MECHANICAL PROPERTIES AND MICROSTRUCTURE OF HYBRID FIBER-REINFORCED GEOPOLYMER COMPOSITES BASED ON COLLABORATIVE ACTIVATION OF MULTI-SOURCE SOLID WASTE

Abstract

The accumulation of industrial solid waste and the high carbon footprint of conventional Portland cement present critical challenges for sustainable civil engineering. This study develops environmentally friendly high-performance geopolymer composites using fly ash (FA), granulated blast furnace slag (GGBS), and waste ceramic powder (WCP) as multi-source precursors activated via an alkali process. Hybrid reinforcement systems were constructed by incorporating hooked-end steel fibers (SFs) and monofilament polypropylene (PP) microfibers at varying total volume fractions (0–1.5 %). The influence of multi-scale fibers on mechanical properties and microstructure evolution was systematically investigated.The results indicate that a total fiber contentof 1.0 % optimally balances strength and toughness, achieving 28-day compressive and splitting tensile strengths of 66.1 MPa and 6.20 MPa, representing 12.6 % and 89 % improvements over the unreinforced matrix. Due to two-dimensional directional constraints imposed by the mold, fibers formed orthogonal bridging along the tensile principal stress plane, yielding apparent flexural and splitting tensile strengths of 11.3 MPa and 6.20 MPa under specific 2D spatial constraints, representing 44.9 % and 89 % enhancements, respectively, and demonstrating pronounced deflection-hardening behavior. Microscopic analysis reveals synergistic interactions among the hybrid fiber network, local matrix aggregation, and mass transfer processes, effectively mitigating the intrinsic quasi-brittleness of the geopolymer matrix. These findings provide a theoretical foundation and practical pathway for the high-value utilization of multi-source industrial and construction waste, advancing sustainable and high-performance geopolymer composites for civil engineering applications.