Surface Treatment For Concrete Forms
A discussion started in 2004 but continuing through 2018(2004)
Q. I am a consultant working on behalf of a significant U.S. manufacturer of aluminum forms for pouring concrete walls (residential construction)for basement structures. Customers ask that the face of the aluminum forms be etched (or treated )so that, on the first use of the form, the hydration reaction of the curing concrete will not react with the aluminum form to cause bubble marks and bubble paths up the face of the concrete wall. The first few walls poured with a new set of forms have surface flaws caused by the concrete / aluminum reaction. We are seeking a surface treatment to use during production of the forms which will eliminate this initial reaction. The present method of treatment is to roll lime slurry onto the surface of the forms. This treatment looks terrible and is sometimes ineffective.
We would prefer a treatment whereby the face of the completed form could be dipped (not the entire form)into a solution which would react with the face and then could be washed and neuturalized in an automated line process. The forms are hand mopped with lime, one at a time, in the existing process.
Thank you in advance for your reply/replies.Wendall Kitchens
Aluminum Forms for concrete - Atlanta, Georgia, USA
A. The bare aluminum is probably oxidizing and generating Hydrogen gas when contacted by the wet concrete. Once a natural oxide layer is formed, the reaction slows down or stops. Anodizing is a forced, controlled oxidation of the aluminum. Hardcoat anodizing is a thicker, denser version of anodizing. Hardcoating would also control the oxidation process and extent the wear life of your forms.
Luke Engineering & Mfg. Co. Inc.
March 30, 2011
A. I have used aluminum extrusions for mold side rails. They had standard anodizing. I was distressed at the first usages as the concrete stuck horribly, although it was a weaker lightweight concrete so not possessed of regular tensile strength.
It ended up taking about six pours of the mold to finally stop the reaction and get a clean release. After that point they behaved fine, but only by using a secret ingredient (very common) as the release.
One attempted solution was to use a sodium hydroxide solution to pre-react the extrusions. It might have helped reduce the number of bum mold usages, but still required multiple pours to finally stop the sticking.
- Roberts Creek, British Columbia
Treatment for Concrete Release on Steel FormsApril 16, 2018
Q. Looking for a coating to be applied to carbon steel molds which we use for a concrete composite mixture.
Right now we have glossy finish powder coated molds which we spray a thin layer of soy oil on for easy release; problem is the oil makes a terrible mess of things.
Any coating advise would be great!
Thanks for your time!
- waverly Iowa, usa
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