Rheology evolution of a geopolymer precursor aqueous suspension during aging

Abstract

Geopolymer‐based glass‐ceramic matrix composites can be processed at room temperature and a heat treatment below 100°C leads to matrix hardening thanks to the geopolymerization mechanisms. The stabilization of the matrix into glass‐ceramics is achieved via a post‐curing at high temperature. This paves the way of the utilization of cost‐effective liquid composite molding processes, for which all the necessary equipment is already available for processing temperature ranges related to polymer matrix composites, provided that the rheological behavior of the precursor is suitable to conveniently permeate the fibrous preform. The paper describes the thixotropic rheological behavior of a reference suspension at processing temperature (10°C‐20°C) and its evolution along aging at −18°C. The changes are interpreted in terms of geopolymerization mechanisms (dissolution and polycondensation) and suspension rheology (predominance of hydrodynamic effects at high shear rate). On this basis, a phenomenological modeling framework, combining two Krieger‐Dougherty equations, is proposed to build a relationship between the effective viscosity of the suspension and the phenomena involved during aging (dissolution of aluminosilicate particles) and shearing (microstructure scalar variable).

Circular economy and durability in geopolymers ceramics pieces obtained from glass polishing waste

“…In mixtures with the addition of the waste, there was a great reduction in water absorption after exposure, compared to the specimens before the salt spray cycles. Part of this reduction is due to the behavior of the waste within the matrix, in the formation of crystallization gels, in relation to the condition of exposure, and another also due increase bulk density before durability test 58 . For example, in thermal curing for the specimens with the addition of waste in the ratio SiO 2 /Al 2 O 3 = 4, the bulk density increased from 1.51 to 1.65 g/cm 3 , justifying the reduction in water absorption.…”

“…Part of this reduction is due to the behavior of the waste within the matrix, in the formation of crystallization gels, in relation to the condition of exposure, and another also due increase bulk density before durability test. 58 For example, in thermal curing for the specimens with the addition of waste in the ratio SiO 2 /Al 2 O 3 = 4, the bulk density increased from 1.51 to 1.65 g/cm 3 , justifying the reduction in water absorption. The saline atmosphere of the test collaborates strongly in the potentiation of geopolymerization reactions, which contributed to this process of abrupt drop in water absorption, compared to the specimens before the cycles.…”