An investigation on the effect of accelerated weathering on strength and durability of Tertiary sandstones (Qazvin province, Iran)

Damages to stones induced by the action of freeze-thaw and salt crystallization are considered to be of great importance in engineering construction. These processes can influence the strength and durability of porous materials and consequently deteriorate them. In this study, the effects of freeze-thaw (F-T) and salt crystallization (S-C) phenomena on strength and durability of Upper Red Formation sandstones were investigated. Nine specimens of sandstones were collected from different parts of Qazvin area (Iran), and then their physical and mechanical characteristics were determined. To assess the effect of F-T and S-C on physical and mechanical characteristics of sandstones, 60 cycles of F-T test and 20 cycles of S-C test were performed. Physical and mechanical characteristics of these sandstones including wave velocity (V (p)) changes, weight loss (%), point load index and Brazilian tensile strength were determined after different cycles. For assessing the effect of freeze-thaw and salt crystallization phenomena on slake durability index (SDI) of sandstones, slake durability test was performed on specimens subjected to F-T and S-C. Then changes occurred in the SDI after 15 cycles were investigated. Finally, the long-term durability of sandstones against freeze-thaw and salt crystallization action was evaluated using a decay function model. This model postulates a first-order process, and provides some meaningful parameters such as decay constant and half-life for the evaluation of long-term durability of stones. Based on results obtained from current study, it can be concluded that in comparison to freeze-thaw, salt crystallization can considerably reduce the strength and durability of sandstones. Also, parameters obtained from decay function model showed that the rate of integrity loss is different for different weathering processes, and stone durability can be predicted by this method with good accuracy.