To designers, architectural concrete is a magnificent art form. To specifiers, it is a stimulating challenge to their interpretive powers. For contractors, this art form provides perhaps their most outstanding opportunity to display pure craftsmanship on a truly monumental scale. But as in any complex undertaking, all must work together to ensure that the final results meet everyone's expectations. Each one must understand which options the others have at every step from conception to completion. We have been able to cooperate with designers and specifiers to overcome several pitfalls common to most architectural concrete projects. These are scabbing from grout or paste leakage, color variation, and bugholes or entrapped air.
There are at least five areas in which specifiers can definitely influence the quality of architectural concrete surfaces. These require: that joints in formwork be sealed by calking or gaskets; that concrete in forms be double-vibrated; that formwork be built and sealed rigidly enough to remain sealed when double-vibrated; that formwork not be lapped over uneven architectural concrete surfaces (this generally requires help from designers); and that an 8-to-2 ratio of coarse to fine aggregate, with a proportionally greater cement content, be specified for structural exposed-aggregate concrete.