THE PROBLEMS WITH CONCRETE
Concrete structures are considered to be highly porous materials. The porosity primarily exists in the form of pores that are connected through capillary channels. Concrete voids are also formed as a result of air entrapped as well as water movements through the settling process and evaporation due to heat generated by the exothermic reaction of cement hydration. While it is important to maintain to a certain degree voids within the concrete in order for the so-called process of concrete breathing to take place, the porosity of concrete enhances the permeability of water in liquid and vapor phases through flow, diffusion, or sorption. This induces well documented water-associated problems within the concrete, such as the Alkali-SilicaReaction, freeze and thaw spalling as well as chloride ion penetration Such problems result in concrete deterioration which in return reduces the concrete structure's life span, especially if the reinforcement steel starts to corrode as a result of anoxidation process that is greatly enhanced by water and chloride ions.
There are several water-associated problems in concrete. The most severe problems caused by water take place under wet conditions as a result of dissolving concrete alkalis, repeated freezing and thawing cycles and chloride ion penetration. Such conditions may result in further problems like spalling, silicate dusting, stress cracks, laitance and efflorescence.
The hydration of cement produces calcium silicate hydrates with an amorphous structure that binds sand and aggregate to form a rigid concrete structure. The hydration process also produces calcium hydroxide, Ca(OH).sub.2, as a bi-product, which makes the concrete a highly alkaline material. In the presence of water, either in the liquid or the vapor stage, the hydroxide material becomes in the solution form with a pH value that can exceed 12.5, within the concrete matrix. This solution is considered chemically aggressive to the cement paste itself and to some minerals in the aggregate.
Siliceous materials, such as volcanic glass, opal, strained quartz, and cristobalite are particularly susceptible to hydroxide material in this solution form what results is known as the Alkali-Silica Reaction, commonly referred to as "ASR". ASR is a heterogeneous chemical reaction that takes place within concrete between the alkaline pore solution of the cement paste and silica containing parts of the aggregate particles. The product of such reaction is silicate gel that is able to combine with more water and swell. The swelling process results in an internal tensile strength build-up within the discontinuous aggregate pores. Over time, the internal pressures caused by the swelling process is sufficiently strong to cause cracking of thepaste matrix which then can result in a compromised concrete with an open door to an increasing rate of deterioration.
In climates where repeated cycles of freezing and thawing occur, concrete with sufficient moisture is susceptible to damage. When temperature drops below the freezing point ice starts to form within the pores of concrete. Since water increases its volume by 9% on freezing, water confined in pores between freezing bodies are therefore under compression and pores may dilate causing an increase in the internal stress against the surrounding concrete particles. Repeated freeze and thaw cyclesresult in the rupture and deterioration of the concrete structure due to fatigue stresses.
The permeability of concrete allows chloride ions, such as from de-icing agents, to penetrate through the osmotic process in which the ions diffuse from the high concentrate zone to the low concentration zone. Under wet conditions, theconcentration of chloride ions within the concrete becomes diluted, therefore, results in an increase in the driving force of ions diffusion. Chloride ions are considered as a high oxidizing agent. In concrete pavements, these ions acceleration thecorrosion of steel reinforcing bars, thus reduce the life expectancy of the concrete structure itself In addition, chloride ions attack the concrete matrix by breaking the cement paste bond. This leads to the formation of more cracks that weakens the structure.
More particularly, the present invention, being a complex water-based mixture of several active chemicals, was developed for the purpose of minimizing water penetration into concrete pavements from the surface, utilizing a chemical repelling agent, as well as minimizing the transmission of water and vapor through the concrete matrix (including from below) with a crystallization system, preferably a double action crystallization system of hygroscopic and hydrophilic behavior, all preferably based upon a single treatment, the chemical mix is shipped and stored in a single container and preferably applied by spraying. The invention is primarily intended for the treatment and protection of concrete bridges, concrete highways and concrete airport runways and taxiways and the like by a single application that results in essentially permanent maintenance-free and worry-free concrete pavements when it comes to water problems. As a further benefit, the treatment should prolong the concrete service life.
