![Cypress unit4](https://upload.wikimedia.org/wikipedia/commons/d/dd/Cypress_unit4.jpg)
Precast concrete is a construction product produced by casting
concrete
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...
in a reusable
mold
A mold () or mould () is one of the structures certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal seco ...
or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast
beam
Beam may refer to:
Streams of particles or energy
*Light beam, or beam of light, a directional projection of light energy
**Laser beam
*Particle beam, a stream of charged or neutral particles
**Charged particle beam, a spatially localized grou ...
s, and wall panels for
tilt up
Tilt-up, tilt-slab or tilt-wall is a type of building and a construction technique using concrete. Though it is a cost-effective technique with a shorter completion time, poor performance in earthquakes has mandated significant seismic retrofit r ...
construction. In contrast,
cast-in-place concrete
Cast-in-place concrete or Cast-in-situ concrete is a technology of construction of buildings where walls and slabs of the buildings are cast at the site in formwork. This differs from precast concrete technology where slabs are cast elsewhere a ...
is poured into site-specific forms and cured on site.
Recently lightweight
expanded polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
foam is being used as the cores of precast wall panels, saving weight and increasing thermal insulation.
Precast stone is distinguished from precast concrete by the finer
aggregate used in the mixture, so the result approaches the natural product.
Overview
Precast concrete is employed in both interior and exterior applications, from highway, bridge, and hi-rise projects to
tilt-up building construction. 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. Using a precast concrete system offers many potential advantages over onsite casting. Precast concrete production can be performed on ground level, which maximizes safety in its casting. There is greater control over material quality and workmanship in a precast plant compared to a construction site. The forms used in a precast plant can be reused hundreds to thousands of times before they have to be replaced, often making it cheaper than onsite casting in terms of cost per unit of formwork.
[Allen, EA. (2009). Fundamentals of building construction materials and methods. Hoboken, NJ: John Wiley & Sons, Inc..]
Precast concrete forming systems for architectural applications differ in size, function, and cost. Precast architectural panels are also used to
clad all or part of a building
facade or erect free-standing walls for landscaping,
soundproofing
Soundproofing is any means of impeding sound propagation. There are several basic approaches to reducing sound: increasing the distance between source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound wav ...
, and security. In appropriate instances precast products - such as
beams for bridges, highways, and parking structure decks - can be
prestressed
Prestressed concrete is a form of concrete used in construction. It is substantially "prestressed" ( compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Post-tensioned concreted i ...
structural elements. Stormwater drainage, water and sewage pipes, and tunnels also make use of precast concrete units.
Precast concrete molds can be made of timber, steel, plastic, rubber, fiberglass, or other synthetic materials, with each giving a unique finish. In addition, many surface finishes for the four precast wall panel types – sandwich, plastered sandwich, inner layer and cladding panels – are available, including those creating the looks of horizontal boards and
ashlar stone. Color may be added to the concrete mix, and the proportions and size aggregate also affect the appearance and texture of finished concrete surfaces.
History
Ancient Roman builders made use of concrete and soon poured the material into moulds to build their complex network of
aqueducts,
culvert
A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom ...
s, and tunnels. Modern uses for pre-cast technology include a variety of architectural and structural applications – including individual parts, or even entire building systems.
In the modern world, precast panelled buildings were pioneered in
Liverpool
Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a popul ...
,
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
, in 1905. The process was invented by city engineer
John Alexander Brodie
John Alexander Brodie (1858 – 1934) was an English civil engineer. He was especially known for his contribution to town planning in Liverpool, notably as one of the engineers who led the design of the Mersey Tunnel under the River Merse ...
. The tram stables at Walton in
Liverpool
Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a popul ...
followed in 1906. The idea was not taken up extensively in Britain. However, it was adopted all over the world, particularly in Central and Eastern Europe as well as in
Million Programme
The Million Programme ( sv, Miljonprogrammet) was an ambitious public housing program implemented in Sweden between 1965 and 1974 by the governing Swedish Social Democratic Party to ensure the availability of affordable, high quality housing t ...
in Scandinavia.
In the US, precast concrete has evolved as two sub-industries, each represented by a major association. The precast concrete structures industry, represented primarily by of the Precast/Prestressed Concrete Institute (PCI), focuses on prestressed concrete elements and on other precast concrete elements used in above-ground structures such as buildings, parking structures, and bridges, while the precast concrete products industry produces utility, underground, and other non-prestressed products, and is represented primarily by the National Precast Concrete Association (NPCA).
In
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, The
New South Wales Government Railways
The New South Wales Government Railways (NSWGR) was the agency of the Government of New South Wales that administered rail transport in New South Wales, Australia, between 1855 and 1932.
Management
The agency was managed by a range of differe ...
made extensive use of precast concrete construction for its stations and similar buildings. Between 1917 and 1932, it erected 145 such buildings.
