Pavement design and construction in reactive clays

One of the key parameters considered for pavement design in Australia is the subgrade CBR. In reactive clays the soaked CBR value is low and influenced by many factors such as moisture conditioning of the sample, variability within the sample, surcharge during soaking and duration of soaking. These clays are also prone to volume change with changing moisture condition, which is typically reflected as shape loss and cracking in overlying pavements. Measures such as provision of a low permeability capping layer, provision of minimum cover over the subgrade and moisture conditioning of the subgrade are provided to improve the long term performance of the pavements constructed on reactive clay subgrades. Preparation of reactive clay subgrades also generally encounter difficulties. This paper presents a review and discussion on the above issues. A method of assessment of the potential long term surface movements in pavements constructed in reactive clays is also presented and discussed.