Comparison between Salt crystallization weathering test and natural weathering in Mesozoic’s anisotropic rocks, a case study: Arakʾs Calcareous slates, Iran

Salt crystallization can severely damage anisotropic foliated rocks, therefore it is necessary to have an understanding of crystallization process. The present study was conducted to investigate the effect of salt crystallization on Arakʾs calcareous slates, as anisotropic rocks of Mesozoic. To compare salt crystallization weathering (EN 12370 norm was used up to 30 cycles) with natural weathering conditions, some samples were exposed to natural weathering conditions for 12 months. The samples exposed natural condition were tested every 3 months. The measurements show a decrease in physical and strength properties with an increase salt crystallization cycles. At the end of cycle 30, the average weight, ultrasound wave velocity, uniaxial compressive strength (σc), Brazilian tensile strength (σt), and point load index value (Is) of the samples were reduced by 0.32%, 11.52%, 23.72%, 32.15%, and 16.09%, respectively. In comparison, after about 12 months of exposure to natural climatic conditions, these values were 0.18%, 8.84%, 12.64%, 22.23%, and 15.04%, respectively. To establish a relationship between salt crystallization and natural weathering conditions, weathering ratio (WR) was presented. The results of this study can be used to predict the behavior of the anisotropic slates of Arak, upon which the city is planned to be developed.