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Exploratory study of crushed coconut shell as partial replacement for fine aggregates in concrete

A.W. Otunyo, C.C. Ofurum, C. Benson

Abstract


An exploratory study of crushed coconut shell (CCS) as partial replacement for fine aggregate in concrete was carried out. Mechanical and Physical properties of the CCS and fine aggregate (river sand) were determined and compared. A total of 36 concrete cubes of size 150 x 150 x150mm with mix ratio of 1:2:4 and  water/cement ratio of 0.5 using proportions, 0:100, 25:75, 50:50 and 100:0 CCS  to fine aggregate (river sand) were cast, cured and tested for compressive strength after 14, 21 and 28 days. Compressive strength for 0:100, 25:75, 50:50, and  100:0 CSS: river sand proportions for the 14, 21 and 28 days are (23.85, 24.8, 32.0), (12.29,12.73, 13.80), (15.17, 15.40, 16.44) and (3.23, 3.70, 4.78)  respectively. The trend shows a decrease in strength as the quantity of CCS in the concrete cubes increases. The workability of the concrete decreased as the quantity of CSS increased with the mould slumping at 100% CSS. Aggregate Crushing Value (ACV) for CSS is 8% and that for fine sand is 17.89%,, while Aggregate Impact  Values (AIV) for the CCS is 1.22% and that for river san is 11.8%. Sieve analysis, moisture content, and bulk densities of the CCS, rivers sand and coarse aggregates were also determined. The unit weight of the concrete cubes decreased as the  quantity of the CSS increases in the concrete. The compressive strength of the  50:50 sand: CSS replacement at 28 days for the 1:2:4 mix ratio is 16.44N/mm2. It therefore follows that at 50% CSS replacement, the concrete produced can be used as lightweight concrete. It is estimated that cost reduction of 50% will be achieved.

Key Words: crushed coconut shell, concrete, fine aggregate, workability,   compressive strength and slump.




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