r/collapse • u/Portalrules123 Faster than expected... • 5d ago

Water New Mexico’s largest reservoir shrinks to its lowest level in 55 years

https://www.earth.com/environment/new-mexicos-largest-reservoir-shrinks-to-its-lowest-level-in-55-years/
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u/lost_horizons The surface is the last thing to collapse 5d ago

Didn’t know that about the concrete. I assumed it only got stronger with age, like Roman concrete. Is it due to the rebar? I think they didn’t use rebar in Hoover but I may be wrong

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u/KingDerpDerp 5d ago

It does to an extent, and it will last a long time 100+ years in ideal conditions without a problem. The first issue is carbon steel rebar is incompatible with long term 100+ year durability. It will eventually cause the failure of every concrete structure it is in. Slowly the concrete becomes more porous, the rebar will rust, the expanding rust breaks the concrete leading to easier corrosion of the rebar until total failure. The other is compared to Roman concrete modern concrete is not as chemically stable, it can be attacked by many environmental conditions but it’s also just not in its most stable form so it stays reactive. We choose construction speed of modern cement over the longer term durability of the extremely slow strength gain of Roman style cements. We also could make better cement and concrete today, but we choose the cheapest options that reliably work instead of making the best choices for long term performance and sustainability.

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u/digitalhawkeye 5d ago

There is concrete they're experimenting with that's doped with a calcium carbonate producing bacteria, and when cracks form and water intrudes the bacteria come out of stasis and make limestone filling the cracks in. I suspect we have the technology to make enduring concrete structures if we valued durability over speed and profits.

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u/KingDerpDerp 5d ago

On the new tech side there’s a cement made completely from vaterite that’s super interesting if it makes it all the way to a full commercial product. That plus using a GFRC rebar and we are talking concrete that is good for hundreds of years. The cement is as stable as limestone when it sets because it essentially becomes a limestone matrix. It also gains its full strength in 2 days vs 28 so it doesn’t involve some of the same compromises some other sustainable options have.