Coefficient of thermal expansion of cement paste and concrete: Mechanisms of moisture interaction

Crack sensitivity calculations for young concrete are strongly influenced by the coefficient of thermal expansion (CTE) values for the concrete. This paper demonstrates the strong effect of moisture content on CTE, and discusses the mechanism(s) based on experimental results on mature cement paste. The temperature variation of the relative humidity (RH) exerted by the pore water is quantified and used to explain the high CTE of partly dried specimens. The relevance for early age crack sensitivity is that the concrete should be kept as wet as possible. This minimizes CTE and will largely eliminate autogenous shrinkage. However, trustworthy procedures to separate autogenous- and thermal deformations require a better fundamental understanding of moisture effects and the nature of delayed deformations.