ABSTRACT
In mega hydro power structures and for mass underwater concreting projects like construction of Weir, concreting for dams, erection of cassions, concrete placed under water is inherently susceptible to cement washout, laitance, segregation, cold joints, and water entrapment. It must posses some unique workability characteristics.The essential workability requirements are that the concrete must
(a) Flow easily, (b) Retain adequate cohesion against washout and
segregation, (c) Possess self-consolidating characteristics (because
it is impractical to consolidate concrete under water by using mechanical vibration).
