Roman Concrete Durability

I remember in grad school there was a visiting professor who did a fun seminar on Roman aqueduct design (I was doing a thesis with fluid mechanics fundamentals). Yes, rudimentary technology, but the basics all covered.
 
I’m fascinated by this, as concrete seems to have a lifetime in our area. It isn’t as bad as other colder areas, but still can see things degrade.
Just last week I went and looked to see if the patio my Grandpa had made in 1976 is holding up. Sure enough, looks fine to this day.
 
Innovations in concrete formulations are happening regularly. Low CO2, feedable out of a nozzle, use of carbon fibre to make thinner, stronger concrete that uses much less input material and does not suffer from the “Florida condo problem”.

But it is about time this trick was rediscovered.

dave
 
They used lime mortar in the forts in Rajasthan, they are durable as well.
The quality of sand, and more important, the curing, is crucial.
Due to a sand shortage, stone powder is being used in Hyderabad, and we get PPC with fly ash / gypsum etc. added to OPC, as the coal fired power stations had too much ash lying around.
So the quality will suffer, though somebody did tell me that ash is added to slow down the curing time, so less cracks will develop, at the plant when concrete is supplied in transit mixers.
All in all, changes have occurred, good or bad only time will tell.

OPC is Ordinary Portland Cement, PPC is Portland Pozzolana Cement.
 
I remember in grad school there was a visiting professor who did a fun seminar on Roman aqueduct design (I was doing a thesis with fluid mechanics fundamentals). Yes, rudimentary technology, but the basics all covered.
Romans were masters at aqueduct building.
For instance Lyon in France Lugdunum at Roman time had a network 60 miles around to bring water in the city.
About no Frenchman is aware of this.
I happened to read about this from an enthusiast amateur archeologist who documented about the little known remains of these great works, some worth a visit.
 
Freezing and thawing is what did my porch in. It's all too common here; one little crack lets the water in and the process starts. The streets here can turn to rubble in a matter of days during the winter.

You can see the process in abandoned buildings in places like Detroit. Once water seeps behind the bricks, the wall starts to disintegrate. Within ten years or so, the wall is falling down. Every freeze/thaw cycle does more damage.

Ice melt can hasten the process. It degrades concrete, turns rebar to dust, and exacerbates the freeze/thaw cycle.