Precast concrete

This article may need to be wikified to meet Wikipedia's quality standards. Please help by adding relevant internal links, or by improving the article's layout. (June 2008)

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (October 2007)

A precast concrete walled house in construction

Precast concrete is a form of construction, where concrete is cast in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site specific forms and cured on site. Precast stone is distinguished from precast concrete by using a fine aggregate in the mixture so the final product approaches the appearance of naturally occurring rock or stone.

By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Many states across the United States require a precast plant to be certified (either by APA, NPCA or PCI) for a precast producer to supply their product to a construction site sponsored by State and Federal DOTs. There are many different types of precast concrete forming systems for architectural applications, differing in size, function and cost.

Ancient Roman builders made use of concrete and soon poured the material into molds to build their complex network of aqueducts, culverts and tunnels. Modern uses for precast technology include a variety of architectural and structural applications featuring parts of or an entire building system. Precast architectural panels are also used to clad all or part of a building facade free-standing walls used for landscaping, soundproofing and security walls. Stormwater drainage, water and sewage pipes and tunnels make use of precast concrete units. The advantages of using precast concrete is the increased quality of the material, when formed in controlled conditions, and the reduced cost of constructing large forms used with concrete poured on site. The New South Wales Government Railways made extensive use of precast concrete construction for its stations and similar buildings. Between 1917 and 1932, they erected 145 such buildings^[1].

Precast Concrete Products

The following is a sampling of the numerous products that utilize precast/prestressed concrete. While this is not a complete list, the majority of precast/prestressed products can fall under one or more of the following categories:

Agricultural Products

Precast concrete products can withstand the most extreme weather conditions and will hold up for many decades of constant usage. Products include bunker silos, cattle feed bunks, cattle grid, agricultural fencing, H-bunks, J-bunks, livestock slats, livestock watering troughs, etc...

Building and Site Amenities

Precast concrete building components and site amenities are used architecturally as cladding, trim products, accessories and in structural applications such as foundations, beams, floors, walls and other structural components.

Precast concrete wall veneer formed to replicate brick. In the UK the biggest supplier of precast concrete for the construction industry is Tarmac, who cast from timber moulds supplied from B&B Moulds who lead the field in the fabrication of pre-cast concrete timber moulds. Examples of both companies' work can been seen throughout the UK in football stadiums, and will feature heavily in the 2012 Olympics.

Cemetery Products

Underground vaults or mausoleums - calls for quality watertight structures that withstand the tests of time and the forces of nature.

A precast concrete hazardous material storage container.

Hazardous Materials Containment

Storage of hazardous material, whether short-term or long-term, is an increasingly important environmental issue, calling for containers that not only seal in the materials, but are strong enough to stand up to natural disasters or terrorist attacks.

Marine Products

Floating docks, underwater infrastructure, decking, railings and a host of amenities are among the uses of precast along the waterfront. When designed with heavy weight in mind, precast products counteract the buoyant forces of water significantly better than most materials.

Modular Paving

Available in a rainbow of colors, shapes, sizes and textures, these versatile precast concrete pieces can be designed to mimic brick, stone or wood.

Prestressed/Structural Products

Prestressing is a technique of introducing stresses of a predetermined magnitude into a structural member to improve its behavior. This technique is usually found in concrete beams, spandrels, columns, single and double tees, wall panels, segmental bridge units, bulb-tee girders, I-beam girders, etc...

Retaining Walls

An example of a precast concrete retaining wall.

Precast concrete manufacturers located throughout North America^[where?] produce a wide range of engineered earth retaining systems. Products include: commercial retaining wall, residential retaining walls, sea walls, mechanically stabilized earth (MSE) panels, modular block systems, segmental retaining walls, etc...

Sanitary and Stormwater

Stormwater management products are structures designed for underground installation that have been specifically engineered for the treatment and removal of pollutants from stormwater run-off. These precast concrete products include stormwater detention vaults, catch basins and manholes.

