Why Roman concrete still stands strong while modern version decays

[Viggen]

Scientists have cracked the secret to Roman water-based structures’ strength – and findings could help today’s builders

via Guardian

[caldrail]

I think it's worth remembering that someof Rome's concrete structures have survived. There were very few building regulations in those days and no universal standards. The 'cowboy builders' of the Roman era were infamous for their quick and jerry built constructions to maximise profit at the expense of any notion of safety. Also, in the Colosseum, we have at least one example of builders using a cheap non-waterproof alternative to avoid costs.