Experimental Study of the Mechanical Properties and Microstructure of Basalt Fiber-Reinforced Concrete

Basalt fiber (BF) is an environmentally green building material; the incorporation of basalt fiber into concrete structures can contribute to improving their strength and durability. In this work, basalt fiber reinforced concrete (BFRC) was designed and prepared with eight kinds of volume fractions of BF (0%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%). The dynamic mechanical properties with various volume fractions of BF were investigated using a 75 mm-diameter split Hopkinson pressure bar (SHPB) apparatus. Based on the experimentally obtained stress-strain curves at different strain rates, the effects of volume fraction and strain rate on the dynamic compressive strength were investigated, and the dynamic constitutive law of BFRC was derived. From the microscopic point of view, by analyzing the scanning electron microscope (SEM) photographs and mercury intrusion porosimetry measurements (MIP), this paper researched the microproperties and pore structure of BFRC. The interface between the fibers and the cement was observed, and the effect of the pore size ratio on the dynamic strength of BFRC at different strain rates was analyzed. The test results showed that volume fractions of BF at 0.3% had the most significant improvement in the concrete's compressive strength and flexural strength. At high strain rates, the specimens without BF were broken into powder form, and those with 0.3% BF were broken into small pieces. By studying the microproperties and pore structure of BFRC, the proportion of multiharmful holes was reduced, and the proportion of less harmful holes was positively correlated with the BFRC dynamic compressive strength after the incorporation of BF. The results indicate that the BF improves the compactness of the concrete and optimizes its pore structure, thus contributing to its dynamic mechanical properties.