Exploratory Study on Agro-Waste Ashes Combination with Industrial Waste as Alternative Binders in Concrete

Abstract

Portland cement (PC) been the world's most commonly used binder in mortar/concrete applications is adjudged a non-environmental-friendly material due to its greenhouse (carbon dioxide, CO2) gas emission mainly during production. Previous studies on the search for alternative binders had centered on the utilization of natural Pozzolan or ashes from agricultural wastes (agro-wastes) as partial replacement of PC in mortar or concrete construction while reports on total replacement are scarce in the literature. Incinerated ashes from agro-wastes at controlled temperature have been found to be pozzolanic with major components been amorphous silica which combines with lime in the presence of water to give cementitious properties. This paper report on an exploratory study on agro-waste ashes (RHA and SHA – silica sources) in combination with industrial waste materials (calcium carbide waste (CCW) – a CaO source) as alternative binder for total PC replacement in mortar/concrete construction. Pastes from the different combination ratios RHA/CCW and SHA/CCW were studied for setting times, degree of hydration, and strength development. The study revealed the RHA and SHA samples to be of high SiO2 (93% and 84%) while CCW is majorly CaO (66% content). The agro-industrial binders (RHA/CCW and SHA/CCW) showed good binding properties at a slow hydration rate. Mortar samples from 60/40 RHA/CCW and 70/30 SHA/CCW give the best performance having 28day compressive strength of 5.3 N/mm2 [MPa] and 7.5 N/mm2 [MPa] representing 25% and 35% of CEM I strength.