The Effect of Using Waste Automobile Tires and Palm Kernel Shells as Coarse Aggregates in Concrete on Tensile Strength and Failure Modes

Abstract

The use of waste materials as aggregates in concrete is hailed by many as a huge step towards addressing the overreliance on granite stones as aggregate in concrete. It also offers a strategic eco-friendly means of disposing these wastes to minimize their impacts on the environment. This study assessed the tensile strength and modes of failure of concrete that utilizes waste automobile tire chips and palm kernel shells (PKS) as partial to full replacement of the conventional crushed granite stones as coarse aggregates in concrete. Portland cement concrete with the mix ratio: 1: 1.5: 2.5 (cement: sand: granite coarse aggregate) based on the mass of the constitient materials was prepared as control from which twenty additional mixes were generated by replacing portions of the granite stones with PKS and tire aggregates while the sand and w/c ratio were kept constant.  A total of 105 cylindrical specimens (150 x 300mm) and 155 beams (100 × 100 × 500 mm) were cast to evaluate the split tensile (fspt) and flexural tensile (fct) strengths of the concrete mixes at 7, 14, 21, 28, 56 and 90 days of curing while observing their modes of failure. The results showed that, there is systematic decrease in the tensile strengths of the concrete with increase in the volume of tire and PKS particles. However, up to 50% replacement level, adequate tensile strength can be achieved for structural purposes. At this replacement level, the mix with P50T50 recorded fct of 3.10 N/mm2, representing 59% of the control mix. From the failure patterns observed, the mixes with high volume of tire exhibited ductile failure mode; thus giving ample warning before the ultimate failure while the PKS concrete’s failure were more brittle and explosive.  In conclusion, a blend of PKS and tire as aggregates in concrete is recommended especially for structures subjected to sudden loadings such as those located in earthquake zones.