Correlation between Schmidt Hammer Hardness, Strength Properties and Mineral Compositions of Sulfate Rocks

The use of non-destructive testing methods is a well-known practice in civil engineering studies, Geotechnics, engineering geology, and building inspection. The Schmidt Hammer Rebound Test (SHRT) is the most prevalent of these and can be performed both in the field on rock outcrops and in the laboratory on the rock blocks and cores. During this investigation, by collecting sulfate rock blocks from the 4 under-construction, reservoir dam sites in Iran, experiments such as petrographic analysis, Uniaxial Compressive Test (UCT), and SHRT (both on rock blocks and cylindrical rock cores) were carried. Furthermore, the regression analysis of the results was performed. The investigations carried out in this study yielded several significant results. The use of ISRM criterion results in larger values of the SHRTs (N-Values) than ASTM standard criterion. In a rock consisting of gypsum-anhydrite, N-Value advances with increasing the amount of anhydrite. The presence of clay minerals in sulfate rocks can lessen the Schmidt hammer hardness. There were different correlations between the results of the SHRT and the sulfate rocks' strength properties, depending on the mineral composition of the rocks. Subsequently, because of the difficulty and time-consuming process of drying and saturating of sulfate rock samples, rock surface wetting can lead to an estimation of the saturated Uniaxial Compressive Strength (UCS) of the sulfate rocks.