In 2014, London City Airport commissioned Fjøri to carry out a PCN evaluation of its runway and link taxiways. The airport also required Fjøri to consider the effects of future-proofing the runway for the potential of heavier aircraft operating from the airport, including for example the Airbus A319Neo and the Bombardier C-Series. The report concluded that the runway would require an overlay to both increase the pavement PCN from declared 30 to 44 and increase the residual life of the 30-year old pavements, which were reaching the end of their technical life. The airport subsequently appointed Fjøri as lead designer for the overlay project. The project design included a number of pre-overlay measures installed into the existing pavements to delay the appearance of reflection cracking within the overlay. This included dowel bar insertion, patch replacement, sealant removal, stress absorbing membrane interlayers at expansion joints, sub-slab grouting and targeted bay replacements.
Fjøri designed the overlay specifically to ensure that all temporary surfaces had sufficient macro texture to satisfy the operating minima set by the airlines on this short, fast approach runway. This included the inclusion of a Stone Mastic Asphalt binder course, which provided good negative texture, immediately beneath the grooved Marshall Asphalt wearing course. The upper 100mm of the 220mm overlay included polymer modified binders in order to inhibit deformation and further assist in delaying reflection cracking.
The works have also included the installation of new centerline AGL in addition to replacement of existing AGL with LED units.
Through close collaboration between the airport, Fjøri and Lagan Construction, work started in Q2 2016 and completed in Q1 2017.
Key Project Details
- The airport operates from only one runway, and therefore all works had to be designed and planned to be carried out at night in order that the runway and taxiways were available for operations during daytime;
- The runway operation includes a fast and steep approach over London with specific enhanced runway surface friction needs for airlines. This required detailed materials planning and evaluation to ensure that all temporary surfaces would meet the strict criteria for texture and water dispersal;
- The overlaying of the original concrete slabs with asphalt required a series of innovative measures, some not used at UK airports previously, in order to delay reflection cracking;
- The project design, planning and construction employed specific contract measures in order to fast-track the project to completion;
- The ground conditions at the airport have resulted in close coordination between the project management, design and construction teams in order to rapidly re-design project elements and maintain progress.