Microstructure-based three-dimensional study of sulfate deterioration in variably saturated concrete

Sulfates from external or internal sources can react spontaneously with the alumina components of concrete and generate expansive ettringite gel, causing strength reduction of concrete. The multi-chemophysics nature of sulfate attack and the heterogeneous matrix of concrete collectively challenge the study of sulfate attack using continuum mechanics. This study presents a microstructure-based multi-chemophysics model for investigating the mechanisms of sulfate attack in concrete, in which the key processes involved in sulfate deterioration are coupled across the three-dimensional microstructure of concrete reconstructed using X-ray computed tomography. Theories of diffusion reaction and continuous damage are synchronized in the multi-inclusion concrete matrix and solved concurrently using finite element analysis. Results show that a latency period exists before sulfate deterioration and that the variably-saturated condition of concrete tends to prompt the occurrence and severity of sulfate attack. The methodologies developed herein benefit the evaluation of novel materials and methods for making durable concrete.