Unacceptable levels of dust are generated on the unsealed road networks in most countries. In the past, dust has mostly been considered as a safety hazard and nuisance. However, research on unsealed roads has revealed that the loss of fines associated with road dust contributes to increased gravel loss and the need for more frequent maintenance. By controlling this dust, the rate of gravel loss and maintenance expenditure can be significantly reduced. Research into the performance and benefits of using dust palliatives for unsealed road maintenance in South Africa has resulted in the development of calibration factors for unsealed road performance prediction models. These factors can be used in road management systems to determine where the dust palliation products can be used cost-effectively. In a study with a South African road authority, the factors for calcium chloride were first validated in a pilot project, before being implemented in a computerised road management system. Output from the system indicated that calcium chloride could be cost-effectively used on 20 per cent of the road network. Considerable savings accrued to both the authority and the road user. The regravelling frequency changed from seven years to fourteen years resulting in a significant conservation of already scarce gravel resources. The performance of various other dust palliatives is currently being monitored in order to develop calibration factors for their inclusion in management systems. (a)
Abstract