Beyond cladding panels and structural elements, entire buildings can be assembled from precast concrete. Precast assembly enables fast completion of commercial shops and offices with minimal labor. For example, the Jim Bridger Building in Williston, North Dakota, was precast in Minnesota with air, electrical, water, and fiber utilities preinstalled into the building panels. The panels were transported over 800 miles to the Bakken oilfields, and the commercial building was assembled by three workers in minimal time. The building houses over 40,000 square feet of shops and offices. Virtually the entire building was fabricated in Minnesota.
Reinforcement
Reinforcing
concrete
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...
with steel improves strength and durability. On its own, concrete has good compressive strength, but lacks tension and shear strength and can be subject to cracking when bearing loads for long periods of time. Steel offers high tension and shear strength to make up for what concrete lacks. Steel behaves similarly to concrete in changing environments, which means it will shrink and expand with concrete, helping avoid cracking.
Rebar
Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a Tension (physics), tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concr ...
is the most common form of concrete reinforcement. It is typically made from steel, manufactured with ribbing to bond with concrete as it cures. Rebar is versatile enough to be bent or assembled to support the shape of any concrete structure. Carbon steel is the most common rebar material. However, stainless steel, galvanized steel, and epoxy coatings can prevent corrosion.
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 typically fall under one or
Agricultural products
Since precast concrete products can withstand the most extreme weather conditions and will hold up for many decades of constant usage they have wide applications in agriculture. These include bunker silos, cattle feed bunks,
cattle grid
A cattle grid – also known as a stock grid in Australia; cattle guard, or cattle grate in American English; vehicle pass, or stock gap in the Southeastern United States; Texas gate in western Canada and the northwestern United States; and a ...
, agricultural fencing, H-bunks, J-bunks, livestock slats, livestock watering trough, feed troughs, concrete panels, slurry channels, and more.
Prestressed concrete
Prestressed concrete is a form of concrete used in construction. It is substantially "prestressed" ( compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Post-tensioned concreted i ...
panels are widely used in the UK for a variety of applications including agricultural buildings, grain stores, silage clamps, slurry stores, livestock walling and general retaining walls. Panels can be used horizontally and placed either inside the webbings of RSJs (
I-beam
An I-beam, also known as H-beam (for universal column, UC), w-beam (for "wide flange"), universal beam (UB), rolled steel joist (RSJ), or double-T (especially in Polish language, Polish, Bulgarian language, Bulgarian, Spanish language, Spanish ...
) or in front of them. Alternatively panels can be cast into a concrete foundation and used as a cantilever retaining wall.
Building and site amenities
![Precast parking structure](https://upload.wikimedia.org/wikipedia/commons/0/00/Precast_parking_structure.jpg)
Precast concrete building components and site amenities are used architecturally as fireplace mantels, cladding, trim products, accessories and curtain walls. Structural applications of precast concrete include foundations, beams, floors, walls and other structural components. It is essential that each structural component be designed and tested to withstand both the tensile and compressive loads that the member will be subjected to over its lifespan.
Expanded polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
cores are now in precast concrete panels for structural use, making them lighter and serving as thermal insulation.
Multi-storey car park
A multistorey car park (British and Singapore English) or parking garage (American English), also called a multistory, parking building, parking structure, parkade (mainly Canadian), parking ramp, parking deck or indoor parking, is a build ...
s are commonly constructed using precast concrete. The constructions involve putting together precast parking parts which are multi-storey structural wall panels, interior and exterior columns, structural floors, girders, wall panels, stairs, and slabs. These parts can be large; for example, double-tee structural floor modules need to be lifted into place with the help of
precast concrete lifting anchor system
This information sets out some of the basic considerations taken into account by the lifting design engineer.
Compliance
Statements like those in AS3850, "Because of the mode in which failure can occur, it may be necessary to test complete syste ...
s.
Retaining walls
![Precastconcreteretainingwall-3](https://upload.wikimedia.org/wikipedia/commons/e/e4/Precastconcreteretainingwall-3.jpg)
Precast concrete is employed in a wide range of engineered earth retaining systems. Products include commercial and residential
retaining wall
Retaining walls are relatively rigid walls used for supporting soil laterally so that it can be retained at different levels on the two sides.
Retaining walls are structures designed to restrain soil to a slope that it would not naturally keep to ...
s,
sea wall
A seawall (or sea wall) is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation ...
s,
mechanically stabilized earth
Mechanically stabilized earth (MSE or reinforced soil) is soil constructed with artificial reinforcing. It can be used for retaining walls, bridge abutments, seawalls, and dikes. Although the basic principles of MSE have been used throughout ...
panels, and other modular block systems.
[McCormac, JCM. (2006). Design of reinforced concrete. Hoboken, NJ: John Wiley & Sons, Inc..]
