Influence of thermal and cooling cycles on the mechanical properties of building stones with carbonate texture

Rocks are frequently subjected to environmental stress, with one of the most prevalent being heating and cooling cycles. Rocks with calcareous origin, in particular, show significant responses to fluctuations in temperature. This study investigates the mechanical characteristics of two types of carbonate rocks , travertine and marble, under various temperature conditions (+300 °C, +100 °C, ambient temperature, -10 °C, and -30 °C). Key property assessed include uniaxial compressive strength , three-point bending strength , Brazilian tensile strength , and pressure wave velocity. These tests were conducted across different thermal cycles (one and three) to observe the effects of repeated temperature fluctuations. Advanced analytical techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and CT scans were employed. Additionally, image processing techniques were used to detect and quantify cracks, analyze crack areas, and measure strain in each particle of the samples. The results demonstrated that tensile and flexural strength decreased with rising temperatures and increased as temperatures fell. However, after exposure to +100 °C, the compressive strength of travertine nearly doubled, while in marble, it increased by 1.3 times. Following exposure to +300 °C and the repetition of heating-cooling cycles, the compressive strength declined compared to the +100 °C condition. Analysis using XRD, XRF, SEM, and CT-Scan revealed significant effects from the presence of calcite , moisture within the sample, and the formation of microcracks on the mechanical properties. Travertine, with its sedimentary and porous texture, exhibited a greater response to these changes than marble.