Abstract
The management of plastic waste is a massive challenge and the recycling of plastics for newer applications is a potential solution. This study investigates the feasibility of using polyethylene terephthalate (PET) powder in cementitious composites. The changes in the strength and microstructure of Portland cement incorporating PET powder with different replacement ratios were systematically analyzed through the measurements of compressive strength, isothermal calorimetry, X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy. In addition, the possible chemical changes of cement paste samples were studied upon exposure to different conditions, including deionized water, seawater, and simulated pore solution. Based on the test results and analysis, no apparent chemical changes were observed in the cement paste samples, regardless of the exposure conditions. In contrast, the PET powder incorporated into concrete exhibited remarkable changes, which may have occurred during the mixing process. The results also suggested that the maximum replacement ratio of PET powder should be less than 10% of the binder (by mass) to minimize its influence on cement hydration, due to the interaction between water and PET. The PET-containing samples showed the presence of calcium aluminate hydrates which were absent in the neat paste sample.
Highlights
The generation and disposal of plastic waste is a global concern
Single-use plastics make up the majority of the plastics produced and are directly related to the generation of plastic waste, and the demand for plastics is dramatically increasing in many areas, including the medical sector, owing to the outbreak of COVID-19 [3]
It was observed that the incorporation of up to 10% polyethylene terephthalate (PET) powder did not reduce the heat of hydration significantly, while there was a remarkable decrease in the cumulative heat released over 50 h when the PET content was increased to 20%
Summary
The generation and disposal of plastic waste is a global concern. It is estimated that 99 million metric tons of plastic waste was generated in 2015, and the number is expected to triple to 155–265 million metric tons by 2060 [1]. Environmental problems related to the disposal of plastic waste have become more serious since China, which previously imported 45% of globally produced plastic waste, banned the import of most plastics a few years ago [2]. Single-use plastics make up the majority of the plastics produced and are directly related to the generation of plastic waste, and the demand for plastics is dramatically increasing in many areas, including the medical sector, owing to the outbreak of COVID-19 [3]. The issues of plastic waste are compounded by microplastic pollution in ecosystems [4]. It is essential to create value-added applications for reused and recycled plastic products
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