While concrete or cement has been used for thousands of years, the first appearance of reinforced concrete took place just 160 years ago. First, wire netting was placed within concrete to make pots for trees and flowers. Jean Monier, a French gardener interestingly enough, received a patent for his idea in 1867.
Reinforced concrete was born. From there, other materials were used to make concrete more durable and available for larger operations. This process was used for pipes, bridges, reservoirs, and more throughout Europe.
Concrete has been refined over the years and is one of the primary building blocks in stadiums and infrastructure around the world. But why does the addition of steel reinforced bars, or rebar, make concrete so much stronger?
Two Kinds of Strength
When concrete gets tested for strength, inspectors are looking at two measurements: compressive and tensile. Compressive strength is tested by squeezing a concrete sample between two hydraulic cylinders. Concrete fares pretty well in this test, especially if it’s made in a controlled environment. If concrete has a strength of 4,000 psi, it can withstand a load of 4,000 pounds of stress for every square inch. That’s two tons!
When it comes to tensile strength, however, the rating drops quite a bit. Instead of being compressed, the concrete is stretched from either end. The same concrete from the above example would only have a tensile strength of around 400 psi.
Rebar to the Rescue
To improve the concretes ability to handle tensile stresses, rebar is placed at specific intervals within the concrete. These steel bars can handle stretching much better than concrete, so it absorbs those stresses. But rebar is only as good as the crew putting it together.
Let’s say an engineer has determined that concrete needs to be reinforced by a specific type of rebar every 4 inches. If that rebar is placed any further apart, the integrity of the product is compromised. Placing that same rebar every five inches apart degrades the strength by 20 percent!
While concrete is a really strong material to begin with, the addition of rebar makes it that much stronger. The experienced crew at Columbia Precast Products follows all engineered plans to the letter to make sure our pieces are as strong as they can be. Manufacture these products in a controlled environment greatly reduces the imperfections that are constant factors when poured in place.
If you need concrete pipes, vaults, water basins, or any other large precast pieces, contact Columbia Precast Products today. Our products are found throughout the Pacific Northwest and we’re ready to help.