WHAT IS WATERPROOF CONCRETE?
There are several degrees of waterproofing to be considered, all loosely defined under 4 categories in BS 8102.

At the lowest level, Grade 1, there is 'Water-tight' which simply means that water will not run or flow freely through the concrete; at the upper levels, Grades 3 & 4, there is 'Damp-proof', which not only requires there to be no visible water ingress but also that very high levels of water-vapour resistance will be achieved. This applies whether or not hydrostatic pressures are present.

http://www.waterproof-concrete.co.uk/