A DESIGN STRATEGY FOR OPEN GRADED FRICTION COURSE ASPHALT (OGFCA)

The technique of open graded friction course asphalt has been used since the early 1950s, and its use has developed considerably. Some advantages of open graded asphalt with respect to road safety are now accepted. They are the reduction in aquaplaning and the provision of improved skid resistance characteristics in rainy weather, as well as the minimisation of splash and spray behind vehicles and light reflection. In addition it provides a favourable impact on the environment, through a reduction in noise levels. As OGFCA has limitations such as high construction costs, short service life and maintenance in general, there is potential for improvement. It is generally realised that most specifications of OGFCA are based on experience and vary from country to country and even from state to state within Australia. Not only the nominal size of the aggregates differs, but also the bitumen type and bitumen content, the thickness of the layer placed, the temperature of mixing and the air void content. These differences could be explained by the fact that there is, at present, no rational design method for OGFCA which would include the effects of changing the components, such as type and grading of aggregates, bitumen type, etc. on the performance of the mix. This paper presents a strategy for a rational design of Open Graded Friction Course Asphalt. (a) For the covering entry of this conference, please see IRRD abstract no. 878543.