A multiscale approach to estimate the interfacial transition zone effects on the temperature rise of heterogeneous cement based materials at early age

This paper presents a novel numerical model for solving the thermochemical problem of hydration of cement paste and its combination with mortar aggregates, with the aim of determining the temperature rise in massive structures considering adiabatic and semi -adiabatic problems considering the Interfacial Transition Zone (ITZ) effects. The model presented here takes advantage of recent advances in the computer -aided homogenization technique known as FE2 to fully model the massive structure based on the description of the microstructure. Each integration point of the massive structure is associated with an RVE whose matrix consists of cement paste and the fillers (inhomogeneities) of sand particles, which also takes into account the Interfacial Transition Zone (ITZ) effects, given by a thermal resistance. The presented strategy allows the prediction of the macroscale thermal behavior based only on the microscale thermal properties and heat generation. Despite the large variability/uncertainty in cement and mortar (chemical-physical) mixes, thermal properties, and ITZ effects, a validation study is also performed to show the adequacy of the proposed approach. Macroscale and microscale predictions are presented for mortar recipes and for different boundary conditions unveiling the combined effect of convection, volume fractions of sand in mortars, and ITZ on the predicted temperature and hydration evolution, showing that an imperfect interface between the matrix and the fillers causes a faster hydration reaction in the cement paste.