Development of lightweight and impact-resistant basalt fiber-reinforced slag-based geopolymer composites

The development of geopolymers with high impact resistance and energy absorption capacity is essential for protective engineering applications. In this study, basalt fiber-reinforced lightweight slag-based geopolymer composites (LGCs) were prepared. Low-field nuclear magnetic resonance, quasi-static compression and split Hopkinson pressure bar tests were conducted to systematically investigate pore microstructure, quasi-static and dynamic mechanical responses of LGCs. The effects of fiber content and strain rate on the strain-rate sensitivity, failure modes and energy dissipation characteristics were analyzed. The optimal fiber content was determined by comprehensively considering dynamic strength, energy absorption capacity and post-impact integrity. The results indicate that with increasing fiber content, the compressive strength and elastic modulus decrease, whereas the deformation capacity is enhanced. Under dynamic loading, the LGCs exhibit pronounced strain-rate sensitivity, with their dynamic compressive strength, dynamic elastic modulus, dynamic increase factor, strain energy density and dissipated energy increasing with strain rate. Basalt fiber content significantly affects the strain distribution and post-impact integrity of the LGCs by promoting strain homogenization and suppressing crack coalescence. The LGC with 1.5% fiber content achieves the most favorable balance among dynamic strength, energy absorption capacity and post-impact integrity while retaining its lightweight characteristics, demonstrating considerable potential for lightweight impact-resistant geopolymer applications in protective engineering.