The assessment of salt weathering and freeze-thaw effect on strength and durability of Upper Red Formation sandstones

Strength and durability of sandstones and also natural condition effects on these properties, is one of the most important parameters which have to be taken in to consideration in engineering constructions. In this study, the effect of freeze – thaw and salt crystallization phenomena on strength and durability of upper red formation sandstones collected from southern part of Qazvin province was investigated. 9 specimens of sandstones (specified by A, B, C, CG, S, S1, Tr, Min and Sh) were collected from different part of studied area, then their physical and mechanical characteristics were determined. In order to assessing the effect of freeze – thaw on physical and mechanical characteristics of sandstones, 60 cycles of freeze-thaw test was performed. Also in order to investigate the effect of salt crystallization on strength of studied sandstone, sodium sulphate crystallization test (100% weight solution of Na2SO4) was carried out in 20 cycles. Physical and mechanical characteristics of studied sandstones such as point load index, Brazilian tensile strength, wave velocity (Vp) and weight loss were determined after different cycles. For assessing the effect of freeze – thaw and salt crystallization phenomena on durability of sandstones, slake durability test was performed on specimens subjected to mentioned processes and changes occurred in slake durability index in 15 cycle were investigated. Based on results obtained from current study, it could be concluded that in comparison to freeze – thaw, salt crystallization can considerably reduce the strength and durability of sandstones and deteriorate them. Also it was found that index tests such as point load index, Brazilian tensile strength, wave velocity (Vp) and weight loss can predict the behavior of sandstones in different cycles of freeze – thaw and salt crystallization tests.