Effects of nanomaterials on mechanical properties, durability characteristics and microstructural features of alkali-activated binders: A comprehensive review

• An overview of the research from 2010 to 2021 summarizes the use of nano materials in alkali-activated binders. • The review covers nano-silica, nano alumina, nano titanium dioxide, and carbon nanotubes. • The effects of nanomaterials on mechanical properties and durability characteristics were comprehensively discussed. • Future trends, potential, and implications of nanomaterials alkali-activated based materials were suggested. The incorporation of nanomaterials in the concrete industry has recently received attention to enhance the concrete mechanical and durability properties. Besides, alkali-activated binders have become a viable option to replace conventional Portland cement- binders due to their superior mechanical properties and environmental advantages. This review paper summarizes the published work within the period 2010 to 2021 on the effect of the incorporation of selected nanomaterials in alkali-activated binders. A comprehensive review covers four nanomaterials (i) nano-silica, (ii) nano alumina (iii) Nano titanium dioxide, and (iv) carbon nanotubes. It was found that the incorporation of such nanomaterials led to promote of geopolymerization reactions, densifying the microstructure and thus enhancing the mechanical properties. The inclusion of nano-silica up to 3 wt% significantly enhances the rate of geopolymerization reaction. The addition of 2% of nano-alumina was found to reduce the porosity with a minor effect on geopolymerization. Incorporation of nano-TiO 2 up to 5% and Carbon nanotubes up to 0.1% enhances geopolymerization by offering additional nucleation sites. Furthermore, the addition of nanomaterials was found to significantly enhance the durability of geopolymers against severe chemical conditions. The potential health issues related to the use of nano-based materials have been discussed along with the cost-efficiency. At the end of this review, the future trend, potential, and implication of nanomaterials alkali-activated based materials were discussed.