What Is Precast Concrete?
Precast concrete is an advancement of the 20th century
in the construction technology that permits casting of concrete into structural elements under factory environments. Later, it is transported to the construction site. The precast technique, also called prefabricated, includes such construction where the bulk of structural elements are identical and manufactured in factories located away from the construction site. These elements are produced by the industrial practices of mass production that ensures economy of scale and reduction in the production time. The technique of precasting increases the strength and durability of the concrete element, and reduces the curing time and the cost of construction. Normal concrete reaches the designed strength twenty eight days after the initial application. However, the precast concrete removes the time lag between the placing of concrete and the application of loads. The components that can be precast include beams, slabs, columns, stairways, and several other construction elements.
Design Considerations of Precast Concrete
Precast concrete structures are mostly constructed as a curtain wall or a thin covering in which building loads are not transferred. The precast concrete wall systems are designed to endure the lateral loads imparted directly on it, like winds, and the vertical loads due to the weight of the precast walls. These loads should be transferred through the wall system and other structural elements to the building structure. Additional loads like erection and impact associated with construction and transportation should also be considered during the design of precast concrete structures. Other important design parameters that are considered while designing precast concrete applications are strength, ductility, durability, fire resistance, and constructability. Joints amid panels should be adequately wide to control the thermal expansion and relative shifting between the panels. Panel joints are usually sealed with sealants to avoid infiltration of water in the wall cavities.
Cost Comparison Cast in Place With Precast Concrete
In addition to the advantages of speed, quality, cleanliness, and safety involved in the use of precast concrete, it is also economical for structural applications. To illustrate, the cost of a construction work that involves excavation, pouring, curing, damping, and installation, is $3,900 using cast-in-place concrete; the same work can be completed at a cost of $ 2,400 with precast concrete. Expenditure is also reduced by using precast concrete since fewer days are required for the construction. The use of precast concrete eliminates other issues related to the construction, such as engaging numerous tradesmen for work and their supervision costs, unnecessary risks of downtime, and quality control management.