The Preparation of the Engineered Geopolymer Composites and Their Tensile Strain Capacity Research

This study optimized the mix proportions of ultra-high-toughness fly ash-based geopolymer composites (EGC) and investigated the effects of sub-elevated temperature curing on its tensile properties using dumbbell-shaped tensile tests, microstructural analysis, and Digital Image Correlation (DIC). The results indicate that fiber incorporation significantly mitigates matrix brittleness, enabling EGC to achieve an ultimate tensile strain of up to 4.5%. Under ambient curing, both tensile strength and strain capacity improved with age. Sub-elevated temperature curing markedly enhanced early-age mechanical properties; at later ages, tensile strength further increased while strain capacity slightly declined. Microstructural analysis revealed that sub-elevated temperature curing accelerated geopolymerization, resulting in a denser matrix, with DIC confirming that EGC’s high ductility stems from multiple micro-cracking propagation. By adopting the Menetrey–Willam damage model, numerical simulations successfully captured the stress concentration and damage redistribution process, mechanically confirming the pseudo-plasticity and multiple damage evolution of EGC.