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Mistakes in application of polymer cement waterproof coatings
Polymer cement waterproof coating, commonly known as JS waterproof coating, has seen rapid development and widespread application since the late 20th century. Its popularity stems from its excellent physical properties, ease of application, and ability to be applied on wet bases. However, in recent years, many quality issues have emerged, leading to a negative perception among construction companies and regulatory authorities. It’s unfortunate that a product once praised now faces challenges due to inferior alternatives within just a decade. The reasons for this are not only due to low-price competitors sacrificing quality and weak supervision during construction, but also improper use of the product itself.
Why is it misused? This is largely due to misunderstandings within the industry. Here are some key points identified by Qinglong waterproof experts:
1. **Misunderstanding of Latex Selection and Ingredient Ratios**
JS waterproof coatings work by modifying inorganic cementitious materials with synthetic polymer latex. The goal is to maintain high strength and water resistance while improving flexibility. However, the type and amount of latex used significantly affect performance. For example, polyacrylate latex performs better than polyvinyl acetate latex, but many people mistakenly believe that more latex means better quality. Some manufacturers even dilute raw latex with water to create the illusion of higher content, leading to poor-quality products. In some cases, unqualified materials like white glue or 107 glue are used instead of proper latex, resulting in serious damage to the product's reputation. Today, less than 10% of JS coatings actually use high-quality polyacrylate latex, which contributes to their poor image.
2. **Lack of Understanding of Classification**
JS coatings are divided into two types based on their elongation and water resistance. Type I has higher elasticity (over 200%) and is suitable for areas with frequent movement, such as roofs. Type II has lower elasticity (80%) but better long-term water resistance, making it ideal for basements or bathrooms. However, many projects mix these types, leading to inefficiency and potential defects. Using the wrong type can result in poor performance and long-term issues.
3. **Incorrect Coating Thickness and Application Times**
Even the best coatings require sufficient thickness for effective protection. Standards recommend a minimum of 1.5 to 2.0 mm. Unfortunately, many projects focus only on the number of coats rather than the final thickness. Some contractors dilute the coating with water to reduce costs, compromising quality. This practice undermines the performance of even the best products.
4. **Neglecting the Importance of On-Site Mixing**
JS coatings are two-component products, and proper mixing is crucial for film formation. Many construction teams rush the process or lack proper tools, leading to incomplete mixing and reduced performance. Few understand how to judge the correct phase separation point, further affecting the final quality.
5. **Misunderstanding Tensile Strength**
Some believe higher tensile strength is always better. However, excessive strength can indicate unstable performance, especially if it increases rapidly after heat curing. Products with abnormal tensile strength should be tested carefully, as they may not last long under real conditions.
6. **Improper Base Positioning**
Proper base placement helps distribute stress and prevent cracking. Yet, many projects place the base randomly, sometimes even on top of the coating. One worker admitted, “We do it because the contractor pays us.†Such practices compromise the integrity of the entire system.
7. **Misconception About Wet Base Application**
While JS coatings can be applied on wet bases, this doesn’t mean they can be used in any moisture condition. Excessive moisture can hinder latex curing, reducing flexibility. Similarly, too dry conditions can negatively affect cement hydration. Ideal conditions are between 5°C and 35°C, with humidity between 50% and 70%.
8. **Misunderstanding Water Addition**
Although some manufacturers allow water addition during the first coat to improve adhesion, many misuse this by adding excessive water. This disrupts the balance between polymer and cement, severely affecting the coating’s performance. In some cases, contractors use JS coatings to cut costs, further damaging the product’s reputation.
In conclusion, proper understanding and application of JS coatings are essential for achieving long-term waterproofing success. Misuse, whether due to cost-cutting, lack of knowledge, or poor execution, leads to substandard results and erodes trust in the product.