Improvement of Road Subgrade using Waste Tyres

The increasing number of waste tyres globally is imposing huge threats on the environment, deeming a necessary proper disposal. One way of disposing these waste tyres is by using it in subgrade as stabilizers. In this paper, research has been carried out on the improvement of road subgrade using waste tyres by conducting laboratory experiments to economically increase the strength of subgrade. Sieve analysis, Atterberg Limits test and free swell test were performed on the soil for classification and suitability purposes. Different percentages of waste tyre crumbs ranging from 2% - 8% were mixed with soil on which California Bearing Ratio test and Modified Proctor Tests were performed to determine the soils strength and their respective optimum moisture contents. Results revealed that inclusion of 6% waste tyres by soil weight was the optimum percentage. Design of pavement for natural and tyre-reinforced subgrade soil revealed a reduction in pavement thickness by 92 mm for tyres-reinforced subgrade. Cost analysis of pavement constructed over weak subgrade by conventional method and reinforcement with tyres showed a saving of 8.39% when tyres were used, thereby inculcating economic benefit. The use of waste tyres in sub-base layer and its environmental impacts are recommended to be explored.