Decorative Concrete Expert

Reinforcement and mix design
Most precast contractors use reinforcement. Wire mesh, fiber reinforcement and rebar are all used with this process, depending on the thickness of the countertop and the project specifics.

But concrete countertops are not the same as sidewalks poured on-grade. Countertops have different reinforcement requirements, Girard points out. "The topic of reinforcing is one of the most misunderstood in the industry today. It's basically an engineering problem - you need primary and secondary reinforcement with the right materials and in the right places to ensure proper compressive, tensile and flexural strength."

With precast concrete countertops, aesthetics goes hand-in-hand with structural performance, so any old concrete mix won't do.

"Choice of ingredients is highly dependent on the desired workability, final appearance and structural performance. I designed my mix to have a high early strength in order to speed fabrication and deliver in a timely fashion," says Girard, who designed his mix to be cast on a Friday and stripped on a Monday. "I use Type I Portland cement, sand as aggregate, integral powder pigments and superplasticizer in a very dry zeroslump mix."

Rhodes also uses a thicker, drier, zero-slump mix when he is trying to achieve his "pressed finish." With this technique, handfuls of the thick concrete are hand-pressed into the mold. The haphazard voids thus created are intentional, and are filled later with a slurry mix.