Properties of nano silica modified cement less geopolymer composite mortar using fly ash and GGBS

Abstract

Geopolymer concrete/mortar has been gaining attention worldwide since it has become an alternative option to overcome various sustainability and environmental related problems associated with construction as the source material fly ash is obtained as a byproduct due to the firing of coal in power stations. In the present study, geopolymer mortar was synthesized using the pozzolanic source materials like fly ash blended with Ground Granulated Blast Furnace Slag (GGBS) along with alkaline activator liquids with inclusion of different percentages of nano silica. Relevant test standards were used to determine the fresh characteristics of geopolymer mortar such as time for initial setting and workability. The hardened properties like flexural strength, compressive strength and water absorption were also explored. Parameters like the ratio of fine aggregate to pozzolanic material and the ratio of alkaline activating solutions to pozzolanic material are correspondingly 1:1.5 and 0.4:1. Alkaline solutions consist of one part of Sodium Hydroxide (NaOH) and 2.5 parts of Sodium silicate (Na2SiO3). The pozzolanic material is composed of 10% of GGBS and 90% of fly ash. Five mixes were prepared by adding nano silica as an additive in 0%, 1%, 2%, 3%, and 4% by weight of cementitious material. Mortar samples were prepared and cured under ambient conditions for various tests. Addition of Nano silica by 1% to the mortar mix contributes positively to various properties of geopolymer mortar.