The objective of this research, which was carried out between 2006 and 2007, was to propose methods to disseminate and incorporate local as well as international knowledge of OGPA performance into the current New Zealand asset management systems.
Compared with asphalt overlay practices in Europe and the UK, the current New Zealand maintenance practice of multiple OGPA overlays is not considered to be optimal from a structural point of view. This study undertook a literature and database review, and determined the terminal stiffness of OGPA mixes.
An analysis of the South Auckland State Highway dataset showed that the life of multiple OGPA overlays shortens with successive overlays. Statistical evidence suggested that binder ageing was the limiting factor in this phenomenon, and a correlation was found between pavement surface condition and mix stiffness. Repeated-load indirect tensile strength (ITS) tests were undertaken on cores retrieved from network pavements and on production mixes from the 2006/07 resurfacing contract. Terminal OGPA mix stiffness was found to be in the order of 2300MPa at 25 degrees Celsius, with corresponding binder penetration of 11Pen as determined from back-calculation through the use of the Shell nomograph.
This research recommends a gradual move away from the current multiple-overlay approach, and the utilisation of OGPA for its functional rather than structural integrity.