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Experts revive ancient techniques to make concrete more sustainable

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Re: Experts revive ancient techniques to make concrete more sustainable

#21

Post by thejohnconway »

gumby wrote: post #15

The proposed approach (stacking irregular rocks) is much more labor and probably time intensive, one of the reasons it’s not done any more. Another is the difficulty of estimating the load bearing strength when you don’t have predictable uniformity in the structure. And transporting irregular large rocks is less efficient than gravel. The good news is these problems can be solved down the road! On the labor side, I i…

There was a rock stacking robot on HN a couple of days ago.

https://wonderfulengineering.com/this-new-monster-robot-can-...

Re: Experts revive ancient techniques to make concrete more sustainable

#22

Post by gumby »

thejohnconway wrote: post #21
gumby wrote: post #15

The proposed approach (stacking irregular rocks) is much more labor and probably time intensive, one of the reasons it’s not done any more. Another is the difficulty of estimating the load bearing strength when you don’t have predictable uniformity in the structure. And transporting irregular large rocks is less efficient than gravel. The good news is these problems can be solved down the road! On the labor side, I i…

There was a rock stacking robot on HN a couple of days ago. https://wonderfulengineering.com/this-new-monster-robot-can-...

Nice!

Re: Experts revive ancient techniques to make concrete more sustainable

#23

Post by devoutsalsa »

wconrm wrote: post #4

Ancient methods were lost because...earthquakes?

A big reason the Romans stopped using concrete is because they no longer wanted to build projects that needed concrete. r/AskHistorians has a good post on this...

Why Was "Roman Concrete" Not Used for Centuries After the Fall of the Empire?

https://www.reddit.com/r/AskHistorians/comments/d79rpp/why_w...

Re: Experts revive ancient techniques to make concrete more sustainable

#24

Post by droopyEyelids »

101008 wrote: post #16
cm2187 wrote: post #10

I was a bit shocked when I learned that reinforced concrete only has a lifespan of about 100 years. That means that if you buy a condo in a building built in the 1970s, the building will become unsafe and need to be demolished in your life time. I don't know if people are pricing this consideration. It also means there will be pretty much nothing left of our architecture, all those appartments, offices, museums, brid…

> That means that if you buy a condo in a building built in the 1970s, the building will become unsafe and need to be demolished in your life time. I don't know if people are pricing this consideration. Isn't possible to do some repairs to make it safe again, instead of completely demolish it? I live in a big city (South America) with a lot of old buildings. People treats property as something that will last forever,…

> Isn't possible to do some repairs to make it safe again

This ends up being a complex question that's unique to every building, and needs to take into account the architecture, the soil (reinforced concrete is used in footers/pilings) and a ton of other factors.

But what makes it extra scary? In most countries there is always a company that will tell you "Yes, it can be done, and for less than the cost of replacing the building". Even in the USA this happens and then we have deadly condo building collapses.

I say "most countries" because I hope that there's some country where they have tight enough regulations to prevent it. Like maybe Norway or Luxembourg or something.

Re: Experts revive ancient techniques to make concrete more sustainable

#25

Post by alentred »

cm2187 wrote: post #10

I was a bit shocked when I learned that reinforced concrete only has a lifespan of about 100 years. That means that if you buy a condo in a building built in the 1970s, the building will become unsafe and need to be demolished in your life time. I don't know if people are pricing this consideration. It also means there will be pretty much nothing left of our architecture, all those appartments, offices, museums, brid…

Worth noting that 100 years is not exactly the hard deadline, but a typical (default) *target* for the calculations made by the engineers planning the construction.

What I mean is that this number is defined by design, although they are of course also constrained by what is possible within the set budgets.

Reinforced concrete lifespan depends on a lot of factors, including some that can be controlled, such as isolation of the reinforcement, materials used, various qualities of the concrete itself. When the new structures are designed, engineers do the calculations to achieve a specific goal in terms of lifespan, construction cost and maintenance cost.

