Single, low environmental requirements, with good water resistance and durability features.
Composition of chemical complexes of active functional groups. It can not only form an effective waterproof coating, but also contains reactive chemical complexes that can penetrate into the interior of the concrete, chemically react with moisture and free active substances in the concrete, form insoluble crystal complexes, and rely on crystal growth. Fill the capillary channel. These crystals can usually grow to a maximum size of Q4nm above the concrete capillary, making the concrete dense and waterproof. Due to the chemical reaction, the waterproof performance of the entire body is improved, which not only makes the waterproof performance easy to maintain for a long time, but also improves the strength and compactness of the base concrete.
1 The overall development of foreign cement-based penetrating crystalline waterproof materials This type of material was originally created during the Second World War by the German chemist Lawrence. Lauritz Jensen invented the practice of solving the seepage of cement vessels. At the time, German steel was nervous and began to use cement to build ships. However, the cement boat is seriously leaking and cannot be used normally. Under this background, the production and development of cement-based penetrating crystalline waterproof materials are promoted. After the Second World War, the rapid economic growth in Europe and Japan led to the continuous expansion of the engineering application of this material. The products also extended from the early German VANDEX brand (now resold to Switzerland) to the Canadian XXPEX. (Sybercos), Canada's KRYSTOL Singapore (expansion), France's DPSEC, Australia's CRYSTAL Japan's DIPSEC and dozens of brands. In the process of exploiting engineering applications, cement-based osmotic crystalline materials were initially advocated for waterproofing the outer surface of fully underground concrete structures, and later found its special effects on the back surface (inner surface of the structure). It is ideal for applications such as sewage treatment tanks and ground water storage tanks. Since the 1960s, CCCW as an effective coating for the waterproofing of concrete structures on the back surface (inside waterproofing method) has gradually expanded its variety and has entered new areas of construction and construction applications. 111. Research and Application of Materials China's cement-based penetrating crystalline waterproof material, an XXPEX product, was introduced in the 1980s. Began to apply to the Shanghai Metro project. Since the early 1990s, other similar products of Xypex have entered the Chinese market one after another. In Shanghai, Beijing, Guangzhou, Wuhan, Dalian, Chongqing, Hangzhou, Urumqi and other places to obtain more applications.
In the middle of 1990s, it began to produce in China. It has established Beijing Chengrong Waterproof Material Co., Ltd., Shanghai Jicheng Dashen Waterproof Material Co., Ltd., Kunshan Kaidun Baisen High-efficiency Waterproof Material Co., Ltd., Urumqi Gusite Waterproof Material Co., Ltd., and Shanghai Huihui. Qi Industrial Development Co., Ltd. and other enterprises. At present, the designed production capacity is about 13,000 t/year. And some agents distribute products from the United States, Canada, Australia, France and other countries. This type of product has been successively used in the lower dam room of the Xiaolangdi Power Station of the Yellow River, plugging of the diversion tunnel of the Sichuan Bridge Reservoir, seepage prevention of the machine room, reinforcement of the dam surface, leakage trapping of the sedimentation basin of the Gaobeidian Sewage Treatment Plant in Beijing, and the basement of Beijing Millennium Base. Waterproofing and jointing of immersed tube tunnels on the Shanghai Overseas Ring Line have significant waterproof effects and are well received by the engineering community. The diversion tunnel of Xikang Hydropower Station in Shaanxi was inspected for the entrance hole. Because of the diversion tunnel's high speed and high pressure water flow, the leakage of the inspection entrance hole was more serious. After the joint repair of the rice cement-based permeated crystalline waterproof material series products, it played a role. The effect of complete leakage prevention 121. Cement-based penetrating crystalline waterproof material is different from traditional waterproof materials. The traditional waterproof material forms a water-repellent layer on the concrete surface, which plays a role in waterproofing. It is very effective in the initial stage, but over time. As it grows, its performance gradually degrades and loses its waterproof effect.
However, the water resistance of the crystalline waterproof material continues to increase over time, and permanent waterproof does not age. This feature makes the waterproof material superior in the field of concrete waterproofing, which is unmatched by other waterproof materials. It is also different from other cement-based waterproof coatings 111. The performance comparisons are shown in Table 1. Table 1 Comparison of the performance of cement-based waterproof coatings (for underground concrete structures) Water-repellent mortars (with water repellent) Water-tightness Reparability Safety materials Labor costs Duration Construction Frost Heaving Adhesion Wet Surface Adhesive Cracking Follow-up Resistance Impact Resistance Tear-resistance The strength and density of the partial pressure, so as to improve the impermeability. This theory was established based on this reaction.
When the cement-based permeation-crystalline waterproof material is applied to the surface of concrete, the active chemical substance penetrates into the concrete through the presence of water in the pores of the concrete, due to the presence of active chemicals in the coating. The free lime and oxides in the pores react chemically to form water-insoluble crystals 13114|. The capillary networks, capillary pores, and micro-cracks in the sealed concrete act as water blocking and waterproofing. At the same time, it reacts with the oxides on the surface of the steel bar to form a stable film to prevent carbon dioxide from intruding into the concrete and prevent the IH value in the concrete from declining, which acts as a protective steel bar. As follows: Cement-based penetrating crystalline water-repellent coating (inorganic coating) Polymer cement-based coating (organic coating) (Note: Excellent; â–³ Normal; X: Poor; * â–³ Film is soft; must have protective layer) It can be seen that the superiority of the cement-based pervious crystalline waterproof coating is mainly manifested in: 1 strong permeability; 2 permanent waterproof effect; 3 unique self-repair ability; 4 unique overall waterproof performance; Protection; 6 non-toxic, non-pollution; 7 construction is simple, and has good adaptability to complex concrete base etc. 3 The mechanism of action of cementitious capillary permeation crystalline waterproof material bookmark3 Permeate crystallization mechanism of cement-based pervious crystalline waterproof coating Explanation has not yet reached a consensus, but there are two explanations that are currently accepted: one is the mechanism of precipitation reaction, and the other is a precipitation-network. The reaction mechanism.
