The Effect of Salt Crystallization on Degradation of Limestones Used as Heritage Building Stone in Lorestan, Iran

The carbonate rocks found in the Lorestan province of Iran are widely used as building materials in historical bridges. Unfortunately, the presence of salt decay poses a significant threat to the integrity of these building stones, often resulting in extensive damage to our architectural heritage. This study investigates the behavior of two carbonate building stones, Asmari limestone and Talezang limestone, against salt crystallization weathering. To achieve this, 30 salt crystallization test cycles were conducted in Na₂SO₄ and MgSO₄ solutions for each type of limestone. After every 10 cycles, the visual changes and the physico-mechanical properties of the salt-weathered samples were characterized by Damage Rate (DR) of Mass (m), P-wave velocity (V_p), Porosity (n), and Point Load Index (PLI). SEM observations were conducted to observe the structural changes of the building stones following the salt crystallization tests. The visual observations of the weathered specimens before rinsing indicate that Na₂SO₄ is more effective in causing weathering compared to MgSO₄. According to the findings, it can be concluded that Na₂SO₄ saline solutions are more damaging to ASR and TLZ samples compared to MgSO₄. Specifically, ASR samples exhibited significant deterioration with DR values of 95.55%, 36.51%, 61.20%, and 86.78% for n, m, Vp, and PLI, respectively, after undergoing 30 cycles in the Na₂SO₄ solution.