Crystalline Concrete Waterproofing

When concrete cures a complex series of reactions occur between water and the chemicals in the concrete mix. The water becomes an integral part of the structure of the concrete, but microscopic capillaries, pores, and cracks are left behind. After curing, when water penetrates these voids it accelerates the deterioration of concrete. Cementitious crystalline waterproofing is designed to reduce the porosity and permeability of concrete by plugging these voids. Available products can either be incorporated as an admix in the concrete or as a coating applied to fully cured or fresh concrete. This Common Product covers products applied as coatings. 

Crystalline waterproofing not only protects against water penetration, but it also protects concrete against chemicals in the air, allows it to be subjected to a wide range of pHs, and protects against alkali aggregate reactions (AAR). In addition, it can prevent deterioration that occurs from oxidation and expansion of steel reinforcement. Products can be applied on either the positive (the wet side, e.g. the exterior of a foundation) or the negative side (the dry side, e.g. the interior of a foundation) of the concrete and are used for a wide range of applications such as foundations, basements, slabs, water reservoirs, dams, water and effluent treatment plants, parking foundations, and tunnels. Crystalline waterproofing usually comes as a powder that must be mixed with water prior to application. Two component systems are also available that may incorporate polymeric additives, but these products were beyond the scope of this Common Product. The coating then must generally be applied within twenty minutes of mixing. Cured concrete is first wetted with water, and then the coating is either sprayed or brushed on the surface. The chemicals in the coating migrate into the capillaries via diffusion and react with the byproducts of cement hydration, primarily lime, forming a structure of crystals that plugs the voids created during cement curing. Products may also be shake applied on fresh concrete. In this application method the dry powder is not mixed with water but is sprinkled directly onto fresh concrete and the same type of chemical reaction occurs. 

Product formulations are generally simple, but some manufacturers indicated the use of proprietary additives in formulations that may not be reflected in this Common Product. In addition, some literature indicated that nano materials could be used. Nano materials could introduce additional hazards but were not found to be common.