Evaluation of rheology and strength development of alkali-activated slag with different silicates sources

This study provides a detailed investigation on the reproducibility of two groups of alkali-activated slag (AAS) mixtures, from both fresh properties and strength development perspectives. Three different commercial sodium silicate solutions and one lab-produced silicate activator (made of silica fume and sodium hydroxide) were used to prepare AAS pastes with the same nominal composition in each group. The reaction process of each AAS mixture was monitored by calorimetry and ultrasonic pulse velocity (UPV) measurements. Meanwhile, minislump and flow curve tests measured by rheometer were conducted in the first hour to characterize the evolution of fresh properties. The compressive and flexural strength of hardened AAS mortars were measured at different curing ages. The results revealed that AAS pastes prepared with three different sodium silicate solutions exhibited almost identical reaction kinetics, as well as the evolution of fresh properties and strength development. However, the reaction took place rather fast in AAS pastes made of silica fume. These mixtures showed worse rheology and less strength than the corresponding mixtures prepared with sodium silicate solutions. Furthermore, the present study also showed the feasibility of making the same AAS paste through different class commercial sodium silicate solutions.

Automated summary

This study provides a detailed investigation on the reproducibility of two groups of alkali-activated slag mixtures, focusing on both fresh properties and strength development. The results show that AAS pastes prepared with different sodium silicate solutions exhibit similar reaction kinetics, fresh properties, and strength development. However, AAS pastes made of silica fume show faster reaction and inferior rheology and strength compared to those prepared with sodium silicate solutions. This study also demonstrates the feasibility of making the same AAS paste using different types of commercial sodium silicate solutions.