Experimental investigation on the performance of Schmidt hammer test in durability assessment of carbonate building stones against freeze–thaw weathering

Abstract

Although Schmidt hammer test has been widely used for assessment of weathering state of rocks, its application for evaluation of rock durability remains rare. This study aims at investigating the performance of the Schmidt hammer test in the durability assessment of carbonate building stones against frost weathering. For this purpose, nine types of carbonate rocks were collected from various quarries of Iran and subjected to a series of tests including determination of petrographical, physical, mechanical, ultrasonic, and rebound hardness properties. Moreover, long-term weathering test of freeze–thaw, up to 100 cycles, were carried out and ultrasonic detection was used to detect the weathering-induced damages of rocks. In ultrasonic detections, ultrasonic parameters of maximum amplitude (Amax), spatial attenuation (αs), and compressional wave velocity (Vp) were determined before and after freeze–thaw tests and then their change rates were determined. The change rates of Amax, αs, and Vp including KA, Kα, and KP, respectively, were considered as the functions of the degree of the frost-induced damages of rocks, and consequently as indications of the rock durability. Results showed that there are close correlations between the Schmidt hammer rebound value (Rn) and KA, Kα, and KP. However, the correlation between Rn and KP was weaker than those between Rn and KA and Kα because of the disproportionate response of Vp to the rock deterioration. It was concluded that the Schmidt hammer test is capable to evaluate the durability of carbonate building stones and can be used for a rapid and onsite evaluation of rock durability at different quarry faces. Hence, it allows selecting more durable rocks for different applications in new constructions and also in replacement works in historical sites.