Evaluation on reactivity of fly ash from different sources in alkali activated system-progressing environmentally construction through waste utilization

Abstract

Fly ash, a byproduct of coal-fired thermal power stations, is among the most intricate artificially produced substances. The challenge of its suitable disposal has emerged as both an ecological issue and a squandering of potentially resources. Fly ash has good pozzolanic activity and contains reactive Al and Si components, it has the potential to dissolve under alkaline conditions to form a dense green gel, i.e. alkali activated binder. But, the widespread implementation of fly ash from different sources in generation of products is constrained by the heterogeneity of raw-material supply. In this work, physical performances, chemical-compositions, microstructures, element distribution, crystal structure, chemical-bonds, glassy content, as well as existence form of glassy-phases of eleven fly ashes sourced from different province in China were investigated via FESEM-EDS, XPS, XRD-Rietveld, FTIR, TEM NMR analysis. Then, a reactivity index of fly ash (R value) that concerned the effects of both initial state, particle morphology, internal composition was proposed. R value has been demonstrated to exhibit high predictive accuracy (R² = 0.81–0.93) for predicting the strengths development of alkali activated products prepared with different activator modules, especially at early period. A further eleven literature datasets were utilized to validated against the accuracy of the predictions. R value facilitates an effective evaluation of fly ashes' fitness for fabricating high-strength alkali activated composites.