Waterproofing of an underground facility

The designed and implemented Kilo Apron Substructure (KAD) project at Heathrow Airport involved the construction and waterproofing of a 100 m x 190 m x 15 m underground facility located in the airside of the airport, between Terminal 2A and Terminal 2B.

Initially, pending further development of the airport, the underground KAD building would be equipped with minimal life safety services. As the airport developed, along with baggage handling facilities, the underground facility would eventually function as a subway for passengers to travel between terminal buildings. This possibility was included in the design, as early as the initial construction stage, with a section dedicated to passengers movement.

The specification of a waterproofing system for the upper deck of the underground structure also had to be carefully considered. Such system required provision of a robust solution for backfill, as well as the resilience required under the airport taxiway to withstand heavy aircraft traffic.

Since concrete screed is difficult to apply on vertical surfaces, the walls were protected with TILTEX 12. Flexible before hydration, it could be easily installed on vertical surfaces and hydrated, to provide a thin protective layer of concrete with a compressive strength of 40 Mpa.

This was an extremely important part of the specification, enabling the project to be completed quickly, by avoiding the use of poured-in-place concrete, reliability of the installation during the winter construction program, and cost and time savings.