Behavior of mortar exposed to different exposure conditions of sulfate attack

Abstract

The sulfate deterioration of cement-based materials has become severe durability problems for the offshore structures. Considering the various service conditions such as splash and tidal zone with/without sulfate attack, the behavior of mortar samples under full immersion and dry-wetting cycles with 0% and 5% Na2SO4 solution, i.e., four exposure conditions, was investigated in this research. Compressive strength, elastic modulus, permeability (water permeability coefficient), expansion behavior and SEM images were tested and analyzed. The results showed that the behavior of mortar evolved in two stages, initial improvement followed by later degradation, determined by two competitive effects under each condition. Different deterioration mechanisms worked in the different exposure conditions. We proposed binomial formulas to describe the evolutions of the compressive strength and water permeability, and we further applied them in other researches well. Meanwhile, there was a linear relationship between elastic modulus and square root of compressive strength. Furthermore, the relation between water permeability and compressive strength was highly dependent on exposure types and time. Study showed that compressive strength and water permeability coefficient can be selected as controlling parameters in in-situ tests, and a possible approach to evaluate the sulfate deterioration level of concrete structures in-situ was represented.