What Is Precast Concrete, Exactly?

Author

Published

Adam Bombini

June 18th 2020

The use of precast concrete is rising quickly in the construction industry. Whether due to its cost savings, durability, or eco-friendly nature, more and more project managers, designers, and architects are choosing precast concrete in their buildings. 

But what exactly is precast concrete? If you’ve heard the term before but you’re not quite sure what it is and how it differs from poured concrete on site, read on to find out everything you need to know. 

The Basics

At its most basic, precast concrete is concrete that is prepared, cast, and cured in a controlled environment off site. It is poured over wire or rebar in pre-made molds and cured in ideal conditions in a factory setting. Once it hardens and is ready to use, it’s then delivered on site to be installed. 

The Manufacturing Process

Precast concrete is produced under strictly controlled conditions in an enclosed factory. As a result, the tolerances can be precisely controlled, on-site waste can be minimized, and a higher quality concrete can be ultimately produced. 

During the manufacturing process, the concrete is cast into either plywood or steel forms. Water-reducing, retarders, accelerators, or air-entraining admixtures are sometimes added into the concrete. Colour pigments may be added and steel reinforcements are typically incorporated to resist loading stresses as well. It’s then left to cure.

Once they’re ready, the precast concrete elements are then delivered to the construction site for on-site installation. 

Applications

Precast concrete is known for its versatility. It can be made in any shape and even moulded to create unique, one-off forms. As a result, its applications vary widely. 

It’s commonly used to create structural components, such as beams, tunnels, pipes, staircases, columns, wall panels, foundations, and floor slabs. These components can also be joined to other precast structure elements to form a complete structure. 

Large precast concrete structures that you’ll often see include office buildings, sound walls, retail shops, multi-housing units, parking garages, hospitals, schools, and even stadiums. 

This type of concrete can also be used to create prestressed elements for buildings, to make infrastructure components like metro line viaducts and bridge spans, and to make a number of different products, such as railway sleepers, water tanks, septic tanks, drainage chambers, and water pipes. 

How Does Precast Concrete Differ from Site Cast Concrete? 

If you’re going to use concrete in your construction project, you can choose between site cast poured concrete or precast concrete. How are they different?

Site cast concrete can be considered just as versatile as precast because it’s custom to the build. However, it can often cost more time and money, and it requires more on-site labour. On-site forms need to be created, and poor weather can delay the process. However, the forms don’t need to be moved far with site cast concrete. In-situ concrete, however, leads to more waste on site. Further, several factors, including temperature, humidity, and wind, can impact its final strength and durability.

Precast concrete, on the other hand, can reduce costs, help you meet tight deadlines since the elements can be manufactured at the same time as other project components are completed on site, and reduce waste. Because it’s produced in a factory environment with climate control, it also offers unparalleled quality and longevity.

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