Durability of Portland-limestone cement-based materials to physical salt attack

Because salt solution ingress is governed by permeability and diffusivity and because salt crystallization pressure is directly related to pore size, changes in cement composition and hydrated microstructure may influence the durability of cement-based materials in salt-laden environments in complex ways. Here, performance of portland limestone cement (PLC) and ordinary portland cement (OPC) mortars exposed to sodium sulfate and calcium nitrate salt solutions was assessed, relative to their pore structure and sorptivity. At high w/b (0.60), increased salt crystallization damage was observed in the PLC mortar and was linked to its refined pore structure. At low w/b (0.40) performance was similar and was attributed to higher tensile strength and the inability of the salts to penetrate smaller pores. These results show that a w/b of 0.40 should provide adequate protection from capillary rise and evaporation-induced salt crystallization in both PLC and OPC mortar, but that at higher w/b differences in performance are possible.