Polymer cement waterproof coating, referred to as JS waterproof coating, has been rapidly developed and widely applied from the end of the last century to the beginning of this century due to its good physical properties, simple construction methods and construction on wet base. However, in recent years, such products have experienced great quality problems, leaving a bad impression on many construction units and management departments. It is regrettable that new products have been faced with inferior products in less than ten years. The reasons for this are not only because the market low-price competitors intentionally sacrifice quality and the poor supervision of the construction process, but also the improper application of this product. . Why is it improperly applied? This is related to the misunderstanding of many people in the industry about this product. Qinglong waterproof experts summarize the following for you:
1. Misunderstanding of the choice of latex and the ratio of ingredients
The basic principle of JS waterproof coating is to modify the inorganic cementitious material with cement and quartz sand as the main component in the synthetic polymer latex. The formed coating film basically maintains the high strength and water resistance of the cementitious cement material. Based on the characteristics, the flexibility (ie, elongation) is increased as much as possible. At the same time, the polymer latex also brings a negative effect, that is, the decrease of hardness and the long-term water resistance and aging resistance are weakened. The magnitude of the negative effect is closely related to the type and amount of latex used (ie, the modification ability of the latex). There are two main types of latex used in the market for JS coatings - polyacrylate latex and polyethylene-vinyl acetate latex. The former has better modification ability than the latter, and the former has significantly less than the latter, and its negative effect is also significantly smaller than the latter. However, most people mistakenly believe that the JS coating should be the larger the amount of latex. The choice of different manufacturers is based on the same price as the product. Therefore, some manufacturers or merchants in order to show that their products have a large amount of latex, they will mix the purchased latex raw materials with water and then prepare JS coatings. The quality of the products is far from the real JS coatings. What's more, some construction teams are After the low-cost contracting waterproofing project, the commercially available polyvinyl acetate latex (commonly known as white latex) or polyvinyl alcohol glue (commonly known as 107 glue) was mixed and applied, and the consequences were unimaginable, which seriously damaged the reputation of JS coating. At present, less than 10% of JS coatings used in construction projects are really using polyacrylic latex, which is the main reason why JS coatings slip into the ranks of “poor†products.
2. Insufficient understanding of classification
The elongation of JS waterproof coating is directly related to the amount of latex. However, the amount of latex directly affects the long-term water resistance of the coating. In order to solve this contradiction, the technical treatment of engineering specifications and product standards is to apply JS coating. Divided into two types, type I is a large amount of latex, the elongation requirement is more than 200%, used for intermittent water-immersed engineering parts (such as roofing, exterior wall surface, etc.) to meet the requirements of large deformation. Type II is a slightly less amount of latex, and the elongation is as long as 80% to meet the engineering parts (basement, toilet room, etc.) with small deformation and long-term water resistance requirements, but it is not used in many projects, from the basement to There is one type of roofing, type I or type II, which not only fails to achieve the expected results, but also has many quality hazards, which is disappointing.
3. Relationship between coating thickness and construction times
Even the best waterproof coatings must have a certain thickness of the coating as a quality guarantee. In the "Technical Specifications for Roofing Engineering" and "Technical Specifications for Underground Engineering Waterproofing", the basic thickness of JS coatings is 1.5 to 2.0 mm. In the actual project design and construction monitoring, it is often only pay attention to the number of constructions but ignore the final thickness of the coating. It is often seen that some design drawings only indicate "several coatings with JS waterproof coating" but no thickness requirements. On-site management is also only concerned with painting several times. Give some construction teams lacking in good faith a hole, and after the paint is diluted with water, it is more than one or two times more than the design requirements, and it is also praised by the on-site management personnel. After the low-cost contracting to the project, it can earn a lot of profits. Products with superior performance can't withstand such damage.
4. Ignore the importance of the effect of on-site mixing on film properties
JS coating is a two-component product. In fact, the final process of product production, mixing and phase separation, is left to the on-site construction team. I don't know, the "mixing" and "phase separation" states of two-component products are crucial for the formation of coating properties. In addition, JS coatings are "powder-liquid" two components and are not as good as other "liquid-liquid" two components. The mixing and dispersing of the products is easy. Although the product specifications of each manufacturer have the correct method for on-site mixing, many mixing processes of the construction team are perfunctory, and some even do not have a special agitator. Very few people know the judgment and mastery of the “phase separation end pointâ€, so that the final film performance is greatly reduced due to the incomplete phase separation.
5. Misunderstanding of tensile strength
In the product standard of JS coating, the tensile strength requirements of the coating film are I type ≥1.2MPa, type II ≥1.8MPa, many people mistakenly believe that the higher the tensile strength, the better, in fact, the stretching of JS coating In the performance test method, there is a standard curing process of heating at 50 ° C for 24 hours after 7 days of curing. Many coating products are rapidly increased in tensile strength due to volatilization of plasticizer during heat curing at 50 ° C, indicating that these products are exposed. The performance of using heat aging changes rapidly and the life is not long. Therefore, the product with abnormally high tensile strength should be alert, and if necessary, the heat aging retention test can be performed. Rather than one-sidedly, the higher the tensile strength, the better.
6, free to set the base position
In some engineering joints, in order to avoid stress concentration, the base layer is added to extend the dispersion stress to reduce the cracking of the coating. Therefore, the setting of the base position directly affects the use effect. It should be that the closer the base is to the base layer, the more the dispersion stress can be achieved. In fact, many projects randomly set the position of the base to be unattended, so as to be placed in the middle of the coating. Some projects have placed the tire base on the surface of the coating. After discovering this phenomenon at a construction site, the author asked the construction personnel why the base was exposed on the surface. The workers answered: "The money will be settled with the contractor." People are ridiculous.
7. One-sided understanding "can be applied in wet base"
Compared with other waterproof coatings, JS waterproof coatings can be used in wet base construction. There is a problem of moisture level, which is not to say that any wet climatic conditions or very high base water content can be applied because JS coating latex It is cured by volatilization. Excessive base layer moisture content and too humid climatic conditions are unfavorable for the solidification of the latex film, which will reduce the elongation of the film. At the same time, the cement in JS coating is solidified by hydration, too dry base layer and climatic conditions, and it is not good for cement curing. Therefore, in the hot and dry season, it is necessary to spray some water on the base layer before construction. In fact, JS coatings still have some requirements for the temperature and humidity range of the construction, generally the temperature is 5 ° C ~ 35 ° C, the humidity is 50% ~ 70% is appropriate, regardless of temperature and humidity conditions for forced construction, although it can also form a film, However, the film properties are quite different.
8. Misunderstanding about the possibility of adding water
Most manufacturers specify in their product specifications that water can be added during the first application of the coating to dilute the coating to improve the penetration of the substrate and improve the adhesion to the substrate. Therefore, many people misunderstand that JS coatings can be added with water, which is very harmful. The ratio of two components in JS coating - the ratio of polymer to cement (the ratio of polymer to cement) and the ratio of water to cement (the ratio of water to cement) It is determined by the manufacturer through many experiments. Any change in the composition of one of the components has a great influence on the performance of the film. In actual engineering, the phenomenon of increasing the amount of powder and then adding water to adjust the consistency is everywhere. Many of the projects are based on the use of JS coatings to steal material, so the application, JS coatings are on the way.
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