Physical properties and microstructure of nickel slag/metakaolin-based geopolymer with different contents of nickel slag

Geopolymer pastes based on nickel slag/metakaolin (NS/MK) were prepared and their physical properties and microstructure as a function of NS content were studied. The results showed that the addition of NS in an appropriate proportion not only enhanced the compressive strength but also led to volume-expansive behaviour of the hardened pastes. Analysis of the pore size distribution indicated that increasing the NS content reduced the total pore volume and increased the average pore size. The silicate species dissolved from the NS participated in the geopolymerisation and influenced the mineralogical composition and microstructure of the gel phase. The addition of NS had no detrimental effect on the concentrations of alkali metals and pH of the leaching solution obtained from the geopolymer samples. In addition, the addition of NS had no detrimental effect on the dissolution behaviour of MK. This work presents a further step in the development of alternative ‘low-carbon’ binders for the construction industry.