Technical feasibility of pet plastic wastes as a partial replacement for fine aggregates in concrete mix

Abstract

The consumption of plastic has grown substantially all over the world in recent years and this has created huge quantities of plastic-based waste. The use of polyethylene terephthalate (PET, PETE) which is commonly used for carbonated beverage and water bottles (resin code 1) are increasing in day to day activities. The increase in use of plastics without recycling is going to yield environmental pollution as well as many undesirable effects on our health. Plastic waste is now a serious environmental threat to the modern way of living. In order to manage this environmental problem the plastic waste bottles (PET) should be recycled or reused. The aim of this research was to examine the technical feasibility of PET plastic wastes as a partial replacement for fine aggregates with in a concrete mix for better environmental management. The research was carried out by conducting tests on the raw materials to determine their properties and suitability for the experiment. Concrete mix designs were prepared using the DOE method and a total of 6 mixes with 72 samples were prepared consisting of concrete grade C-25. The specimens were produced with percentage replacements of the fine aggregate by 1, 2, 3, 4 and 5% of PET plastic waste aggregate. Moreover, a control mix with no replacement of the fine aggregate was used to make a comparative analysis. The prepared samples consist of concrete cubes, cylinders and beams. Furturemore, laboratory tests were carried out on the prepared concrete samples. The lists of tests conducted were; material property, slump, unit weight, compressive strength, splitting tensile strength and flexural strength tests. The data collection was mainly based on the tests conducted on the prepared specimens in the laboratory. The test results were compared with the respective conventional concrete properties and show that there is slight increase in compressive strength of the concrete up to 3% replacement and reduction in Compressive strength increases beyond 3% replacement due to the inclusion of PET aggregates. Also like compressive strength there was an increase of tensile strength recorded with increasing PET bottle aggregate content up to 3% replacement. But more than 3% replacement of fine aggregate with PET bottle fiber results in reduction in tensile strength. Increased flexural strength was observed by replacing amount of PET bottle fiber with fine aggregate up to three percent (3%) used. But when percentage of PET bottle fiber increased more than three percent (3%) flexural strength becomes reduced was observed. Even though this may limit its use, it has few desirable characteristics such as lower density, enhanced ductility, and a slight increase in flexural strength. The overall results show that it is possible to use recycled PET bottles in concrete tile production as a partial replacement for fine aggregates. Nevertheless, the percentage of replacement should be limited to a specified amount.