Pre Cast Concrete The Architects Solution Handouts

Precast Concrete: The Architects’ 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 final position, thereby contributing to the aesthetics of the structure or site. • Structural Precast - Precast concrete that supports or transfers loads other than its own 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 – Structural Elements

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Buildings – Structural Elements

Site Amenities & Accessories

Site Amenities & Accessories

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Sound Walls

Retaining Walls

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 per form • 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 chamfers for 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 meet ASTM C 1602 • Admixtures • Air

Manufacturing – Mix Design Water-cementitious ratio, lower the better (0.40 – 0.45) TypeType I I Type

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Manufacturing – Mix Design Water-cementitious ratio – by volume

300 lbs = 0.50 600 lbs

4.81 ft3 3.05 ft3

240 lbs = 0.40 600 lbs

3.85 ft3 3.05 ft3

Hardened Properties • • • • • •

Appearance Strength Durability Moisture penetration Abrasion resistance Dimensional stability

Appearance • Precast concrete can be made in many: – 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 product’s 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 a mass to the total mass itself • Permeability – is a measure of the flow of a liquid or a gas through a substance • Water resistant – reduces wetting, but permits passage of moisture under hydrostatic pressure • Water proof – impervious to water in either 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 volumetric change due to: – – – –

Temperature Moisture Chemical External forces

What Effects Concrete’s 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 field conditions.

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Stripping/Form Removal • Must have appropriate stripping strength • Forms must be removed properly and completely • Always lift pieces level and as designed

Curing • Why cure? • Proper curing temps, procedures • Concrete is the only material that gains strength over time • Curing affects color • Curing affects strength • Why precast is cured better than concrete 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

Design Flexibility • Concrete can be made into any shape that can be formed • Modular • High level of detail • Finishes are able to simulate almost any material

Aesthetic Versatility Wide 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 course aggregate (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 monitored environment • Shelter from weather • Consistent – quality materials & trained labor • Quality control personnel • Documentation of production for each piece • Certified plants

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Superior Strength • Precast concrete has superior strength over many other cladding materials such as: – EIFS, masonry, metals, wood, glass, etc.

• Precast concrete can be multipurpose i.e. used as a primary structural material, shear walls, etc.

Green and LEED • Precast concrete can relate directly to four LEED credits and a total of eight 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 or existing 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 Service Life • 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 from both outside and inside sources • Concrete is a good sound insulator

Thermal Benefits • Reduced air infiltration • Reduced utility costs • Acts as thermal mass

Security • Extremely difficult to break into • Pest entry – no vermin, termites • Terrorist threats • Hard to steal

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Speed of Construction • Reduce building enclosure time and overall construction time • Quicker Occupancy = making money faster

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 of storage space required, site access and duration of that access, limitations on other trades during that access • Precast can be delivered to the site as needed • Other trades can start sooner

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Low Site Impact

Reduced Weather Impact • Precast can be erected in all temperatures and 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-in faster than conventional construction

Saves Time and Money • Precast products can be made while the excavation and foundations are being 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 the structure, not the panel • Use repetition – Master mold concept, forms are expensive, allow enough 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 the process – initial design phase

Design and Use – Total Precast Construction

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Design and Use – Total Precast Construction

Design and Use – Total Precast Construction

Design and Use –Mock Ups • Build a full scale mock up of a typical section 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 construction issues

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Design and Use – Colors and Finishes • Visual characteristics are usually determined 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 and uniformity

Design and Use – Piece Design & Componentizing • Size & geometry by engineer, precaster • Open and closed piece design

Open

Closed

• Returns

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 and shipping • Tolerances

Design and Use • When not to use precast – Mass pours or when monolithic pours are 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 and project 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 Precast Concrete! Thank You!

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