Impact of chemical weathering on microstructures and mechanical properties of karstic limestone

Abstract

Dissolution and chemical weathering of carbonate rocks have complex effects on their mechanical properties, accelerating their rate of deterioration that can lead to early failure under external stresses. To investigate the effects of acidic solutions on the mechanical properties of inherently low-porosity karstic limestone, compression tests were performed on sound and weathered samples exposed to different corrosive environments and for different durations. The tested samples exhibited a general increase in porosity and decrease in peak strength and Young's modulus for higher acidity and exposure duration. To establish links between these mechanical changes and those at the micro-scale, microstructures and mechanisms of deformation were also studied. As indicators of the sample degradation, the distribution, orientation and intensity of the fractures in the tested samples and their twinning density were used. Based on these parameters, it was found that chemical erosion influences microcrack propagation, orientation, distribution and intensity, due to modification of the competence contrast between the constituents of the rock. These effects significantly influence the semi-brittle behaviour of the samples, including the distribution and intensity of microcracking and crystal plasticity.