Effect of Super-plasticizer on Setting Time and Strength of Mortar made using Rice Husk Ash (RHA) and Calcium Carbide Waste (CCW) as Binder

Abstract

Portland cement (PC) is a binder that is most commonly used as construction material in the production of mortar in masonry and concrete. The manufacturing process of PC during clicker production is however noted to contribute to CO2 emission which makes it a non-eco-friendly material. Notwithstanding, reports on the total replacement of PC are scarce in the literature. Sorghum husk ash (SHA), which is an incinerated ash from agricultural by-product consisting majorly of amorphous silica (SiO2), when combined with calcium carbide waste (CCW) an industrial by-product generated from an acetylene gas production process with major component of lime (CaO) in the presence of water forms compounds possessing cementitious properties. This paper reports on the early-age properties of SHA (as SiO2 source) and CCW (as CaO source) binder in mortar. Paste from different binder combinations of SHA/CCW was studied for setting time while the mortar samples were used to study the rate of hydration and strength development. The study revealed the SHA sample to be of high SiO2 (84%) and CCW is majorly CaO (66% content). The results obtained showed improvement in the performance of binders with superplasticizer formulated from 70/30, 60/40 and 50/50 SHA/CCW respectively, having 28days compressive strength of 7.6 N/mm2 [MPa], 7.0 N/mm2[MPa] and 5.7N/mm2[MPa] representing 36%, 34% and 28% of cement type I (CEM I) strength. The study showed that the addition of superplasticizer reduced the water demand and improved the rate of hydration. The binder combinations of 70/30, 60/40, and 50/50 SHA/CCW with water-reducing admixture can be adopted for use in masonry works as it conforms to type N of ASTM C270 mortar.