Flexural strength of reinforced revibrated concrete beam with sawdust ash as a partial replacement for cement

This article examines the flexural strength of reinforced and re-vibrated concrete beams using Saw Dust Ash (SDA) as a partial replacement for Ordinary Portland Cement (OPC). Chemical analysis of the SDA sample contains the major chemical oxides found in cement: SiO2 (27.23%), Al2O3 (29.05), Fe2O3 (9.32%). Seven beams of sizes 150mm x 150mm x 600mm reinforced with 12mm diameter steel bars (Y12) were cast for each 0%, 5%, 10%, 15% and 20% replacements of OPC with SDA. The beams were re-vibrated for 20 seconds at an interval of 10 minutes successions up to 1 hour after initial vibration. Another set of three beams of same size and reinforcement for each percentage replacements of OPC with SDA were also cast but were not revibrated. Fifty beams were cast in total: thirty-five revibrated and fifteen non-revibrated beams and were all cured for 28 days. Flexural strength test carried out on each beam shows maximum flexural strength at 0% followed by 5% replacement at twenty (20) minutes revibration time lag interval. The maximum flexural strength attained were 10N/mm2 at 0% then 9.5N/mm2 at 5% for the revibrated beams respectively, while for non-revibrated beams 8.87N/mm2 and 6.67N/mm2 for 0% and 5% replacements were attained. Revibration is thus seen to improve the flexural strength of reinforced concrete beams and thus SDA can be used up to 5% to replace cement.