SHEAR BEHAVIOR OF CONCRETE BEAM WITH RECYCLED AND POLYPROPYLENE AGGREGATES

Abstract

The disposal of recycled concrete and plastic waste is an environmental concern. Hence, using this recycled aggregate (RA) and waste polypropylene (PP) aggregate in new concrete can provide a workable solution for disposal. Incorporating these waste or recycled materials in concrete will introduce more inhomogeneity, voids, and weaker interfacial transition zones (ITZs). Therefore, the replacement percentages of recycled aggregate (RA) and PP aggregate, and the shear-span-to-depth ratio of the reinforced concrete beams have been examined in this study. A total of 24 longitudinally reinforced concrete beams with 1100 mm length, 100 mm width and variable depth (150 mm, 200 mm, and 300 mm) are made. Additionally, waste polypropylene (PP) is acquired through a procedure and incorporated into the concrete as a partial replacement of coarse aggregate. Four distinct polypropylene aggregate (PPA) replacement percentages 0%, 5%, 10%, and 15%, with natural aggregate (NA) and RA are considered. The beam specimens are subjected to a fourpoint bending test at 56 days. The peak load and corresponding deflection, shear capacity at first crack, ductility, toughness of the beam, and strain in the steel and concrete are all measured in this test. According to the test results, adding 5% of PPA with NA concrete increases shear capacity by 8.1 % to 9.8%. Except for one case with a 200 mm depth beam, RA concrete also shows a rise in shear capacity for 5% PPA. A similar trend is also observed for the peak load. Peak load up to 24.3% and 22.6% is observed with 5% PPA in NA and RA concrete. Yet, if more PPA is added, the shear capacity and peak load decrease. The application of RA in concrete reduces the shear capacity and peak load. Polypropylene and recycled aggregate show an increase in the ductility of the beam, especially with 5% PPA. Based on the test results, it is concluded that up to 5% PPA can be adopted in concrete with NA and RA.