A Beginner's Guide to Concrete

Concrete is one of the most commonly used construction materials used in the world today. Every year, millions and millions of feet are poured and used for foundations, industrial applications, and even sidewalks. If you think concrete and cement are terms that can be interchanged, or that concrete needs to dry, read on for some tips about this building material.

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.