Self-sensing properties of alkali-activated materials prepared with different precursors

Abstract

The development of smart concretes with self-sensing properties has gained increasing attention recently. In this study, the effect of different precursors, including blast furnace slag, fly ash, silica fume, and metakaolin, on the electrical conductivity and piezoresistive properties of alkali-activated materials (AAMs) with and without carbon fiber (CF) was investigated. The experimental results revealed that the electrical and self-sensing properties of AAMs were significantly influenced by the raw materials, both with and without carbon fiber. However, distinct trends were observed. The use of silica fume (25 wt%) was beneficial to the self-sensing property of CF-AAM mortars. Mixtures containing fly ash and pure slag exhibited higher sensitivity but with reduced repeatability of the piezoresistivity. Due to the poor dispersion of carbon fibers, as well as the porous microstructure, mixtures with metakaolin had poorer conductivity and piezoresistivity. AAM mortars had evident piezoresistivity under cyclic loading, but their stability was inferior to that of AAM with carbon fibers. The pore size distribution and gel pore quantity of the binder phase were important factors determining the conductive and piezoresistive properties of CF-AAM mortars.