Sanitary and stormwater
Sanitary and stormwater management products are structures designed for underground installation that have been specifically engineered for the treatment and removal of pollutants from sanitary and stormwater run-off. These precast concrete products include
stormwater detention vault
A stormwater detention vault is an underground structure designed to manage excess stormwater runoff on a developed site, often in an urban setting. This type of best management practice may be selected when there is insufficient space on the si ...
s,
catch basin
A storm drain, storm sewer (United Kingdom, U.S. and Canada), surface water drain/sewer (United Kingdom), or stormwater drain (Australia and New Zealand) is infrastructure designed to drain excess rain and ground water from impervious surface ...
s, and
manhole
A manhole (utility hole, maintenance hole, or sewer hole) is an opening to a confined space such as a shaft, utility vault, or large vessel. Manholes are often used as an access point for an underground public utility, allowing inspection, m ...
s.
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,
hollow-core products, light pole bases, meter boxes, panel vaults, pull boxes, telecommunications structures, transformer pads, transformer vaults, trenches, utility buildings,
utility vault
A utility vault is an underground room providing access to subterranean public utility equipment, such as valves for water or natural gas pipes, or switchgear for electrical or telecommunications equipment. A vault is often accessible directly fro ...
s, 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
Aeration (also called aerification or aeriation) is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration processes create additional surface area in ...
, distribution boxes, dosing tanks,
dry well
A dry well or drywell is an underground structure that disposes of unwanted water, most commonly surface runoff and stormwater and in some cases greywater. It is a gravity-fed, vertical underground system that captures surface water from imper ...
s,
grease interceptor
A grease trap (also known as grease interceptor, grease recovery device, grease capsule and grease converter) is a plumbing device (a type of trap) designed to intercept most greases and solids before they enter a wastewater disposal system. Co ...
s, leaching pits, sand-oil/oil-water interceptors,
septic tank
A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater (sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatme ...
s, water/sewage storage tanks, wet wells, fire cisterns, and other water and wastewater products.
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 culvert
A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom ...
s, 3-sided culverts, bridge systems, railroad crossings, railroad ties,
sound wall
A noise barrier (also called a soundwall, noise wall, sound berm, sound barrier, or acoustical barrier) is an exterior structure designed to protect inhabitants of sensitive land use areas from noise pollution. Noise barriers are the most effecti ...
s/barriers,
Jersey barrier
A Jersey barrier, Jersey wall, or Jersey bump is a modular concrete or plastic barrier employed to separate lanes of traffic. It is designed to minimize vehicle damage in cases of incidental contact while still preventing vehicle crossovers resu ...
s, tunnel segments, concrete barriers, TVCBs, central reservation barriers, bollards, and other transportation products. Precast concrete can also be used to make underpasses, surface-passes, and pedestrian subways. Precast concrete is also used for the
rail ways of some
rubber-tyred metro
A rubber-tyred metro or rubber-tired metro is a form of rapid transit system that uses a mix of road and rail technology. The vehicles have wheels with rubber tires that run on rolling pads inside guide bars for traction, as well as traditional ...
s.
Modular paving
Modular paving is available in a rainbow of colors, shapes, sizes, and textures. These versatile precast concrete pieces can be designed to mimic brick, stone or wood.
Specialized products
Cemetery products
Underground vaults or mausoleums require watertight structures that withstand natural forces for extended periods of time.
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
Seawalls
A seawall (or sea wall) is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation ...
, 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.
Structures
Prestressed concrete
Prestressing is a technique of introducing stresses into a structural member during fabrication and/or construction to improve its strength and performance. This technique is often employed in concrete beams, columns, spandrels, single and double tees, wall panels, segmental bridge units, bulb-tee girders, I-beam girders, and others. Many projects find that prestressed concrete provides the lowest overall cost, considering production and lifetime maintenance.
Precast concrete sandwich wall (or insulated double-wall) panels
Origin
The precast concrete double-wall panel has been in use in Europe for decades. The original double-wall design consisted of two
wythe
A wythe is a continuous vertical section of masonry one unit in thickness. A wythe may be independent of, or interlocked with, the adjoining wythe(s). A single wythe of brick that is not structural in nature is referred to as a masonry veneer
...
s of reinforced concrete separated by an interior void, held together with embedded steel trusses. With recent concerns about energy use, it is recognized that using steel trusses creates a "thermal bridge" that degrades thermal performance. Also, since steel does not have the same thermal expansion coefficient as concrete, as the wall heats and cools any steel that is not embedded in the concrete can create thermal stresses that cause cracking and spalling.
