Compressive strength of class F fly ash blended geopolymer- hybrid mortar

Abstract

Day by day construction industry require large amounts of cement to satisfy development of buildings, facilities and infrastructures, that demand presented undesirable increase in CO2 emitted the environment as 1 ton of cement produce approximately 1 ton of CO2. Aiming to reduce usage of Portland cement new technology of binders was researched such as Geopolymer binders. General composition of geopolymer contain aluminosilicate source materials such as fly ash or fly ash combined with GGBFS, and alkaline activator such as a mixture of sodium hydroxide (NaOH) and sodium silicate solution. However, geopolymers suffer from some limitations such as the variation in chemical content, the calcium content, dosage of alkaline activator and Na2SiO3/NaOH ratio, additionally geopolymers has brittleness and low toughness which require additional materials to mitigate normally some sort of reinforcement fibres which can drive the cost very high. The objective of this research is to investigate the enhancement in compressive strength of geopolymer mortar by incorporating Ground Granulated Blast Furnace Slag (GGBFS) with class F fly ash in blended geopolymer, also the addition of commercial grout to form blended geopolymer–hybrid mortar. GGBFS replaced fly ash by 10%,20% and 30% of total mass, and commercial grout then was added by 10%,20% and 30% to each blended mixture. All samples where cured in ambient temperature. It was found that incorporating GGBFS and commercial grout increase the compressive strength in early age of curing and slightly at 28 days. Furthermore, 10M concentration of NaOH yielded the highest strength with the blended geopolymer-hybrid mortar.