Research on mechanical properties and microstructure of basalt-polyvinyl alcohol hybrid fiber reinforced concrete

This study utilized basalt fiber (BF) and polyvinyl alcohol fiber (PVA) to produce basalt-polyvinyl alcohol hybrid fiber reinforced concrete (BPFRC). The effect of fiber content on water absorption and mechanical properties of concrete was discussed, and the distribution form of hybrid fiber in concrete was also studied. Nine groups of concrete with different fiber content were designed, in which the total volume content of hybrid fiber was controlled within 0.6%. The results show that hybrid fibers can effectively reduce the water absorption of concrete. When the content of BF is 0.3% and the content of PVA is 0.2%, the initial water absorption and secondary water absorption decrease the most, which are 29.80% and 24.40%, respectively. The mechanical properties of concrete can be improved effectively by adding a proper amount of hybrid fiber. Basalt fiber enhances the compressive strength and splitting tensile strength of concrete more effectively than polyvinyl alcohol fiber, whereas polyvinyl alcohol fiber has a greater impact on the flexural strength of concrete compared to basalt fiber. Grey correlation entropy analysis of mechanical properties and permeable pore volume demonstrated that compressive strength exhibited the strongest correlation with permeable pore volume. Accordingly, a predictive model was developed, which accurately captured this relationship. Microstructural analysis revealed that BF and PVA formed a three-dimensional network within the concrete matrix. However, excessive fiber content led to agglomeration, adversely affecting the mechanical properties of the concrete.