Both due to water which contains soluble salts from cement. When penetrated through the paint film and evaporated, salts residue is left behind.

To avoid:

1. To make sure new cementatious substrate had been cured for at least one month before application.
   
   
2. To make sure the substrate is dry during application.
   
   
3. To make sure there is no leakage from roof or hidden piping (to seal any possible water seepage) before application.
   
   
4. To prime with good quality water based or solvent based primer before application for the top coats. Do not dilute the primer if possible or slight dilution (according to manufacturer instruction) only to ease handling during application.
   
   
5. Old affected substrates need to be washed to remove the salts. Let it dry and paint with quality primer (water based or solvent based). Critical areas might need to neutralize with mild acid, wash it with running water, before primer application.