Roman concrete was awesome stuff ! All those marble buildings were actually just poured concrete with a thins skin of the expensive stuff.
It's taken over 2000 years to work out what made it so special, and I read an analysis when the report came out. Most of it went over my head, but it's something to do with the way the ingredients work together at a molecular level. It gets stronger with time, and adding quicklime creates small pockets of lime that modern concrete makers treat as an impurity that they try to remove, but which dissolves slightly in the presence of water and then rapidly re-hardens to fill and fix any minor cracks.
The Romans were clever chaps, it's a shame they never solved the Imperial Succession issue that eventually fatally weakened the Empire.
Yeah! That's likely the same thing I read. Very cool findings I thought!