Setting and hardening concrete

Cement hydration is an exothermic, heat-activated reaction. In solid (or heat-insulated) parts, exothermicity results in a rise in temperature which, in some areas, can reach around 50 degrees. In thinner parts, thermo-activation can be used, on site and especially in prefabrication plants, to accelerate resistance growth. After a review of the main thermal properties of cements and concretes, this article presents the three main thermomechanical effects that are important to the engineer, namely :

• the risks of cracking in massive structures or structures with complex geometries, and the numerical models that can be used to analyze these risks (and, where appropriate, to choose between techniques to limit crack openings);

• industrial techniques for accelerating the growth of a material's mechanical strength on site or in the factory, using various types of heat treatment (thermomaturation);

• on-site methods which, in the hours following concrete setting, enable us to estimate the mechanical strength acquired at selected points in the structure, based on temperature recordings in the structure itself (maturometry).