Modified wheel tracker as a potential replacement for the current conventional wheel trackers

Abstract

This research introduces a modified method for the wheel tracker test. Conventionally, the test is conducted by placing asphalt slabs or cylindrical cores in a fully confined steel or polyethylene moulds. The research work undertaken by the author has shown that having the specimen fully confined in all directions by the steel or polyethylene mould would limit or prevent it from lateral (shear) deformation. It is also well-known that shear related permanent deformation is identified as the primary cause for high severity rutting. As a result, a new wheel tracker test set-up was designed and manufactured to capture the true material response under the applied load. In the conventional wheel tracker, the large majority of samples will only show the primary stage and very small part of the secondary stage of the permanent deformation curve and most of the time the curve will plateau regardless of the number of cycles applied. Therefore, in the conventional wheel tracker test, the tertiary stage never reached in the vast majority of the tested specimens. In the modified wheel tracker, the three stages of permanent deformations are always captured; therefore, the flow number can be determined. In addition, the effect of the major mix parameters and test conditions such as air voids content, aggregate gradation, binder type and test temperature can be captured and analysed.