LABORATORY PERFORMANCE-BASED DESIGN OF SURFACE DRESSINGS

The authors present an original experimental procedure that allows the performance-based design of surface dressings. A previously developed laboratory apparatus for the direct surface shearing of hot mix asphalt surfaces treated with emulsion and aggregates has been employed. It is believed to be highly simulative of the in-service conditions and gives reliable results with a simple and low-cost test. A wide set of samples prepared by varying emulsion type and dosage and aggregate type has been tested after increasingly long curing times (from 0 to 14 days). A special stripping procedure has also been devised in order to assess the water sensitivity of the different surface dressings after two weeks of curing. Based on the evaluation of a particular ravelling index a rapid procedure for the design of the optimal surface dressing has been defined. Some examples of its application are given together with some tentative theoretical explanation of the different experimental behaviour of the various surface treatments. (A) For the covering abstract see IRRD 885061.