mock up of a typicalsection on the site
Build mock ups early in the project View in sun, shade, wet, dry
Use for variation control and acceptance
Establish patching and repair procedures
Evaluate the effects of weathering
May help identify other constructionissues
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Design and Use Colors andFinishes
Visual characteristics are usuallydetermined by the architect
How color is achieved
Recommendations:
Match paste, sand and stone
Use white cement or blends
Use slightly darker matrix with deep exposures
Rounded aggregates help with weathering anduniformity
Design and Use Piece Design& Componentizing
Size & geometry by engineer,precaster
Open and closed piece design
ReturnsClosedOpen
Design and Use Piece Design
& Componentizing
Stress concentrations, handling
Joints and corners
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Design and Use Piece Design& Componentizing
Larger pieces are better Repetition of pieces = reduces costs
Involve the precaster early in the
design process
Consider constructability andshipping
Tolerances
Design and Use
When not to use precast
Mass pours or when monolithic poursare required i.e. dams, nuclear reactors
Slabs on ground
Summary
Precast Concrete: Offers a virtually endless array of colors,
finishes and textures Can allow you to be creative in design
Can reduce construction times, delays andproject costs Is extremely durable 100 year service life Reduces overall life-cycle costs Is produced in a quality controlled
environment Can qualify for LEED credits
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Everybody Wins
with PrecastConcrete!
Thank You!