event of a fire. The biggest challenge for the Gibraltar crew came in preparing the mud bed for the setting of the tiles. After the tunnel flooded, the removal of the original tiles left an extreme profile on the surface of the concrete walls. This profile had to be completely filled and leveled with a non-sagging mor- tar in order for the tiles to prop- erly set. Further, engineers from the Triborough Bridge and Tunnel Authority (TBTA), operator of the Brooklyn-Battery Tunnel, required the most efficient system for recon- structing the tunnel and specified very stringent requirements for res- toration of the walls and the appli- cation of new tiles. The Gibraltar crew turned to MAPEI tile installa- tion products for the high-quality durability the job specified. The Gibraltar Contracting crew applied two lifts (float coats) of MAPEI’s Modified Mortar Bed, a premixed, cement-based, poly- mer-modified, thick-bed and ren- der mortar that includes a blend of select aggregates. This was a great solution because, rather than requiring the use of a latex addi- tive, Modified Mortar Bed only requires mixing with water to pro- duce a high-performance bond. This mortar was applied to the damaged tunnel walls providing a smooth, curved substrate for the setting of the tiles. With that challenge well met, the Gibraltar crew moved on to setting the nearly 800,000 white and blue tiles with yellow accents. Around the tunnel’s periodic maintenance access areas, they installed mint- green tiles to make these areas easily visible. Regardless of color, all of the tiles were set with Ultraflex™ 3, the strongest mortar in MAPEI’s Ultraflex series. The crew then grouted all the joints with Ultracolor® Plus FA, MAPEI’s fine-aggregate, fast-setting, efflo- rescence-free grout. Ultracolor Plus FEATURE: MAPEI helps restore and repair historic Hugh L. Carey/Brooklyn-Battery Tunnel View of the exterior entrances of the Hugh L. Carey Tunnel in New York. The maintenance access areas are desig- nated with mint-green tiles 40 TileLetter | September 2018