Cement itself was mostly replaced by the various graphenated composites, in the so-called Anderson Trifecta, very elegant: carbon was sucked out of the air and turned into graphene, which was fixed into composites by 3-D printing and used in building materials, thus sequestering it and keeping it from returning to the atmosphere. So now even building infrastructure could be carbon negative (meaning more carbon removed from the atmosphere than added, for those of you wondering).
