Abstract: A concrete form including a rigid substrate having at least one of a flat and curved surface, which are presented to poured concrete, and a flexible membrane lining at least the one flat or curved surface of the rigid substrate so as to have at least one flat or curved surface due to the respective flat or curved surface of the rigid substrate. In some embodiments, at least a portion of the flexible membrane comes into contact with the poured concrete, whereupon the cured concrete may be separated from the concrete form, in the absence of a release agent, to provide one or more corresponding flat or curved surfaces on the cured concrete, which surfaces require little to no finishing work.