CONCRETE POURING

How to get rid of adding water at site during mass concreting and how to rectify the same for example :-

Sometimes considering the mass concreting of the footing, where total quantity to be poured is 100cum.
The consequences may arise where the time management of the transits mixers are not maintained at regular intervals, resulting to hard concrete.
thus concerned contractor add water and compromises in the quality and workability of concrete.

how to vanish all this practices technically and smooth process.