Prediction of elastic properties of cement pastes at early ages

Cementitious materials are known to be sensitive to cracking at early ages. During the first days which follow the contact between water and cement, the system is continuously evolving, as its mechanical characteristics follow a rapid rate of change and the material is prone to cracking. One of the parameters that highly influence the behavior of the material at early ages is the Young's modulus. Analytical calculations, based on existing homogenization models and finite element calculations, applied on a discrete generated microstructure, are first considered in order to predict the elastic properties of the material. As long as the cohesive role played by the hydrates is not taken into account, results at early age remain inaccurate, especially for low watercement ratios. The need of modeling an intrinsic characteristic of cementitious materials setting arises. An approach, based on percolation and on the so-called burning algorithm, which takes into account explicitly the bonding role of hydrates and reveals a degree of hydration threshold below which the rigidity of the material is negligible, is therefore proposed. The evolution of the elastic characteristics is obtained by applying the previous computation methods to the percolation cluster given by the burning algorithm.

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