What Is a Smooth Form Finish?

The new edition of the American Concrete Institute's Standard Specifications for Structural Concrete (ACI 301-96) has redefined smooth form finish. Since ACI 301-96 is to be used by reference or incorporated in its entirety in project specifications, it's important for both contractors and specifiers to understand what the new definition calls for. ACI 301-96 vs. ACI 301-89 In the context of ACI 301-96, both rough and smooth form finishes are listed under as-cast finishes. Both require tie holes and defects to be patched. The rough form finish--required for surfaces not exposed to public view--calls for removal of fins 1/4 inch or more in height, otherwise leaving the surface with the texture imparted by the forms. For a smooth form finish--required for all surfaces exposed to public view-- all fins must be removed and the surface must have a rubbed finish. In the earlier version of this specification (ACI 301-89) a smooth form finish did not require rubbing. Under ACI 301-96, therefore, the specifier who wants a smooth, off-the-form finish (untouched by rubbing) on concrete exposed to public view will have to call this out as a special finish.