Is electrodeless resistivity method suitable for monitoring the early-age reaction of Na2SiO3-activated slag? Mechanism and application

Abstract Electrodeless resistivity method was newly applied to investigate the early-age reaction of Na2SiO3-activated slag, one branch of eco-friendly alkali-activated materials (AAMs). Under the proposed model, physical meanings at different stages of 0–24 h resistivity curves of pastes with water-solids ratios ranging from 0.35 to 0.5 were explained, in which reaction heat, TEM, MIP, pH value, compressive strength providing comparative analyses from three aspects: rate of product formation, structural development and pore solution. Besides, initial/final setting time were linearly correlated with the turning points on resistivity curve respectively and, unlike the case of ordinary Portland cement (OPC), the initial setting time was not coincided with turning point on resistivity, probably due to the quick formation of initial gel on the slag particles. For a given water-solids ratio or curing age within 24 h, compressive strength and resistivity were actually inverses of one another, but the relationship seemed to be blurred by other factors beyond 24 h. This study shows that resistivity could be used as indirect index for monitoring the early-age reaction of AAMs and subsequent setting and hardening behavior, by which fresh vistas may be opened up for mechanisms understanding and engineering applications.