Early age volume changes in metakaolin geopolymers: Insights from molecular simulations and experiments

The early age volume changes occurring during the geopolymerisation reaction are not sufficiently understood yet, due to shortage of experimental data and theoretical models. This work presents new results on chemical autogenous deformation sodium-activated geopolymers from metakaolin, focussing first 72 h reaction. show that undergo early-age expansion, shrinkage. A model is proposed explain result, leveraging recent advances molecular simulations. predicts how extent expansion controlled by confined water in structure geopolymer. However, despite this underlying geopolymer samples shrinkage at macroscale, which excludes self-desiccation as origin deformation. better insight gained monitoring kinetics using isothermal differential calorimetry. Two kinetic regimes identified, with apparent activation energies approximately 90 kJ/mol 70 kJ/mol. suggests two microscopic mechanisms concur determine pastes.