These deleterious effects can be avoided through the use of crystalline waterproofing technology, which effectively improves the durability and life span of concrete structures, there by reducing long-term maintenance costs. This article explore & show crystalline technology provides a high level of performance to Concrete mixtures, materials, and structures, and what design professionals need to know in order to specify and understand how this chemical technology will enhance building projects.
The Nature of Concrete
Concrete is also a water-based product. To make this mixture workable, easy to place, and consolidate, more water than is necessary for the hydration of the cement is used. This extra water, known as the water of convenience, will bleed out of the concrete, leaving behind pores and capillary tracts. Although concrete appears to be a solid material, it is both porous and permeable.
Water reducers and super plasticizers are used to reduce the amount of water in the concrete mix, and maintain its workability. However, pores, voids, and capillary paths will remain in cured concrete and can carry water and aggressive chemicals into structural elements that will corrode steel reinforcement and deteriorate concrete, thus jeopardizing the structure’s integrity.
The Porous and Permeable Nature of Concrete
Permeability is described by a quantity known as the permeability coefficient, commonly referred to as D’Arcy’s Coefficient. The water permeability of a concrete mix is a good indicator of the quality of the concrete for durability reasons. The lower D’Arcy’s Coefficient, that is, the more impervious, the higher the quality of the material. Never–theless, a concrete with low permeability may be relatively durable but may still need a waterproofing agent to prevent leakage through cracks.
Despite its apparent density, concrete remains a porous and permeable material that can leak and deteriorate rapidly when in contact with water or the intrusion of aggressive chemicals, such as carbon dioxide, carbon monoxide, chlorides, sulfates or other substances. But there are other ways in which water can be transported through concrete.
Vapor Flow and Relative Humidity
The direction of flow could vary base on environmental conditions. The direction of vapor flow is critical when applying water proofing treatment in situations where an unbalanced vapor pressure gradient exists. Typical examples include:
- Applying a low vapor permeable membrane, such as a traffic deck coating over a damp concrete surface (even if the very top surface is dry) on a warm day will result in pressure vapor pressure build-up and pin-holing or blistering.
- Applying a coating or sealant to the outside of a building wall may trap moisture into the wall if the sealant is not sufficiently vapor permeable.
- Applying low vapor permeable flooring over a slab-on-grade where there is high sub surface moisture content may resulting delamination of the flooring. Generally, a low vapor permeable sealant or coating should not be placed on the down stream face of a building or structure. Either the vapor pressure or water pressure will act to damage and blister the membrane. Some types of coatings and water permeability reducing admixtures in the concrete accommodate considerable vapor movement, thus allowing them to be placed successfully on the down stream side. Primary examples are cement-based waterproof coatings and water permeability reducing admixtures.
How Crystalline Waterproofing Technology Works
Crystalline water proofing technology improves the water proofness and durability of concrete by filling and plugging pores, capillaries, micro-cracks, and other voids with a nonsoluble, highly resistant crystalline formation. The water proofing effect is based on two simple reactions, one chemical and one physical. Concrete is chemical in nature. When a cement particle hydrates, the action between waterand the cement that causes it to be come a hard, solid mass. The reaction also generates chemical by products that lie dormant in the concrete.
Crystalline waterproofing adds another set of chemicals to the mixture. When these two chemical groups, the byproducts of cement hydration and the crystalline chemicals, are brought together in the presence of moisture, a chemical reaction occurs. The end product of this reaction is a non soluble crystalline structure.
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 goes, crystalline water proofing will form filling the pore, voids and cracks. When crystalline water proofing is applied to the surface, either as a coating or as a dry shake application to a fresh concrete slab, a process called chemical diffusion takes place. The theory behind diffusion is that a solution of high density will migrate through a solution of lower density until the two equalize.
Thus, when concrete is saturated with water prior to applying crystalline water proofing, a solution of low chemical density is also being applied. When crystalline waterproofing is applied to the concrete, a solution of high chemical density is created at the surface, triggering the process of chemical diffusion.The crystalline waterproofing chemicals must migrate through the water (the solution of low density) until the two solutions equalize.
The reaction will continue until the crystalline chemicals are either deplete do run out of water. Chemical diffusion will take these chemicals about 12 inches into the concrete. If water has only soaked two inches into the surface, then the crystalline chemicals will only travel two inches and stop but, they still have the potential totravel 10 inches further, if water reenters the concrete at some point in the future and reactivates the chemicals.
Instead of 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.
Because these crystalline formations are within the concrete and are not exposed at the surface, they cannot be punctured or otherwise damaged like membranes or surface coatings. Crystalline waterproofing is highly resistant to chemicals where the pH range is between three and 11 under constant contact, and two to 12 under periodic contact.Crystalline waterproofing will tolerate temperatures between-25 degrees Fahrenheit (-32degrees Centigrade) and 265 degrees Fahrenheit (130 degrees Centigrade) in a constant state. Humidity, ultraviolet light, and oxygen levels have no impact on the products ability to perform.
Crystalline waterproofing offers protection against the following agents and phenomena:
- Inhibits the effects of CO, CO2 , SO2 and NO2 , the gasses responsible for the corrosive phenomenon known as ‘carbonation.’ Carbonation is the process where exterior gasses create a corrosive phenomenon that’ softens the surface layers of the concrete. Carbonation testing shows that the multiplicative crystalline formations also reduce the flow of gases into concrete, thus significantly retarding the carbonation at the surface in which the alkalinity is reduced and the surface layer is softened.
- Protects concrete against alkali aggregate reactions (AAR) by denying water to those processes affecting reactive aggregates.
- Extensive chloride-ion diffusion testing shows that concrete structures protected with a crystalline waterproofing treatment prevent the diffusion of chlorides. This protects reinforcing steel and prevents deterioration that could occur from oxidation and expansion of steel reinforcement.
The more traditional methods of protecting concrete, such as membranes and other coatings, may still leave it susceptible to water and chemical damage. Only with the addition of crystalline technology the pores and micro cracks that normally result from the process of setting and curing, allow concrete to be sealed.