Its not that surprising. Even though Romans had concrete, they didn't build many building wholly of concrete. The British Romans did use concrete in their build

Its not that surprising. Even though Romans had concrete, they didn't build many building wholly of concrete. The British Romans did use concrete in their buildings. Especially in floors, walls, and as mortar to bind building elements. But there is no evidence of any Roman building in Britain made with concrete as the primary building material. https://www.cambridge.org/core/journals/journal-of-roman-studies/article/abs/notes-on-buildingconstruction-in-roman-britain/16E4A959BE685AEAF9DDC83C9FBA240A https://www.cambridge.org/core/journals/journal-of-roman-stu...