Reaction Rate of Alkali-Activated Metakaolin-Based Geopolymers

Author: Abu Naser Rashid Reza, Department of Civil and Environmental Engineering

Mentor: Dr. Christopher Shearer, Department of Civil and Environmental Engineering

Geopolymers are viable alternative cementitious materials to ordinary portland cement (OPC). Aluminosilicate precursors can be activated with an alkaline solution to make structural geopolymer materials. But in part due to the lack of understanding about their reaction mechanisms, the usage of geoploymers as a construction material has been limited. Understanding the role of water during the formation of geopolymer gels is necessary to fully understand their reaction. It is assumed that most of the water bound in the alkaline activating solution is eventually released as free water during the reaction of the solution with an aluminosilicate powder. In this research, the waste product of silicon manufacturing metakaolin, was used as precursors for geopolymers. Sodium hydroxide and sodium silicate solutions were used to activate the metakaolin at three different temperatures during curing. The reaction characteristics of the geopolymer pastes were analyzed for setting time, chemical shrinkage, free water loss and kinetics via calorimeter. Microwave characterization was also performed on the geopolymer pastes to find the dielectric properties in terms of permittivity and loss factor. This data is then correlated to quantify the role of water and rate of reaction of the geopolymers.