Effect of temperature on durability of cement-based material to physical sulfate attack

Physical salt attack (PSA) is a deterioration mechanism caused by crystallization of salts in pores. Many experimental studies have shown that pore size distribution influences cement-based materials susceptibility to PSA. However, the deterioration of concrete due to PSA is also governed by environmental conditions. In this paper, mortars with water to cement ratios of 0.4, 0.5, and 0.6 were subjected to cycles of salt contamination, immersion in 5% sodium sulfate solution separately at 5 degrees C and 20 degrees C, and then dried at 50 degrees C. The assessment methods were based on visual appearance and weight change. In the meantime, X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectroscopy, and X-ray computed tomography were used to elucidate the damage mechanism. The results showed that the damage pattern depended on the temperature: uniform surface crumbling at 5 degrees C; edges and corners scaling at 20 degrees C, and the damage was more severe at 20 degrees C than at 5 degrees C. Besides, the evolution of salt uptake indicated that the crystallization of sodium sulfate occurred deeper below the surface of the specimens when the temperature of the sodium sulfate solution was higher. Moreover, lower water to cement ratio was more beneficial to prevent PSA. (C) 2020 Elsevier Ltd. All rights reserved.