Ranking of Five Salt Weathering Regimes Conducted on Oolitic Limestone Using Two Sulfates

Abstract

The weathering of a given rock has been previously reported to be a result of many processes acting on it but one of them should dominate based on the prevailing environmental conditions at this site. In case of salt weathering, it has been reported to be prevailing and destructive for a wide range of materials but its regime has received little attention particularly ranking of salt weathering regimes on a given rock. Not only that but also the same salt differs in its impact on a given rock rather than other one based on the rock's properties and the acting weathering regime. The current study aims to compare and rank rock's damage by salts at five weathering regimes (that imitate all possible regimes in the world particularly in the Middle-East and Europe) using sodium and magnesium sulfates. The rock's pore size distribution "PSD" has been measured using mercury intrusion porosometry "MIP" before and after conducting the artificial weathering to find out rock's Salt Susceptibility Index "SSI" to be correlated with rock's damage visually recorded and numerically expressed by samples' weight loss at the end of each regime. The rock's weathering on micro-scale as well as salt's form and distribution have been investigated using scanning electron microscope "SEM" along profiles scanned on nano-scale from sample's surface to its deep inside. This is finally to rank weathering regimes on one hand and to rank the severity of these salts on the other hand. Also, to find out the rock's pore size that controls rock's susceptibility to salt weathering. This study enables a best choice for limits of rock properties in case of its use for reconstruction of archaeological sites at salty environments with regimes as that conducted in the current study. The results indicated that SCI-S15 is the most aggressive weathering regime, particularly with sodium sulfate, followed by CPI 12-12, particularly with sodium sulfate, but the least has been recorded for samples exposed to CPI, particularly with magnesium sulfate, CPI-CC, particularly with sodium sulfate, and CPI-HC, with both salts. Sodium sulfate is almost more destructive than magnesium sulfate for such rock but to have a clear view in ranking these two salts they must be applied for other facies in another study.