Because I m covering the basics here, I may oversimplify a few points. Experts in the industry could point out exceptions to many of the general statements I may make. But by and large, the ideas I m about to explain hold true. Components of Concrete Figure 1. Rock and sand make up the bulk of a batch of residential concrete.
Good aggregate is actually stronger than cement, and much cheaper.
The main idea when you make concrete is to use as much aggregate as practical, with just enough cement paste to glue the mix together. This magnified photo of a slice of concrete shows a well-graded aggregate mix locked into a matrix of hardened cement paste. This helps to hold down costs, improve strength, and minimize shrinkage of the concrete. For one thing, it helps reduce shrinkage. A lot of shrinkage happens when water evaporates out of the cement paste which means the more stone and sand there is, the less overall shrinkage.