Strength and microstructural properties of binary and ternary blends in fly ash-based geopolymer concrete

Carbon dioxide emissions and the consumption of natural resources related to the cement manufacturing have prompted the need to develop more sustainable and environmentally friendly types of concrete. Geopolymer concrete is considered eco-friendly concrete because it is free of cement. Otherwise, nanomaterials have been introduced into geopolymer concrete in previous works with the aim of improving its properties. However, very restricted studies have focused on the combined utilizing of nano-clay and nano-titanium in geopolymer concrete. Therefore, in the current research, geopolymer concrete was developed from industrial wastes (fly ash; FA) by using a novel mixture of different nanomaterials: nano-clay (NC) and nano-TiO2 (NT). Mixtures with constant water to FA (12 %), and different alkaline contents: (40 %, 45 %, and 50 %) by FA, were performed and divided into three groups. In the first group, only FA was used as a binder, meanwhile, a combination of (FA+NC) and (FA+NT) was used separately in group two (binary). In the third group, (FA+NC+NT) were mixed together (ternary). Several hardened tests have been investigated: compressive, tensile strengths and density. Also, microstructural characteristics were monitored using XRD and SEM tests. The findings revealed that the addition of nanomaterials obviously enhanced the density of the microstructure, reducing the pores of the produced geopolymer concrete. Moreover, the compressive strength was enhanced up to 38 % for NC, and 24 % for NT in the binary blends while the improvement reached 55 % in the ternary blends.