I don't know how this works in practice, but I would hope that various factors such as the total cost and environmental impact (yes, I can hear my inner self laughing at my naivety here) are taken into account to arrive to the optimal target.

Re: Experts revive ancient techniques to make concrete more sustainable

#26

Post by tantalor »

thejohnconway wrote: post #21
gumby wrote: post #15

The proposed approach (stacking irregular rocks) is much more labor and probably time intensive, one of the reasons it’s not done any more. Another is the difficulty of estimating the load bearing strength when you don’t have predictable uniformity in the structure. And transporting irregular large rocks is less efficient than gravel. The good news is these problems can be solved down the road! On the labor side, I i…

There was a rock stacking robot on HN a couple of days ago. https://wonderfulengineering.com/this-new-monster-robot-can-...

Incidentally, both the rock stacking robot and this sustainable-concrete resarch are at ETH Zurich.

https://rsl.ethz.ch/robots-media/heap.html

https://sc.ibi.ethz.ch/en/

Re: Experts revive ancient techniques to make concrete more sustainable

#27

Post by culi »

semi-extrinsic wrote: post #8

While it's interesting to explore ancient concrete, actually scalable improvements of concrete production will be made elsewhere. For instance HeidelbergCement has successfully piloted and is currently implementing technologies that bring the CO2 emissions from cement production close to zero. The OxyCal hybrid process that they are deploying in Bulgaria and Belgium will capture >97% of all emissions from the cement…

I tried looking it up but don't fully understand. What exactly is the OxyCal hybird process?

Re: Experts revive ancient techniques to make concrete more sustainable

#28

Post by willmadden »

semi-extrinsic wrote: post #8

While it's interesting to explore ancient concrete, actually scalable improvements of concrete production will be made elsewhere. For instance HeidelbergCement has successfully piloted and is currently implementing technologies that bring the CO2 emissions from cement production close to zero. The OxyCal hybrid process that they are deploying in Bulgaria and Belgium will capture >97% of all emissions from the cement…

Does it turn into rusted out rubble in 100 years like the reinforced concrete we use today?

I remember reading an article about the longevity of Roman concrete. The best they could come up with was the use of volcanic ash and much slower curing in salt water.

Re: Experts revive ancient techniques to make concrete more sustainable

#29

Post by culi »

cm2187 wrote: post #10

I was a bit shocked when I learned that reinforced concrete only has a lifespan of about 100 years. That means that if you buy a condo in a building built in the 1970s, the building will become unsafe and need to be demolished in your life time. I don't know if people are pricing this consideration. It also means there will be pretty much nothing left of our architecture, all those appartments, offices, museums, brid…

The oldest buildings in the world[0] are as old as they are because they use materials with lifespans of much less than 100 years. Instead they make them modular. Make it so that you can take out parts of the building to replace them without collapsing the whole thing. Instead we build our buildings in such a way that makes maintenance very hard and costly. We prefer to pretend like our buildings will last forever rather than actually plan for the inevitable degradation

There's small scale movements towards changing this. Some cities are specifically building buildings in a way that makes them modular and reusable[1]

[0] https://en.wikipedia.org/wiki/H%C5%8Dry%C5%AB-ji

[1] https://www.bbc.com/future/article/20230207-can-we-design-ci...

Re: Experts revive ancient techniques to make concrete more sustainable

#30

Post by greenpresident »

semi-extrinsic wrote: post #8

While it's interesting to explore ancient concrete, actually scalable improvements of concrete production will be made elsewhere. For instance HeidelbergCement has successfully piloted and is currently implementing technologies that bring the CO2 emissions from cement production close to zero. The OxyCal hybrid process that they are deploying in Bulgaria and Belgium will capture >97% of all emissions from the cement…

Their CFO gave a talk this summer that I went to. He noted that green energy does not solve their sustainability goals, as about a third of the CO2 emissions are process related. He talked about their capture plans but noted that they are unlikely to be big enough to capture ongoing emissions, essentially admitting that this looks good on slides but would work at scale.
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