This disclosure relates to a pre-assembled fastener assembly having a retainer, a nut member, and a cold expansion mandrel that is forcibly removable after the assembly is installed into an opening of a structural workpiece. The mandrel is captured between a portion of a retainer and a portion of a nut member. The forced removal of the mandrel expands the retainer into the opening, securing the fastener assembly therein. The assembly may also include a cap coupled to the retainer to seal the opening in the structural workpiece. The nut member can be fixed or free-floating with respect to the retainer. In addition, the nut member can be threaded to receive a fastener. The mandrel is recyclable or disposable.