Utilization of Recycled Plastic Waste in Fiber Reinforced Concrete for Eco-Friendly Footpath and Pavement Applications

Abstract

The use of concrete in road construction has grown over the past decade due to the material’s great durability. However, concrete has poor tensile strength, ductility, and energy absorption. This paper aims to investigate the utilization of plastic waste, namely polypropylene (PP), to create a novel fiber to enhance the engineering properties of fiber reinforced concrete (FRC), an eco-friendly concrete that can reduce environmental problems. The 28-day design strengths of 28 and 32 MPa were used in this study because the compressive strength requirements for concrete footpaths and pavement specified by Austroads and the Department of Highways, Thailand, were at least 25 and 32 MPa, respectively. The fiber (F) was a mixture of virgin PP and recycled PP (RPP). The study used F contents of 0.25, 0.50, 0.75, and 1% by weight of cement and PP:RPP ratios of 100:0, 75:25, 50:50, 25:75, and 0:100. The compressive strength, flexural strength, leaching, and CO2 emissions savings of FRC were evaluated. Improvements in the compressive strength, flexural strength, and toughness of the samples with F were observed in comparison to the control concrete samples for all design strengths. All mixtures met the compressive strength requirements for concrete footpaths, except for F contents of 0.75 and 1% and a PP:RPP ratio of 0:100. By contrast, the 32 MPa FRC samples with F contents of 0.25 and 0.5% and all PP:RPP ratios met the requirements for rigid pavement. From an environmental perspective, the heavy metal contaminants of the 32 MPa FRC sample were within the allowable limits for all mixtures. Regarding incineration disposal, the maximum CO2 emissions savings of 28 MPa and 32 MPa FRC with an F content of 0.5% and a PP:RPP ratio of 0:100 were 1.0 and 1.11 kg CO2-e/m3, respectively. This research will enable plastic waste, traditionally destined for incineration and landfill disposal, to be used as a sustainable fiber in the construction industry.