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