PERFORMANCE EVALUATION OF ENGINEERED CONCRETE WITH RECYCLED WASTE POLYPROPYLENE

Abstract

Plastic waste generation is a major threat to the environment due to its non-biodegradable nature where polypropylene (PP) includes more than 35 percent of the total waste generation. These plastic wastes can be recycled and reused in concrete as an alternative to natural stones, thus preserve the environment. Therefore, this study aims to investigate the structural and durability performance of concrete partially mixed with recycled waste polypropylene (PP) plastic chips as coarse aggregate. To evaluate the performance of concrete, twelve different mixes were considered where crushed stones were replaced by PP at 10% and 20% (by volume replacement) with four different water-cement ratios (0.35, 0.40, 0.45, and 0.50) and compared with concrete with no polypropylene aggregate (control specimen). Water reducing admixture was used with samples of 0.35 and 0.4 water-cement ratios. The physical performance of concrete was evaluated in terms of strength parameters like compressive strength, tensile strength, flexural strength, stress-strain behavior, pull out strength, etc. Additionally, durability performance was evaluated through the shrinkage test, chloride ion penetration, and compressive strength at high-temperature exposure. It appears compressive strength and tensile strength reduction were 12% and 21% respectively for 10% of PP replacement. The results of pull-out strength indicate that PP can be used in structural concrete safely as these parameters were reduced up to 24% with 10% of PP replacement. The reduction rate for modulus of elasticity was 19%. However, the toughness index has shown improvement with an increment of up to 25%. In the case of durability, all the concrete samples have been fallen under a moderate category according to the test method for chloride ion penetration which indicates adequate durability of the concrete sample. Moreover, PP can also be used to produce lightweight concrete due to its lower unit weight, as the relative reduction was up to 10% in density for 20% of PP replacement than regular concrete. It also appears, at high-temperature exposure xv (more than 200° C) for 1 hour, the compressive strength of concrete was still more than 20 MPa. Therefore, concrete with a low to moderate proportion of PP is safe and can generate strong structural elements is not only in the context of sustainability and environmental protection but also in engineering aspects.