Admixture Compatibility in Special Concretes

Concrete is no longer produced as a rational mixture of just cement, stone and water. It has matured to a mixture which includes both chemical and mineral admixtures. A mixture of admixtures is used to obtain special concretes that are characterized by very high flow, good cohesion and self-leveling properties, that can be placed underwater without the aid of tremies, that expand and induce compressive stresses or reduce shrinkage, and can be placed and cured at sub-zero temperatures. The use of a mixture of admixtures in a single mix however, raises compatibility issues which need to be rectified prior to field use. Specific incompatibilities between certain admixtures are cited and the manner of resolving such problems discussed.