In recent years, with the construction of large-scale infrastructure in various complicated service environments, higher demands are put forward for the mechanical and durability properties of concrete. At present, the application of fiber-reinforced technology to improve the performance of concrete has become one of the research hot spots in the field of building materials (Dhand et al.,
2015; Khaled et al.,
2011; Sukontasukkul et al.,
2010). As a kind of high brittle material, ordinary concrete has disadvantages such as low splitting tensile strength and poor cracking resistance (Kayali et al.,
2003; Rashiddadash et al.,
2014), which brings some troubles to many engineering applications. Adding fiber to concrete can improve the brittleness of concrete and to improve the strength and durability of concrete (Afroughsabet & Ozbakkaloglu,
2015; Kuder & Shah,
2010; Lau & Anson,
2006; Yang et al.,
2019; Yao et al.,
2019). Made of natural basalt ore as raw material through hot melting and wire drawing at high temperature (Gzigany et al.,
2005; Sim et al.,
2005), basalt fiber is a new type of inorganic fiber possessing a series of advantages of high strength, excellent size stability, insulation and heat insulation, strong corrosion resistance, easy processing, low price and high compatibility (Flore et al.,
2015; Wang et al.,
2013; Yew et al.,
2015). Compared with those of metal fiber, the insulation performance and corrosion resistance of basalt fiber make it more suitable for road and high-speed railway engineering. Basalt fiber is also an environmental-friendly material (Krasnovskih et al.,
2014; Ludovico et al.,
2012), the application of which in the field of concrete will meet the two requirements of green and sustainable development of concrete and concrete modification at the same time, which has great research value.
After studying the basic properties of carbon fiber, glass fiber and basalt fiber based on concrete, Sim and Park (
2005) found that basalt fiber concrete had better performance than carbon fiber concrete and glass fiber concrete. Basalt fiber can improve engineering mechanics and durability. The experimental results of Kizilkanat et al. (
2015) showed that the splitting tensile strength of basalt fiber concrete would increase with the increase of fiber content. The mechanical test results of Afroz et al. (
2017) also showed that even after 56 days, the modified basalt fiber could still significantly improve the splitting tensile strength and flexural strength of concrete. Zeynep and Mustafa (
2018) studied the influence of basalt fiber of different lengths on the mechanical properties of self-compacting concrete, and the results indicated that the compressive strength of concrete would be the highest when the volume content of basalt fiber was 0.1% and the length was 12 mm. When the volume content is 0.5% and the length is 24 mm, the splitting tensile strength will be the highest. Branston et al. (
2016) studied the application of short-cut basalt fiber in concrete. Among the basalt fiber with the same quality content, the compressive strength of 50-mm basalt fiber concrete is higher than that of 36-mm basalt fiber concrete. Basalt fiber content over 12 kg/m
3 will lead to fiber aggregation. Dias and Thaumaturgo (
2005) believe that basalt fiber can substantially enhance the mechanical properties of concrete when the fiber volume content is of 0.5%, and it can also significantly reduce the early shrinkage of concrete and improve the early performance of concrete. Khan et al. (
2018) studied the influence of different content of basalt fiber on the mechanical properties of concrete, through the stress–strain curve and load–deflection curve of which, it is found that the mechanical properties of basalt fiber concrete decreased significantly when the content of basalt fiber exceeded 0.68%. By adding chopped basalt fiber into concrete, High et al. (
2015) studied the change of bending resistance and found that the bending resistance of concrete could be significantly promoted. In research of Li and Wu (
2009), basalt fiber has a certain improvement in deformation ability of geopolymer concrete. Sadrmomtazi et al. (
2018) studied the influence of silica fume on the mechanical properties of basalt fiber reinforced cement-based composites, and the results showed that the working performance of concrete would decrease with the increase of fiber content. When the fiber content was 1.5% and silica fume content was 15%, the fiber in concrete would appear agglomeration. The flexural strength of concrete increased while the compressive strength decreased with the addition of fiber, while the flexural strength increased twice with the addition of fiber and silica fume. The study of Zhang et al. (
2017) shows that the interface adhesion between basalt fiber and concrete is high, but the adhesion between cement base and aggregate cannot be improved, and basalt fiber has a good crack resistance effect on concrete. Adding basalt fiber into shotcrete can significantly augment the mechanical properties and working performance of basalt fiber shotcrete (BFRS) as well as the microstructure of shotcrete, and effectively suppress the deformation of roadway surrounding rock (Bernard,
2015; Dong et al.,
2017; Khooshechin & Tanzadeh,
2018). The basalt fiber mixing in concrete formed irregular three-dimensional network, which is closely connected with cement paste and aggregate. Doped fiber can decrease the porosity to a certain extent, delay the development of the internal microscopic cracks, and concrete more compact structure (Monaldo et al.,
