Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 21 Issue 6

Experimental Study on Effect of Plastic Waste as Coarse Aggregate on Concrete Properties Babatunde Olawale Yusuf α , Adebayo, Halir Shola σ & Shuaib, Qudus Ajidagba ρ Abstract- High demand for aggregate to meet day-to-day activities in construction industry has intensified mining of the natural aggregate resources, thereby resulting in depletion of the resources and which raised concerns on compromise of the future generation needs. Over time, the cost of construction kept increasing due to high cost of aggregates. Serious environmental concerns have been raised on the ineffective management of the plastic waste generated globally and which has caused environmental, ecological and economic sabotage. Interest in the environmentally friendly recycling of plastic waste as materials for concrete is being considered. This study investigates the performance of concrete with addition of plastic Poly ethylene terephthalate (PET) aggregate. The plastic PET aggregate was used as substitution for coarse aggregate at 10%, 20% and 30% replacement levels. Effects of the presence of plastic PET aggregate in concrete on workability, density, compressive strength, flexural strength and water absorption were determined. The results showed that the workability increases as the proportion of PET plastic waste increases in the concrete matrix. In comparison with the control concrete, the compressive and flexural strength of concrete reduces as the content of plastic PET aggregate increases. Compressive and flexural strength reduction trends of 25%, 47% and 53% and 38%, 43% and 51% for concrete containing 10%, 20% and 30% of plastic PET aggregate respectively. The loss of strength can be attributed to the ineffective bonding between plastic PET aggregate and mortar due to the smooth surface of the plastic PET aggregate. Also, plastic PET aggregate has relatively no water absorption and which makes excess water in the concrete. Upon hydration, the excess water gets evaporated and which creates voids in the concrete and weak region around the aggregates in the concrete. However, improvement in water absorption capacity were observed. As the content of plastic PET aggregate increases, the water absorption capacity reduces. However, significant reduction in strength properties was obtained for concrete with 20% and 30% of PET plastic waste. Meanwhile, the water absorption capacity of the concrete composite gets higher as the proportion of the PET plastic waste increases. From the study, it can be said that sand can be substituted with PET plastic waste up to 10% replacement levels in concrete matrix. Keywords: alternative materials; compressive strength; environmental impact; coarse aggregate; flexural strength; and plastic pet aggregate. I. I ntroduction here has been yearly rapid growth in the demand for construction materials, largely due to rise in population, urbanization and industrialization. Concrete is one of the major construction materials, and aggregates represents about 65 – 85 % by volume in concrete composite (Bahij et al., 2020). Currently, the yearly demand for concrete is estimated to be about 10 billion tons, and which has been projected to increase to 18 billion tons by the year 2050(Asadi et al., 2018). The high rate of usage of aggregates for day-to-day activities in construction has raised concern on the depletion and overexploitation of the natural resources, thereby, hindering the future needs of this resources by future generations. It becomes imperative to seek for alternative materials that could match up with the engineering properties of the conventional aggregates for structural and non-structural purposes. Ecosystem and ecological systemsare becoming unsafe from generated plastic waste. Continuous increase in plastic usage and plastic waste generation growth have posed serious environmental concerns. In the year 2012, about 280 million tons of plastic waste was generated globally, and it rose to 335 million tons in the year 2016. It has been estimated to be around 1 billion tons by the year 2050 (Bahij et al., 2020).However, the global management of the large chunk of plastic generated is still low, as 22 % was recycled, 27 % incinerated and the majority ended up in landfills and dumpsites(Li et al., 2020). In Nigeria, about 32 million tons of plastic waste is generated annually, below 12% is recycled and about 80%finds their way to landfills and dumpsites (Kehinde et al. 2020). It has been reported that over 10 million tons of plastic waste ended up in ocean annually, and which contributed to the death of 100,000 marine animals and 1 million sea birds (Faraj et al., 2020). It has been forecasted that oceans will have more plastics than fishes by 2050 (Kehinde et al. 2020). It becomes necessary to improve the management of plastic waste generated. One of the effective ways is the recycling of plastic waste as aggregate for construction purposes. Being a new material, there is need to investigate the performance of concrete produced with plastic waste as aggregate. There are different types of plastics, but plastic Polyethylene Terephthalate (PET) is one of the larger percentages of plastic waste as it is commonly used T 1 Global Journal of Science Frontier Research Volume XXI Issue VI Year 2021 43 ( H ) © 2021 Global Journals Version I Author α σ ρ : Department of Civil Engineering, University of Ilorin, Ilorin, Nigeria. e-mail: babatundeyusuf990@gmail.com