Inthe completion of the Walnut Lane Memorial Bridge in Philadelphia, Pennsylvania, signaled the beginning of the precast concrete industry in North America. Virtually unknown in the United States until the construction of this prestressed concrete bridge, today, precast concrete structures, including bridges, are commonplace in the United States.
Precast concrete is widely used in low- and mid-rise apartment buildings, hotels, motels, and nursing homes. The concrete provides superior fire resistance and sound control for the individual units and reduces fire insurance rates. Precast concrete is also a popular material for constructing office buildings.
The walls of the building can be manufactured while the on-site foundations are being built, providing significant time savings and resulting in early occupancy. The speed and ease with which precast structures can be built has helped make precast a popular building material for parking structures. Precast concrete allows efficient, economical construction in all weather conditions and provides the long clear spans and open spaces needed in parking structures.
For stadiums and arenas, seating units and concrete steps can be mass produced according to specifications, providing fast installation and long lasting service. In addition, pedestrian ramps, concession stands, and dressing room areas can all be framed and constructed with precast concrete. The smooth surfaces produced with precast concrete and the ability of precast, prestressed concrete to span long distances makes precast suitable for use in manufacturing and storage structures.
Additional applications for precast concrete include piles and deck for railroad and highway bridges, railway crossties, burial vaults, educational institutions, commercial buildings such as shopping malls, and public buildings including hospitals, libraries, and airport terminals. A benefit of precast concrete is that the product is created in ideal manufacturing conditions. Although some products are cast outdoors, especially in temperate climates, many precast plants operate indoors where the climate can be fully controlled.
There are two types of precast products. Standard products such as beams, decks, and railroad ties are shaped in one way and used repeatedly. The other type of product is a specialty product, designed especially for the building, bridge, or structure where it will be used. Most precast companies have their own carpentry shops where skilled workers create forms for the many specialty-precast products available. Architectural concrete is often cast specially for each new project.
The forms, whether standard or specialty, are well oiled. Concrete is placed in the forms and allowed to cure. After curing, the product is carefully lifted from the form and taken to a yard for further curing before it is shipped to the project site The form is then carefully cleaned and prepared for the next batch of concrete.
Many precasters can turn over their forms every one or two days. Cement Industry Annual Yearbook U. Greg Halsted, P. Joshua Gilman, P. Precast Concrete.
Standard or Special There are two types of precast products. Return to Products.The concept of precast concrete is not a new one. However, we have seen a huge cultural shift in the past few decades towards precast concrete. This shift includes products and processes becoming more streamlined, more eco-friendly, more efficient, and less expensive.
With rapid time-tables, a competitive market that seeks affordability and efficiency, and a desire for high quality finished products, the process of precast concrete has found its niche. In this day and age of advanced technology, when anything that can be conceived can usually be achieved, it seems reasonable to assume that precast concrete is a recent invention.
However, the beginnings of this innovative process are believed to date back to Ancient Rome and definitely has its more modern beginnings in the middle of the 20th century. The first permit for the process of creating a precast concrete building was acquired by Englishman John Alexander Brodie, though the first major structure using precast concrete was erected in the U.
The Walnut Lane Memorial Bridge in Philadelphia was built in using precast concrete and is recognized as the beginning of the precast industry we know today in the United States. Soon after this major achievement, the Precast Concrete Institute was created.
This would allow standards for production to be set as this emerging industry quickly began to grow. The types of buildings and structures that can be designed, cast, and created using precast concrete are truly unlimited. Structures that withstand a significant amount of wear, weather, or use are excellent candidates for precast concrete. The durability of this type of design lends itself to bridges, parking garages, any kind of underground structure, as well as retaining walls or sound barriers.Precast 101: How Precast Concrete Is Made
Being able to create a structure in a controlled environment not only ensures a precision on the production end; it also reduces the length of time spent on-site fitting the structure into place.
