A 50 mm asphalt overlay was applied to the existing runway at Hosea Kutako International Airport in Windhoek in 2000. Over the subsequent years, water has penetrated the overlay and caused delamination, posing a potential safety risk to aircraft.
Aurecon was appointed in 2008 to investigate the factors facilitating moisture ingress into the asphalt and to determine the extent of asphalt delamination. The investigation identified that high asphalt permeability, cracking of longitudinal construction joints, inadequate cross-fall and insufficient maintenance had contributed, in conjunction with traffic loading and environmental deterioration, to the deterioration and subsequent delamination of the asphalt surfacing.
It was determined that the cross fall on the runway was less than the required 1,5% and innovative measures were required to improve the drainage and geometry. This included the application of an appropriate asphalt design where delamination took place, as well as the replacement of the existing layer with a new asphalt overlay.
The runway was surfaced with an Ultra-Thin Friction Course to further improve the drainage, increase the impermeability of the pavement to water ingress and achieve the stringent skid resistance and riding quality criteria.
The runway at the airport was successfully rehabilitated during 2010 with the majority of the work being undertaken at night in order to ensure continued flight operations throughout the construction.
Remedial measures were implemented on the secondary runway, taxiways and aprons while additional funding will make it possible to rehabilitate the infrastructure further.