January 22, 2018
PENETRON Helps Keep Tennessee State Legislators Dry
Completed in time for the New Year, the Cordell Hull Capitol Connector Tunnel provides government employees in Nashville, TN, a weather-proof underground connection to the State Capitol building. PENETRON ADMIX-Enhanced Shotcrete (PAES) was applied to ensure a waterproof – and durable – tunnel structure.
The Cordell Hull Capitol Building Connector Tunnel is part of a comprehensive renovation project encompassing the Cordell Hull Office Building and the Central Service Building in downtown Nashville. Both buildings are immediately adjacent to the Tennessee State Capitol; the Cordell Hull office building has office space for approximately 1,000 government employees.
Keeping construction on time
The Connector Tunnel now provides a protected underground connection from inside the State Capitol Building to the Cordell Hull Office Building and, eventually, a parking garage. During construction, while government employees continued their daily routine in the Tennessee State Capitol building, the construction crews cleared the way for the underground tunnel. Blasting crews worked through the night when no one was in the office building.
“This project involved a lot of on-the-spot problem-solving. Irving Materials (imi), the ready-mix supplier, supplied concrete to the construction crews working underground to complete the Cordell Hull Capitol Building Connector tunnel,” notes Christopher Chen, Director of The PENETRON Group, about the effort to keep the project on time and minimize disturbances to the work being carried out underneath the government offices.
Shotcrete for a waterproof tunnel
The project included excavation of a 430-foot (130 m) long tunnel, extending the depth of two elevator shafts, and excavating a stairwell and mechanical shafts that now tie-in to the new tunnel. PENETRON ADMIX-enhanced shotcrete (PAES) was applied along the entire length of the Cordell Hull Capitol Building Connector Tunnel. About 1,500 cubic yards (1,150 m3) of shotcrete, 90,000 pounds of steel fiber and over 2,600 pounds of synthetic macro fiber (as a shotcrete reinforcement) were required to complete the tunnel.
“The construction crew devised a plan to drive trucks inside the tunnel to feed the shotcrete pump directly,” adds Mr. Chen. “The shotcrete mix was fiber-reinforced and the added crystalline technology in the PENETRON ADMIX ensured that the tunnel walls would be waterproof as well.”
Admixture added during batching
PENETRON ADMIX is added during batching when used in shotcrete mixtures like PAES. An optimal waterproofing solution for tunnel projects, PAES forms a durable, self-supporting arch roof through the action of the crystalline technology that reduces shrinkage cracking and seals micro-cracks. Shotcrete tunnel linings can be sprayed in a layer thickness of 150 mm (6”) in a single spray application, resulting in a robust, waterproof structure.