Effects of temporal salt accumulation during accelerated drying-wetting cycles on physical properties of cement mortars and determining of ocean salt crystallization pressure stress

Elucidating the degradation mechanism of inorganic materials in special service environments such as ocean environment has important scientific and engineering significance. Research on drying-wetting cycles deterioration caused by ocean salt crystallization for cement-based materials is more significant. Current researches mainly focused on the phenomenon of drying-wetting cycles deterioration, with little attention paid to the effects of salt accumulation process on physical properties of materials. By applying the designed accelerated drying-wetting cycles test for cement mortars with ocean salt, sodium sulphate salt and sodium chloride salt solutions, we proposed a continuous two-stage physical model for the salt accumulation process in drying-wetting cycles. During the latent stage, cement mortar compressive stress increased mainly due to the infilling of salt. With the salt accumulating, the principle tensile stress continuously increased caused by the confined salt crystallization pressure stress. During the deterioration stage, cement mortar compressive stress decreased mainly due to micro cracks rapidly generated by the principle tensile stress exceeding the ultimate tensile stress of cement mortar. Baded on the concise physical model, we proposed a crystallization pressure stress calculation equation. The determined crystallization pressure stress of ocean salt ranged between those of sodium sulphate and sodium chloride salts. The outcomes provide novel method for in-depth research of crystallization phenomenon in cement-based materials and have significant engineering value.