Effect of activator properties on drying shrinkage of alkali-activated fly ash and slag

Abstract

Alkali-activated fly ash and slag (AAFS) pastes with a CaO content of 10%–20% are cementitious materials with high strength and good durability. The correlation between the drying shrinkage and microscopic characteristics of the pastes is investigated. By affecting the reaction degree of the pastes, the alkali content and activator modulus cause different pore-size distributions and deformation abilities, leading to different capillary pressures and shrinkage of the pastes during drying. The elastic deformation of the pastes under the capillary pressure during drying only accounts for a small part of the whole drying shrinkage. The long-term development of drying shrinkage mainly depends on the viscous behavior of the pastes under capillary pressure. The change law of the elastic deformation part with the activator modulus and alkali content is positively correlated with that of the corresponding capillary pressure. Moreover, the change law of the creep contribution part with the activator modulus and alkali content negatively correlates with that of the corresponding strength.