| Efflorescence is a white, powdery substance | | | | Tougher deposits can be removed with special |
| that appears on the surface of concrete, | | | | cleaning products. Acid washing with diluted |
| masonry, and stucco products. It's a very | | | | muriatic acid should only be used as a last |
| common occurrence and, although it's usually | | | | resort because it will etch away some of the |
| harmless, efflorescence can be a real | | | | cementitious material on the surface. |
| eyesore. It goes unnoticeable on plain, gray | | | | Muriatic acid should be diluted to1 part acid |
| concrete and block but becomes very visible | | | | and 12 parts water. The surface then needs to |
| on colored concrete and brick. Normally, the | | | | be neutralized with a solution of baking soda |
| problem doesn't show up until weeks or months | | | | or diluted household ammonia. This will stop |
| after installation and often becomes a | | | | the acid from attacking the material any |
| dispute between angry customers and | | | | further. |
| contractors. | | | | |
| | | | Preventing Efflorescence |
| Efflorescence is caused by water moving | | | | |
| through concrete and masonry products. As it | | | | When it comes to concrete, there are a few |
| travels through in a process called capillary | | | | steps that can be taken to limit or prevent |
| action, the water dissolves salts contained | | | | efflorescence. Proper drainage away from a |
| in the material. When the water reaches the | | | | slab will help reduce moisture moving up from |
| outside, it evaporates and leaves the salts | | | | the subgrade. This also includes eliminating |
| on the surface. Overtime the buildup of the | | | | any unnecessary sources of water such as |
| salty deposits can become quite significant. | | | | downspouts that dump water underneath a slab. |
| Lower temperatures, humidity, rain, or | | | | |
| anything that will keep the material wet such | | | | Concrete sealers can also prevent |
| as sprinklers facilitates this process. | | | | efflorescence from reoccurring. Although |
| | | | regular film forming sealers will stop water |
| Despite efforts of manufacturers and | | | | from seeping down into the pores, they still |
| contractors to limit efflorescence in their | | | | allow moisture from the sub-grade to pass |
| products, they are using raw earth materials | | | | through. This can create and trap |
| that contain salt and will vary in salt | | | | efflorescence between the sealer and the |
| content from batch to batch and from one | | | | concrete. Penetrating sealers are the best |
| location to another. | | | | defense against efflorescence. These |
| | | | silicone-based sealers work by penetrating |
| Removing Efflorescence | | | | the surface and reacting with free lime to |
| | | | form calcium silicate. It's like filling the |
| Most efflorescence can be removed by pressure | | | | capillaries and pores with cement to block |
| washing with water or scrubbing with water | | | | the migration of water. If the water can't |
| and a brush. The water will dissolve most of | | | | get to the surface, then salts can't be left |
| the salts but must be rinsed away completely. | | | | behind. |