Effect of diatomite on the reaction kinetics, early-age chemical shrinkage and microstructure of alkali-activated slag cements

Abstract

Understanding and revealing the relationship between the early-age chemical shrinkage, reaction characteristic and microstructure of alkali-activated slag (AAS) pastes are of importance for the application of this cementitious material. This study investigates the effect of diatomite on the early-age compressive strength and the first 72-h chemical shrinkage of AAS pastes. A novel approach is proposed based on isothermal conduction calorimetry and 1H low-field nuclear magnetic resonance analyses to identify the internal correlation between chemical shrinkage and reaction situation. Results show that the early-age chemical shrinkage is dominated by the reaction process and reaction degree of AAS pastes. The incorporation of diatomite makes a great contribution to the control of chemical shrinkage even though it slightly sacrifices the development of compressive strength. This suggests the controls in the reaction process and chemical shrinkage of AAS pastes can be achieved by incorporating diatomite. The proposed approach can be used to assess chemical shrinkage of AAS, which contributes more to deeper understanding in the early-age volume change of alkali-activated cements.