Questions To Ask When Choosing A Form Release Agent

The best way to evaluate a form release agent is to try it out under actual job conditions. Make a test panel or use the unfamiliar release agent on a non-architectural portion of the concrete. Also get the manufacturer’s advice on what types of forms it can be used on and how it should be applied. Here are a few things to consider:

• Will coatings be applied to the finished concrete? If the concrete surface is to be plastered or painted, the release agent should not leave any residues the prevent adhesion. Waxes and silicones are known to do this.
  
  
• Are the forms being used for architectural concrete? If so, stains, dusting, and conspicuous bug-holes are probably unacceptable. Use the same release agent throughout the entire job, and take care to apply it in a thin, uniform coating. As far as the appearance of the concrete is concerned care in applying the release agent is probably as important as the choice of any particular type.
  
  
• Is a superplasticizer used in the concrete mix? Increased slump that occurs with super plasticized concrete facilitates the movement of air bubbles and water drops but the early slumps loss trends to trap these voids at the surface. Form releases agents with special additives can help reduce friction at the form face so air bubbles and water drips can rise and escape more easily.
  
  
• Is concrete surface retarder used? Many retarder manufacturers recommend applying a volatile type release agent before applying retarder, so form cleaning is easier after stripping.
  
  
• How long can the release agent stay on the forms before concrete is placed? Some release agents must be applied the same day that the concrete is placed; others are effective after they have been on the forms several weeks. Get the manufacturer’s recommendation.
  
  
• Will the form release agent still be effective, if the forms are not stripped for a long time?
  
  
• How does the release agent affect the form surface? Does it rust metal? Does it soften plastic? Is it absorbed by wood? Or does it provide a waterproof barrier that preserves the form?
  
  
• Does the release agent dry out on the forms? Dry release agents aren’t slippery, and they don’t get tracked onto reinforcement as easily as others.
  
  
• In what environment will the concrete be placed? How cold will it be? What is the freezing point of the release agent? What is the flash point? Can it be used in dusty areas? In ice and snow? Will it wash off in the rain? If the concrete is to be steam cured can the release agent tolerate the high temperatures?
  
  
• Does the release agent produce toxic fumes or cause skin rashes?
  
  
• What is the cost per square foot? Bulk material costs and coverage rates vary. The material that costs more per gallon may cost less per square foot.
  
  
• Is the release agent premixed or a concentrate? With a concentrate you can save on shipping and storage costs. But a premixed release agent saves time on the job.