Role of cement paste composition on the self induced stress in early-age mortars: Application of the Cosserat size number

Highlight
• A multi-scale approach based upon the hygro-Cosserat theory has been proposed.
• The Cosserat size effect number is defined as the ratio between a characteristic length scale and a representative volume elementary length of the material.
• The self-induced stress field at very early-age and risk of micro-cracking are particularly investigated.

The self-induced stress in mortars caused by autogenous shrinkage phenomenon at very early age has been investigated by taking advantage of the experimental results and application of hygro-Cosserat theory. Three cement matrices, prepared with three different types of cement, have been considered to analyze the role of cement paste composition on the development of these initial stresses surrounding the aggregates. The induced bulk deformations around the aggregates have been thereafter scrutinized by means of hygro-Cosserat elasticity taking into account the size effect in an explicit manner and a newly defined parameter called Cosserat size effect number (CS). By taking advantage of the autogenous shrinkage experiments on the cement pastes, the parallel time-dependent finite element analyses have been achieved considering the aggregate-to-cement ratio. The aforementioned parameters are put into practice to create an analytical pseudo-stochastic geometry using a spherical-packing algorithm. The numerical outcomes were analyzed and compared to the experimental outcomes coming from the Scanning Electronic Microscopy observations at 48 h after hydration.

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