Thermal deformations

Concrete elements at early age experience temperature increase due to the exothermic nature of cement hydration. Further cooling leads to a contraction of hardened concrete and buildup of thermal stresses. This is often leading to macro-cracking that can seriously impair durability and serviceability of the structures.
Prediction of thermal deformations requires precise measurements of coefficient of thermal expansion (CTE). Studying the CTE is especially challenging at early ages (first days of hydration), due to ongoing evolution of material properties (in particular mechanical properties, internal RH). In the case of low w/c cement pastes, the thermal deformations occur simultaneously with autogenous shrinkage, calling for special measures for separating the two types of deformations.
In addition to the measurements of CTE with linear and volumetric methods (buoyancy method), the mechanisms affecting thermal deformations are studied, in particular effects of temperature on internal RH (water activity and sorption measurements at changing temperature), water redistribution in the microstructure (NMR studies), delayed thermal deformations.