Review on the deterioration and approaches to enhance the durability of concrete in the freeze–thaw environment

The freeze–thaw durability of concrete is an important factor for determining the service life of concrete in cold regions. This overview expounds three stages of freeze–thaw damage in the concrete from the micro perspective and proposes the three main deterioration mechanisms of concrete based on the concrete pore system. In addition, this overview summarizes various measures for enhancing freeze–thaw durability. Observations have revealed that concrete additives can effectively enhance the freeze–thaw durability of concrete, which due to the following mechanisms: (a) improving internal pore systems using air-entraining agent, supplementary cementitious materials and nanoparticle materials, (b) reducing water absorption of concrete using supplementary cementitious materials, nanoparticle materials and hydrophobic materials, (c) controlling the crack resistance of concrete using fibres and nanoparticle materials. The corresponding degree of improvement of various additives with different dosages has been reasonably analyzed, and the optimum content range of additives is summarized. In general, the mechanical properties of concrete mixed with additives are improved when subjected to freeze–thaw cycles, and the degradation rate of concrete is much slower than that of control concrete. This paper also proposes a concept of designing a durable concrete cover system by enhancing the chemical stability of cement hydrates, rapid self-healing and intelligent alkalinity control. This paper is helpful in deeply understanding enhancement in freeze–thaw durability mechanism and provides a basis for finding reasonable and effective enhancement measures for engineering.