Transportation and traffic related products

Precast concrete transportation products are used in the construction, safety and site protection of road, airport and railroad transportation systems. Products include: box culverts, 3-sided culverts, bridge systems, railroad crossings, railroad ties, sound walls/barriers, Jersey barriers, tunnel segments and other transportation products. Used to make underpasses, surface-passes and pedestrian subways, so that traffic in cities is disturbed for less amount of time.^[2]

Utility Structures

For communications, electrical, gas or steam systems, precast concrete utility structures protect the vital connections and controls for utility distribution. Precast concrete is nontoxic and environmentally safe. Products include: hand holes, hollowcore products, light pole bases, meter boxes, panel vaults, pull boxes, telecommunications structures, transformer pads, transformer vaults, trenches, utility buildings, utility vaults, utility poles, controlled environment vaults (CEVs) and other utility structures.

Water and Wastewater Products

Precast water and wastewater products hold or contain water, oil or other liquids for the purpose of further processing into non-contaminating liquids and soil products. Products include: aeration systems, distribution boxes, dosing tanks, dry wells, grease interceptors, leaching pits, sand-oil/oil-water interceptors, septic tanks, water/sewage storage tanks, wetwells, fire cisterns and other water & wastewater products.

Double Wall Precast

The double wall process has been in use in Europe for many years. The walls consist of 2 wythes of concrete separated by an insulated void. The most commonly specified thickness of the wall panels is 8 inches. The walls can also be built 10 and 12 inches thick if desired. A typical 8-inch wall panel consists of two wythes (layers) of reinforced concrete (each wythe is 2-3/8 inches thick) sandwiched around 3-1/4 inches of high R-value insulating foam. The two wythes of the interior and exterior concrete layers are held together with steel trusses. The insulation is continuous throughout the wall section. The composite sandwich wall section has an R-value exceeding R-22. The wall panels can be made to any height desired, up to a limit of 12 feet. Many owners prefer a 9-foot clear height for the quality of look and feel it affords a building.

A single-family detached home being built up from precast concrete parts

The walls can be produced with smooth surfaces on both sides because of the unique manufacturing process which form finishes both sides. The walls are simply painted or stained on the exterior surface to achieve the desired color or textured surface. When desired, the exterior surface can be manufactured to have a wide variety of brick, stone, wood or other formed and patterned appearances through the use of reusable, removable formliners. Interior surfaces of the double-wall panels are drywall quality in appearance right out of the plant, requiring only the same prime and paint procedure as is common when completing conventional interior walls made of drywall and studs.

Window and door openings are cast into the walls at the manufacturing plant as part of the fabrication process. Electrical and telecommunications conduit and boxes are flush mounted and cast directly in the panels in the specified locations. The carpenters, electricians and plumbers do need to make some slight adjustments when first becoming familiar with some of the unique aspects of the wall panels. However, they still perform most of their job duties in the manner to which they are accustomed.

Double-wall precast concrete sandwich panels can be used on most every type of building including but not limited to: Multi-family, Townhouses, Condominiums, Apartments, Hotels/Motels, Dormitories/Schools and Single Family homes. Depending upon building function and layout, the double-wall panels can be easily designed to handle both the structural requirements for strength and safety, as well as the aesthetic and sound attenuation qualities the owner desires. Speed of construction, durability of finished structure and energy-efficiency are all hallmarks of a building that utilizes the double-wall system.

This system seems to be the way of the future as more attention is being paid to fortified housing. Systems like these can save many lives in areas at risk of dangerous weather.^{[citation needed]}

See also

• Carboncast

References

External links

• Precast Solutions
• APA- Architectural Precast Association
• Canadian Precast/Prestressed Concrete Institute
• British Precast Concrete Federation
• BIBM - A Precast Concrete Association of Associations
• Midwest Precast Association
• National Precast Concrete Association (NPCA) – One of the largest trade associations representing the precast concrete production industry in the United States
• Building a Concrete House – Series of videos documenting the construction of a concrete house
• A Comfortable House for $1,000, Popular Science monthly, February 1919, page 39, Scanned by Google Books: [2]
• Precast/Prestressed Concrete Institute – The industry leader on information on Precast and Prestressed Concrete
• Quickcell Technology Products Leading Prestressed and Precast Concrete Manufacturer in Queensland and Northern NSW, Australia.