A Micromechanics-based Study on Cracking Characteristics of Engineered Geopolymer Composite

Abstract

This study aims at experimentally and analytically characterizing cracking characteristics of Engineered Geopolymer Composites (EGCs) and at identifying optimal combinations of micromechanical parameters for enhancing the composite tensile performance. Fly ash-based EGCs with different volume fractions of polyvinyl alcohol fibers are investigated. The number of cracks and residual crack widths are measured for EGC specimens uniaxially loaded to 1% and 2% tensile strain. The observed crack patterns are analyzed by a micromechanics-based model that relates matrix, fiber, and interface properties to the macroscopic composite behavior. The experimental results demonstrate the lognormal distributions of crack widths and more tightly controlled cracking compared to Engineered Cementitious Composites. The simulated fiber bridging stress-crack opening relationship (σ-δ relationship) suggests that relatively high chemical bond and low frictional bond lead to the tight crack width. The simulation results also suggest that the first-cracking strength and the subsequent micro-cracking stress during the hardening stage should be below the analytical σ-δ curve peak. Higher chemical bond is beneficial for meeting these conditions, but if it is too high, fiber rupture dominates over pull-out, which lowers the complementary energy. Lower frictional bond or slip-hardening coefficient can suppress the fiber rupture tendency.