INVESTIGATION OF COTTON DUST ASH AS A SUPPLEMENTARY CEMENTITIOUS MATERIAL FOR CONCRETE PRODUCTION

Abstract

A supplementary cementing material (SCM) is a material that when used in conjunction with Portland cement contributes to the properties of the hardened concrete. The objective of this research work was to investigate the Cotton Dust Ash (CDA) as SCM and thus to determine the effect of CDA on strength and durability properties of concrete. Then after determining the properties of CDA, sand, and coarse aggregate, C-25 grade concrete mix was designed and the cement was replaced by CDA at 5 % replacement interval up to 25% by weight. The concrete mix was produced and tested using slump test, concrete cube test, split test, water absorption test, sorptivity test, and carbonation test. The research results reveals that the workability of concrete decreases due to water-absorbent property and high specific surface area of CDA. The maximum strength for compressive and tensile strength was obtained at 5% replacement, and it increases until 20% of CDA by a decreasing rate. The cause of increment is when CDA is added in concrete the reactive silica present in CDA reacts with Ca(OH)2 liberated during cement hydration and forms additional (C-S-H) gel. The CDA addition until 25% causes reduced water absorption and sorptivity of the concrete by making the pores discontinuous due to their pore blocking effect. The specimens starting from 5%, 20%, and 25% of CDA concrete shows highly alkaline, a purple-red color as 0% CDA concrete, which means un-carbonated. This is due to when CDA is available in concrete it reduces the availability of surplus lime by way of pozzolanic reaction. From the cost-benefit analysis finding the optimum point is the point that attains the target strength with higher benefits, which is an economical point, was 10.8 % CDA. Finally, this research has attempted to provide an approach to introducing cotton dust ash a cement replacement in concrete, aiming to improve the pozzolanic activity. The experimental results verified the feasibility of this approach.