Concrete Aggregate

Any concrete mix is an attempt to balance cost, placeability and setting time while maintaining the necessary qualities of strength and durability. Ready-mix producers use different ingredients from region to region depending on what's available and what kind of weather the concrete will experience before and after curing.

Coarse aggregate makes up more than 40 percent of a typical concrete mix. The type of aggregate that is available varies in different areas. In the northern parts of North America, round gravel occurs naturally, the result of glacial action during the Ice Ages. Other aggregates available are crushed rock, which is angular in form, and recycled concrete.

So what is the best aggregate to use for stamping applications? To answer this question requires an understanding of aggregate's role in the mix.

A tale of two mixes
There's no such thing as "the best mix" for decorative applications. "There's not necessarily one right way, but there are upper and lower limits for each ingredient, and if you work within them, you'll get better results," says Bruce Chattin, executive director of the Washington Aggregate and Concrete Association. Examining two mixes from decorative concrete contractors in different parts of North America shows how great regional and personal differences can be.