The Effect of Salt Weathering and Water Absorption on the Ultrasonic Pulse Velocities of Highly Porous Limestone

Abstract

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.