Ever wondered what the white powder is on your pavers? It could be efflorescence.
Efflorescence is a white powdery deposit on the surface of unsealed concrete, brick or pavers and can be seen as a white blush "under" the sealer on sealed surfaces. It is caused by moisture vapor (not necessarily water) migrating through the substance bringing soluble salts to the surface. It is increased by low temperatures, moist conditions, condensation, rain, dew or water on or under the surface of the concrete, brick or pavers. Salts must be dissolved by water before efflorescence can occur.
Efflorescence occurs as the surface heats up from exposure to the sun and the water inside the concrete, brick or pavers evaporates and wicks the water and salts to the surface.
Power washing can be effective in removing efflorescence but if the spray is too intense, it can actually open pores in the concrete or brick and encourage further efflorescence. Acid washing can do the same thing as it cleans by removing a fine layer of the substance and opening the pores. In order to remove efflorescence we recommend SealGreen Efflorescence Remover - a biodegradable and environmentally friendly phosphate free formula to remove efflorescence, mineral and salt deposits from virtually any hardscape surface with minimal or no brushing.
Generally, removing or cleaning efflorescence from a surface is an ongoing solution rather than a cure. Ideally the solution involves finding the source of the water or moisture and stopping the problem there. Sealing may help but if the moisture still finds its way into the substrate, you could end up with spalling.
The salts brought to the surface are rarely harmful. However, the fact that efflorescence keeps returning is an indication that water is moving through the concrete, brick or pavers in ways that were not intended. It is the transfer or water or moisture through the substrate that can result in serious issues such as mold or structural concerns. Moisture left unchecked during times of freeze-thaw can cause the slab to weaken, spall or crumble in some cases.
Not all white stains are efflorescence. Efflorescence is usually white, may be sparkly, flakes off the surface. It is composed of the salts left behind by water evaporation through the slab. SealGreen Efflorescence Remover will cause immediate effervescence when applied to the efflorescence. SealGreen Efflorescence Remover information