Lab and Field Study of Physical Sulfate Attack on Concrete Mixtures with Supplementary Cementitious Materials

Physical salt attack (PSA) or salt weathering occurs as a result of the crystallization pressures in concrete pores exerted by phase changes of salts that penetrate the concrete. The crystallization pressures cause microcracking of the concrete and mass loss. Different concrete materials have been reported to affect the concrete resistance to PSA. This study examined the effect of incorporating supplementary cementitious materials (SCMs) in concrete on its transport properties and, ultimately, on its resistance to PSA. The effect of SCMs on PSA durability was found to be directly related to their role in altering the pore network. Moreover, results from field specimens were compared with those obtained in the lab. Correlations between the resistance to PSA and formation factor, absorption rate, and chloride migration coefficient were explored in this study. The results showed that slag and silica fume binary mixes had high resistance to PSA, and ternary mixes that included slag, in addition to Class F fly ash, were also resistant to PSA. The study found some correlation between the mass loss in full submersion tests with respect to their formation factors and transport properties. The field specimens were evaluated over a 1-year period, and the results showed PSA manifestation. It was found that the measured mass loss in PSA full submersion lab tests correlated well with the concrete formation factor. It was also found that the damage in some binary fly-ash specimens in the field and partially submerged lab tests was greater than expected based on the results in the fully submerged test. (C) 2020 American Society of Civil Engineers.