2019). Jiao et al. (
2019) showed that basalt fiber reduced the number of macropores through NMR studies. To explore basalt fiber concrete’s ability to resist impact load, Elmahay and Verleysen (
2019) studied the basalt fiber reinforced concrete under high strain rate effect of tensile properties, finding that basalt fiber reinforced concrete in the filling direction and bending direction are sensitive to strain rate, whose material stiffness, Poisson's ratio and ultimate tensile strength and ultimate tensile strain increases with the increase of strain rate. With the application of SEM, it was found that the fracture morphology was independent of strain rate, and there were stratification phenomena at all strain rates. Compared with ordinary concrete, basalt fiber concrete exhibited excellent energy absorption capacity at high strain rate, which makes it a good candidate material for impact resistance construction. Through the investigation of the dynamic characteristics of basalt fiber reinforced concrete under high temperature, Ren et al. (
2016) found that the dynamic strength, critical strain and impact toughness of basalt fiber reinforced concrete at different temperatures achieved an positive correlation with dynamic load rate, showing obvious rate sensitivity. Zhao et al. (
2018) observed the internal loss process of concrete under freezing–thawing conditions, whose results showed that basalt fiber could inhibit the internal damage and failure of concrete, however, it had little relation with the content of fiber. Shengji et al. (
2015) has conducted an experimental study on the durability of basalt fiber reinforced concrete in engineering application. It is concluded that basalt fiber has a significant effect on enhancing the freezing–thawing damage resistance of concrete under corrosion conditions. Aybu et al. (
2014) believed that basalt fiber could significantly improve the chloride ion permeability resistance of concrete, whereas some scholars held opposing views (Huang et al.,
2015). Taha et al. (
2020) found that basalt fiber reinforced concrete (BFRC) has higher bonding strength with steel bar in saline–alkali environment and higher reliability in bonding slip test. Lee et al., (
2014) studied the chemical stability of basalt fiber in alkaline solution, finding that basalt fiber soaked in weak alkaline solution will be very stable, the mass loss rate of which is low after soaking in Ca(OH)
2 solution for 3 months. The compressive strength of early-age concrete in corrosion solution is negatively correlated with the content of basalt fiber (Lu et al.,
2017). Gao et al. (
2013) studied the corrosion process of sulfate on concrete under bending load and dry–wet cycle, indicating that stress level has greatly influenced the concrete durability. Bassuoni and Nehdi (
2009) studied the sulfate resistance of concrete under dry–wet cycles and bending loads. It is denoted by the results that the mechanism of concrete erosion is different from that of a single failure mechanism (sulfate erosion) under combined action. Sahmaran et al. (
2007) carried out an experimental study on the long-term properties of concrete under the dry–wet cycle sulfate erosion, the results of which showed that, compared with the total sulfate immersion environment, the damage degradation rate of mechanical properties of concrete under the dry–wet cycle erosion increased significantly.
At present, studies on the influence of basalt fiber on concrete properties are mainly focused on the influence of basalt fiber on concrete mechanical properties, or the durability of concrete in a single environment, but durability studies under the coupling effect of multiple environments relatively in deficiency. In northeast and northwest China, many construction projects are geographically faced with the cold environment for a long time, during which concrete structures will be damaged by freezing–thawing under the condition of low temperature and high cold, which seriously threatens the long-term safe use of building structures and brings huge economic and property losses along with huge repair costs. The structures in service in some specific environments, such as roads in industrial factories and sewage pipeline systems, face the coupling effects of freezing–thawing cycle (mostly frozen on single side), sulfate erosion, drying–wetting cycle and so on. The drying–wetting cycle accelerates sulfate erosion, causing more obvious durability loss of concrete (Bassuoni & Nehdi,
2009; Gao et al.,
2013). Therefore, the study of the mechanics and durability of basalt fiber reinforced concrete under the complex coupling action of single-side salt-freezing–drying–wetting cycle is of positive practical significance for improving the service stability of such structures, yet currently, this kind of research has not been reported. According to the actual service environment of this kind of structure, we designed an experimental method of single-side salt-freezing–drying–wetting cycle, and carried out the research on the mechanical properties and mesostructure of basalt fiber reinforced concrete with different volume content under the single-side salt-freezing–drying–wetting cycle. This paper mainly studied the influence of single-side salt-freezing–drying–wetting cycle on compressive strength and splitting strength of basalt fiber reinforce concrete, exploring the pore structure, basalt fiber morphology and hydration product changes by MIP (mercury intrusion porosimetry) test and SEM (scanning electron mircroscopy) test, and explored the damage reason from the microscopic structure.