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.
