The Science of Concrete Mixes

Although it seems like a simple formula — cement, sand and water — every decorative concrete contractor knows it’s far from it. Decorative concrete mixes are often altered to lend the contractor some control over durability, efflorescence, its response to high or low temperatures and seemingly a million other factors. The problem is how altering the mix changes can be handled for various decorative techniques. What’s a contractor to do?

Let’s say you’re starting a large stamped concrete project. At first, the concrete is exactly the right consistency to accept a well-defined imprint. But as the project goes on, the concrete starts drying out.

“If you order a full truckload of concrete, that means all of it is ready to stamp at the same time, so you need to have enough people and enough stamps to be able to do it all within that window of time,” says Gabriel Ojeda, president of Fritz-Pak Corp. “Often, they’ll start at one end, and by the time they reach the opposite end, it’s too hard already.”