Effect of Cow Dung Ash and Recycled Concrete Aggregates on the Mechanical and Physical Properties of Concrete: Central Composite Design (CCD) Optimisation
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Date
2023-11-15
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East African Nature and Science Organization
Abstract
Globally, concrete constructions are dependable due to their performance under diverse conditions and the availability of concrete components. However, the potential for waste concrete is high as a result of changes in human needs. For the concrete industry’s sustainable development, the ability to use recycled concrete is very important. This study aimed to investigate the effect of blending cow dung ash (CDA) with cement and waste concrete aggregates with natural coarse aggregates on concrete’s mechanical and physical properties. The approach adopted involved natural coarse aggregates (NCA) substitution with recycled coarse aggregates (RAs) derived from demolished concrete fragments as well as the use of CDA as a fractional replacement for Portland cement in the production of concrete. Response surface methodology with the central composite design (CCD) option was employed in the establishment of the effect of varying the CDA and RA on the mechanical and physical properties of concrete. Results revealed that while embedding elevated amounts of CDA lowered concrete’s compressive strength, a smaller percentage of less than 10% enriched the concrete strength past that of normal concrete. Furthermore, increases in the RA proportions from 20% to 30% translated to increases in the concrete compressive strength. The 5% CDA and 20% RA, 5% CDA and 30% RA and 10% CDA and 30% RA registered 0.88, 7.67 and 3.54% respectively greater than compressive strengths in the control experiment. In relation to water absorption, increases in proportions of CDA and RAs translated in 3.2% to 5.9% greater than water absorption rates in the control experiment. Therefore, optimised concrete of 8.80% CDA and 31.69% RA gives concrete with compressive strength of 36.82 MPa, 2315.4 kg/m3 bulk density, and 5.18% water absorption. However, CDA/RA concrete should not be used in areas where water accumulates and/ or structures that are in contact with water
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Nabuuma, R., Tigalana, D. & Otim, D. (2023). Effect of Cow Dung Ash and Recycled Concrete Aggregates on the Mechanical and Physical Properties of Concrete: Central Composite Design (CCD) Optimisation East African Journal of Engineering, 6(1), 167-187. https://doi.org/10.37284/eaje.6.1.1573