This research work detailed the report of an experimental study into the strength of modified concrete produced from mixes containing partial replacements of Ordinary Portland Cement (OPC) with groundnut shell ash (GSA). The experiments were designed to include two main mixes (with variations in the water/cement ratios) with different percentages by weight of OPC to GSA in the order of 100:0, 95:5, 90:10, 85:15 and 100:0, 90:10, 80:20 for mixes 1:2:4 and 1:2.3:2.6 respectively. For the ratio 1:2:4 mix, a total of 32 concrete cubes of sizes 150 × 150 × 150 mm and 32 cylindrical concrete specimens (100 mm diameter and 200 mm long) were cast and tested. Also, for the 1:2.3:2.6 mix, 24 concrete cubes and 24 cylindrical concrete specimens, with the same sizes as above, were cast and tested at 7, 14, 21, 28 days of curing. Compressive and splitting tensile tests were conducted to assess the strength of concrete. Generally, strengths of modified concrete increased with curing period but decreased with increased GSA percentage. For mix ratio 1:2:4, the highest compressive and tensile strengths were 24.06 (2.67) and 21.34 (2.11 N/mm2) at 28 days for 0 and 10% GSA respectively. While mix ratio of 1:2.3:2.6 gave the highest compressive and tensile strengths of 35.11 (4.21) and 27.33 (4.01 N/mm2) at 28 days for 0 and 10% GSA respectively. It was observed that 10% GSA replacement was appropriate for both mixes. GSA therefore seems to be a promising and local partial replacement material for cement in concrete making.
Key words: Concrete, pozzolana, partial replacement, groundnut shell ash (GSA), concrete strength.
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