Curing

Moist curing of the waterproofing system is essential for proper performance and is extremely important for two reasons. First, it uses water as a diffusing medium, which allows the reactive chemicals to transfer from the coating into and through the saturated concrete substrate. If adequate curing of the crystalline waterproofing does not take place,evaporation will first dry out the coating and then begin to pull moisture from out of the concrete. As the concrete substrate dries out, it will prevent further chemical transfer from occurring, crystallization will not take place and thus no waterproofing effect will be achieved. Second, crystalline waterproofing uses a sand and cement coating as a carrying agent for the active chemicals, and it is necessary to properly cure the coating so that it hardens and bonds properly to the concrete. Curing of the treatment is achieved either by spraying with water or through the use of a specialized evaporation retardant.

Curing the crystalline waterproofing coating should begin as soon as it has hardened sufficiently, so as not to be damaged by a fine spray. Under normal conditions, the treatment will be ready for moist curing two to three hours after application. This is accomplished by misting with a fog spray of clean water at least three times a day for two to three days to prevent early drying.

In warm climates or on hot windy days, more curing will be required to keep the coating from drying out. This can be done by misting the coating five or six times per day for two to three days. Curing should be carried out is if 70 percent of the coating is dry and 30 percent is still damp. In this case, then the next fog spray should be applied.

During the curing period, protect treated surfaces from damage by rain, frost, and freezing temperatures. If plastic sheeting is used for protection, it must be raised off the waterproofing coating to allow sufficient air circulation. The overall process of crystalline formation may take two to three weeks to reach full maturity.

Use of Crystalline Waterproofing as an Admixture for Concrete

Adding crystalline waterproofing treatment to the concrete mix at the batch plant ensures that the crystalline formation occurs uniformly throughout the structure, rather than penetrating from the surface, as would be the case with a surface application. This admixture reduces the water loss, resulting in less shrinkage and increased compressive strength. When the technology is used as an admixture, the same chemical reactions take place. However, the construction cost is significantly reduced, because the labor associated with a surface treatment application is eliminated.

Brushed on surface application. Photo courtesy of Xypex

The crystalline waterproofing admixture is added to concrete at the time of batching. The sequence of procedures for addition will vary according to the type of batch plant operation and equipment. For most mixtures, the dosage rate is two to three percent, based on the Portland cement content.