Inside the Little Plastic Castle

Another reason I adore the podcast 99percent invisible is they publish several articles on their site between each audio release. This one is catnip to an infrastructure fan like myself:

It all clicked when researchers realized that unexpected materials they found in ancient concrete weren’t added ingredients — instead, a chemical reaction had created them in place. Components in the mix dissolved, interacted and changed, leaving new materials to crystallize in the gaps over the centuries. Today’s researchers working to create things like self-healing concrete may be able to draw lessons as they endeavor to create resilient structures and revise concrete mixes.

http://99percentinvisible.org/article/cracking-case-secret-ingredient-explains-durability-roman-concrete

This could point the way to concrete without Portland cement, which might mean concrete without the huge energy burden.