Optimizing density, water absorption and compressive strength of paving blocks molded from plastic waste to address plastic pollution
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Date
2024
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Busitema University
Abstract
The production and usage of plastics are rapidly increasing in our daily lives, leading to significant disposal challenges, including landfill overflow, environmental pollution, microplastic formation, emissions from incineration, and increased economic costs associated with waste management. This study, therefore, aims to mitigate these effects by investigating the optimization of the physical properties of paving blocks molded using plastic waste as a binding material, thus offering a sustainable solution for plastic disposal through construction. Two types of waste plastic materials were used: Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC). Additionally, two sand particle sizes, 0.5 mm and 1.2 mm, were selected to comprehensively evaluate their impact on the physical properties of the paving blocks and to identify the optimal mixture for enhanced performance. These particle sizes represent a range of fine and coarse sand, allowing for a thorough investigation of how varying sizes influence the response variables. PET plastic was collected from disposal points, dustbins, and surroundings in Tororo municipality while PVC from construction sites still in Tororo municipality, Eastern Uganda, while the sand was sourced from a construction site at Tororo Girls’ School in Tororo municipality. The molten waste plastic and sand were mixed in different proportions based on Central Composite Design (CCD), a statistical method within Response Surface Methodology (RSM) that systematically explores multiple factors affecting response variables, ensuring the optimal combination for the desired physical properties. RSM was employed to analyze the experimental data and model the relationships between the variables, enabling the identification of optimal conditions for achieving the desired physical properties, (density, water absorption, and compressive strength) of the paving blocks. Models were developed to fit the experimental results, with all density models being successful. The water absorption model for PET was successful for both sand particle sizes, the water absorption model for PET was successful for both sand particle sizes; in contrast, no model could be established for PVC molded pavers, as absorption values consistently registered at 0.000 across all composition ratios. This outcome indicates that the hydrophobic nature of PVC not only contributes to its resistance to water absorption but also facilitates effective bonding of sand particles, without pore spaces formation. Only the combination of PET with a sand particle size of 1.2 mm produced a successful model for compressive strength, while other combinations did not yield satisfactory results. This combination exhibited successful models for all evaluated responses, highlighting its potential as the optimal combination for molding the desired paving blocks. Using the Response Surface Methodology (RSM), the optimal combination for molding the paving blocks was determined to be 148.28 g of sand and 50.0 g of PET plastic, which meets the parameters of low density, low water absorption, and high compressive strength. The results imply that utilizing plastic waste as a binding material in paving blocks not only offers a sustainable solution for reducing plastic waste but also producing high performance pavers, thereby addressing the critical issue of plastic pollution while creating durable paving blocks.
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This is a master thesis about Optimizing density, water absorption and compressive strength of paving blocks molded from plastic waste to address plastic pollution.
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Citation
Ronald, H. K. (2024). Optimizing density, water absorption and compressive strength of paving blocks molded from plastic waste to address plastic pollution [Master’s thesis]. Busitema University.