Engineering properties of geopolymer concrete incorporating hybrid nano-materials

Abstract Geopolymer concrete is considered to be a sustainable alternative to Portland cement in construction industry. The incorporation of nano materials into geopolymer matrix contributes to enhance the mechanical and durability properties of concrete. Carbon nanotubes (CNTs) are characterized by high tensile strength and good durability properties. However, CNTs particles have significant large specific surface area that leads to encounter adhesion and dispersion difficulties in geopolymer matrix. Nano clay (NC) is utilized to increase pozzolanic activity and decrease the adhesion problems in geopolymer concrete. This research aims to investigate the hybrid effect of NC and CNTs on the resulting performances of hybrid fly ash/slag geopolymer concrete. In this study, geopolymer mixes were produced using fly ash/slag as an aluminosilicate source. The utilized alkaline activator was composed of both; sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions. Mechanical properties of the mixes were determined based on compressive and flexural strengths tests. Also the impacts of the inclusion of NC and CNTs on the air content, chloride resistance and water penetration depth on hybrid fly ash/slag geopolymer concrete were demonstrated. It was observed that the superior compressive strength for geopolymer mix was found to be in the mix incorporated by (2.5%) NC blended with (0.01%) CNTs. The engineering properties were significantly improved by using hybrid nanoparticles. The high pozzolanic effect of NC led to improve the compressive strength, as long as the nanotubes were used to reinforce the geopolymer concrete and hence enhance the durability properties.