Methods to evaluate and quantify the geopolymerization reactivity of waste-derived aluminosilicate precursor in alkali-activated material: A state-of-the-art review

The utilization of industrial waste as an aluminosilicate precursor (AP) for alkali-activated material (AAM) production can provide an outlet for the growing waste stream and relief to landfill. However, to achieve the transformation of extremely varied waste into normalized APs with stable performance on an industrial scale, a universal testing method and criteria for quantifying the geopolymerization reactivity (GR) of APs are crucial. To facilitate the establishment of a more consistent method for determining the GR of APs, this paper reviewed and compared four mainstream methods for GR quantification: quantitative X-ray diffraction (QXRD)-based methods, energy-dispersive X-ray spectroscopy (EDS)-based methods, selective dissolution, and leaching tests. QXRD-based and EDS-based methods, as conventional and robust methods for material characterization, have gained excellent agreement with each other on the determination of inherent amorphous phases of APs, which have been proven indicative of GR to some extent. However, the inability of QXRD-based and EDS-based methods to evaluate GR under real reaction environments should also be highlighted, as not all the amor-phous phases are chemically involved in the reaction. Selective dissolution and leaching tests have also been developed to address this issue, and these have proved more indicative. However, the parameters of these two methods-such as reagent type, contact time, and temperature-should be optimized further and unified to improve their accuracy and viability.