The stabilization of urban pavements founded on expansive clay subgrades in Victoria, Australia

Expansive clays cover vast areas of the globe including the United States, Canada, South Africa, Middle East, Europe and Australia. Movements in expansive clays are the result of moisture change. The migration of moisture is affected mainly by the suction characteristics of the clay and by the neighbouring tree roots. The clay profile near the surface that is within the depth of seasonal movement experiences cycles of shrinkage and heave that causes pavements to crack and lose their shape Moisture control of expansive soil subgrades for Local Government pavements continues to cause problems that are responsible for maintenance and performance of these pavements. Pavement damage is featured through the presence of longitudinal cracks, loss of shape and rotation of the kerb and channel. The current stabilization techniques are not entirely suitable for either existing or new urban pavements founded on expansive soils. The presence of trees and underground services will always remain the biggest challenge to the practical and economical viability of any method. Therefore, there is a need to seek a new technique of creating a stable moisture regime beneath urban pavements. The use of conventional heating in a road construction process was investigated in the early 1900s. This treatment method was abandoned for many reasons, including the insufficient depth of heat penetration, economics and environmental concerns. The hypothesis of this research is that clay processing using microwave (M/W) heating may provide a solution to expansive subgrades of new and existing pavements due to a number of factors. These include: penetrating radiation, controllable electric field distribution, rapid heating, selective heating of materials through differential absorption, self-limiting reactions, and finally the potential for portability and remote processing. The M/W processing of expansive clays, which is non-intrusive nature, is a completely new approach that is examined by the author. It involves the use of microwaves to change the clay particles to produce a new microstructure that is not capable of rehydration. The research provides an evaluation of the conditions or parameters needed for a successful application of M/W processing. It also identifies its limitations and weaknesses, and finally provides a list of further research work required for a prototype insitu application. The M/W method is shown to be an attractive and favorable possibility for future large-scale insitu applications.