ADVERSE EFFECT OF HOT WATER SPRINGS ON DURABILITY OF CONCRETE AND REMEDIAL MEASURES – A CASE STUDY

Even with the perfect concrete mix design, it is possible that the durability/performance of concrete get adversely affected under certain hostile environment like lying of fresh concrete in hot water zone. 1500 MW Nathpa Jhakri HE Project is a major hydroelectric power project on river Satluj situated near Rampur Tehsil in Himachal Ptradesh comprises of construction of 60.5m high concrete dam, an underground desilting complex and powerhouse  including 27.4Km long Head Race Tunnel. During excavation for HRT at Wadhal adit, hot water springs having a temperature ranging 57- 65^o centigrade were observed at several locations inside the Head Race Tunnel. This poses a great challenge in laying fresh concrete mix for lining work and special measures had to be taken in formulating concrete mix design for concrete lining work. CSMRS evaluated the water quality of the hot water at regular intervals. After assessing the quality of the hot water under reference, an attempt was made to classify the aggressiveness of water using JJ Basson and BJ Addis approach which quantify the aggressiveness due to temperature as corrosion indices like Leaching/Spalling/Overall corrosion indices to identify the class of concrete. Finally, remedial measures suggested to the project authorities for minimizing the adverse effects of hot water springs on the concrete lining inside HRT. This paper covers the above aspects in brief.