The deterioration of concrete microstructures in freeze–thaw (F–T) cycles is the primary reason for the reduction in the service life of concrete. This paper reviews recent progress in the theory of damage mechanisms and damage models of concrete in F–T cycles. It is a detailed review of the salt-freeze coupling condition, microstructure testing, and models for the evolution of concrete properties that are subjected to F–T damage. Summarized in this paper are the deterioration theory of water phase transition; the mechanism of chloride-F–T and sulfate-F–T damage; the microstructure testing of hydration products, pore structure, microcracks, and interfacial transition zones (ITZ). Furthermore, F–T damage models for the macrostructure are presented. Finally, the issues that are existing in the research and outlook of concrete F–T damage are highlighted and discussed. This paper is helpful in understanding the evolution of F–T damage, and also provides a comprehensive insight into possible future challenges for the sustainable design and specifications of concrete in cold environments.

Steel-fiber-reinforced concrete (SFRC) is being increasingly applied to various buildings and civil infrastructure as an advanced cementitious composite. In recent years, the requirements for SFRC in the construction industry have increased. Additionally, the fire resistance of SFRC has attracted attention; therefore, numerous investigations regarding the residual properties of SFRC have been conducted. This paper critically reviews the mechanical properties of SFRC subjected to elevated temperatures, including its residual compressive strength, flexural strength, tensile strength, elastic properties, fracture properties, and stress–strain relationships. The residual mechanical performance of SFRC and the action mechanism of steel fibers are reviewed in detail. Moreover, factors affecting the explosive spalling of concrete at high temperatures as well as the effect of steel fibers on the microstructure of heated concrete are discussed. It is demonstrated that, in general, SFRC exhibits better residual mechanical properties when exposed to elevated temperatures than plain concrete and can prevent the risk of explosive spalling more effectively. The purpose of this literature review is to provide an exhaustive insight into the feasibility of SFRC as a refractory building material; additionally, future research needs are identified.

In order to explore the drying–wetting cycle test method of concrete under sulfate accelerating erosion, the influence of dry–wet time ratio on concrete sulfate erosion was studied. Under the condition of 7 days for one cycle, five different dry–wet time ratios were designed: 1:3, 1:1, 3:1, 5:1, and 10:1. The basic properties such as compressive strength, splitting tensile strength and dynamic elastic modulus of concrete were tested. Scanning electron microscopy (SEM) was used to analyze the microstructure of concrete before and after erosion. The test results show that under the environment of sulfate drying–wetting cycle erosion, the change of mechanical properties of concrete are divided into three stages: ascending period, fluctuating period and rapid descending period. Concrete is subjected to periodic damage process of initial damage followed by filling compaction, cracking, further filling, and cracking again, in that order. Dry–wet ratio has a significant effect on concrete sulfate attack. Under the same drying–wetting cycle period, as the dry–wet ratio increases, the degree of deterioration of concrete by sulfate attack increases first and then decreases. When the dry–wet ratio is 5:1, the deterioration is the most serious.