Abstract:
The utilization of agro-industrial waste as an alternative binder to Portland cement (PC) through alkali-activation has gained prominence, particularly in developed countries, due to concerns about greenhouse gas emissions from PC production and the desire to enhance the properties of agro-industrial waste-based concrete. This investigation focuses on the development of mortar using an alkali-activated binder composed of millet husk ash (MHA) and calcium carbide waste (CCW), aiming to characterize the materials and assess the fresh and hardened characteristics of the resulting mortar. MHA, an agricultural by-product, and CCW, an industrial by-product, were studied as potential alternatives to PC. Three blend proportions of MHA and CCW (40:60, 45:55, and 50:50) were determined based on their CaO and SiO2 content. These blends were activated using sodium hydroxide (NaOH) concentrations of 5, 10, 15, and 20 molar, and mortars were fabricated with a binder-to-sand ratio of 1:3 and a water-to-binder ratio of 0.5. The binding ability, strength development, and water absorption of the mortars were evaluated at various curing durations (3, 7, 14, 28, and 56 days) following the BS EN 196-1:2016 standard. Chemical analysis via X-ray fluorescent (XRF) revealed that MHA contains 73.4% silica (SiO2) and an aggregate of main oxides (SiO2 + Al2O + Fe2O3) totaling 88.1%, exceeding the 70% minimum stipulated by ASTM C618 (2015). CCW predominantly contains 66.1% CaO. Fresh properties testing of the binder pastes demonstrated that the 45-55 (MHA-CCW) blend with 15M NaOH exhibited comparable fresh properties to the PC control. The examined mortar samples exhibited improved performance in both properties with increasing NaOH concentration up to 15M, although performance decreased at 20M for all blend proportions. At 7 and 14 days, the strength of the 45-55 MHA-CCW blend activated with 15M NaOH reached 67% (10.72 N/mm2) and 79% (15.96 N/mm2) of the PC-based sample, respectively. At 28 days, the strength gain for the 45-55 MHA-CCW blend activated with 15M NaOH was 29%, surpassing the 23% gain of the PC-based mortar. Prolonged curing of alkali-activated MHA-CCW mortar up to 56 days resulted in an additional 24% strength increase over the 28th day, in contrast to the 7% increase in the control. This trend was consistent for all alkali-activated MHA-CCW blends studied up to 15M NaOH concentrations. The study identifies the 15M NaOH activation of the 45-55 MHA-CCW blend as optimal for achieving robust strength. The research recommends employing the 45-55 MHA-CCW blend activated with 15M NaOH in a 1:3 binder-to-sand ratio and 0.5 water-to-cement ratio for masonry applications. Additionally, the study suggests further investigations into the hydration morphology, nature, and formed microstructure of alkali-activated MHA-CCW mortars.
Utilizing Alkali-Activated Millet Husk Ash and Calcium Carbide Waste Binder for Enhancing Mortar Characteristics. GET MORE, ACTUARIAL SCIENCE PROJECT TOPICS AND MATERIALS
