Micromechanical and mineralogy analyses on extremely ductile engineered geopolymer composites with different activator pretreatments

Abstract

In this study, the effects of activator pretreatments on properties of fly ash-based extremely ductile engineered geopolymer composites (ED-EGCs) were investigated. Two ED-EGC mixtures were designed using the same binder system and polyethylene fiber reinforcement, but different pretreated activators. A sequence of experiments including mechanical testing, micromechanical analysis, and chemical characterization was performed. The test results indicate that ED-EGCs were lightweight with density values lower than 1.7 g/cm3, had moderate compressive strengths over 21 MPa, and exhibited extremely ductile behavior with tensile strain capacities over 11 %. Overall, the warming pretreatment was beneficial to improve strengths but less effective to enhance tensile ductility of ED-EGCs. In contrast, the ED-EGC mixture adopting the cooling pretreatment showed tensile strain capacity up to 18.6 %, which has been unprecedented in the literature. The micromechanical analysis explained the extremely ductile behavior of ED-EGCs. SEM observation also confirmed that the fibers were robustly embedded into the geopolymer matrix. Through chemical analysis using EDS, it was found that N-A-S-H gel was the dominant geopolymeric product of ED-EGCs.