Ensuring the success of your flooring installations involves more than just skill and precision. It requires a keen understanding of the materials you’re working with, particularly the concrete substrate.
One critical factor that often goes unnoticed is the pH level of the concrete slab. High alkalinity can compromise adhesive performance, leading to bond failure and costly repairs.
This challenge has come increasingly to the fore of recent years as adhesive compositions are being updated to meet sustainability requirements.
Let’s delve into the importance of pH levels in concrete and how you can manage them effectively.
Understanding pH Levels in Concrete
The pH scale ranges from 0 to 14, with 7 being neutral. Values below 7 indicate acidity, while those above 7 indicate alkalinity. Freshly poured concrete is highly alkaline, typically exhibiting pH levels between 12 and 13. As the concrete cures and carbonates over time, the pH level decreases, ideally stabilizing between 9 and 10, which is suitable for most flooring adhesives.
The Impact of High pH on Adhesives
When the pH level of a concrete slab exceeds 11, it can adversely affect flooring adhesives. High alkalinity may lead to adhesive degradation, weakening the bond between the flooring material and the substrate. The direct results will be delamination, bubbling, or complete flooring failure, necessitating costly repairs or replacements.
The Effect of Grinding on pH Levels
Recent research by MARKHAM has demonstrated that mechanical processes like grinding can temporarily increase the pH level of a concrete surface. Grinding removes the carbonated layer of the concrete, exposing fresh, highly alkaline material beneath, besides reducing the surface layer to fine dust.
This exposure will almost certainly raise the surface pH, potentially impacting adhesive performance if the flooring is installed immediately afterwards. It takes some days for the pH levels to revert to suitable levels.
Regrettably, this fact is not common knowledge across the flooring industry, leading failures to be blamed on other factors.
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Best Practices for Managing pH Levels
To ensure optimal adhesive performance and flooring longevity, consider the following steps:
- Test pH Levels Before Installation: Utilize pH testing kits to assess the alkalinity of the concrete surface prior to installation. This assessment will help determine if the substrate is within the acceptable pH range for your chosen adhesive.
- Allow Time for pH Stabilization After Grinding: If grinding is part of your preparation process, MARKHAM recommends waiting 5 days before installing flooring. This waiting period allows the pH level to stabilize, reducing the risk of adhesive failure.
- Select Appropriate Adhesives: Some adhesives are formulated to withstand higher pH levels. Consult with adhesive manufacturers to choose products that are compatible with the pH level of your concrete substrate.
- Monitor Moisture Levels: High moisture content (RH, Relative Humidity) can exacerbate pH-related issues. Ensure that moisture-control treatment has been applied, if the RH levels are excessive.
- Follow Industry Standards: Adhere to guidelines set forth by industry standards, such as AS1884, which recommends that the pH level of the concrete surface should be between 9 and 10 before flooring installation.
Conclusion
This is a real-world challenge.
By paying close attention to the pH levels of concrete substrates and following best practices for preparation and adhesive selection, you can enhance the durability and success of your flooring installations. Regular testing and adherence to industry standards will help prevent adhesive failures and ensure customer satisfaction.
And don’t forget that key point about waiting a while after grinding!
The MARKHAM team would be happy to discuss your next project with you. Why not get in touch?
You’re invited to learn about FLOOR-TECT®, the MARKHAM response to AS1884:2021.
