Cyclic Shear Deformation of Asphalt at Melbourne Airport

In 2010 and 2011, the two runways and associated taxiways at Melbourne Airport were resurfaced over a ten month period. Approximately six months after the completion of the works, a number of localised horizontal surface deformations were identified in one runway, concentrated in the heavy braking and turning zones and only in one traffic direction. A preliminary investigation found no evidence of inadequate design, non-compliance with the specification or construction related issue. Inadequate bond to the underlying asphalt leading to delamination was also excluded as the cause. The aim of this subsequent investigation was to determine whether a cause could be identified to explain the failures. The difference in field performance was assessed in relation to the forces applied to the surface under aircraft braking during landing operations. Performance under laboratory Direct Shear and Inclined Repeated Interface Shear testing was also compared. It was concluded that the likely cause of the deformations at Melbourne Airport was a lack of resistance to Cyclic Shear Creep in the asphalt mix. Further investigation would be required to determine which constituent within the asphalt was responsible for the poor asphalt performance. The correlation between field performance and the change in dust source suggests the properties of the dust should be concentrated on