Effective asphalt reinforcement

Perth Airport is the fourth busiest airport in Australia in terms of passenger traffic, operating 24 hours a day, seven days a week. In 2009, after repeated maintenance works over many years, an effective rehabilitation of the extensively cracked Runway 06 Threshold was required to restore its serviceability. The existing pavement consisted of 300 mm concrete slabs constructed in 1960, which were later overlaid with 20 mm asphalt surfacing. Due to the severely cracked condition of the existing pave¬ment, resurfacing by using just a thin asphalt overlay was not expected to provide a long-term success. To solve this problem, the propagation of existing cracks and expansion joints from old concrete slabs into the new asphalt overlay needed to be prevented.

To effectively retard reflective cracking and thus extend the service life of the rehabilitated pavement an asphalt reinforcement was used. This solu¬tion comprises a flexible reinforcement grid made from high-modulus polyester yarns with an ultralight nonwo¬ven backing for ease the installation. Both the grid and the nonwoven have a polymer-modified bituminous coating (with a minimum of 60% bitumen content) to enable an optimum bond between the asphalt layers. The rehabilitation procedure involved firstly texturing of the existing asphalt surface and construction of a 25 mm thick asphalt layer. Subsequently, the asphalt reinforcement was placed in accordance with the installation guidelines, and then covered with a 40 mm asphalt wearing course.

This case study demonstrates that through effective crack retardation, service life of the rehabilitated pavement can be extended considerably. Positive effects include increased maintenance intervals, lower maintenance costs and reduced disruption to flight operations.