A multi-scales approach for the physico-chemical deformations of solidifying cement-based materials

At early stages of hydration, solidifying cementitious systems exhibit dimensionalvariations caused by their thermal, hydrous, chemical and microstructural evolutions. Ifrestrained, these deformations can induce the development of internal stresses high enough togenerate cracking of the hardening material. This study focuses on early-age autogenousstrain of cement-based materials, which develops following two main processes: Le Chateliercontraction (also called chemical shrinkage) and self-desiccation shrinkage. Chemicalshrinkage results from the difference of absolute density between reactants (anhydrous cementand water) and hydration products. Early-age self-desiccation shrinkage is generally attributedto the development of a negative capillary pressure in the porous network related to the waterconsumption by the hydration reactions. The purpose of this research work is to propose amultiscale approach to model the rate of autogenous shrinkage of cement-based materials atvery early-age, between 0 and 48h. Le Chatelier contraction is computed from the chemicalequations of hydration and the specific volume of each phase, whereas a homogenizationmethod based on the self-consistent scheme is applied to calculate the self-desiccationshrinkage. Computed results are discussed and analyzed. Good agreements betweenexperiments and simulations are achieved and a sensitivity study is performed to assess theinfluence of the cement fineness and the fraction of granular inclusion on early-ageautogenous strain