This, in turn, reduces mistakes and miscalculations, allowing for accuracy and speed in the building process without sacrificing quality. Here are some common types of structures in which precast concrete is preferred over on-site pours:. Our molds can be customized, as well, to match the decor of the housing development, school, church, government building or public works facility our walls surround, giving them an aesthetically-pleasing look that only adds to their functionality.
Curb Inlets and Catch Basins: Aiding in storm-water and wastewater drainage, retention of rainwater, and stormwater runoff are all possible despite the different specifications that vary from state to state, and even in different municipalities.
You can be sure your pieces reflect the exact manufacturing specifications when you choose precast concrete since these are customized to each specific project. Culverts: Underground tunnels and wastewater drainage systems are no joke to construct. Imagine already having the major pieces completed before arriving at the site! Box and three-sided culverts can be manufactured in all different shapes and sizes to fit the specific project perfectly. Start with the end in mind when you design the perfect culverts for your underground construction and finish the project on time- or sooner!
A precast basement will fit perfectly the first time, without rain delays or other environmental factors to sidestep. Plus, providing a moisture-free, energy-efficient basement for your new building will lead to huge savings in the future of your design. From columns and paving slabs to stairs and traffic barriers, bringing each piece pre-designed from the factory aides in the economic construction of a durable, efficient parking structure.
Whether single structure or multi-level, the sleek, modern look of precast concrete can enhance any urban area design or blend into the existing local decor. Plus, in growing metropolitan areas, completing a reliable, useful structure in a fraction of the time is a huge bonus.
Bridges: This is a great example of how to make precast concrete work with and for you. With molds that can be customized to match the local environment, your bridge can fulfill a historical context that will blend beautifully. Obviously the reliability of your bridge and the longevity of its construction are of utmost importance- so why take a chance with on-site poured concrete?Architectural precast concrete has been used since the early twentieth century and came into wide use in the s.
The exterior surface of precast concrete can vary from an exposed aggregate finish that is highly ornamental to a form face finish that is similar to cast-in-place.
Some precast panels act as column covers while others extend over several floors in height and incorporate window openings. In most cases, the architect selects the cladding material for appearance, provides details for weatherproofing, and specifies performance criteria. The structural engineer designs the structure to hold the cladding, designates connection points, and evaluates the effects of structural movement on the cladding. The precast concrete manufacturer designs the cladding for the specified loads, erection loads, connection details, and provides for the weatherproofing, performance and durability of the cladding itself.
Precast concrete wall systems offer a wide variety of shapes, colors, textures, and finishes to the designer. As a result, the assessment of samples is a key component in the use of precast concrete.
The majority of the review and approval process is conducted at the precast plant prior to precast panel production. This assessment is in addition to the quality control and field testing that takes place during the production phase. Typically, each precast panel is independently supported to the building structure using an assemblage of metal components and anchors.
Joints around each of the precast panels are usually filled with sealant. Precast cladding or curtain walls are the most common use of precast concrete for building envelopes. These types of precast concrete panels do not transfer vertical loads but simply enclose the space. They are only designed to resist wind, seismic forces generated by their own weight, and forces required to transfer the weight of the panel to the support. Common cladding units include wall panels, window wall units, spandrels, mullions, and column covers.
These units can usually be removed individually if necessary. Load-bearing wall units resist and transfer loads from other elements and cannot be removed without affecting the strength or stability of the building. Typical load-bearing wall units include solid wall panels, and window wall and spandrel panels.
Precast concrete shear wall panels are used to provide lateral load resisting system when combined with diaphragm action of the floor construction. The effectiveness of precast shear walls is largely dependent upon the panel-to-panel connections. In some cases, precast panels are used as formwork for cast-in-place concrete.
14. TYPES OF PRECAST CONSTRUCTION.pdf
The precast panels act as a form, providing the visible aesthetics of the system, while the cast-in-place portion provides the structural component of the system. The connections for precast concrete panels are an important component of the envelope system. Precast manufacturers utilize numerous different types of anchors but they are often characterized as gravity and lateral types of connections.
