Pre-dissolution activation of glass powder: ionic release mechanisms and their limited impact on mortar performance

Abstract

This study evaluates the influence of different pre-dissolution methods on the ionic release behavior of glass powder (GP) and the mechanical and microstructural performance of mortars incorporating 25% volumetric cement replacement. Green bottle glass waste was milled and fractionated, and the GP25 fraction—whose particle size is comparable to cement and fly ash—was selected. The powder was immersed in water for 6 h under six conditions: static resting, orbital agitation, magnetic stirring, mechanical stirring, ultrasonic bath, and ultrasonic probe. The release of Naþ and Ca2þ ions was quantified prior to mortar production. Ultrasonic treatments promoted the highest ionic dissolution but also increased porosity and slightly reduced strength. In contrast, conventional agitation methods produced moderate ion release and more balanced microstructures. Complementary analyses (TGA, electrical resistivity, capillary absorption, chloride migration and mercury intrusion porosimetry) showed that increased ionic release does not necessarily translate into improved hydration, strength or durability of GP-modified mortars.