JFK Airport, Pedestrian Tunnel

New York, New York, USA

Part of the terminal construction involved building a new 460 meter (1,500-foot-long), 46 meter (150-foot-wide) concrete pedestrian tunnel, which runs 7.6 meters (25 feet) below finished grade with a water height of 3.6 meters (12 feet) at high tide.

Background

In 1999, American Airlines began construction on a $1.4 billion USD, 50,000 acre (200,000 square kilometer) terminal complex to replace Terminals 8 and 9 at New York's JFK Airport. When completed in 2007, the complex will serve domestic and international passengers on three concourses, and will include a customs and immigrations facility, a 930 square meter (10,000 square-foot) retail and concession space, and a new 1,900-space parking garage. To allow for uninterrupted passenger service, the complex is being built in four stages. 

Part of the terminal construction involved building a new 460 meter (1,500-foot-long), 46 meter (150-foot-wide) concrete pedestrian tunnel, which runs 7.6 meter (25 feet) below finished grade with a water height of 3.6 meters (12 feet) at high tide. During the original construction of the tunnel, conventional PVC waterstop and membranes were used to waterproof the structure. 

Before long, however, shrinkage cracks began to form and they, along with the cold joints and construction joints in the walls and floors, began to leak. Over the next 18 months, the foundation contractor tried numerous solutions to fill the cracks and stop the leakage. Despite spending many thousands on repair solutions, the cracks continued to grow and the tunnel continued to leak.

Solution

After a number of failed repair attempts, the foundation contractor contacted the Crystal Group, a Kryton International distributor in New York. The Crystal Group offered to undertake a 15 meter (50-foot) test repair using Krystol Crack Repair & Waterproofing System.

Krystol T1/T2 is a cementitious mixture that can be brush-applied to existing concrete structures to repair cracks, fortify and waterproof the concrete and protect it against contamination and steel reinforcement corrosion. After application, chemicals from Krystol T1/T2 are absorbed into the concrete by the natural wicking action of concrete. Once inside the concrete, the chemicals cause crystals to grow, self-sealing cracks and filling the spaces between concrete particles, permanently blocking the movement of water in all directions.

The majority of active Krystol chemicals migrate into the concrete within the first 28 days, meaning the surface-applied slurry can be completely removed from the surface after this time without impacting its waterproofing properties. Krystol T1/T2 can be applied to positive or negative surfaces, making it well-suited for repairing sub-grade structures where access to outside walls may be difficult or impossible.

Once the 15 meter (50-foot) test repair proved watertight, the project team gave the go ahead for full repairs to begin. The repair team began by grinding out the cracks and joints to remove the epoxy and other materials that had been used in an attempt to stop the leakage. Honeycombed sections where air had not entrained properly were also chipped out. The Krystol T1/T2 system was applied on all cracks and joints successfully. Even cracks greater than .75 mm were able to self-seal when allowed adequate time for crystal growth to occur.

After the shrinkage cracks and cold and construction joints were repaired, the Crystal Group used Krystol T1/T2 to repair a shifting armored joint, which connected two 150 meter (500-foot) concrete tunnel sections. The 26.5 meters (87 feet) of repairs were made more difficult by freezing temperatures and a continuous flow of 40°F (4°C) ground water at 15 psi (100 KPa). Furthermore, the JFK project team wanted to pressure-test the repairs just 7 days after completion, which is earlier than recommended. Despite the adverse conditions and shortened timeframe, the test was successful and the armored joint proved watertight.