It not desirable to produce concrete mixtures of a higher consistency than normal because the strength of the concrete decreases. Consistency plays an important role in the determination of strength of concrete. Less water than normal quantity in concrete increases the consistency but decreases strength due to incomplete chemical reaction while on the other hand, adding more water would increase water-cement ratio and reduces consistency as well as strength of the concrete so that's why necessary amount of water and cement should be added to get higher strength.
