Reactive Transport Numerical Model for Durability of Geopolymer Materials

Abstract

Geopolymers are alternative binders made solely from industrial by-products and/or natural alumino-silicates, comprising no traditional cements. Reactive transport processes in geopolymer materials play a crucial role in both the degradation process of building materials as well as in the containment of hazardous wastes. A numerical model is presented for solving transport coupled to nonlinear ion-exchange equilibria between solid-liquid phases. Bound alkalies provide the geopolymer paste with a large reservoir of exchangeable (soluble) alkalies that allow for a more gradual drop in pH of the pore solution, as compared to a sudden drop when considering only diffusion transport mechanism. The model is robust enough to handle non-linearity of the ion-exchange equations, and presents a more reliable way to obtain long term durability predictions of geopolymer materials.