Investigation of the Effects of Recycled Powder HDPE on Fresh-Hardened Concrete with Polycarboxylate Based Admixture

As of 2020, annual global plastic production was reported to be 450 million tons [1]. It is estimated that 19 to 23 million tons of plastic waste enter the ocean each year. Given the long natural decomposition time of plastic waste, addressing this issue through recycling and reusing plastic waste is essential [2]. One of the most common application areas for recycling waste materials and reintroducing them into the economy is the construction sector [3]. In Turkey, annual ready-mixed concrete production was 105 million cubic meters according to 2022 data. According to the 2022 data from the European ReadyMixed Concrete Organization (ERMCO), while the total production volume of all EU member countries was 262 million cubic meters, Turkey alone produced 105 million cubic meters of concrete [4]. In this study, the effects of recycled high-density polyethylene (HDPE) in powdered form on fresh and hardened concrete were examined. Concrete mixes with varying proportions of HDPE substitution were prepared using natural sand as per the concrete design. Studies were conducted using the same concrete mix design and incorporating a polycarboxylate-based chemical additive to enhance the technical properties of concrete containing powdered HDPE. Eight different concrete mixtures were tested to evaluate workability and technical characteristics. Tests included slump, unit weight, and air content experiments. Compressive strength tests were performed to assess the mechanical properties of the concrete mixes. According to the study results, it was observed that the technical properties of concrete mixtures with recycled HDPE were superior compared to those of conventional concrete mixes, especially when a polycarboxylate-based chemical admixture was used. However, increasing the amount of HDPE led to higher air content in the concrete and reduced concrete strength. This highlights the need to investigate replacing HDPE with lightweight aggregates, particularly in concrete mixes requiring higher air content for freeze-thaw resistance.<br style="font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-alternates: normal; font-variant-position: normal; line-height: normal; text-align: -webkit-auto; text-size-adjust: auto;">