Evaluation of Cement- and Water-Free Concrete Using Waste Plastic Binder (Plasticrete)

Abstract

Concrete is a ubiquitous construction material that has enabled unprecedented economic growth and development worldwide. However, the production of cement, the main binder used in concrete, contributes significantly to greenhouse gas emissions and poses a major environmental threat. Therefore, sustainable alternatives to traditional concrete are imperative for mitigating the environmental impact of concrete production. This study examined the feasibility of producing “plasticrete” by mixing sand and plastic in different ratios, types, and aggregate size. The water absorption, hardened density, and compressive strength of the resultant concrete were assessed. Plasticrete cubes 50 mm in size were made using nine mix designs containing two plastic-to-sand (by volume) ratios of 50/50 and 70/30, three plastic types of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP), and four aggregate size ranges of 0.075–0.6, 0.6–2, 2–5, and 0.075–5 mm. The experimental findings revealed that including higher plastic content and larger aggregate size in concrete enhanced the mechanical properties of plasticrete. Specifically, HDPE plasticretes containing a plastic-to-sand ratio of 70/30 by volume and a sand aggregate size between 2 and 5 mm yielded the highest strength of 36 MPa. Specimens made with LDPE exhibited the highest water absorption, with a recorded value of 10.4% for specimens comprising 50% plastic content and a smaller than 0.6-mm aggregate size. Moreover, the difference in hardened density among the three different plastic types was small and not noticeable without precise measurements. The eliminated need for cement hydration for plasticrete resulted in water consumption savings. This approach holds great potential for mitigating the adverse environmental effects of concrete production by fabricating concrete with a compressive strength comparable to conventional concrete yet with a lower environmental impact. The findings of this study have significant implications for the construction industry, sustainability, and environmental preservation.