A Beginner’s Guide to Concrete
Concrete is composed of two main materials, cement and aggregate. Together they make up what is known as a concrete mix. Cement is like the glue in the concrete; it holds the aggregate together. The aggregate makes up the bulk of a concrete mix, and can be made of small stones or even sand. When water is added to the mix, the cement in the concrete mix reacts with the water to form a chemical reaction.
You can work with the concrete during the beginning stages of the chemical reaction. Concrete does not dry; it hardens or cures. This is why concrete workers must work fast during the first stages of the chemical reaction. If they wait, the concrete will continue to harden, no matter how much more water is added to the mix. Construction professionals know that by adding a small amount of sugar to the mix, the chemical reaction that causes concrete to harden can be slowed. Concrete actually cures better underwater.
When evaluating the strength of materials, construction professionals often talk about a material’s strength in compression and in tension. When something is in compression, it means that the force it must withstand is pushing towards the center of the object. When a material is in tension, the force is pulling away from the center of the object. Concrete has very little strength in tension, but enormous strength in compression. It actually takes concrete 28 days to cure before it can be tested to determine if it reaches an engineer’s specifications.
This is why steel reinforced concrete was such an important discovery for the building industry. By using steel on the inside of concrete floors and beams, the concrete could withstand more tension. Therefore it could be used for a variety of other construction purposes. Although it is often considered a rough material, concrete can be used for interior work as well. Many buildings have exposed their concrete floors to seal and stain them in place of other traditional interior floor materials.
Architects and material’s specialists have long been concerned with the effect that concrete has on the environment. One small specification that has lead to enormous waste savings in the industry is using fly ash in concrete. Fly ash is created through the burning of coal. When added to concrete, in place of some of the Portland cement required, the concrete actually gains strength. The construction industry estimates that using fly ash in concrete can represent a savings of millions of tons of waste each year.
Concrete has become an increasingly prevalent feature in our local environments. By becoming informed about the uses and composition of this versatile material you can better understand the world around you.