PRODUCTS OF THE PAST
Application of water repellant materials to the surface of concrete pavements can be effective in reducing water penetration from the surface as they increase the surface tension of water to a degree that prevent it from passing through capillaries. However, such methods alone do not address moisture transmission from the negative side of the substrate.
Other treatment methods have utilized tartaric acid and soda ash with Portland cement in a slurry phase that has been applied to the surface in a thin coat. The presence of tartaric acid and soda ash produces insoluble hygroscopic crystals that block moisture transmission because of the so-called crystal growth process as a result of the relatively high affinity to moisture of these crystals. However, such method has been inefficient because of the complexity in application (must block off and keep wet for four days) as well as its need for repeated maintenance (because it is an inherently surface adhering application as opposed to a penetrating material).
As a further disadvantage, available methods of treatment have historically attempted to solve the water and moisture problems in concrete pavement by application of single techniques at a time. Therefore, complex problems have not been overcomewithout the implementation of multiple treatments. There is a need for an affordable material that can address multiple significant water and moisture-associated problems in concrete pavements in a single application, especially for large areas ofpavements such in the case of concrete highways, bridges and airport runways.
WE HAVE SOLVED THE PROBLEM
A water-based mixture of multi compounds was invented for the purposes of treating and providing an ultimate protection for large areas of concrete pavements against moisture and moisture-associated problems. The mixture preferably works from within the concrete as well as at the surface. A water-repelling function prevents water from penetrating the concrete matrix. A hygroscopic and hydrophilic behavior of its crystallization system within a concrete matrix minimizes moisture transmission through capillaries and connected voids. As a result, the mixture promises to provide a permanent treatment for moisture related problems, such as damage caused by repeated freeze and thaw cycles and chloride ion penetration as from deicing salts, as well as a permanent treatment for the so-called alkali-silica reactions. ( http://www.understanding-cement.com/alkali-silica.html )
A method for protecting concrete pavement, comprising: applying the aqueous mixture to the concrete pavement; and curing the mixture; thereby, by the means of the application of the mixture, repelling water penetration at thepavement surface; and blocking water penetration within concrete matrices of the pavement by hydrophilic crystallization. (molecule which bonds with water)....molecular bond...
A method for protecting concrete pavement, comprising; applying the aqueous mixture to the concrete pavement; and curing the mixture; thereby, by the means of the application of the mixture, repelling water penetration at the pavement surface; and blocking water penetration within concrete matrices of the pavement by hygroscopic crystallization. (absorbing moisture: capable of easily absorbing moisture)
#100 product was introduced to the market in 1969 as a waterproofing material for concrete structures. It has gone through several stages of research and development to improve its performance and efficiency by adjusting its formulation as well as raw materials involved and manufacturing conditions. It is commonly referred to as the "Original Formula". #100 Original Formula, based on sodium silicate,is used globally as a waterproofing and hardening agent for old concrete structures as well as for its ability to work as a curing compound for fresh concrete. The waterproofing capability of #100 is achieved by an internal reaction that is triggered by a catalyst contained within the material to produce insoluble hydrophilic crystals which fill the pores and capillary channels inside the concrete.
More particularly, #100 is a combination internal waterproofing agent and curing agent for new concrete or a waterproofing agent for cured concrete. The product reacts with hydroxides (Portlandites) and tri-calcium silicate elements within the pore structure of a concrete assembly. The result of the reaction is the creation of a calcium-silicate hydrophilic grain with non-dilutent properties that absorb penetrating liquids and block the liquid passage through the concrete assembly that isunder the influence of hydrostatic pressures. #100 is a colorless, transparent liquid that penetrates concrete and masonry building materials--protecting, preserving and strengthening them by:
Curing: #100 eliminates hairline cracking and temperature cracking on new concrete. When applied to freshly finished concrete, #100 will uniformly cure the concrete through a chemical reaction as well as form a moisture barrier which eliminates temperature cracking.
