Micromechanics of intergranular cracking due to anisotropic thermal expansion in calcite marbles

• Material microstructure influences bowing of cladding marble slabs.
• Theoretical model describes progressive bowing of marble slabs under thermal cycles.
• Grain decohesion mechanism due to grain anisotropic thermal expansion.
• Grain geometric and optic orientation from image processing of thin marble sections.
• Simulation of bowing evolution for random distributions of grain orientation.

Marble slabs are frequently used as façade panels to externally cover buildings. In some cases a bowing of such façade panels after a certain time of environmental exposure is experienced. The bowing is generally accompanied by a reduction of strength which increases with increasing degree of bowing. In the present paper, a theoretical model to calculate the progressive bowing of marble slabs submitted to temperature cycles is applied to a specific Carrara marble sample. The marble is investigated by a microscopic analysis of thin sections cut along three orthogonal directions. The digital photographs are treated by an image analysis code which is capable of extracting grain size and shape distributions. In this way the anisotropic microstructure of the marble is quantified and taken into account in the numerical analyses. The influence of size distribution of grains as well as of their distribution of optic axis orientation on the slab bowing is discussed with the attempt of offering a quantitative tool for a better understanding of in situ bowing measurements.