Precast concrete

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A precast concrete walled house under construction Precast concrete house in construction.JPG
A precast concrete walled house under construction
An example of low-quality precast concrete with exposed dowels, connectors, indications of cracks, and malformations, even during its installation, Barangay Lantic, Carmona, Cavite, Philippines Cypress unit4.jpg
An example of low-quality precast concrete with exposed dowels, connectors, indications of cracks, and malformations, even during its installation, Barangay Lantic, Carmona, Cavite, Philippines
Interior view of the walls, supports, and roof of a precast commercial shop in Williston, North Dakota, US. Utilities are preassembled into the precast components. Precastbuilding.jpg
Interior view of the walls, supports, and roof of a precast commercial shop in Williston, North Dakota, US. Utilities are preassembled into the precast components.

Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels for tilt up construction. In contrast, cast-in-place concrete is poured into site-specific forms and cured on site. [1]

Contents

Recently lightweight expanded polystyrene 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 high-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. [2]

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, and security. In appropriate instances precast products – such as beams for bridges, highways, and parking structure decks – can be prestressed 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. [3] 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, culverts, 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, England, in 1905. [4] The process was invented by city engineer John Alexander Brodie. The tram stables at Walton in Liverpool 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 [5] as well as in Million Programme 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, The New South Wales Government Railways made extensive use of precast concrete construction for its stations and similar buildings. Between 1917 and 1932, it erected 145 such buildings. [6]

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 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 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. [7]

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, agricultural fencing, H-bunks, J-bunks, livestock slats, livestock watering trough, feed troughs, concrete panels, slurry channels, and more. Prestressed concrete 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) 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 showing an interior column, girders, and double-tee structural floors. The two gray circles are covers to close the lifting anchor holes. Precast parking structure.jpg
Precast parking structure showing an interior column, girders, and double-tee structural floors. The two gray circles are covers to close the lifting anchor holes.

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 cores are now in precast concrete panels for structural use, making them lighter and serving as thermal insulation.

Multi-storey car parks 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 systems. [8]

Retaining walls

A retaining wall made of modular precast concrete blocks Precastconcreteretainingwall-3.jpg
A retaining wall made of modular precast concrete blocks

Precast concrete is employed in a wide range of engineered earth retaining systems. Products include commercial and residential retaining walls, sea walls, mechanically stabilized earth panels, and other modular block systems. [9]

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 vaults, catch basins, and manholes. [10]

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 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, wet wells, fire cisterns, and other water and wastewater products.

Precast concrete box culvert Pre-cast concrete box culvert.jpg
Precast concrete box culvert

Precast concrete transportation products are used in the construction, safety, and site protection of roads, airports, and railroad transportation systems. Products include: box culverts, 3-sided culverts, bridge systems, railroad crossings, railroad ties, sound walls/barriers, Jersey barriers, tunnel segments, concrete barriers, TVCBs, central reservation barriers, bollards, and other transportation products. Precast concrete can also be used to make underpasses, surface crossings, and pedestrian subways. Precast concrete is also used for the roll ways of some rubber-tyred metros.

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.

A precast concrete hazardous material storage container PrecastHazardousMaterialStorage.JPG
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.

A precast concrete armour unit (Accropode) Accropode Gomera P8080013.jpg
A precast concrete armour unit (Accropode)

Marine products

Seawalls, 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. [9] [11]

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 wythes 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.[ citation needed ]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.

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.[ citation needed ]

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. [12]

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[ citation needed ] [13] 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

Related Research Articles

<span class="mw-page-title-main">Masonry</span> Building of structures from individual units of stone, bricks, or blocks

Masonry is the craft of building a structure with brick, stone, or similar material, including mortar plastering which are often laid in, bound and pasted together by mortar. The term masonry can also refer to the building units themselves.

<span class="mw-page-title-main">Reinforced concrete</span> Concrete with rebar

Reinforced concrete, also called ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel bars (rebar) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.

<span class="mw-page-title-main">Structural insulated panel</span>

A structural insulated panel, or structural insulating panel, (SIP), is a form of sandwich panel used in the construction industry.

<span class="mw-page-title-main">Prestressed concrete</span> Form of concrete used in construction

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.

This page is a list of construction topics.

<span class="mw-page-title-main">Insulating concrete form</span> Construction material

Insulating concrete form or insulated concrete form (ICF) is a system of formwork for reinforced concrete usually made with a rigid thermal insulation that stays in place as a permanent interior and exterior substrate for walls, floors, and roofs. The forms are interlocking modular units that are dry-stacked and filled with concrete. The units lock together somewhat like Lego bricks and create a form for the structural walls or floors of a building. ICF construction has become commonplace for both low rise commercial and high performance residential construction as more stringent energy efficiency and natural disaster resistant building codes are adopted.

<span class="mw-page-title-main">Concrete slab</span> Flat, horizontal concrete element of modern buildings

A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel-reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving (see below).

<span class="mw-page-title-main">Steel frame</span> Building technique using skeleton frames of vertical steel columns

Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.

