What is the chalky residue on my patio?

Chalky residue on the surface of a wall or paver may indicate the presence of efflorescence. Efflorescence is a naturally occuring mineral deposit that exists to some degree in all concrete. It is not a defect in the material. Efflorescence can often be brushed away and sometimes dissipates on its own. Persistent efflorescence can be removed from the surface of concrete with a dedicated efflorescence remover. Some efflorescence cleaners have the potential to damage concrete and should only be used by experienced contractors.