Impact of Simulated Rainfall on Engineering Properties of Carbonate Building Stones

This study evaluates the effects of both simulated natural rainfalls with pH = 7 and acid nitric rainfalls with pH values of 5 and 3 on the engineering behaviors of seven carbonate building stones including three travertines and four limestones collected from some quarries in Iran. They were subjected to 15 wetting–drying cycles of the simulated rainfalls provided by rainfall simulating test apparatus in the laboratory. The changes in some stone properties namely weight, apparent color and surface texture, mineral content, dry unit weight, porosity, P-wave velocity, and surface Vickers hardness were determined by calculating different loss indices after each cycle of the test. The maximum values of WLI, DLI, WVLI, and HVLI are equal to 99.97%, 99.92%, 94.49%, and 76.10%, at pH = 7, respectively. The minimum values of these indices are equal to 98.60%, 98.82%, 74.08, and 45.18%, at pH = 3, respectively. The maximum and minimum values of PLI are obtained for the samples of MT at pH = 7 and SL at pH = 3 equal to 88.88% and 16.13%, respectively. The mentioned properties are highly affected by the simulated rainfalls, especially acidic ones. The properties are linearly or nonlinearly decreased depending on the pH value, except porosity which is increased. The change of the above-mentioned properties for the travertines is higher than the limestones in all test solutions. As an important finding of the research, it was revealed that weight loss, and dry unite weight are related to the weight changes of the stones, and porosity, wave velocity and Vickers hardness are related to the volume changes during the tests. The parameters of the second group are more affected by the rainfalls than the parameters of the first group.