A better way to measure moisture in concrete block
Concrete masonry units (CMUs) are a popular method of building construction. But because of its porous nature, moisture can readily infiltrate CMU during construction prior to application of coatings; via vapor diffusion through walls after the building is in service; from leaks in defective gutters, flashing, etc; and even from the use of pressure washing to remove staining or old coatings.
Regardless of where the moisture comes from, the walls must be dry when it is time to paint. Unacceptable amounts of moisture within the block often lead to blistering and peeling failures, and since moisture levels can rarely be detected visually or by touch, testing is required.
There are a number of moisture meters on the market, but unfortunately, not all provide an accurate assessment of moisture content in CMU. Tests conducted by the authors over bare and coated smooth face and split face block indicated that some instruments that are generally reliable on wood and insulation did not adequately distinguish between wet and dry concrete. The presence of a coating on the block caused especially erratic readings with some instruments, as did the use of split face block versus smooth.
The instrument that appeared most reliable for measuring moisture content in CMU is the GE Protimeter Aquant® Moisture Meter. The moisture meter uses a radio frequency signal that penetrates up to 3/4” into the surface coating and underlying concrete. The instrument was not influenced by the presence of a coating on the block, and proved effective on the irregular split face surface, although the readings were lower than on smooth face.
Even with this RF instrument, readings can vary, so it is important to take a minimum of three readings at each test location and average them. And if doing comparative readings (e.g. before and after power washing to confirm that the wash water has evaporated), it is critical to return to the precise locations for the post-wash tests, as the moisture content in CMU walls can vary significantly within a few feet or inches from each other.
From Ken Trimber and Kevin Brown, KTA-Tator, Inc.
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New Listing Manufacturers
California Paint Recycling
California Paint Recycling (CPR), headquartered in Sacramento, CA, now has the following product approvals with MPI:
• MPI #52 RR: Latex, Recycled (Remanufactured), Interior (Gloss Level 3): Global-Green Interior Eggshell
• MPI #53 RR: Latex, Recycled (Remanufactured), Interior (Gloss Level 1): Global-Green Interior Flat
• MPI #54 RR : Latex, Recycled (Remanufactured), Interior (Gloss Level 5): Global-Green Interior Semi-Gloss
Click here to see their complete list of Approved Products.
California Paint Recycling Inc. produces remanufactured interior and exterior latex paint from virgin paint and other waste paint, offering a wide range of colors.
Samhwa Paint Ind. Co. Ltd.
South Korea-based Samhwa Paint is now an MPIListing manufacturer, with products approved in these MPI categories:
• MPI #19: Primer, Zinc Rich, Inorganic: Superzinc Primer
• MPI #21: Heat Resistant Coating (up to 402°F/205°C): Hion 260
• MPI #39: Primer, Latex, for Interior Wood: Latex WP
• MPI #42: Textured Coating, Latex, Flat: Latex EX
• MPI #116: Block Filler, Epoxy: Superpoxy 320
Click here to see their complete list of Approved Products.
Founded in 1946, Samhwa Paint manufactures architectural paint products as well as specialty commercial coatings. Geographical distribution areas include Korea, China, Vietnam and other Asian countries.
SSPC Hosts Seminar on Painting Big Box Stores
SSPC: The Society for Protective Coatings’ “Greencoat” show in Las Vegas earlier this month included a full day seminar analyzing the challenges that face specifiers, contractors, and facility managers involved with painting commercial buildings such as big box stores. Presentations included:
- Identification of the Coating Problems Faced by Commercial Building Owners by Ken Trimber and Kevin Brown. This keynote paper used Lowe’s as an example, and described challenges for extending the life of coating systems on metal components, concrete masonry units, EIFS, and more.
- The Science of Moisture Migration in CMU Walls of Commercial Buildings from Kevin Knight gave an overview of the problems faced in maintaining coatings on the interior and exterior of CMU buildings, including suboptimal design and construction practices that lead to moisture being trapped in walls.
- Coatings Supplier Perspectives presented by Sherwin-Williams, PPG, Rust-Oleum, and Dryvit, as well as MPI
- Contractor Perspectives by DK Contracting and Final Coat
For more information on SSPC or to obtain copies of the papers, email SSPC’s Terry Sowers at sowers@sspc.org.
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