Low-carbon high-strength engineered geopolymer composites (HS-EGC) with full-volume fly ash precursor: Role of silica modulus

In this study, the influence of the silica modulus of alkaline activators on the overall performances of pure fly ash (FA)-based High-Strength Engineered/Strain-Hardening Geopolymer Composites (HS-EGC/SHGC) was comprehensively studied. The developed HS-EGC successfully presented simultaneous high compressive strength (over 90 MPa) and high tensile ductility (over 6.0 %) for the first time. Tensile strain-hardening and over-saturated cracking phenomena were observed for all the HS-EGC mixes. It was found that the increase of the silica modulus from 1.0 to 2.0 reduced the tensile strength and strain energy density of HS-EGC, but the most distinguished overall mechanical index was achieved in the mix with the silica modulus of 1.5. Additionally, the underlying mechanism behind the mechanical performances was explored by Back Scattering Electron and Energy Dispersive Spectroscopy (BSE-EDS) tests. According to the data comparison from literature review, the good sustainability and market potential of the developed material were successfully demonstrated, and the developed HS-EGC pushed the performance envelope of pure FA-based EGC materials. The findings could help promote the future development and practical applications of this strain-hardening geopolymer material with both good sustainability and high mechanical performances. • Full-volume fly ash-based HS-EGC was firstly designed with simultaneous high compressive strength (over 90 MPa) and high tensile strain capacity (over 6.0 %). • The developed HS-EGC successfully pushed the performance envelope of EGC with full-volume fly ash precursor. • Over-saturated cracking phenomena were observed in all the HS-EGC mixes. • The underlying mechanism behind the influence of silica modulus on the mechanical performance was revealed. • The developed HS-EGC presented the lowest embodied carbon, embodied energy, and cost per strength-ductility index among all the existing fly ash-based EGC.