Physical Chemistry and Rheology of Alkaline Solutions for Geopolymer Pastes Formulations

摘要

Geopolymers constitute a potential sustainable alternative to Portland cement. They are amorphous silica-aluminates products of the reaction of metakaolin or fly ashes with an alkali silicate solution. The usage of geopolymer pastes as cementing materials is hindered by a lack of data, understanding and control concerning the rheology of the paste before hardening. As a first step, using diverse methods such as Nuclear Magnetic resonance (NMR) and Small Angle X-ray Scattering, we showed that the high viscosity of the alkali solutions can be rationalized by ion pairing and molar excess volume considerations. This allows further studies on the evolution of the rheology of the fresh geopolymer as a function of time and temperature and suggests possible ways to improve the workability of the geopolymer pastes.