Effect of water on the strength and microstructure of Carrara marble axially compressed at high temperature

In this study, we aimed to (i) answer the question if water affects the strength of marble deforming at high temperature and (ii) establish criteria that allow assessment of the role of water in microstructure development in marble. Samples of Carrara marble were axially compressed at temperatures ranging 600-1000 °C and strain rate ∼10−5 s−1, with or without addition of 0.4-2.1 wt% water. Water-added samples were found to be slightly weaker than dry samples. Microstructurally, all samples showed grain flattening and twinning at 600 °C and dynamic recrystallization dominated by grain boundary migration at higher temperature. Grain boundaries in wet samples showed isolated or semi-continuous remnants of fluid pockets. The average grain roundness R and fractal dimension D relating grain diameter d and grain perimeter P (P∝dD) for wet recrystallized samples were systematically lower than for dry samples. At 600 °C, high pore fluid pressure probably enhanced dilatation of wet samples and helped grain boundary sliding (GBS), thereby lowering the strength. At higher temperature, fluid-enhanced grain boundary migration served as a recovery process, reducing the contribution of GBS to creep. Overall, water has little effect on strength and microstructure of marble experimentally deformed at high temperature.