Effect of PVA Fiber on the Dynamic and Static Mechanical Properties of Concrete under Freeze-thaw Cycles at Extremely Low Temperature (−70 °C)

In order to study the effect of PVA fiber on the dynamic and static mechanical properties of low-temperature freeze-thaw concrete under the saturated surface dry state, different contents of PVA fiber were added to prepare concrete in this experiment. The concrete was subjected to compression, flexural and SHPB impact tests combined with scanning electron microscopy for microstructure analysis, after different times of freeze-thaw cycles in the temperature range of 20–−70 °C. The experimental results show that the compressive strength of the PVA fiber reinforced concrete first increases and then decreases after freeze and thaw cycles, and the compressive strength is positively correlated with the fiber content. The flexural strength gradually decreases with freeze-thaw cycles. The flexural strength of the concrete with 1.2 kg/m3 of PVA fiber presents the lowest strength loss after 45 freeze and thaw cycles, which is about 14%. The dynamic failure strength gradually decreases with the increase of freeze-thaw times, and the reduction amplitude decreases with the increase of PVA fiber content. The best impact resistance is achieved when the PVA fiber dosage is 1.2 kg/m3.