The primary purposes of the connection are to transfer load to the supporting structure and provide stability. The criteria used to design precast connections including but not limited to:. The numerous joints in a precast concrete envelope are an important aspect of the facade design.
The joints between precast units or between precast and other building components must be maintained to prevent leakage through the precast wall system. Joint design should consider the structural, thermal, and all other factors that affect the performance and movement of a joint. The joint seal should of course be adequately designed to withstand the movement of the joint.
In commercial construction, the most common back-up wall element for architectural precast concrete wall systems is an insulated, metal stud back-up wall assembly. Precast concrete wall systems are most often constructed as a curtain wall or veneer, in which no building loads are transferred to the concrete panels.
Most typically the precast concrete wall system must resist lateral loads directly imparted on it, such as from wind and earthquake ; as well as vertical loads resulting from the self weight of the precast wall system.The construction methodologies are improving day by day due to the latest technologies that provide many advantages to both builders and site owners.
Precast techniques are gaining popularity over the recent years because they help to reduce the expenses considerably in a construction project.
Concrete is the most used component in the precast structure because it contributes more to transform the conditions with high success rates. Precast concrete is a type of concrete material which is made by casting concrete. It is ready to install product available in the markets that come in reusable form.
Some of the benefits offered by precast concrete include less manpower, highly resistant to weather conditions, scaffolding reduction, noise reduction, eco-friendly, and so on. Before planning a precast structure, we should know the types of components used for the construction.
This will help to complete a project on time with high accuracy. A precast slab is the most used component in several construction sites because it suits any type of architecture which adopt to the requirements. Moreover, it comes in different types in order to fulfill the expectations of a construction project. Some of them include hollow core units, double -tee units, solid core slabs and bi axial voided slabs which ultimately help to gain more advantages. A hollow core slab provides maximum structural efficiency by reducing the dead weight.
Double-tee units are primarily designed for flooring purposes and lighter in weight. At the same time, the depth of units may vary depending on the span. A solid core slab is a prefabricated one that looks similar to a solid slab which can help to meet essential needs in the construction process.
The biaxial voided slabs are the latest one that are more efficient than traditional floor structure. A precast beam is primarily used as a ledge for other precast flooring types which ultimately give ways for obtaining optimal results. Some of the types include Tee-beams, beamshells, L-beams, U-beams, and rectangular beams. A precast column is typically used to support a beam and the sizes and shapes can vary with a building project. It is usually rectangular or circular in a section which ultimately gives ways for planning the construction process accordingly.
A precast wall is an ideal solution for providing stability to a frame structure that can carry vertical loads. Most construction companies use precast walls with floor slabs to form a complete structure. The precast walls are a suitable one for enhancing the stability to a building thereby showing ways for ensuring optimal results. Curtain walls, load-bearing wall units, shear walls, and form work for cast-in-place concrete are the four types of precast walls are available for the buildings allowing us to maintain a better environment.
The precast staircases give ways for eliminating the need for an expensive framework. Apart from that, they are a suitable one for improving the look of a building with unique styles.
It is possible to install them in a building for saving more time.The concept of precast construction includes those buildings where the majority of structural components are standardized and produced in plants in a location away from the building, and then transported to the site for assembly.
This type of construction requires a restructuring of the entire conventional construction process to enable interaction between the design phase and production planning in order to improve and speed up the construction.
One of the key premises for achieving that objective is to design buildings with a regular configuration in plan and elevation. Precast concrete slabs, beams, and structural tees are one-way spanning units that may be supported by site cast concrete, precast concrete, or masonry bearing walls, or by steel, site cast concrete, or precast concrete frames. The precast units are manufactured with normal density or structural lightweight concrete and prestressed for greater structural efficiency, which results in less depth, reduced weight, and longer spans.
National Institute of Technology, Surat.
Why Should We Prefer Precast Concrete Construction?
Page Prestressed Concrete. Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those found when in use. Prestressed concrete refers to concrete that has applied stresses induced into the member. Typically, wires or tendons are stretched and then blocked at the ends creating compressive stresses throughout the member's entire cross-section.