1 precipitation reaction mechanism This reaction mechanism is mainly for the presence of a large number of Ca 2+ .Ca(OH) 2 in hydrated cement stone is an important factor affecting the durability of concrete, through the chemical reaction to reduce the content of free Ca 2+, transform it into the strength of concrete. Material with favorable solidity can not only improve the crack resistance and seepage resistance of concrete, but also improve the concrete. If there are many structural defects in the concrete of the matrix and water penetrates easily, the penetration depth of chemically active substances in the coating will become more pronounced. . Tests have found that the depth of penetration can be extended to more than 150mm. 16. If the base concrete is a very compact waterproof concrete, the chemical remains in the surface coating when the coating is applied to the substrate surface. If water infiltrate later (for example, by shrinking cracks, construction joints, etc.), the chemical substances in the paint will be activated and migrate with the penetration of water into the defects of the concrete structure, and the above-mentioned crystallization reaction will occur. The crystallization product seals the cracks, thereby repairing the structural defects and making the substrate waterproof again.
Another argument for penetrating crystalline waterproofing materials is the complexation-precipitation mechanism theory. This theory holds that there is a chemical active substance that can be complexed with Ca<2+> in the coating, and when mixed with water, the substance quickly disperses into water; when the coating is applied on the surface of the concrete substrate, a high concentration of such substances is formed in the surface layer. Area. Due to the concentration gradient, the active material will enter the interior of the matrix with water.
When cementite is the main hydration product of calcium silicate gel, a large amount of hexagonal platelet Ca(OH)2 crystals are produced. The Ca(OH)2 in the hardened cementitious stone contributes little to the strength, and its dissolution can easily cause damage to the concrete structure. The active chemical that enters the interior of the concrete encounters a high concentration of Ca(OH)2 and complexes with the calcium ion ionized in the concrete to form a water-soluble, unstable calcium complex. The complex diffuses with the water in the pores of the concrete and encounters highly active and unhydrated cements, cement colloids, etc. The active chemical substances are replaced by more stable silicates, aluminates, etc., and crystallization and precipitation reactions occur. The Ca(OH)2 is converted into a crystalline composition with a certain strength, filling the cracks and capillary pores in the concrete. Active chemicals, on the other hand, become free radicals and continue to migrate internally with water. The basic process of the crystallization of the crystallization of cement crystals occurs in the complexation-precipitation reaction. It can be known that Ca2+ = Ca2+, which is Ca2+, diffuses into the water in the pores of the concrete. In the presence of the reactive SO, the insoluble CaS3 (the main crystal of the cement) is formed due to the difference in solubility and precipitates into the concrete pores. In the process, the separated A2- ions diffuse again, react with Ca2+ again at a place where the Ca2+ concentration is high, and convert into Ca2+=A2-, which diffuses inside the concrete. This reaction is repeated in concrete, producing cement crystals that block the pores in the concrete and form a denser concrete. This is the basic mechanism of the precipitation-complexation reaction.
It can be seen that in this reaction, the concentration gradient is the main factor for the diffusion, the crystallization reaction is the driving force for further diffusion, and the diffusion provides the necessary conditions for the crystallization reaction.
When the concrete is dry, the active material is in a dormant state due to lack of a diffusion medium. When water penetrates, the substance will be activated again, and a new crystallization reaction will occur, resulting in a dense and waterproof structure.
Therefore, the paint is permanently waterproof.
In addition to the above reactions, there is also a cycle, which also makes a great contribution to the permeation crystallization process. The specific description is as follows: In the normal hydration process, about 25% of the cement does not hydrate due to the package of calcium silicate hydrate. In the above reaction, due to the absorption of hydrated lime, the hydration of the cement will be more in-depth than usual, and some unhydrated cement will continue to hydrate, which is generally referred to as the reactivated cement reaction. Reactivated cement hydration increases the compactness of the concrete. It may also cause the gel to crack due to the increase in volume. This causes more water to enter the unhydrated cement. This process will produce a larger volume of coagulation. Glue, such a benign cycle, makes the larger capillary pores smaller or closed, giving the concrete the ability to "automate healing and repair cracks." Because it is the reactivation of unhydrated cement, the quality of the concrete can be improved as a whole, and the impermeability and durability can be improved.
These chemical reactions not only occur on the surface of the concrete and its vicinity, but also continue deep into the concrete structure. The depth of penetration and the time involved depend primarily on the presence of moisture and the composition of the concrete. It also depends on the physical properties of the concrete, such as cement content, density, porosity, porosity characteristics, and shrinkage. Therefore, it is very necessary to keep the concrete surface fully wet while treating the concrete.
Because these crystals are similar to the crystals of the concrete itself, they will eventually integrate with the matrix, closing the capillary system and making the water unacceptable. However, water vapor can still pass through so that moisture that is not trapped in the crystal can evaporate in the form of steam during the crystallization process until the minimum internal pressure is reached and is completely terminated.
This theory holds that the crystallization reaction does not consume active chemical substances. It only exists as a form of catalyst, thus a more complete description of the process of permeation and crystallization has great breakthrough. However, it still needs verification, and it needs practical support and theoretical improvement.
From the foregoing, it can be seen that cement-based osmotic crystalline waterproofing materials have good effects in engineering applications, simple construction, low environmental requirements, good water resistance and durability, and are very promising waterproof materials.
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