Mass Transport in Alkali-Activated Slag Concrete under Compressive Load

Abstract

As an alternative binding material with prosperous application potential, alkali-activated slag (AAS) has attracted more and more attention. Similar with ordinary portland cement concrete, transport properties are commonly evaluated for alkali-activated slag concrete (AASC), but little for damaged concrete under mechanical load. In this paper, the effects of activator types and fly ash (FA) substitution of slag on mass transport process were evaluated. Furthermore, the effect of uniaxial compressive load on mass transport properties of AASC involving chloride diffusivity and capillary absorption were also investigated experimentally. A certain compressive stress level from 0.35 to 0.8 were applied on the concrete specimens respectively, and then the coefficient of chloride diffusion and water capillary absorption were evaluated after unloading. The results show that, compared with NaOH-specimens, specimens by waterglass without loading shows a higher rate in transport due to the more initial cracks by serious shrinkage; under the stress level of 0.35, initial microcracks tend to close while new cracks are generated at the same time, which leads to an indistinct transport behavior; the composite activated by waterglass is more sensitive to Na2O concentration than that by NaOH, which influences creep and durability greatly. Furthermore, the Poisson's ratio during the loading process was recorded and discussed, which confirms that the stress level of 0.8 for AAS does not attain to critical stress.