Statement (I): Quick-setting cement with initial setting time of 5 minutes is used in underwater constructions.Statement (II): Aggregate and cement are mixed dry, and the mixture is then dumped in water.

Concepts:Quick Setting Cement: It is a special type of cement, where the setting time of the cement is to be less and hardening of cement to be fast and where aluminium sulphate is used as an accelerating AGENT to accelerate the setting time of cement.The initial setting time for this kind of cements are about 5 minutes and the final setting time is about 30 minutes.It is used in under-water construction, in running water conditions, in rainy & cold WEATHER conditions, in ANCHORING & tunnelling and also where quick strength is needed in short span of time.Hence, statement I is correct.The under-water concreting is predominantly done by tremie pipe by with concrete poured in a semi liquid form at the desired under water location. Thus, the SLUMP needed is about 150-200 mm so that the liquid concrete can flow out easily without jamming inside the tremie. So, the concrete is well mixed with cement, aggregates and water before pouring into under the water.Hence, statement II is incorrect.