Road pavement defect investigation using treated and untreated expansive road subgrade materials with varying plasticity index

Abstract

Road pavement defect has been a major issue in the construction industry leading to a high cost of maintenance and sometimes a total reconstruction of the road. Expansive road subgrade materials are one of the major causes of these road defects. In this study subgrade materials with varying plasticity index were formulated at a ratio of 25% bentonite + 75% kaolinite, 35% bentonite + 65% kaolinite and 75% bentonite + 25% kaolinite respectively. Cement and lime were used as binders to improve the engineering properties of these expansive subgrade materials to make them usable in road construction. A road pavement defect analysis was conducted to investigate the effect of varying California Bearing Ratio (CBR) and traffic load on treated road subgrade in terms of failure. Atterberg limit, compaction, characteristics, mineral structure, California Bearing Ratio (CBR), Swell and microstructural properties (Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX)) of the subgrade were also investigated in this study. The results show an increase in CBR value with a reduction in swell values translating to lesser stresses within the pavement structure which reduced rutting, fatigue and permanent deformation of the road. The study concluded that the service life of the pavement can be prolonged by reducing road pavement defects using cement and lime as binders in subgrade stabilisation.