Most Prestressed concrete is precast in a plant. Slip-form construction slip forming, continuous poured, or continuously formed is a construction method in which concrete is poured into a continuously moving form. Basically, this method involves the continuous placing of concrete in a shallow mould having the same plan as the building to be constructed.
This rigid mould, or "slip-form" as it is called, forms the working deck which is jacked slowly upwards at a controlled rate until the required elevation is reached. Tilt-up Construction. Tilt-up construction is a method of casting reinforced concrete wall panels on site in a horizontal position, then tilting them up into their final position. The principal advantage of tilt-up construction is the elimination of the costs associated with constructing and stripping vertical wall forms; this cost saving is offset by the cost of the crane required to lift the completed wall panels into place.
Tunnel form is a formwork system that allows the contractor to cast walls and slabs in one operation in a daily cycle. The result is a cellular reinforced structure, the surfaces of which are sufficiently high quality to require only minimal finishing for direct decoration, while the end walls and facades are easily completed with thermally insulated units that can be clad as required.
Timber construction wood framing is the predominant method of building homes and apartments in the United States. Increasingly, wood framing is also being used in commercial and industrial buildings. Wood frame buildings are economical to build, heat and cool, and provide maximum comfort to occupants. Wood construction is readily adaptable to traditional, contemporary and the most futuristic building styles.
Various Types of Precast Concrete Slabs
Its architectural possibilities are limitless. Light gauge steel construction is the non-combustible equivalent of wood light frame construction. The external dimensions of the standard sizes of light gauge members correspond closely to the dimensions of the sizes of nominal 2-inch framing lumber, and these steel members are used in framing as closely spaced studs, joists, and rafters in much the same way as wood light frame members are used.
Prefabrication in construction is the practice of assembling components of a building in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the building is to be located. The term is used to distinguish this process from the more conventional construction practice of transporting the basic materials to the construction site where all assembly is carried out.
The term prefabrication also applies to the manufacturing of things other than structures at a fixed site. Portable are often used temporarily and taken away later. They have been used since prehistoric times. The most familiar modern type of portable buildings are designed so that one can be carried to or from site on a large lorry and slung on and off by a crane.
It is a common fact that we find a wide variety of construction equipment on every construction site, which makes the construction jobs easy, safe and quicker. The selection of the appropriate type and size of construction equipment often affects the required amount of time and effort and thus the job- site productivity of a project. Learn more about Scribd Membership Home. Read Free For 30 Days.In America, modern concrete homes are becoming very, very popular.
This makes a lot of sense, especially since, according to Chemistry World Magazineconcrete is the most widely-used building material in the world.
From this same issue of Chemistry World Magazine, we learned that over two-billion tons of concrete are produced every year. Keep in mind that this issue is fromand that number has certainly gone up since then. Besides the fact that cement is a very popular and very familiar building material, it is also an incredibly durable building material that can withstand noise.
You can use concrete in a variety of ways, to create some very interesting homes, and due to a variety of advances in the cement industry, concrete has become a very sustainable material for the environment.
4 Types of Modern Concrete Homes (Plus Costs, Pros, Cons & Siding Options)
Modern concrete homes are made using a combination of cement, water, sand, and stone aggregates. This is also combined with various chemical properties so that the material becomes strong and durable. Usually, though, concrete homes are made in much the same way that regular houses are made.
From the concrete that is created, it is used to follow a blueprint that is very similar to a blueprint for a regular, wood-frame house. Usually, this concrete is paired with steel reinforcements and various other materials — these depend on the house itself — to strengthen it, increasing its durability, while also ensuring that it is aesthetically pleasing, rather than drab and ugly.
Concrete blocks are being used more and more due to their lack of a carbon footprint — they are very sustainable — and also because of their versatility. This reusable mold is taken to a controlled environment and cured, which means to provide the adequate amount of moisture, along with the ideal temperature, for the concrete mold to achieve the needed effects. From that process, it is then taken to the work site, and used.
