Rising damp is caused by water being drawn up through a permeable surface. This most commonly happens on slab that did not have the correct subgrade/lining when it was poured. It also happens when concrete blocks are exposed to bare earth on one side. Common is garages/basements Efflorescence is the salt that is left behind as the water evaporates.
This causes unwanted dampness or even the paint to be pushed off of the blocks or floor.
In most cases we can solve this with an epoxy seal to seal the pores of the concrete/blocks. This can be painted over, or in unexposed areas can be left bare.