Mechanical properties and impact resistance of hybrid kenaf and coir fibre reinforced concrete

Concrete is brittle and weak in tensile but strong in compressive strength. To improve concrete weakness, fibres are added as reinforcement. In this research, kenaf fibre was hybridized with coir fibre in order to achieve optimum mechanical properties and impact resistance of fibre reinforced concrete (FRC). Since, kenaf fibre has high tensile strength and water absorption but low in ductility while coir fibre possess the opposite, the hybridization of these two fibres could complement each other. Five mixes with different kenaf:coir fibre ratios (S1100:0, S250:50, S360:40, S440:60,S50:100) at 4% fibre content by concrete volume and fibre length of 3-5 cm were tested for their mechanical properties (compressive, split tensile and flexural strengths) and ultimate energy absorption (via drop-weight impact test). It has been observed that FRC containing 100% kenaf fibre (S1) and 100% coir fibre (S5) shows the increment in all mechanical properties and impact resistance compared to control. For hybrid fibres, samples with higher content of kenaf fibre, S3 shows the highest increase for all mixes in mechanical properties, the increments are 10.8%, 37%, and 9.8% for compressive, split tensile and flexural strengths, respectively, but for impact resistance, the increment is 66.7%. For samples with higher content of coir, S4, the increment in mechanical properties are lower than S3 (8.1%, 17.6% and 3.5% but the impact resistance is the highest at 8 number of blows and 339.03 Nm of ultimate energy absorption with an increment of 166.7% compared to all mixes. The results reveal that hybrid kenaf and coir FRC exhibit enhanced mechanical properties and impact resistance compared to single kenaf/coir FRC and if application where mechanical properties is in need, hybrid fibre mix S3 is suggested and for impact resistance application, hybrid S4 is proposed