The effect of freeze-thaw cycles performed with salt solutions (NaCl and Na2SO4) on carbonate building stones

Three types of carbonate building stones from Turkey were selected for testing their physical and mechanical properties after freeze-thaw cycles with salt solutions. In this study, two types of basic experimental studies were conducted. First, material characterization was performed. For this purpose, chemical (XRF) and mineralogical-petrographic (polarized microscope, XRD, SEM analysis) tests, pore size distribution (MIP), and physico-mechanical tests were performed on the tested samples. The aging test was conducted by applying immersion-freeze-thaw cycles with water, sodium sulfate, and sodium chloride solutions. In the freeze-thaw experiment, the water absorption, uniaxial compressive strength, and ultrasonic wave measurement values of all examined samples increased in the 10, 20, 30, and 40 cycles. At the end of the 40 cycles for silver travertine, water absorption decreased by 1.93% and 14.95% for NaCl and Na2SO4 solutions, and for Burdur limestone, the water absorption decreased by 7.24% and 10.39%, respectively. The presence of pores with a diameter of fewer than 0.1 µm in the silver travertine (7.34%) and Burdur limestone (43.75%) also directly affected this. After 10, 20, 30, and 40 freeze-thaw cycles with Na2SO4 solution, the ultrasonic pulse velocity (UPV) values of the travertine samples decreased by 11.95%, 26.24%, 34.85%, and 42.78%, respectively. Uniaxial compressive strength (UCS) values of all tested samples for 10, 20, 30, and 40 freeze-thaw cycles decreased gradually in all solutions (water, Na2SO4, and NaCl). These results were realized due to the water in the pores turning into crystallization pressure caused by the ice and salt crystals, and forming new micro-cracks.