Salt crystallization resistance of four travertine types: integrated petro-physical and microstructural evaluation

Abstract Salt crystallization is a major agent of deterioration in natural stones used in architectural and geotechnical applications. This study evaluated the resistance of four travertine types—Kütahya Red (KRT), Emirdağ Silver (EST), Antalya Noche (ANT), and Karaman Light (KLT)—to salt-induced weathering under controlled laboratory conditions. A comprehensive experimental program was implemented, including physical and mechanical characterization, chemical and mineralogical analyses (XRF, XRD), petrographic examination, and scanning electron microscopy (SEM). Salt crystallization tests were conducted over 15 cycles using Na₂SO₄·10 H₂O, MgSO₄·7 H₂O, NaCl, and KCl solutions. The results indicate that Na₂SO₄ produced the most severe deterioration, particularly in the EST and KLT samples, owing to the high crystallization pressures associated with phase transitions. MgSO₄ induced moderate damage, whereas NaCl and KCl caused limited surface alteration and internal degradation. ANT exhibited the highest resistance, retaining its mechanical strength, low porosity variation, and structural integrity across all salt exposures. In contrast, the EST and KLT experienced marked reductions in real density, ultrasonic velocity, and uniaxial compressive strength, along with increased water absorption and microcrack formation. Despite its initially dense structure, KRT displayed moderate susceptibility to sulfate salts. SEM analysis confirmed salt crystallization within the pore networks and the development of microcracks, particularly in the highly porous samples. These findings emphasize the influence of pore structure, mineralogy, and salt type on the durability of travertine. The results offer practical guidance for the selection and conservation of travertine stones in engineering and architectural settings that are exposed to saline environments.