Systematical investigation of rheological performance regarding 3D printing process for alkali-activated materials: Effect of precursor nature

Abstract

This research aims to illuminate the effect of precursor nature on the rheology of alkali-activated materials (AAM) for providing some understanding for the precursor selection and mixture design of 3D-printing AAM (3DPAAM). Binary AAM pastes were prepared with several precursors, including ground granulated blast-furnace slag (GGBFS), fly ash (FA) and silica fume (SF). Various 3D-printing-related rheological properties were characterized, including static yield stress, thixotropy and viscosity recovery evolutions. Results show that the replacements of GGBFS with FA or SF increase the static yield stress of AAM systems within 30 min after deposition. The FA or SF incorporation affects the structural build-up rates in the flocculation and polycondensation stages as well as their intersection times. The structure build-up rate in the flocculation stage is governed by the inter-particle distance of suspension, while the counterpart in the polycondensation stage depends on the reactivity of the precursor. The effects of FA or SF incorporation on the thixotropy and viscosity recovery are dependent not only on the adopted dosage but also on the rest time. 25 wt% FA or 10 wt% SF is the appropriate incorporated dosage in 3DPAAM to improve the 3D-printing-related rheology.