Continuous Monitoring of the Early-Age Properties of Activated GGBFS with Alkaline Solutions of Different Concentrations

This study monitors the early-age reaction kinetics and measures the heat of reaction of alkali-activated ground granulated blast-furnace slag (GGBFS) using an isothermal calorimeter, and the initial setting and possible product formations by measuring ultrasonic pulse velocity (UPV). The GGBFS was activated with alkaline activator solutions of different concentrations in terms of modulus ratio (M-s) and Na2O% content. Results reveal that GGBFS is highly sensitive to the compositions of the alkaline solutions. Increasing the alkalinity of the activator results in better dissolution of species and consequently an increased heat evolution with a relatively shorter setting time. The activator concentration also affects the rate of product formations as well as the morphological features. Activators with higher Ms lead to homogeneous slag morphology. The abundance of silicate species in the alkaline solution also plays an important role in its structural formation. scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDS) microstructural characterizations supports the advanced dissolution of particles in a more alkaline environment. The presence of C-(A)-S-H gels in alkali-activated slag pastes was detected. (C) 2021 American Society of Civil Engineers.

Automated summary

This study found that GGBFS is highly sensitive to the compositions of alkaline solutions, with higher alkalinity leading to better dissolution of species, increased heat evolution, and shorter setting time. The activator concentration also affects the rate of product formations and morphological features, with higher Ms values resulting in homogeneous slag morphology.