A Validated Multiscale Model Linking Microstructural Features of Fired Clay Brick to its Macroscopic Multiaxial Strength

Abstract

Given the popularity of fired clay bricks in increasingly taller buildings, as well as the large variety of raw materials, additives, tempers, and production technology, microstructure-based modeling of the brick strength is essential. This paper aims at linking the microstructural features of bricks, i.e. the volume, shape, and size of mineral phases, pores, and the glassy binding matrix in between, to the multiaxial failure behavior of bricks. Therefore, a continuum micromechanics multiscale model, developed originally for stiffness and thermal conductivity upscaling, is adopted and complemented with a Mohr–Coulomb failure criterion at the microscale. By micromechanics-based downscaling of uniaxial brick strength tests, quantitative insights into the strength of the binding matrix are obtained for the first time. After successful nanoindentation-based validation of the identified micro-strength, the model is used for predicting the macroscopic multiaxial brick strength, which in turn is successfully validated against independent bi- and triaxial compressive strength test results.