Purpose The purpose of this study is to use waste materials in construction to create sustainable practices. This will contribute towards circular economy which has gained momentum in recent years throughout the world. Design/methodology/approach Waste materials cause enormous environmental problems that can have an adverse effect on the environment. Recycling of waste consists an important part of the circular economy. Therefore, researchers have been investigating the economic use of a variety of waste materials for reducing their environmental impact. One potential usage is in road subbase fill materials where wastes can be incorporated in large quantities. In this study, the engineering properties of road subbase fill materials (i.e. kaolinite) mixed with Granite Waste (GW), coal Fly Ash (FA) and lime are investigated. Kaolinite was replaced with 15% lime and FA, whereas the GW replacement varied from 10% to 20%. Testing included strength of the various soil compositions subjected to different curing times. Also the microstructural analyses and phase changes of samples were conducted using scanning electron microscopy and x-ray diffraction techniques, respectively. The results obtained indicate that GW can be incorporated in road base materials to improve its bearing capacity. The mixture consisting of 15% lime, 15% FA, 20% GW and 50% kaolinite resulted in maximum dry unit weight and optimum moisture content. Using GW exhibited a noticeable increase in the California Bearing Ratio of more than eight times at 1 day and 28 days curing regime compared with the control sample. Findings This study shows that GW and FA can be used for road subbase materials and can contribute toward a better and cleaner environment. Originality/value In this study, the engineering properties of road subbase fill materials (i.e. kaolinite) mixed with GW, coal FA and lime are investigated. This are value added in circular economy.