Potential Use of Plastic Waste Materials in Pavement Structures Applications

Abstract

There have been concerns worldwide on the scarcity of quality traditional construction materials that are associated with the evolution in roads construction industry and growing traffic demands. This has shifted the focus on investigating viable untraditional materials. Plastic waste has recently gained global popularity in the road building industry. The incorporation of different types of plastic waste have been investigated on the performance of the subgrade soil, on stabilizing embankments as well as on the influences of different grades of bitumen binders and hot asphalt mixes (HMA). Notwithstanding the aforementioned studies, consideration of plastic waste resins in pavement structure has not been neither reported practiced nor even allowed in the province of Ontario. That might be ascribed to the lack of compelling evidences on the beneficial impacts and feasible research studies urging the decision makers and the industry to permit and implement part of the national produced polymers in the road infrastructure. Hence, this research study aims to focus on investigating the influence of three different recycled polymers (plastics) and in two different shapes onto the performance of pavement structure components. The focus is given to the underneath granular and subgrade materials currently in practice in the province of Ontario in accordance with Ontario provincial standard specifications (OPSS). Relatively light densities of plastic flakes and pellets resulted in lowering the maximum dry densities of the investigated soil. The types, shape and the adding rate of plastic were also reflected either by an increase or a decrease on the strength of the soil as measured by the CBR test and the resilient modulus. The impact of incorporation of plastic led to a raise in the permeability of the soil samples. Results of examining the subgrade imply that partial replacement of subgrade soil material with plastic waste may prove useful in road subgrade applications. The results revealed a decline in the optimum moisture content and its corresponding maximum dry density for all types of plastic. The results also showed a noticeable improvement in strength despite variation with the shape of utilized plastic. The permeability was reduced, which is favorable to protect pavement subject to moisture. All in all, the pellets brought higher improvements compared to the ground and flake forms. Properties of fresh as well as hardened concrete (i.e., density, workability, strength, permeability, etc.) were evaluated in the final stage of the study. Assorted types of recycled plastic utilized with a 30MPa concrete mixture and based on the findings; few conclusions were made. Results showed more workable concrete mixtures that contain flakes over that contain pellets. Mixtures with plastic waste have easy workability and are suitable for use in pavement or road applications. This plastic aggregates-induced increase in air content is beneficial for the freeze-thaw resistance of the concrete pavement materials. The addition of plastic waste aggregates decreased the compressive, splitting and flexural strength of the concrete pavement samples. Additionally, adding plastic leads to the coarsening of the pore structure of the pavement concrete material and deteriorates the durability properties of the concrete, such as water absorption, sorptivity, and permeability. Outcomes are important in assessing the feasibility of using recycled plastic in producing light weight concrete mixture for various pavement application. The outcomes of the study could possibly have a significant impact on the road industry by providing recyclable source to be utilized in the road structure together with maintaining the sustainability to the environment and the quality of life.