Determination of the Compressive Strength Properties of Alkali-activated Millet Husk Ash - Calcium Carbide Mortar

Abstract

Alkali-activation of agro-industrial wastes as an alternative binder to Portland cement (PC) is receiving more consideration most notably in the developed nations due to issue of green-house gas (CO2) emission from the production process of PC. This research focused on developing a suitable proportion combination of millet husk ash (MHA) – calcium carbide waste (CCW) and evaluate the fresh and hardened properties of alkali-activated MHA – CCW binder-based mortar sample. The chemical analysis of the supplementary cementitious materials via X-ray fluorescent (XRF) revealed MHA having 73.4% silica (SiO2) content, while CCW primarily contains CaO (66.1%). Three combination proportions of MHA – CCW (40:60, 45:55 and 50:50) were activated with different molar concentrations of sodium hydroxide (NaOH): 5M, 10M, 15M and 20M respectively. The mortar was produced at 1:3 binder/sand (B/S) and 0.5 water/binder (W/B) examined for binding, hydration and strength development and water absorption at varied curing ages (3, 7, 14, 28, and 56 days respectively) in accordance to BS EN 196-1: 2016. The MHA – CCW samples tested exhibit increasing performance for both properties examined with increasing NaOH concentration up to 15M but decreased performance at 20M for all combination proportions. At 56 days of curing the 45:55 MHA – CCW at 15M NaOH molarity possessing similar compressive strength and water absorption as the control.