Reducing water is relatively simple: 1 lay down a suitable cloth;

2 Place soaker lines on the cloth at suitable intervals, to keep the cloth just wet everywhere;

3 Cover with a sealed plastic membrane;

4 cover this with an insulating layer, foil backed;

5 Cover with plastic and weight down (or tie to in the case of columns and walls). 

Water can be warmed in cold climates, or slightly cooled in hot climates.

This will  allow you to cure the concrete with a minimum of water.

Slightly less effective is to use two or more coats of curing compound, but only if the water/binder ratio exceeds 0.4.