This crystalline structure can only occur where moisture is present, and thus, will form in the pores, capillary tracts, and shrinkage cracks in concrete. Wherever water can penetrate the concrete, the crystalline formation will follow.
When crystalline waterproofing is applied to the surface as a coating, a process called chemical diffusion takes place. The theory behind diffusion is a solution of high density migrates through a solution of lower density until the two equalize.
Water-filled capillary tracts contain a solution of low chemical density. When crystalline waterproofing is applied to this concrete a solution of high chemical density is created at the surface, triggering the process of diffusion. The crystalline waterproofing chemicals must now migrate through the water (the solution of low density) until the two equalize.
The crystalline waterproofing chemicals now spread through the concrete and become available to the byproducts of cement hydration, allowing the chemical reaction to take place and the formation of a crystalline structure. As chemicals migrate through water, this crystalline growth will form behind an advancing front of chemicals. This reaction continues until the crystalline chemicals are either depleted or run out of water.
Chemical diffusion can take these chemicals about 300 mm (12 in.) into a completely saturated concrete substrate. Where concrete is not completely saturated, the crystalline chemistry only diffuses to the depth of water saturation, but still has the potential to travel deeper into the concrete in the future if water penetrates from the opposite direction, thus reactivating the crystalline chemistry.
Instead of just reducing the porosity of concrete, like water reducers, plasticizers, and super plasticizers, the crystalline formation engages the material filling and plugs the voids in concrete to become an integral and permanent part of the structure.
Since the crystalline formation occurs within the concrete it cannot be punctured or otherwise damaged like membranes or surface coatings. Crystalline technology also improves the durability of concrete structures, lowering their maintenance cost and extending their lifespan by protecting them against the effect of aggressive chemicals. Crystalline waterproofing is resistant to chemicals where the pH range is between three and 11 under constant contact and two to 12 under periodic contact. Crystalline waterproofing tolerates temperatures between –32 C (–25 F) and 130 C (265 F) in a constant state. Humidity, ultraviolet (UV) light, and oxygen levels also have no impact on the material’s ability to perform.
Crystalline waterproofing offers enhanced protection against the following agents and phenomena.
This is the result of the dissolution of carbon dioxide (CO2) in the concrete pore fluid, which reacts with calcium from calcium hydroxide and calcium silicate hydrate to form calcite (CaCO3). This process reduces the pH of concrete and its natural protection of reinforcing steel.
Alkali aggregate reactions
By denying water to these processes, crystalline waterproofing helps prevent these types of swelling reactions.
Extensive chloride-ion diffusion testing shows concrete structures protected with a crystalline waterproofing treatment slows the diffusion of chlorides, thus extending the time-to-corrosion of the reinforcing steel.
Due to their limitations, membranes and coatings may leave concrete susceptible to water and chemical damage. The addition of crystalline technology can seal the pores and micro-cracks.
Matching the right crystalline technology with the application
Crystalline waterproofing and protection technology is sold in powder form and is mixed with water. It can be used in two ways:
- as a coating applied to the surface of existing or new concrete structures, such as foundation walls, floor slabs, or the inside of underground structures; and
- an admixture added directly into the concrete batch at the plant or truck for new construction, shotcrete, and precast applications.
Crystalline waterproofing coating
As mentioned earlier, when applied to clean, bare, and previously saturated substrate as a slurry mixture, the reactive chemical ingredients in crystalline waterproofing can penetrate up to 300 mm deep inside the concrete by using water as the migrating solution. As these chemicals penetrate through the capillaries and pores, the reaction with the mineral byproducts of cement hydration creates the crystalline formation that eventually fills the cracks and pores.
Crystalline waterproofing can be applied by a brush or with spray-on equipment. To ensure the success of the application, care must be taken to ensure correct surface preparation, substrate saturation, coverage rate, and curing time.