Abstract

Sand was partially replaced with prepared sawdust and rice husk respectively to produce light weight blocks. The rice husks and sawdust were used to replace sand in the order of 5, 10, 15, 20, 25, 30 %. A total of 156 blocks were produced, cured and tested for compressive strength, water absorption and bulk density. For the respective replacement materials, the compressive strengths decreased with increase in percentage replacement but increased with increase in curing age. The maximum strength for replacement with sawdust was 1.77 N/mm2 at 5% replacement and curing age of 28 days; while the minimum strength was 0.33 N/mm2 and was recorded at 30% replacement and curing age of 7 days. A maximum strength of 0.79 N/mm2 at 5% replacement with rice husk and curing age of 28 days was recorded; while the minimum strength was 0.30 N/mm2 and was recorded at 30% replacement and curing age of 7 days. Only the blocks produced from replacement with sawdust at 5% replacement and 28 days curing age had strength value greater than 1.75 N/mm2 stipulated in Federal Building Code. Blocks produced from partial replacement with sawdust were of higher strengths compared with the blocks from partial replacement with rice husks. The water absorption capabilities of the blocks grew with increase in percentage replacement with sawdust and rice husks respectively. The water absorption capabilities of blocks produced from replacement with rice husks were higher than those of blocks produce from replacement with sawdust. For replacement with both materials, the highest water absorption capacities were recorded at 30% replacement, the lowest value occurred at 5% replacements. For replacement with rice husk, only blocks produced at 5% replacement had water absorption capacity (11.34%) < 12% (minimum) provided in Federal Building Code. In the case of replacement with sawdust, blocks produced at 5% and 10% replacements had water absorption capacities 10.50% and 11.44% respectively less than 12% set as minimum in the Federal Building Code. There was decrease in bulk densities of all blocks with respect to percentage replacement of sawdust and rice husks respectively. For replacement with sawdust and rice husk respectively, 61. 11% of the tested blocks were of bulk density values less than the minimum of 1500 Kg/m3 specified in British Standard Institute. The blocks from partial replacement with sawdust were of higher bulk densities than the blocks from partial replacement with rice husks.