Recycling High-Density Polyethylene (HDPE) into construction materials as a key step in plastic waste reduction: case of Kigali City

Abstract

Plastic wastes are increasing at an alarming rate and adversely affecting environment as they are not easily degraded. Worse still, roads along with parking yards have significantly shorter design life and so do other alternative road paving techniques such as reinforced concrete slabs and concrete paving blocks (developing countries). Owing to these challenges, this research aimed to minimize the quantity of plastic wastes dumped in Kigali landfills by recycling it into construction materials while considering both economic and environmental benefits. Specific objectives included to maximize the use of post-consumer plastic waste and produce alternative eco-friendly building products.

Similarly, the research aimed at determining the melting point and subsequent effects of temperature on high density polyethylene (HDPE) as well as determining the mix ratio of the material components that gives the highest compressive strength. Finally, the research aimed at assessing the performance of paving material made of sand and plastic wastes.

In order to achieve the stated objectives, three samples per data point were prepared and quantity of sand content was varying by 1:3; 1:4; 1:5 respectively while keeping plastic content constant. The samples were placed in mould of dimension 100,65 mm in diameter and height respectively where they cooled and set. Compaction was done using standard method. Afterwards, the respective samples were tested for compressive strength and water absorption. Compressive strength test showed the values of 21.73 N/mm², 26.15 N/mm², 4.79 N/mm² before heat exposure and 17.79 N/mm², 22.37 N/mm², 3.52 N/mm² after exposure to 35⁰C for 12 hours for the pavers in HDPE and sand mix ratio of 1:3, 1:4 and 1:5 respectively. Water absorption test showed an average value of 0.052% which is lower compared to the cement concrete made pavers.

The research concluded that if made and put into use, these pavers will not only reduce construction costs especially those for repairs, but also assist in environmental conservation. Roads and parking yards will be cheaply constructed, and with the increased durability, accessibility will be improved and economic growth boostered.

Keywords: HDPE, wastes, recycle, paver, compressive strength