EVALUATION OF THE MECHANICAL PROPERTIES OF KENAF BIO FIBROUS CONCRETE COMPOSITES CONTAINING SORGHUM HUSK ASH

ABSTRACT

Fibrous Concrete Composite (FCC) is a high performance concrete that possesses an improved tensile strength and ductility under sustained load compared to Plain Concrete (PC). As a result of global search for sustainable, renewable and green materials to achieve a bio based economy and low carbon foot print environment, the use of fibre to produce fibrous concrete composite has continuously received significant research attention. Due to the growth amount of waste generation from agricultural product, there has been a developing interest in the utilization of waste in producing building materials to achieve potential benefits. This research evaluate the mechanical properties of kenaf bio fibrous concrete composites (KBFCC) containing sorghum husk ash (SHA) as partial replacement of Ordinary Portland Cement (OPC). Five volume fractions of kenaf fibre (KF) varying from 0% to 1.0% at an interval of 0.25% with a uniform length of 50mm was used with OPC concrete mixes. Another five mixes were made that replaced OPC with 10% SHA. Fresh properties of these mixes to evaluate the workability were measured using slump test, VeBe test, compacting factor test and fresh density test. It was observed that the combination of kenaf fibre and SHA decrease the slump values and increase the VeBe time of fresh concrete, the slump value of PC and the mix containing SHA were 160mm and 140mm respectively, also the mix containing fibre volume of 1% of OPC and one with SHA and fibre volume of 1% were 40mm and 25mm respectively. For the compacting factor and fresh density tests, it was observed that, as the fibre content increases there was decrease in both the compacting factor test and fresh density test. The decrease in fresh density and compacting factor was due to the density of the fibre (1200kg/m3) and the lower specific gravity of SHA (2.32) to that of OPC (3.15). The addition of kenaf fibre to either OPC or SHA concrete mixes showed a positive interaction that led to high tensile and flexural strengths, thereby increasing the concrete ductility with higher energy absorption and improved crack distribution. The maximum increases in tensile and flexural strengths compared to those of plain concrete were achieved by the addition of 0.5% kenaf fibre at the age of 56 days for the mix with OPC alone and with the mix that has SHA which are 5.35N/mm2,6.55N/mm2 and 5.15N/mm2, 5.90N/mm2 respectively. For effective waste management, use of agro waste materials such as SHA and agricultural plant such as KF can be effectively put to use in the production of a sustainable concrete material and thus provide optimum economic benefit. It is recommended that SHA and KF should be incorporated into concrete mixes aimed at improving the splitting and flexural strength of concrete. The study showed that the use of KF and SHA in the production of sustainable green concrete is technical and environmentally achievable.