Water effect on subcritical crack growth and fracture behavior of marble

Understanding the fracture properties and subcritical crack growth of rocks in aqueous environments is significant for the effective assessment of the long-term stability of the masonry buildings, cultural heritage structures, and art sculptures. We use double torsion techniques to systematically investigate the subcritical crack growth behavior of marble under air, fluid, saturated and saturated + fluid test conditions. In the fluid condition and the saturated + fluid condition, the load reductions during the relaxation test are larger than other conditions, reaching 12.81% and 12.26%, respectively. There is a water-weakening effect on both the subcritical crack growth index (SCI) and KIC, but the water weakening sensitivity in KIC is lower than that of SCI. Compared to the air condition, the SCI values of the marble decreased by 43.69% under the fluid condition, 17.64% under the saturated condition, and 38.09 % under the saturated + fluid condition, respectively. The introduction of water during the relaxation test results in an immediate increase in the crack velocity and the major principal strain of the specimen, as evidenced by the appearance of the IV region on the KI-V curve. Scanning electron microscope images show that the most triangular pits and dissolution pits are present in the marble under fluid and saturated + fluid conditions, leading to a more pronounced deterioration of the mechanical properties. The test results highlight the significant impact of water on subcritical crack growth in marble. In particular, during rainfall, both dry and saturated marble masonry buildings are more prone to cracking due to the introduction of water.