Study on dynamic mechanical properties and microstructure of basalt fiber reinforced coral sand cement composite *

Abstract

This study investigates the impact of basalt fiber on the static and dynamic compression of coral-sand cement-based composites, as well as the mechanisms for strengthening and toughening. The samples of basalt fiber-reinforced coral sand cementitious composite (BFRCSCC) with varying fiber volume fractions (0%, 0.2%, 0.4%, 0.6%, 0.8%) underwent quasi-static mechanical tests and impact dynamic tests using an MTS universal testing machine and a split Hopkinson pressure bar (SHPB). This study investigates the mechanical properties of BFRCSCC, focusing on static and dynamic compressive strength, dynamic stress-strain curve, strain rate effect, failure strain, toughness analysis, and energy dissipation mechanism. In terms of microstructure, specimens of BFRCSCC were tested using scanning electron microscopy (SEM). The results indicate that basalt fiber can significantly enhance the quasi-static compressive strength (fc)and dynamic compressive strength (fd)of coral sand cement-based composite materials. When the basalt fiber content is 0.4%, the static and dynamic compressive strength of BFRCSCC increases by 28.78% and 37.25% respectively compared to ordinary concrete. The analysis from a micro perspective indicates that the incorporation of basalt fiber in the concrete matrix enhances the hydration reaction between cement and the BFRCSCC interface. The spatial structure formed by basalt fiber contributes to the excellent toughening effect on the mechanical properties of BFRCSCC. As the content of basalt fiber increases (≤0.4%), the bridging effect becomes stronger. The dynamic increase factor (DIF) and toughness index of BFRCSCC exhibit a significant positive correlation with the strain rate effect. Basalt fibers can help drive the hydration products to fill the cracks or voids in the cement matrix, thereby increasing the material's density and enhancing the impact resistance of coral concrete. This can be utilized in practical engineering projects with high dynamic load demands.