2,050-year-old Roman tomb offers insights on ancient concrete resilience
The civil engineering-oriented channel Practical Engineering has a pretty good video on Roman concrete vs. modern.
https://www.youtube.com/watch?v=qL0BB2PRY7kThe primary tldw; is the fact modern concrete uses steel rebar for tensile strength, whereas the Romans relied on architectural techniques to minimize tensile forces on their structures.Steel rebar is the primary route through which concrete deteriorates.