DBL Tunnel, India

THE PROJECT

A road  project for Churhat Bypass, located 55 km away from Rewa in Madhya Pradesh, involving construction of a road tunnel and viaduct for the Rewa Sidhi Section (NH 75E) in Madhya Pradesh. The construction period is 48 months and operation period is 15 years from COD. The total length of the project is 15.35 km; the tunnel length is 2.95 km on one side and 2.65 km on the other. There are 93,000 cubic meters of PQC quantum, the structure is 70,000 cubic meters, the shotcrete is 95,000 cubic meters, and the lining concrete is 125,000 cubic meters.

THE SOLUTION

The tunnel project has an overall volume of 385,000 cubic meters of concrete, including structural concrete, PQC, shotcrete and lining concrete. Each type of concrete has its own requirements, with high levels of water resistance being one of the common requirements. In addition, segment casting concrete requires high early strength, close to 22 mpa at the 24 hour mark.

Locally available fine aggregate had a high volume of fine content, which resulted in a stickiness developing in the concrete under a low w/c ratio. Fortunately, our experienced concrete technologists were able to develop a cost-effective formulation to solve this issue.

The most challenging requirement for PQC concrete is to maintain low slump between 30mm and 15mm for two hours of workable concrete. A range of ether- and ester-based PCEs were well supported by a retarder, viscosity modifying agent and other materials, which helped in developing a custom formulation to meet the demands of this project.

THE BENEFITS

Since the concrete surface was free from cracks both in its plastic and hardened stages, the client and consultant were very satisfied with Fosroc’s product performance, technical competency and quality of service. The product’s consistent quality from one batch to the next was another aspect which further enhanced the contractor and client’s confidence level in Fosroc.