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A concrete permeability testing core comprises a cylinder of
polymeric foam enclosed within an elastomeric envelope under
tension. When placed in a cylindrical concrete mold in an axially
concentric orientation, it can be used to form a concrete test
specimen with a cylindrical cavity. After the concrete is cured
and the outer concrete mold is removed, the polymer foam can
be collapsed by contacting it with solvent for the foam. The
elastomeric envelope, being under tension, contracts to a
smaller size, permitting easy removal from the concrete and
leaving a nascent cavity surface.
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