<span class="mw-page-title-main">Formwork</span> Molds for cast

Formwork is molds into which concrete or similar materials are either precast or cast-in-place. In the context of concrete construction, the falsework supports the shuttering molds. In specialty applications formwork may be permanently incorporated into the final structure, adding insulation or helping reinforce the finished structure.

This is an alphabetical list of articles pertaining specifically to structural engineering. For a broad overview of engineering, please see List of engineering topics. For biographies please see List of engineers.

Glass fibre reinforced concrete (GFRC) is a type of fibre-reinforced concrete. The product is also known as glassfibre reinforced concrete or GRC in British English. Glass fibre concretes are mainly used in exterior building façade panels and as architectural precast concrete. Somewhat similar materials are fibre cement siding and cement boards.

<span class="mw-page-title-main">Sandwich panel</span> Structure made of three layers

A sandwich panel is any structure made of three layers: a low-density core, and a thin skin-layer bonded to each side. Sandwich panels are used in applications where a combination of high structural rigidity and low weight is required.

Studcast concrete, also called "pre-framed concrete", combines relatively thin concrete layers with cold formed steel framing to create hybrid panels; the result is a panelized system usable for cladding, curtain walls, shaft walls, and load-bearing exterior and interior walls. Studcast panels install in the same manner as prefabricated steel stud panels. The technology is applicable for both factory prefabrication and site-cast (tilt-up) wall construction on almost all types of buildings, including multifamily housing, schools, industrial, commercial and institutional structures.

<span class="mw-page-title-main">Structural material</span>

Structural engineering depends on the knowledge of materials and their properties, in order to understand how different materials resist and support loads.

Spancrete is an American manufacturer of precast concrete products and machinery. Spancrete produces precast, prestressed concrete products that are used in commercial, industrial, institutional, residential and multifamily construction projects in the Midwest and Southeast. The company also manufactures and sells hollowcore extrusion machines that are used to produce precast concrete internationally.

<span class="mw-page-title-main">Infill wall</span>

The infill wall is the supported wall that closes the perimeter of a building constructed with a three-dimensional framework structure. Therefore, the structural frame ensures the bearing function, whereas the infill wall serves to separate inner and outer space, filling up the boxes of the outer frames. The infill wall has the unique static function to bear its own weight. The infill wall is an external vertical opaque type of closure. With respect to other categories of wall, the infill wall differs from the partition that serves to separate two interior spaces, yet also non-load bearing, and from the load bearing wall. The latter performs the same functions of the infill wall, hygro-thermically and acoustically, but performs static functions too.

<span class="mw-page-title-main">Double tee</span> Type of load-bearing structure

A double tee or double-T beam is a load-bearing structure that resembles two T-beams connected to each other side by side. The strong bond of the flange and the two webs creates a structure that is capable of withstanding high loads while having a long span. The typical sizes of double tees are up to 15 feet (4.6 m) for flange width, up to 5 feet (1.5 m) for web depth, and up to 80 feet (24 m) or more for span length. Double tees are pre-manufactured from prestressed concrete which allows construction time to be shortened.

This glossary of structural engineering terms pertains specifically to structural engineering and its sub-disciplines. Please see glossary of engineering for a broad overview of the major concepts of engineering.

<span class="mw-page-title-main">Post-tensioned stone</span> Form of stonework used in construction

Post-tensioned stone is a high-performance composite construction material: stone held in compression with tension elements. The tension elements can be connected to the outside of the stone, but more typically uses tendons threaded internally through a duct formed from aligned drilled holes.

References

  1. ↑ "Precast concrete - Future of next Generation". Precast. Retrieved 4 March 2022.
  2. ↑ Allen, EA. (2009). Fundamentals of building construction materials and methods. Hoboken, NJ: John Wiley & Sons, Inc.
  3. ↑ "Precast concrete facades bring buildings to life". Concrete Issues.
  4. ↑ Hogan-O'Neill, William (22 February 2021). Prefabricated and Modular Architecture: Aligning Design with Manufacture and Assembly. The Crowood Press. p. 313. ISBN   978-1-78500-807-8.
  5. ↑ "Port Cities". Mersey-gateway.org. Archived from the original on 13 October 2007.
  6. ↑ Precast Concrete Station Buildings in New South Wales Longworth, Jim Australian Railway History, May, 2005 pp163-185
  7. ↑ "reinforced concrete | building material". Encyclopædia Britannica. Retrieved 24 May 2016.
  8. ↑ "High Precast Parking Systems" (PDF). High Concrete Group. Archived from the original (PDF) on 13 May 2015. Retrieved 3 June 2014.
  9. 1 2 McCormac, JCM. (2006). Design of reinforced concrete. Hoboken, NJ: John Wiley & Sons, Inc.
  10. ↑ "NPCA - Precast Products - Stormwater Management FAQ". Archived from the original on 20 August 2008.
  11. ↑ Paradigm concrete Services
  12. ↑ "Let's grab a sandwich!". Concrete Issues.
  13. ↑ Habibullah Sharifi, Sayed Hafiz Sadat, Zhaoxu Wang, Yuanzhen Liu (2021). "Life Cycle Cost Analysis of Precast Concrete Bridge Projects". North American Academic Research. 4 (4, April 2021): 4(4) 138–147. doi:10.5281/zenodo.4699431.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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