Cement has been used at least since Ancient Roman times, and the building industry continues to find ways to improve and advance the construction material. Made mostly with flyash and sand, Durock EcoCap is a self-leveling underlayment that has a 50% smaller carbon footprint and 45% less embodied energy when compared to conventional Portland cement- or calcium aluminate cement-based underlayment, according to manufacturer USG Corp. EcoCap can handle foot traffic two hours after installation. usg.com