[marcus_holmes]

> and finally Romans developed something resembling concrete (I dont remember kYa).

About 2 kYa, give or take a couple of centuries.

And it was actual concrete, rather than something resembling concrete. In fact, better than the concrete we were making a hundred years ago, and better than most of our concrete fifty years ago.

Roman aqueducts and bridges are still standing 2000 years later. Not sure I'd put money on the same being true of our stuff.

[tim333]

Yeah there was a theory discussed on HN a couple of years ago that superior qualities came from mixing in quicklime (CaO). I'm not sure if they've developed that and tested it against modern concretes. I guess it's hard to tell if they'll last 2000 years without waiting quite a while. (https://news.ycombinator.com/item?id=34280239)

[marcus_holmes]

I heard it was that they used seawater not freshwater.

And yes, we'll have to wait a while. Though probably not 2000 years - we only have to wait until our concrete starts failing, which might be a lot sooner than that.