ABSTRACT
The overall mole ratio of S03 to C3A in most cements is far below 3; typical values range from about 0.7 to 1.2. Thus, according to the classical view of portland cement hydration, the primary ettringite that is formed in the early stage of cement hydration tends to be converted to monosulfate according to the reaction:
The primary ettringite that crystallizes out early in the hydration process has no known adverse effect on concrete properties. However, ettringite generated within a rigid, hardened concrete, due for example to sulfate attack or to extensive delayed ettringite formation (DEF) may produce expansion and cracking.
