Study on effect of sodium hydroxide concentration on geopolymer mortar

Abstract

Geopolymer mortar is an eco-friendly material that may reduce the carbon footprint by using waste material from industries like Ground Granulated Blast Furnace Slag (GGBFS) and fly ash as total replacement of cement. Sodium Hydroxide and Sodium Silicate solutions are combined together and used as alkaline activator solutions to manufacture geopolymer mortar. This paper presents an experimental study to examine the influence of Sodium Hydroxide (NaOH) concentrations viz. 8M, 10M, 12M, and 14M on the compressive strength of geopolymer mortar. Geopolymer mortar mixes were prepared having 1:3 as Fly ash to fine aggregate ratio, sodium silicate and sodium hydroxide ratio being 2.5 and 0.45 as the alkaline solution and fly ash ratio. GGBFS was used as partial replacement of fly ash by 10%, 20%, 30% and 40% to manufacture Geopolymer mortar in ambient curing. The specimens were cast in cube moulds of size 70.6 mm, cured and then tested at 3, 7, and 28 days of maturity. The test results revealed that maximum compressive strength was achieved for geopolymer mortar having 12M NaOH concentration beyond which there is a minimal decrease in the compressive strength.