An initial study on the effect of nano-zirconium on the behavious of alkali-activated slag cement subjected to seawater attack

Abstract

In this article, for the first time, the possibility of adding nano-zirconium (NZ) into alkali-activated slag (AAS) cement as a modifier agent against seawater attack was studied. Different ratios of 1 %, 3 % and 5 % from NZ were added into the neat AAS cement. The effect of these additions on workability and compressive strength was measured. After initial curing, some specimens were exposed to seawater attack for 3, 6 and 12 M, whilst the others were cured in the air and tap water for the same periods for comparison purposes. The variation in the crystalline phases, hydration products and microstructures caused by the inclusion of different ratios of NZ were monitored by using X-ray diffraction (XRD), thermogravimetric analysis and its differential (TGA/DTG) and scanning electronic microscopy (SEM). The results showed a negative effect of NZ on workability. The incorporation of 1 % and 3 % NZ showed a positive effect on compressive strength before and after exposure to different media, whilst the incorporation of 5 % showed a negative effect. The optimum ratio of NZ was 1 %. This ratio can produce a denser and more compact microstructure, which can act as a barrier against ions and chloride diffusion from seawater to the specimens as well as migration of alkalis from the specimens to seawater.