Infrastructure Expansion Act of 2021 This bill precludes absolute liability in any action against a property owner or contractor for projects that are federally owned or operated or are receiving federal financial assistance for infrastructure and transportation development for any injury associated with an elevation- or gravity-related risk occurring on those projects. In any such claim, a state shall apply a liability standard that considers the comparative negligence of the injured person, when such negligence is a proximate cause of an injury.