Performance of Spanish white Macael marble exposed to narrow- and medium-range temperature cycling

摘要

White marble specimens from Macael in the Spanish province of Almeria were exposed to narrow- (50/ -20 ℃) and medium- (100/-20 ℃ and 75/-20 °℃) range thermal stress cycles. The effects were monitored with ultrasound techniques. Ultrasound velocity declined considerably in samples subjected to 100/-20 ℃ cycles, more moderately when the range was 75/-20 ℃ and insignificantly when it was narrowed to 50/-20 ℃. All variations were recorded in the first five to seven cycles, with values flattening thereafter. The Schmidt hardness and compression test results concurred with the ultrasound findings. Petrographic and scanning electron microscope (SEM) imaging revealed some very superficial granular decohesion in the specimens subjected to forty 100/-20 ℃ cycles. The concurrent results from compression testing on the one hand and surface hardness and ultrasound measurements on the other confirmed the validity of the latter two nondestructive techniques (NDT) for determining the effects of thermal stress cycling on stone mechanical strength.