Coloring books: Color the Cement Truck: Page 1 Page 2 Page 3 Page 4

The Life and Times of a Cubic Yard of Concrete
by Con Crete

Do you know me? Yes, you might THINK you know me, but do you REALLY know me? Sure, you can walk on me, ride your bike on me, walk your dog on me (what a mess), you even park your car on me (ouch!) But what am I? Am I just a gray, hard flat surface to use and abuse? Perhaps I need to introduce myself in more detail.

Many things are involved in my creation. A material called "cement" must be manufactured first. Cement and concrete are not the same thing. Cement is just one ingredient in concrete, that holds the other ingredients together. Cement itself is made from several things, primarily limestone. When the limestone is ground up into very fine powder and combined with gypsum and some other materials, it becomes a material that actually "glues" the concrete together. Without cement, concrete would just be a muddy mess.

The most abundant ingredients of concrete are aggregates, which are basically sand and stone. Aggregates make up about 70% of concrete's volume. The larger pieces of aggregate are called "coarse aggregate". Some examples of coarse aggregate are gravel, limestone, and slag. If it looks like a rock, it's coarse aggregate. The "fine aggregate" is usually sand, just like the brown sand used in sand boxes.

To blend the cement, sand and stone, we need to mix them in a concrete mixer. Some concrete plants have large mixers in their batch plants, but most concrete is mixed in concrete mixer trucks. In order to make the mixture into concrete, you must add water. Clean water must be used - if you can't drink it, don't use it for cement. When the water is added to the blended materiel, it reacts with the cement. This reaction is called hydration. Hydration is what causes the concrete to eventually harden, or "set up".

While the aggregate makes up about 70% of a cubic yard of concrete, the Cement only makes up about 10% of the volume. The water needed to properly mix the concrete and hydrate the cement is about 15% of the volume. The remainder of the composition is actually air. Very small, microscopic air bubbles are created by adding a chemical to the mix. These bubbles help the concrete to be more durable when exposed to freezing temperatures.

Now that all the ingredients are mixed together, I have become Concrete. They deliver me to the customer in a concrete mixer truck, and pour me into forms, or molds. Then they smooth me out until I'm level, and finish the surface to the desired finish. All of this work MUST be done fairly quickly, as the concrete starts to set up (harden) within a couple of hours, even faster in hot weather. Once the concrete sets up, it's very important to keep moisture in the concrete. The moisture will continue to react with the cement, which continues to make the concrete harder and more durable.

In areas where cold, freezing weather is present, the concrete will probably have salt or other de-icing agents applied to it. Whether it is purposely placed on the concrete, or just drips off of parked cars, salt can do a great deal of damage to my surface. To help protect me from these damaging chemicals, you need to regularly seal my surface with a high quality concrete sealer. It works on concrete almost like waxing your car protects its finish. Take care of me, seal my surface regularly, keep those nasty de-icers off of me, and I'll be there for you for many years to come.

© 2015 Riverside Builders Supply Inc.

Back to Top