Bloating mechanism in lightweight aggregates: Effect of processing variables and properties of the vitreous phase

The firing behaviour of five waste glasses was studied to define key parameters able to predict bloating performances in industrial lightweight aggregates production. Bloating was investigated by hot-stage microscopy and laboratory kiln experiments, also with SiC as expanding agent. In-situ and ex-situ results were contrasted to shed light on the scale up process. Both macro- and microstructure of aggregates are related to the melt properties and crystallization phenomena. A phenomenological model for SiC-induced expansion was proposed. The glass chemical composition controls melt viscosity and kinetics of expansion, while the increase of aggregate size fosters the extent of bloating.