Self-Compacting Concrete at Teesta-III

The backfill concrete behind steel liner in 650 m deep pressure shaft at Teesta-III was quite challenging as provision of stiffeners hardly left a gap of 300 mm from the excavated rock surface. In view of time constraint the concreting activity was planned by pumping concrete from bottom so as to continue steel liner erection independently. The ease of placement and better flow ability/filling ability of self-compacting concrete (SCC) without vibration prompted the decision of using SCC as backfill concrete though it is little costlier than conventional concrete. The fly ash was used in concrete mix to have better durability and shrinkage characteristics and to avoid thermal problems. Extensive laboratory trials were done to optimize the cement and fly ash content for the SCC mix and achieve the required properties for the hardened concrete and cost competitive at the same time. The SCC was done successfully and its placement and performance was monitored through testing of flow ability characteristics and testing of cubes. This paper summarizes the various mix design and itsfield performanceat pressure shaft of Teesta-III project. This study could provide better understanding and utilization of SCC in upcoming projects in a more economical way.