What kind of form liner is used to produce a dimpled surface?
Although a plastic form liner may be available for producing a dimpled surface (if not, one could be custom made), dimpled surfaces are usually prepared by precasting. The base of the form is covered with a layer of crushed stone or gravel and a sheet of polyethylene film laid over it. Aggregate of 2 inches or more in diameter is usually used depending on the size of dimples wanted. Steel is set in the form and the concrete placed over the polyethylene. The dimpled surface is visible when the form has been stripped and the panel lifted or tilted up.