THERMAL, WATER ABSORPTION AND COMPRESSIVE BEHAVIOUR OF ENERGY EFFICIENT BRICKS FROM AGRICULTURAL RESIDUES IN NAMIBIA

This study centered on ways to develop sustainable and energy efficient housing materials. The study involved determination of thermal, compressive and water absorption behaviour of bricks made from agricultural residues in Namibia. The bricks were produced using 20, 40, 60 and 80 % by weight (% by wt.), mixture of both agricultural residues and sand, with a constant composition of cement which serves as a binder. Bricks, 230mm x 110mm x 85mm, were made; sun dried; and then cured for 7 days. Evaluation of thermal conductivity, water absorption, and compressive strength were done. The thermal conductivity properties were analysed using the EPe 500 Lambda machine. Using the uniaxial Compression Testing Machine, the strength of bricks, were determined. The thermal conductivity was determined using lambda EP500 thermal conductivity test machine; while absorption tests were done by determining the initial and final weight ratios. The tests revealed that A1 bricks with 20:80 (% by wt.) mixed ratio of rice husks - sand ratio had the lowest water absorption (i.e. 3.25%) and highest compressive strength (i.e. 23.50 N/mm2 ). This was followed by B1 bricks with 40:60 (% by wt.) mixed ratio of rice husks – sand ratio in terms of water absorption and compressive strength. In terms of sustainable energy efficiency housing material requirements C1 bricks with percentage mix ratio of rice husks to sand of 60:40 (% by wt.) had the best thermal efficiency in terms of thermal resistivity (i.e. 0.5910 m2K/W), water absorption (i.e. 5.49% ) and compressive strength (i.e. 16.80 N/mm2 ). This is followed by C bricks with percentage mix ratio of maize husks to sand of 60:40 (% by wet).