What is the purpose of formwork release agents and when should they be applied?

• A. Prevent sticking between forms and concrete; apply after pouring.
• B. Improve final surface strength; apply during curing.
• C. Eliminate need for curing; apply after stripping.
• D. Prevent sticking between forms and concrete; apply after initial form set and before stripping.

Answer: (D)

Release agents create a slippery barrier between the formwork and the concrete so the forms can be removed without the concrete sticking and getting damaged. The best timing is after the forms have achieved initial set but before stripping. At this stage the concrete has enough strength to resist damage when the forms are removed, while the release agent on the form surfaces prevents adhesion during removal. If you apply it too early, it may not stay on the form or could affect the surface finish; applying after stripping defeats the purpose of preventing sticking in the first place. It’s not about increasing final surface strength or eliminating curing—the release agent aids stripping and surface quality, not curing.