[robbedpeter]

It's cheaper than many other additives.

Graphene flakes are all that is needed for concrete reinforcement, and it's trivial to produce, even at scale. Carbon chunks are thrown into industrial blenders with water and detergent, resulting in graphene flakes sheared and then separated in suspension. The flakes are separated, washed, and dried.

Large graphene sheets are hard. Tiny flakes are trivial, gradeschool kitchen science.