Achieving superior mechanical performance in one-part geopolymer composites through innovative hybrid fiber systems of recycled steel and PVA fibers

Abstract

Fiber-Reinforced Geopolymer Composites (FRGCs) typically use mono-fiber reinforcement, often overlooking the potential benefits of hybrid fibers. This article examines the effects of different PVA fibers (thick and thin) and steel fibers (straight, hooked, and recycled tire wires) on the performance of one-part geopolymer composites. The study evaluates the impact of singular and hybridized PVA and steel fibers on slump flow, mechanical properties (compressive and flexural strength), and post-crack flexural behavior (first-crack strength, ductility index, and flexural toughness). Key parameters include the average number of fibers crossing a unit area (Ns) and the fibers' Young's modulus (YM). Findings reveal that Ns is crucial for enhancing post-crack behavior, while YM significantly improves compressive and flexural strength in FRGCs. Steel fibers increased compressive strength by 18% (straight), 12% (hooked), and 8% (recycled tire wires), whereas PVA fibers slightly reduced it by 4% (thick) to 14% (thin). However, hybrid fiber configurations balanced the compressive strength loss from PVA fibers. Flexural strength improved with fiber inclusion, regardless of type and geometry, ranging from 6.4 MPa (2% thick PVA fibers) to 10.25 MPa (1% thin PVA fibers & 1% straight steel fibers), a 23%–97% increase over control mixes. Composites with recycled steel fibers showed exceptional post-crack behavior, with mono Recycled Tire Wire (RTW) composites having superior ductility indices (13.3) compared to mono straight and hooked steel fibers. Additionally, RTW combined with thin PVA fibers demonstrated exceptional flexural toughness (21.13 N m) and ductility indices (28.6), indicating superior post-crack performance compared to virgin counterparts. This study underscores the potential of hybrid virgin and recycled fiber-reinforced FRGCs to enhance mechanical and post-crack performance, offering a sustainable pathway for construction materials with reduced environmental impact. The research also develops linear models predicting mechanical properties, providing valuable tools for optimizing FRGC formulations.

Keywords

• Compressive and flexural strengths
• Geopolymer composites
• Hybrid fiber reinforcement
• Post-cracking behavior
• Recycled tire wires
• Sustainability