What is the difference between precast concrete copings and cast stone copings?
Although the terms are sometimes used interchangeably, the materials are different. The primary difference relates to the consistency of the concrete when these elements are made. In cast stone, the concrete mix is very dry and contains no coarse aggregate. This mix is packed into the forms and pressed. The finished product looks very much like natural limestone. Cast stone can be colored and textured to provide a variety of appearances. Cast stone is difficult to air-entrain because some air will be squeezed out when cast stone is pressed into forms. Air-entraining improves the durability of concrete products exposed to cyclic freezing and thawing when wet. Cast stone manufacturers say their products are durable because of the low slump and the consequent low water-to-cement ratio. This gives cast stone a high compressive strength and durability in freeze-thaw environments. Precast concrete is formed with a low-slump fluid concrete that is poured into forms. Precast concrete also can be colored and textured to provide a variety of different appearances. Precast concrete products can be easily air-entrained, improving their durability.