Q: What is the difference between cast stone and precast concrete? Or is there a difference?

A.: The American Concrete Institute's glossary, Cement and Concrete Terminology (ACI 116R-85) defines cast stone as concrete or mortar cast into blocks or small slabs in special molds so as to resemble natural building stone. In the same glossary, precast concrete is defined as concrete cast elsewhere than its final position.

But W. N. Russell III, executive director of the Cast Stone Institute, says those definitions aren't complete enough. He says cast stone is a highly refined architectural precast concrete building stone manufactured to simulate natural cut building stone. The most significant difference between architectural precast concrete and cast stone is that cast stone isn't permitted to contain bugholes or air voids and must have a fine-grained texture. The texture is normally achieved by acid etching. Cast stone is normally used as a masonry product and is included in the masonry section (04435) of standard specifications. Architectural concrete is included in the precast concrete section (03450) in specifications.