Roman concrete has outlasted modern concrete by 2,000 years

Modern reinforced concrete starts to deteriorate after 50–100 years. Roman concrete structures — like the Pantheon dome and Caesarea harbour — are still standing after 2,000 years. A 2017 study in American Mineralogist found the reason: Romans mixed seawater with volcanic ash (pozzolana) and lime. Over time, seawater infiltrating micro-cracks reacts with the ash to form aluminous tobermorite crystals that reinforce the structure. Engineers are now studying Roman concrete as a model for longer-lasting, lower-carbon building materials.

Source: Jackson et al., American Mineralogist (2017)