Crystalline Waterproofing Coating

 Crystalline waterproofing as a coating system can be brush-applied or sprayed. The crystalline waterproofing coating system has a unique chemical diffusion characteristic. Hence, for efficient results, workmanship, viz. surface preparation, surface saturation, dosage and curing, etc. is highly important.

Concrete surfaces where crystalline waterproofing coating is to be carried out should have an open pore texture to allow the transfer of the crystalline additives from the surface coating into the concrete. The surface also needs to be clean and free of dirt, mould release oil, and other foreign matter as this can clog the pores and prevent the effective diffusion of the additives into the concrete.

Surface preparation may be carried out by water jetting, sand blasting or acid etching. Sand blasting is normally required when steel formworks have been used and the concrete has smooth finish. Acid etching can be accomplished using either muriatic acid or citrus-based products when the use of an acid is not environmentally acceptable. It is advisable to clean the area again with water after acid etching to neutralize the surface.

Wetting the Surface: Another prerequisite for an efficient crystalline waterproofing system is that, the concrete surface should be in a saturated, surface damp condition. This is to facilitate the diffusion of the chemicals from the coating into the capillary tracts of the concrete. For vertical surfaces, walls have to be wetted with clean water for about ten hours.

In conditions with hot sun and wind it is better to proceed in small convenient areas at a time.

Coating/Spraying Application: The crystalline waterproofing coating materials are mixed with water at a ratio of 2.5-3 parts powder to 1 part water by volume and is applied with a brush at a coverage rate of 1.0- 1.25 kg per Sqm for 2 coats.

The application can also be carried out with specialized spray equipments. Under normal conditions, the crystalline waterproofing coating will set in 2-3 hours. The second coat can be done at this point. If the first coat has dried, it must be lightly sprayed with water prior to the application of the second coat.

Curing: Curing of the crystalline waterproofing system is crucial for efficient and effective performance and is particularly important for two reasons:

First and foremost, crystalline waterproofing uses water as a medium for diffusion of the chemicals from the coating into 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 concrete. This prevents the effective diffusion of the chemicals into the concrete substrate.

Secondly, curing also ensures proper hardening of the coating and adhesion of the coating to the concrete surface. Curing has to be carried out by spraying with water.

Curing should begin as soon as the coating has hardened sufficiently. Under normal conditions, curing can begin two to three hours after coating, and can be done by misting with a fog spray of clean water at least three times a day for two to three days. In warm climates or on hot windy days, the frequency of curing has to be increased. During the curing period, treated surfaces must also be protected from rain and freezing temperatures. The overall process of crystalline formation may take two to three weeks to reach full maturity.

Crystalline Waterproofing Admixture

Crystalline admixture forms part of concrete and helps in making the concrete dense and watertight. Hence the major part of the waterproofing activity is completed during concreting itself, needing only the joint treatment after the concrete sets and hardens. Adding crystalline waterproofing chemicals to the concrete mix ensures homogenous dispersion of the additives throughout the structure, rather than penetrating from the surface as would be the case with a coating application. This is most efficient in areas such as raft slabs, retaining walls, etc. Crystalline waterproofing admixtures also help to reduce concrete shrinkage and increase compressive strength. When the crystalline admixture is added directly to the concrete mix, the construction costs, especially waterproofing costs are significantly reduced because only the construction joints have to be treated after the hardening of the concrete. Hence labour required for surface treatment application is eliminated and the time required is reduced.

The crystalline waterproofing admixture can be added to concrete at the time of batching as well as at the site immediately before pouring of the concrete.

Crystalline waterproofing admixtures are compatible with other chemical admixtures such as superplasticizers, air entraining agents and water reducers. These can also be used in conjunction with mineral admixtures such as fly ash, and other supplementary cementing materials. When crystalline admixtures are used, it is always advisable to conduct site trials to meet the workability requirements of the design mixes.

Dry-Shake (Broadcasting) for New Slab Construction

Crystalline waterproofing can also be applied by the dry-shake application method to new slabs during construction. This process requires the crystalline powder compound to be sprinkled onto the PCC surface or the top of slabs. When applied over the PCC, the crystalline admixture broadcasting has to be done after the reinforcement is tied. The raft concrete can be cast on the broadcasted surface.

Negative Side Waterproofing

Existing basements that are subject to water seepage through foundation walls and floors can be treated by crystalline waterproofing on the negative side, i.e, the inside of the structure. Coatings that depend on their adhesion to the surface will delaminate. Since crystalline waterproofing penetrates into the concrete and blocks the pores beneath the surface, it does not depend on surface adhesion and therefore will not peel off.

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