The production of plastic bottles by the manufacturing industry has increased drastically over the last six decades across the globe. This rapid production has led to the generation of many waste plastic bottles, thus causing environmental pollution. About 180 tonnes of plastics are generated daily in Kampala, the capital city of Uganda, and around 50% is dumped into the Kiteezi landfill. Instead of putting pressure on the landfill, these plastic bottle wastes could be reused in stabilizing soils with poor engineering properties. The current study investigates the engineering properties of clayey soil reinforced with Polyethylene-terephthalate waste plastic bottle strips. In order to achieve the objectives of the study, the geotechnical and engineering properties of the soil reinforced with waste plastic bottle strips at 0.1, 0.2, 0.3 and 0.4% of the dry unit weight of the soil and non-stabilized soil were determined by conducting laboratory tests, such as particle size distribution, Atterberg limits, compaction test and California Bearing Ratio. The results revealed that the California Bearing Ratio of the soil reinforced with Polyethylene-terephthalate waste plastic bottle strips increased with the increase in the percentage of Polyethylene-terephthalate waste plastic bottle strips up to 0.3%. Beyond 0.3%, a drop in California Bearing Ratio was observed. It indicates that 0.3% Polyethylene-terephthalate waste plastic bottle strips is the optimum percentage for stabilizing low plasticity clayey soils.

Laterite soils mixed with Portland cement are used worldwide in making blocks. However, due to the environmental effects associated with the high usage of cement, quarry dust proved to be a good substitute for partial replacement of Portland cement. This study investigates the optimisation of laterite-cement blocks as walling materials using quarry dust. Physical properties of experimental soil were determined, and other tests such as compressive strength, density, water absorption were conducted on sample blocks under curing periods of 7, 14, 21, and 28 days. The blocks comprised of different percentages of laterite soil (76%, 81%, 85% and 87%), quarry dust (9% and 10% by weight of the soil) and ordinary Portland cement (3%, 5%, 10% and 15% by weight of the soil. The results showed that cement content of 10% and 9% quarry dust was suitable for the block at any curing period above 7 days. The compressive strength increased with an increase in the curing period no matter the percentage of the materials used in the study. The study recommends the usage of quarry dust in cement laterite blocks. However, further investigation on other vital parameters like abrasion resistance test could be conducted.