Development
To achieve better thermal performance, insulation was added in the void, and in many applications today the steel trusses have been replaced by composite (fibreglass, plastic, etc.) connection systems. These systems, which are specially developed for this purpose, also eliminate the differential thermal expansion problem.The best thermal performance is achieved when the insulation is continuous throughout the wall section, i.e., the wythes are thermally separated completely to the ends of the panel. Using continuous insulation and modern composite connection systems, R-values up to R-28.2 can be achieved.
Characteristics
The overall thickness of sandwich wall panels in commercial applications is typically 8 inches, but their designs are often customized to the application. In a typical 8-inch wall panel the concrete wythes are each 2-3/8 inches thick), sandwiching 3-1/4 inches of high
R-value insulating foam. The interior and exterior wythes of concrete are held together (through the insulation) with some form of connecting system that is able to provide the needed structural integrity. Sandwich wall panels can be fabricated to the length and width desired, within practical limits dictated by the fabrication system, the stresses of lifting and handling, and shipping constraints. Panels of 9-foot clear height are common, but heights up to 12 feet can be found.
![Prefabricated house construction](https://upload.wikimedia.org/wikipedia/commons/e/e1/Prefabricated_house_construction.gif)
The fabrication process for precast concrete sandwich wall panels allows them to be produced with finished surfaces on both sides. Such finishes can be very smooth, with the surfaces painted, stained, or left natural; for interior surfaces, the finish is comparable to drywall in smoothness and can be finished using the same prime and paint procedure as is common for conventional drywall construction. If desired, the concrete can be given an architectural finish, where the concrete itself is colored and/or textured. Colors and textures can provide the appearance of brick, stone, wood, or other patterns through the use of reusable
formliners, or, in the most sophisticated applications, actual brick, stone, glass, or other materials can be cast into the concrete surface.
Window and door openings are cast into the walls at the manufacturing plant as part of the fabrication process. In many applications, electrical and telecommunications conduit and boxes are cast directly into the panels in the specified locations. In some applications, utilities, plumbing and even heating components have been cast into the panels to reduce on-site construction time. 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.
Applications and benefits
Precast concrete sandwich wall panels have been used on virtually every type of building, including schools, office buildings, apartment buildings, townhouses, condominiums, hotels, motels, dormitories, and single-family homes. Although typically considered part of a building's enclosure or "envelope," they can be designed to also serve as part of the building's structural system, eliminating the need for beams and columns on the building perimeter. Besides their energy efficiency and aesthetic versatility, they also provide excellent noise attenuation, outstanding durability (resistant to rot, mold, etc.), and rapid construction.
In addition to the good insulation properties, sandwich panels require fewer work phases to complete. Compared to double-walls, for example, which have to be insulated and filled with concrete on site, sandwich panels require much less labor and scaffolding.
Precast Concrete Market
The precast concrete industry is largely dominated by Government initiated projects for infrastructural development. However, these are also being extensively used for residential (low and high rise) and commercial constructions because of their various favourable attributes. The efficiency, durability, ease, cost effectiveness, and sustainable properties
of these products have brought a revolutionary shift in the time consumed in construction of any structure. Construction industry is a huge energy consuming industry, and precast concrete products are and will continue to be more energy efficient than its counterparts. The wide range of designs, colours, and structural options that these products provide is also making it a favourable choice for its consumers.
Regulations
Many state and federal transportation projects in the United States require precast concrete suppliers to be certified by either the Architectural Precast Association, National Precast Concrete Association or Precast Prestressed Concrete Institute.
See also
*
Cast in place concrete
Cast-in-place concrete or Cast-in-situ concrete is a technology of construction of buildings where walls and slabs of the buildings are cast at the site in formwork. This differs from precast concrete technology where slabs are cast elsewhere a ...
*
Million Programme
The Million Programme ( sv, Miljonprogrammet) was an ambitious public housing program implemented in Sweden between 1965 and 1974 by the governing Swedish Social Democratic Party to ensure the availability of affordable, high quality housing t ...
*
Prestressed concrete
Prestressed concrete is a form of concrete used in construction. It is substantially "prestressed" ( compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Post-tensioned concreted i ...
*
Roll way
A roll way or running pad is the pad placed on a concrete slab or on the ties on the outside of the conventional track along both running rails of a rubber-tyred metro or along the unconventional track of a tram. The rubber-tyred wheels roll d ...
*
Structural robustness
Robustness is the ability of a structure to withstand events like fire, explosions, impact or the consequences of human error, without being damaged to an extent disproportionate to the original causeas defined in EN 1991-1-7 of the Accidental Ac ...
*
Tilt up
Tilt-up, tilt-slab or tilt-wall is a type of building and a construction technique using concrete. Though it is a cost-effective technique with a shorter completion time, poor performance in earthquakes has mandated significant seismic retrofit r ...
Precast Concrete Can Be Used
*
*''A Comfortable House for $1,000'',
Popular Science
''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
monthly, February 1919, page 39, Scanned by Google Books
Popular Science
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