Freeze–thaw durability of air-entrained concrete under various types of salt lake brine exposure

Abstract

Properties of air-entrained concrete (AEC) subjected to freeze–thaw cycles in various salt lake brines were investigated in this study. Through the experiment, the relative dynamic elastic modulus (RDEM) and weight loss of the AEC were measured after different numbers of freeze–thaw cycles. In addition, the microstructure and composition of AEC under the combined action of freeze–thaw cycles and salt lake brine attack were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the RDEM and weight losses of AEC subjected to freeze-thaw cycles in Tibet salt lake brine (TB) and Inner Mongolia salt lake brine (IM) decreased sharply. For AEC immersed in Qinghai salt lake brine (QH) and Sinkiang salt lake brine (SK), the RDEM is slightly reduced and the weight loss is slightly increased. Thus, the coupling effect had a slight influence on concrete damage in SK and QH region The XRD and SEM results demonstrated that only chemical corrosion occurred in the AEC under freeze-thaw action in the QH and SK salt lake brines. However, the coupling effects of water frost-heaving force, salt crystallization and chemical corrosion rapidly lead to damage to the concrete under freeze-thaw action in the TB and IM salt lake brines.