Preparation and Characterization of Paving Blocks from Polyethylene-Based Plastic Waste and Natural Fibre

The current methods of managing plastic waste especially in developing countries have become an issue of environmental and public health concern globally. This has led environmentalists and scientists to work on finding day-to-day activities that can help to reduce the plastic waste disposal problem. Recycling and reuse of plastic waste into construction materials is a valid way to reduce the effect of this improper disposal of plastic waste. This will help to reduce the negative impact of the high cost of cement in the construction industry. In this research, polyethylene waste (table water sachet) was used as a replacement for cement in the construction of paving blocks. The sample with a 1:4 mixing ratio was found to have the highest compressive strength among the different mix ratio examined. Paving blocks were then produced with this mixing ratio from plastic-aggregates and plastic-aggregate-fibre and compared with the standard cement-aggregate paving blocks for their compressive and tensile strengths, water absorption, thickness swelling, density, and thermal properties (thermogravimetric analysis (TGA) and horizontal burning rate). Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) was also conducted on the paving blocks to determine the distribution of the particles of the blocks, the compatibility of the matrix, and their elemental composition. The results of the compressive strength test showed 18.1667 Nmm<sup>-2</sup> for plastic-aggregate block, though lower when compared with the cement-aggregate block with a compressive strength of 21.6667 Nmm<sup>-2</sup>. The plastic-aggregate block has the least water absorption value among the three samples. The 0.1350% and 1.8861% water absorption values obtained for the plastic-aggregate and plastic-aggregate-fibre bricks respectively showed an impressive water absorption which falls within the maximum of 5% water absorption for quality paving blocks. The plastic-aggregate and plastic-aggregate-fibre both also recorded lower density when compared with the cement-aggregate block, which gives them a logistic advantage over the cement-aggregate block in the case of transporting them from one location to another. The blocks were found to be stable at low temperatures. The SEM images of the plastic-aggregate and plastic-fibre-aggregate paving blocks clearly showed a consistent dispersion of the plastic waste particles within the aggregate matrix over that of the cement-aggregate paving block. Therefore, plastic-aggregate brick can be recommended for use as paving bricks for low-traffic roads, walkways, parks, and gardens, although there is need to carry out further studies on other material properties of the plastic-based paving block.