PaintSquare.com
Follow us on Twitter Follow us on LinkedIn Like us on Facebook Follow us on Instagram Visit the TPC Store
Search the site

 

Advertisement

PaintSquare


Problem Solving Forum

| More

June 3 - June 9, 2013

How can I determine when concrete has cured sufficiently to be coated, besides waiting the 28 days typically specified?

More items for Quality Control


Selected Answers

From William Slama of International Paint/Ceilcote Products on June 5, 2013:
Most persons concerned with this consider two primary factors - attained strength and residual water content. In most cases, depending on the concrete mix and initial wet curing for hydration to take place, strength is not the critical factor. The typical "requirement" for 28-day cure comes from the engineer and relates to any physical/structural requirement. However, in most cases such as a floor or non-structural wall, that is not a significant factor for coating or lining.

 Moisture content or, more particularly, moisture availability at the surface is the important factor that impinges on coating/lining success. There are several electrical methods to measure internal moisture content on concrete surfaces, but these are all subject to interpretation and most do not measure more than the top inch or two of the concrete. Most coating/lining manufacturers require either the moisture emission rate test method that uses calcium chloride as a desiccant (ASTM F1869) or the plastic sheet test (ASTM D4263). Typically, the calcium chloride test is required to be below about 3 lbs. of water emission per 1,000 sq. ft. of surface area per 24 hours. This usually requires the test specimen to be sent to a lab for analysis before getting a result. It is believed that this result depends on the amount of not yet hydrated water near the surface. That is a combination of theoretical water amount not yet hydrated and excess water (“water of convenience”) that is within the concrete mix. It can also be influenced by availability of water on the reverse side of the concrete that can be an excess due to high water table and lack of vapor barrier below a slab.

We strongly prefer requiring the ASTM Plastic Sheet Test. The reason is that for proper performance of the coating/lining, two requirements must be met. Basically, the concrete surface needs to remain dry for 16 hours. This 1) allows the primer or first polymer layer to properly wet and penetrate the concrete surface while free of water and 2) allows that contacting layer to begin to cure (cross-linking or simple solvent evaporation) also in the absence of liquid water. Beyond that, a system's capability to withstand liquid water later at the concrete/polymer interface depends on the characteristics of the applied system. Worst case will be that high water pressure at that interface will cause loss of adhesion to the concrete surface and subsequent blistering. The system properties necessary to withstand future reverse (osmotic?) blistering are complex and without agreed definition, but most agree that good penetration and adhesion, as well as the rigidity of the system are important to withstand later blistering by water within or from underneath the concrete. Actual experience has shown that well designed systems can be applied as early as 7 days after concrete placement by specifying a high early concrete system with additives to limit the amount of excess water; wet curing for 3 days and then allowing surface water to evaporate for the rest of the time. That will usually allow adequate concrete strength and ability to pass the plastic sheet test.

From MARCIN MAZUREWICZ of Intertek on June 4, 2013:
The 28-day period refers to achieving maximum strength of the concrete. You can determine the level of moisture in the concrete either by drilling a hole and checking humidity level by inserting probe inside the hole (accurate, but destructive) or by  using a non-destructive meter. There may be a discrepancy between these two methods, especially when readings are taken at humidity levels higher than is actual "inside."

From AJAYI OLUWADUNSIN of DAEWOO E&C on June 4, 2013:
Just conduct moisture test on the substrate. e.g.,  plastic sheet method, moisture meter, etc.

Please sign in to submit your answer this question    

Tagged categories: Concrete; Curing


Current PSF Question | Submit a PSF Question | Full PSF Archive

Advertisements
 
Fischer Technology Inc.
 
MP0R with rotating display screen
 
Automatic rotating display screen just like your smart phone. Click for Video
Call 800-243-8417
 

 
KTA-Tator, Inc. - Corporate Office
 
KTA Online
Instrument Catalog
 
• Any Manufacturer
• Any Instrument
• Any Time
Visit www.ktagage.com
Or call 800-582-4243
 

 
HoldTight Solutions Inc.
 
NO FLASH RUST - NO CONTAMINANTS
 
Our HoldTight®102 salt remover & flash rust
preventer prevents flash
rust by removing surface contaminants. Contact us
for your nearest distributor.
(800) 319.8802 sales@holdtight.com
 

 
Corrosion Probe, Inc.
 
From Detection to Correction
 
Corrosion Probe, Inc. has the Most Concrete Coatings Experience and Expertise. Contact us today at
860-767-4402, www.cpiengineering.com
 

 
BASF
 
New resins from BASF will have metals loving water!
 
Excellent corrosion resistance, low VOC, high gloss, thin films www.basf.us/industrialcoatings dpsolutions@basf.com 800-231-7868
 

 
DeFelsko Corporation
 
PosiTector SHD Shore Hardness Durometer
 
PosiTector SHD measures the hardness of non-metallic materials. Features a measurement timer, auto ignore mode and internal memory. Shore A or D available.
 

 
Bullard
 
Upgrade with the Bullard GenVX
 
Click here to learn how you can get a GenVX Helmet and Win.
 

 
SABRE Autonomous Solutions
 
Repeatability
 
The ALPHA1 provides reliable results consistently allowing you to cost your next job with confidence.
 

 
Aggreko
 
Dehumidification & Heating Rental Equipment
 
Dehumidifiers, heating, power and 24/7 service, nationwide. Aggreko offers rental solutions for your painting/coating project.
844-433-9802
 

 
SAFE Systems, Inc.
 
Portable Dust Collectors for Tough Environments
 
Trailer and skid-mounted models in numerous sizes, powered by electric and/or diesel. Sloped roofs, multiple dust inlets, high static, dampered fans. Lockable power & drive compartments.
 

 
 
 

Technology Publishing Co., 2100 Wharton Street, Suite 310, Pittsburgh PA 15203-1951

TEL 1-412-431-8300  • FAX  1-412-431-5428  •  EMAIL webmaster@paintsquare.com


The Technology Publishing Network

Durability + Design PaintSquare the Journal of Protective Coatings & Linings Paint BidTracker

 
EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
MORE:      About PaintSquare.com   |   Privacy policy   |   Terms & conditions   |   Site Map   |   Search   |   Contact Us