This particular process is easy and effortless, with a very small carbon footprint, which has contributed greatly to the popularity of modern concrete homes. Generally speaking, this is the same process that is used for making any type of concrete home, regardless of how many concrete blocks are used.
Each one has its own advantages and disadvantages. Nonetheless, they are all popular for a reason, and that reason is because they are very good and very durable. Concrete blocks are fairly self-explanatory. They are very popular, due to their inexpensive price, and they can be manufactured easily and quickly.
Most people think of concrete blocks as being these big, solid, blocks that are usually three-by-four. Sometimes bigger. Sometimes smaller. But, the image is the same. Some concrete blocks are very small, and made for a very specific aesthetic purpose. Other concrete blocks are very large, and simply designed that way for economical reasons. It depends on the home. Precast panels are often built at a plant, and then transported to the site of where your home is being constructed.
Generally, they look really good, but they can be a bit more expensive. ICFs are foam blocks that are hollow and filled with reinforced concrete. Even when the concrete has been poured in, the foam stays in so that it can provide insulation.A hollow core slabalso known as a voided slab or hollow core plank is a precast slab of prestressed concrete typically used in the construction of floors in multi-story apartment buildings.
This makes the slab much lighter than a massive floor slabs of equal thickness or strength. Reduced weight is important because of transportation cost and less cost of material concrete. The slabs are typically cm wide with standard thicknesses between 15 cm and 50 cm. The precast concrete I-beams between the holes contain the steel wire rope that provide bending resistance to bending momentum from loads.
The single tee sections typically have a deck surface about 1. The beam is usually about 8 inches thick and about 24 inches tall. Double-Tee floor units are produced in standard widths of mm and in depths of between mm and mm.
The system offers greater structural capacity at longer spans than hollowcore or wideslabs, but often requires a deeper floor zone.
The Double-Tee system is the only system which offers a solution for spans over 16m. Solid Wideslab is sometimes referred to as "plate flooring" which is generally used in residential developments. The standard slab width is mm and available in depths of 80, and mm depths our standard sizes are and mm. Wideslab is often used with a structural screed, to aid stability of the structure and increase its load capacity.
Maximum spans are about 8. Beam and Block is a flooring system composed of pre-stressed concrete beams, with standard building blocks laid between the beams. Laid together with purpose made split course and utilising our professional fixing teams, this helps to generate a comprehensive flooring package. With the added design support we can help you achieve a value added flooring solution.
Insulated Infill blocks can be used to achieve improved insulation values within the floor and solid tray blocks can be used to achieve the robust detail for upper floors. Lattice girder slabs act as permanent formwork and as precast soffits for robust, high capacity composite floor slabs. They are cast with most, if not all, of the bottom reinforcement required; the top reinforcement is fixed in situ. The units are typically 50mm to mm thick and mm or mm wide.
They are generally propped during construction and until the in situ concrete has gained sufficient strength. The new BubbleDeck r system takes the concept of the filigree flat floor slab and introduces a revolutionary method of virtually eliminating the concrete from the middle where it is not performing any structural function, so dramatically reducing dead weight.
The reduced environmental impact of the system is also impressive with less concrete usage 1kg of recycled plastic replaces kg of concrete and lower energy and carbon emissions. Solid panel - A panel of constant thickness; an allowance for surface texture must be made in determining effective thickness. Hollow-core panel- A precast panel that has voids within the thickness in one direction for the full length of the panel.
Sandwich panel- A precast panel consisting of two layers of concrete separated by a non-structural insulating core. Ribbed panel A precast panel consisting of a slab reinforced by a system of ribs in one or two directions Mullion wall is a structural system in which the load of the floor slab is taken by prefabricated panels around the perimeter. Concrete Girder A concrete girder bridge is made of prestressed concrete in an I-beam shape. The concrete is also reinforced with steel rods.
This combination is particularly effective in bridge construction. Learn more about Scribd Membership Home.