Sealing: #100 penetrates into the concrete, forming a chemical reaction which locks the pores from within, giving the concrete a deep seal.
Waterproofing: #100 becomes a permanent, integral part of the concrete, thus waterproofing and substantially bonding and strengthening the structure of the concrete.
Hardening: #100 solidifies the component parts of the concrete into one solid mass which increases the density, toughens and hardens. CCC100 treated concrete has been tested 30% harder after 28 days than fully cured, untreated concrete. Thishardening prevents dusting, pitting and rutting of concrete floors and other masonry surfaces.
Neutralizing Alkali: As the #100 progressively penetrates the concrete it neutralizes the alkali and forces it to the surface where it can be washed off.
Bonding: #100 prepares the treated surface for paints, caulking compounds, adhesives and floor coverings and increases the bond and life of these materials. #100 contains no silicone and is coatable and compatible with any type of covering.
Treatment Results: With one application of #100, concrete and other masonry is cured, sealed and waterproofed and is rendered highly resistant to oils, grease and most acids. The component parts of the concrete are solidified into a solid masswhich increases the density, toughens and hardens and prevents dusting, pitting and rutting of the surface. The surface alkali is neutralized and efflorescence and the leaching of lime and alkali is stopped. The surface is prepared for paint, adhesivesand all floor coverings.
Treatable Materials: Concrete, concrete block, mortar, plaster, stucco, terrazzo, exposed aggregate and any sand, aggregate cement combination.
Limitations: Do not apply #100 in the following cases: When temperatures fall below 35.degree. F. To areas previously treated with curing or sealing agents unless these coatings have been removed by chemical or mechanical means.
Note: Must be kept off glass, glazed tile and aluminum
In 1992, and after intensive research our chemists developed another waterproofing product that is used strictly for old concrete, known as #700, based on tartaric acid and anhydrous sodiumcarbonate, has been proven to perform efficiently in waterproofing and hardening old concrete structures with severe moisture problems. Although a similar concept to the #100, when applied to concrete structures #700 penetrates more deeply into thesurface to produce insoluble hygroscopic crystals, which have the ability to block concrete pores and capillary channels. The hygroscopic property of those crystals allows them to travel further within the concrete toward a moisture source in acontinuous process.
More particularly, #700. is a crystallization waterproofing product in liquid form. It has the advantages of similar known prior powder form crystallization waterproofing products, together with the advantages of easy liquid application. The product can be applied to concrete like a paint and results in the same waterproofing quality as the prior known crystallization waterproofing cementitious coatings. #700 is formulated with chemical agents that enhance deep penetration within the concrete capillaries where the active chemicals react to form hygroscopic crystalline material which permanently block concrete pores. The chemical activity of these crystalline materials is reactivated upon further contact with moisture, and thus they keep growing inside the concrete providing dormant additional protection.
The chemicals in #700 may include other active reagents that react with hydroxides (Portlandites) to produce di and tri calcium silicate elements within the pore structure of a concrete assembly, resulting in more dense concrete and creating a hydrophilic crystallization with non-dilutent properties. Under the influence of high hydrostatic pressures, these crystals fill the voids, thus doubling the pore-blocking effects towards the liquid passage through the concrete assembly and vapor moistures.
#700 is a colorless, transparent liquid that penetrates concrete and masonry building materials--protecting, preserving and strengthening them.
USES: Warehouse floors, foundations and slabs, reservoirs, industrial plants, swimming pools, subway tunnels, elevator pits, interior walls in parking garages.
