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Salt weathering is one of the crucial causes of building stone decay. For assessing the durability of stones against salt weathering, a standardised test procedure (EN 12370:2020 Determination of resistance to salt crystallisation) is used: the mass loss of the stone is measured during sodium sulphate crystallisation cycles. Porous, Miocene limestone test specimens collected from the Sóskút quarry (Hungary) were subjected to salt crystallisation cycles in laboratory conditions. The limestone with open porosities of up to 32 V% is composed of ooids, various types of bioclasts and other carbonate grains. Besides the classical measurements of mass changes, the ultrasonic pulse velocity was also recorded after each crystallisation cycle. The ultrasonic pulse velocity values of quarry stones and salt-laden porous limestone specimens were compared. The results indicate that when salt crystal clogs the pores, an increase in ultrasonic pulse velocity is observed. Additional salt crystallisation cycles reduce the pulse velocity. This negative shift in pulse velocities is linked to the opening of micro-cracks, indicating the damage of the studied limestone. Our tests have proved that ultrasonic pulse velocity testing device can detect salt crystallisation damage in a non-destructive way. Its application is recommended in the condition assessment of salt damaged stone heritage structures.

One of the major causes of building stone deterioration is salt crystallization. In this study, changes of ultrasonic pulse velocities of highly porous limestone (obtained from the Sóskút quarry, Hungary) during capillary water absorption, water saturation and during salt crystallization tests were investigated. Capillary water absorption and water saturation tests were carried out according to EN 1925 and EN 13755. In salt crystallization test, the samples were submerged in salt solutions of 14 % Na2SO4 (according to EN 12370) and 5% NaCl solution. The weight changes and ultrasonic pulse velocities of samples were measured after each salt crystallization cycle. During capillary water absorption and water saturation tests, the P and S waves velocities of samples increased as the water content increased. Salt crystallization occurred at the beginning increase of P wave velocity due to the accumulation of salts in the pores. Propagation of P wave was decreased with additional salt crystallization cycles due to the opening of micro-cracks in the samples. The trend of S wave velocity was different from the trend of P wave velocity because it was increasing from non-weathered samples to 50 cycles of salt crystallization. According to the results of the elastic waves measurements and the mass changes, sodium sulphate was found to be more destructive in the weathering of limestone than sodium chloride.

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In this research, the effect of acidic and alkaline chemical solutions on the behavior of loessial soil was investigated. To evaluate the severity of acidity and alkalinity of chemicals, two factors sulfuric acid and sodium hydroxide were used in the pH of 3, 5, 9, 11. In this research, the effect of acidic and alkaline solutions on the collapse potential, shear strength parameters and unconfined compression of collapsible soils were investigated. Experimental tests results showed that acidic solutions with a low pH increase the collapse potential and effective cohesion of soil and decrease effective internal friction angle; on the other hand, alkaline solutions with a high pH decrease the collapse potential and effective cohesion of the soil and increase effective internal friction angle. The results of unconfined compression tests showed that with increasing the acidity and alkalinity in soil, the undrained strength of the soil decreased. SEM test results showed an increase in soil cavities in acidic solution while the soil cavities were fixed in alkaline solution.