Traffic compaction of asphalt concrete surface courses [article]

William Donald Oram Paterson, University Of Canterbury
The subject of this thesis is the compaction of asphalt concrete surface courses occurring under the action of normal traffic with special reference to the behaviour of the high stability materials commonly used in New Zealand. A survey is made of the relevant characteristics of asphalt concrete and of the stresses and temperatures which exist in the surface course during trafficking. A modestly-sized full-scale pavement testing track was designed and constructed. The track had a concrete base
more » ... nd provided control of load, traffic distribution and temperature but not vehicle speed. Two parallel highway studies were conducted. The rate of compaction was generally rapid initially decreasing to zero at what is defined as a "stable state". The magnitude of the stable state for a given mix was found to depend on load and temperature and the relative effects of these were evaluated in terms of tyre contact pressure and viscosity. None of the properties tested proved to be an absolute indicator of stable state. Binder viscosity and film thickness were found to be predominant factors, layer thickness and maximum aggregate size had an interrelated but secondary role and construction density had a significant effect for light traffic conditions which diminished as the contact pressure and temperature were raised. Measurements of transient strain profiles were made using induction coil gauges. Typical profiles were obtained and a marked increase in dynamic stiffness was observed for a decrease in layer thickness. A mechanism of compaction is postulated which emphasises the role of particle orientation. Present specifications are generally supported by the evidence but a number of particular comments are made.
doi:10.26021/10273 fatcat:lt24kywyozcqpoo5dvtaqreg3y