Macro-Mesoscale Mechanical Properties of Basalt-Polyvinyl Alcohol Hybrid Fiber-Reinforced Low-Heat Portland Cement Concrete

To investigate the mechanical properties of hybrid basalt fiber (BF) and polyvinyl alcohol fiber (PVAF)-reinforced low-heat Portland cement concrete (LHPCC), two groups of concrete were formulated. The BF and PVAF were equal in the first group, and the total fiber contents were 0–0.4%. The second group was the total fiber content of 0.3% and the occupancy of BF in the hybrid fiber of 0, 25%, 50%, 75%, and 100%. Two groups of concrete were tested for compressive, splitting tensile, and flexural strengths to illustrate the enhanced mechanism of the mechanical properties of LHPCC by hybrid fiber. The best mechanical property enhancement was achieved when BF and PVAF were in equal proportions and the fiber content was 0.3%. Meanwhile, the test results for the mechanical properties were also compared with the predicted values of ACI 318 and Eurocode 2. Moreover, the hybrid BF-PVAF-reinforced concrete was regarded as a three-phase composite material consisting of fiber-reinforced mortar, coarse aggregate, and an interfacial transition zone. The axial compressive and splitting tensile strengths, damage processes, and mechanical strengthening mechanisms of concrete were investigated for different total fiber content at equal ratios of BF and PVAF, and the results were compared with the macroscopic mechanical test findings. The results show that the conclusion of the meso-simulation matches well with the test. Finally, the effect of aggregate and hybrid fiber content on the mechanical properties of LHPCC was predicted by a simulation. The results of this study can provide references for future mechanical modeling, performance studies, and practical engineering applications of LHPCC.