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

Abstract

The properties of air-entrained concrete (AEC) subjected to freeze–thaw cycles in various salt lake brines were investigated. 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 the AEC under the combined action of freeze–thaw cycles and salt lake brine attack were analysed using X-ray diffraction and scanning electron microscopy. The results showed that the RDEM and weight losses of AEC subjected to freeze–thaw cycles in salt lake brines from Tibet and Inner Mongolia decreased sharply. For AEC immersed in salt lake brines from Qinghai and Sinkiang, the RDEM was slightly reduced and the weight loss was slightly increased. The coupling effect of freeze–thaw cycles and salt lake brine thus had only a slight influence on concrete damage in Sinkiang and Qinghai regions. The X-ray diffraction and scanning electron microscopy results demonstrated that only chemical corrosion occurred in the AEC under freeze–thaw action in the Qinghai and Sinkiang salt lake brines. However, the coupled effects of water frost-heaving force, salt crystallisation and chemical corrosion rapidly led to damage to the concrete under freeze–thaw action in the Tibet and Inner Mongolia salt lake brines.