A comparative assessment of the effects of sodium and magnesium sulfates on the physico-mechanical characteristics of Abasabad Travertine, Mahallat, Urumieh-Dokhtar Magmatic Belt, Iran

摘要

As two of the most abundant and destructive salts in nature, sodium and magnesium sulfates can affect the physico-mechani-cal characteristics of stones and, thus, their durability. In this paper, the effects of these salts are compared on some physico-mechanical characteristics of travertine, including point load index (PLI), Brazilian tensile strength (BTS), P-wave velocity (V_p), and porosity (n). For this purpose, a travertine sample was obtained from the Abasabad quarry in Mahallat (central Iran) and transferred to the laboratory. Next, salt crystallization tests in sodium and magnesium sulfate solutions were carried out for up to 30 cycles. Afterward, PLI, BTS, Vp, and n of the sample were measured after every 5 cycles of the salt crystallization test. The decay constant (λ), half-time (N_(1/2)), and the rate of loss (RL) were used to compare the effects of sodium and magnesium sulfates on the PLI, BTS, Vp, and n of the sample. Here, λ and N_(1/2) were obtained from regression curves developed between the measured PLI, BTS, Vp, and n with cycles of salt crystallization tests. The RL and N_(1/2) of the PLI, BTS, Vp, and n show that the durability of the sample subjected to the salt crystallization tests in sodium and magnesium sulfates was different. The results indicate that the effect of sodium sulfate on the PLI, BTS, Vp, and n of the sample was more severe than that of magnesium sulfate. Generally, PLI, BTS, Vp, and n not only indicate visible changes occurring in the sample due to salt crystallization action (e.g., mass loss, powdering, pitting, and detachments) but also show its inner microstructural modifications due to pores development. In addition, the PLI, BTS, Vp, and n can be good indicators for preventive and monitoring purposes and suitable tools for uncovering the initial stages of building stones' deterioration subjected to salt crystallization action. These parameters are vital when it is not possible to detect the changes in the inner structure of building stones with the naked eye.