FEATURES: Easy application High waterproofing performance Penetrates concrete and seals capillary tracts and hairline cracks Can be applied to old and green concrete Protects concrete in-depth Multiple function: waterproofing, sealing and bonding which increase adhesive properties for products such as: epoxy coatings, polyurethane coatings, asphalt coatings and paints. Stops efflorescence Cost effective Non-toxic Resists high hydrostatic pressure Exterior and interior applications Capillarywaterproofing for concrete
TREATABLE MATERIALS: concrete, concrete block, mortar, plaster, stucco, terrazzo, exposed aggregate and any sand, aggregate cement combination.
LIMITATIONS: Do not apply #700 in the following cases: When temperatures fall below 35.degree. F. To areas previously treated with curing or sealing agents unless these coatings have been removed by chemical or mechanical means.
COVERAGE: Number of coats needed: One coat needed on new concrete after 7 days of placing the concrete at the rate of 200 sq. ft. per gallon. For old concrete: one coat application at the rate of 150 sq. ft. per gallon. Coverage depends onthe temperature and porosity of the concrete.
STORAGE LIFE: One year--Agitate bucket or drum before using.
The preferred hygroscopic and hydrophilic crystalline material, generated by the preferred embodiment of the invention, provides almost efficient protection for concrete pavements by optimally controlling the mass transfer of water and water vapor across the concrete matrix through capillaries and pores. The hydrophilic property of the crystals works mostly against water in the liquid stage while the hygroscopic characteristic works against water vapor.
Because of the hydrophilic behavior, under wet conditions, the crystals absorb water and swell in the form of a compressible gel material to fill the voids. As a result, they prevent further water from passing through Experimental work shows that these crystals have the ability to absorb enough water to make them swell up to sixteen times their size in the dry stage. The swelling stops as soon as the crystals reach the size of the void they are contained in.
On the other hand, the hygroscopic behavior becomes highly effective in the presence of water vapor, especially under relatively high hydrostatic pressures. Because of their extremely high affinity to moisture, the crystals continuously crawl slowly inside the pores and capillaries toward the source of moisture. As they absorb moisture, the sodium tartrate part of the crystals becomes more hydrated. This results in what is called crystal growth. The crystal growth leads to eliminating moisture transmission across the concrete matrix. Our tests show that the crystals were able to grow and travel about 3.5'' over a period of 12 weeks.
Under dry conditions, the crystals release the moisture they absorbed through evaporation. This results in bringing back these crystals to their original size, allowing the concrete to breath The crystals stay dormant till the swelling andcrystal growth processes are reactivated as a result of any increase in the moisture content inside the concrete from any side.
The preferred embodiments of the present invention, as a result, can comprehensively protect concrete pavements against water and moisture associated problems. A crystallization system minimizes the dissolution of calcium hydroxide contained within the concrete by moisture contact. As result, alkali silica reactions are minimized. Furthermore, minimizing water penetration and moisture transmission can dramatically reduce the driving force for chloride ion diffusion into concrete. As aresult, the structure becomes protected against chloride ion attack. In addition, the structure will be protected against damage caused by repeated freezing and thawing cycles. Freeze and thaw test shows that after 150 cyclesof freeze and thaw, the damage to a treated concrete sample was less than the damage caused by 25 cycles to an untreated sample
As a further part of the preferred embodiment, multiple simultaneous chemical reactions take place within the capillaries and pores of the concrete matrix as a result of the application of an embodiment of the present invention. Those reactions are triggered and/or accelerated by the increase in the concentration of chemicals as a result of water evaporation. Two major reactions are: one, tartaric acid reacts with sodium carbonate, triggered by the in increase in concentration as a result ofwater evaporation, to produce hydrated crystals of sodium tartrate. Two, sodium silicate (or an alkali metal silicate) reacts with calcium hydroxide from the concrete matrix to produce tri-calcium silicate. Further, both reactions when present interact chemically and kinetically with each other. As a result, preferably sodium tartrate and tri-calcium silicate become physically bonded to each other in a complex form of insoluble crystallization material These crystals combine both the hygroscopic and hydrophilic properties with a great affinity to water in its liquid and vapor phase.
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