Abrasivity assessment of Triassic limestone and volcaniclastic sandstone in Mae Mon Basin, northern Thailand: comparison between RAI and CAI

The ability of rocks to wear tools used for ground excavation, tunneling, or drilling, is referred to as rock abrasivity. There are a variety of testing methods to estimate rock abrasiveness, ranging from microscopic to pilot scales. This study tests the abrasivity of selected sedimentary rocks observed in the Mae Moh Basin, northern Thailand, using the two abrasivity testing methods, including RAI (rock abrasivity index) and CAI (CERCHAR abrasivity index). The method of RAI involves mineralogical analysis coupling with the uniaxial compressive strength tests of the rock. The mineral assemblage formed in the rock and its content are microscopically observed under a conventional microscope. Each mineral is also compared to quartz in terms of hardness. The CAI method, on the other hand, observes the wear of a steel stylus tip after direct scratching on a rock surface under a systematic setup. The diameter change of the eroded tip is subsequently used for the calculation of the CAI. The results show that the limestone exhibits an RAI of 2.12, indicating it is not abrasive, and a CAI of 1.24, which indicates it has medium abrasivity. The volcaniclastic sandstone exhibits an RAI of 30.88, indicating medium abrasivity, whereas its CAI is 2.72, which indicates high abrasivity. The calculated CAI provides a more abrasive indicator than the RAI and significantly increases with the increasing equivalent quartz content. The findings of this study support a strategy for rock abrasivity assessment and tool wear prediction, which is essential in the fields of mining and georesource engineering.