The method evolved over time, especially in the last century. In this day and age, builders use precast concrete products to create entire building systems.

When was precast concrete invented?

While the method was used in ancient times, the credit for its modern use goes to John Alexander Brodie. He was a City Engineer in Liverpool, England. He designed buildings with precast concrete panels in the city.

How is Precast Concrete Made?

To make precast concrete structures, first, the molds are prepared. The molds are reusable and prepared in the shape that the precast concrete will have.

Once the molds are done, the concrete mix is poured into it. After pouring, the mixture is left to cure. Factors like temperature and humidity are precisely controlled during the curing process.

Once cured, the molds are removed, and the finished product is shipped to the job site.

Since the molds can be shaped in any form, precast concrete comes in many different shapes and sizes. However, when the size of products becomes larger, the weight becomes an issue. Therefore, you won’t find very large single precast concrete panels.

Materials Used in Precast Concrete

Many different components go into making a precast concrete structure. These materials include:

Cement: This is the most important material in precast concrete. The National Precast Concrete Association sets the requirements for what quality of materials you need to use to create high-quality precast concrete as an NPCA-certified plant.

Generally, Ordinary Portland Cement (OPC) Grade 43 and 53 are used in precast concrete. For precast concrete created for harsh conditions (such as tidal environments), Portland Pozzolana Cement and Portland Slag Cement are used.

Water: The ratio and purity of water are key factors in creating a superior precast concrete mix design. The water mustn’t contain any impurities, as particles in water can degrade the mix quality.

Supplementary Cementitious Materials (SCMs): These are generally industrial by-products and sometimes natural materials that exhibit the properties of cement. These are mixed in Ordinary Portland Cement to improve its hydration properties.

Aggregate: The type of aggregate is typically chosen based on the mix design for a specific precast concrete structure. A project manager will typically consider factors such as durability, color, or texture. Special Aggregate can be used.

Some other materials added to precast concrete are:

Waterproofing admixtures: Crystalline waterproofing admixture is one example. It makes the precast concrete products resilient to water damage. This is used in structures like septic tanks, retaining walls, roofs, etc.

Oxides: Since precast concrete is a product ready for installation, it is sometimes produced in different colors. The color is added by using oxide pigments.

Reinforcement bars: Reinforcing bars act as a spine for precast concrete and make the product strong. There are many different designs of reinforcing bars that may be used, depending on the structure to be created.

Steel tendons: Tendons may be bars, wires, or strands. It is best to use steel tendons free from contamination like dust and mud to create a strong adhesion between the steel and the precast concrete. All metal reinforcements require a protective coating to prevent corrosion of the metal.

Joints: These provide stability and strength in a precast concrete building by transferring forces to the structural elements.

Lightweight Aggregate: This type of mix is used in many projects when a lighter concrete structure is required. Air bubbles are present in the concrete to reduce the density and overall weight of the final structure.

Fibers: Adding fibers to concrete further reinforces the strength of the concrete manifold. Different fibers are used in precast concrete, such as steel and polymeric fibers.

Non-shrink Grouts: Non-shrink grouts are generally used to shift the forces between different structural elements.

Epoxy Grouts: The purpose of adding epoxy grouts to precast concrete is to create precast concrete with a very high strength profile. Adding these grouts requires expert supervision since the properties of different epoxies can vary significantly.