Macro-microscopically numerical analysis on expansion response of hardened cement paste under external sulfate attack

A macro-microscopically chemo-mechanical model has been proposed to numerically investigate the expansion response of hardened cement paste (HCP) under external sulfate attack (ESA). In this model, a saturated HCP specimen and a representative volume element (RVE) are regarded as macro- and microscopic objects. At the macroscale, the sulfate diffusion and expansion response in HCP are described by using Fick's law and continuum mechanics. At the microscale, the growth of sulfate products and its induced mechanical response in RVE are characterized by using reaction kinetics and microporomechanics. Meanwhile, the macro-micro transition of relevant parameters, such as sulfate concentration, mechanical property, and expansive eigenstrain, is constructed to bridge the relationship between the macro and micro scales. Numerical simulation on expansion response of a HCP cylinder immersed in Na2SO4 solution is performed. Results show that, there exist some differences in the macro- and microscopic expansion responses induced by the growth of sulfate products in the pore, and the microscopic hoop tensile stress is responsible for the initiation and propagation of microcracks in the cement paste. (C) 2019 Elsevier Ltd. All rights reserved.