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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

#11

Post by icegreentea2 »

adamjc wrote: post #3

> "For centuries, builders tried to cut costs by limiting how much cement they used and incorporating recycled waste materials into their concrete," says Salvatore Aprea, head of the Acm research group. "The challenge now is to revive these old methods—not for financial reasons but for the sake of our planet." I put it to you that if it was financially viable and simple ("ancient methods"), it would already be done.…

These old techniques come from a time with completely constraints. Modern techniques are generally all about creating uniformity as far upstream as possible to them deploy cheaper labour/logistics systems/automation downstream. Think about modern masonry. The "bricks" are uniform, the mason man knows exactly how they can be shipped, moved around the site, and individually placed. Concrete mixes are standardized as much as possible and the optimized so that the man with the trowel can work as efficiently as possible.

Working with off cuts/minimally processed stone is harder. You need to be able to manipulate a greater variety of shapes and sizes. Stuff doesn't stack. It takes way more brain and finesse on the work site to make things work well.

These ancient methods are in many ways much more complicated (not simple) than modern methods. But they are complicated in ways that we're just starting to be able automate well (computer vision systems to sort/group/place irregular blocks for example).

Re: Experts revive ancient techniques to make concrete more sustainable

#12

Post by adhesive_wombat »

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…

Considering the astounding cost of building anything now, I guess being in the mitigation industry (retrofits, shoring-up and general can-kicking) will be rather profitable.

But I can see at least some buildings being profitable even then. A modest London property can easily cost 500k, most of which is the land itself. If it lasts 100 years, that's "only" 5k per year, and you keep the land. Obviously the calculation is different if you're buying a 95-year-old concrete property, rather than building a new one. I imagine mortgage providers are paying attention, they already strongly dislike lending against steel-framed houses.

I don't think we'll be seeing mass demolitions of 100 year old properties and infrastructure, except probably quite a bit of useless office space if RTO continues to not really happen over the next few decades. But we will see some very expensive and disruptive repairs-in-place to infrastructure when it can't be ignored any more.

Re: Experts revive ancient techniques to make concrete more sustainable

#13

Post by gumby »

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…

In the US the accounting treatment of a building (depreciation) is, IIRC 40 years. So a century is considered longer than the typical lifespan.

Looking around Palo Alto, there are a fair number of wood frame building ps of about a century in age, and a LOT built in the 1950s. I dont know about survivorship bias, but a century seems like a pretty reasonable assumption.

(I was built in the 1960s so appreciate the thought that I might still be going strong in the 2070s, thanks!)

Re: Experts revive ancient techniques to make concrete more sustainable

#14

Post by __MatrixMan__ »

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 majority of our debt, and the majority of our bits, are not really aligned with especially meaningful goals. Why would the future keep them around?

Re: Experts revive ancient techniques to make concrete more sustainable

#15

Post by gumby »

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 imagine robots can be used to do the stacking and transporting. Probably 20 years down the road but definitely within the realm of serious possibility. As for the strength, you can watch and assay each large rock as you place it, and use some test + statistical methods to estimate structural integrity (the current model of pouring slurry into a wooden form is just a simplified version of this anyway, one that can be computed with a slide rule). As a bonus the result could be stronger due to its amorphous structure.

Re: Experts revive ancient techniques to make concrete more sustainable

#16

Post by 101008 »

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, but if this is the case, a lot of people are going to lose assets - and I am also scare of the gov to check that these buildings are still safe.

Re: Experts revive ancient techniques to make concrete more sustainable

#17

Post by high_5 »

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…

Imagine the shock for those poor bastards then: https://en.wikipedia.org/wiki/Ponte_Morandi#Collapse

51 years.

Re: Experts revive ancient techniques to make concrete more sustainable

#18

Post by p1mrx »

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…

> reinforced concrete only has a lifespan of about 100 years.

Currently, less than 1% of rebar is made from stainless steel: https://www.youtube.com/watch?v=zn9SzyDhfj8&t=140s

Re: Experts revive ancient techniques to make concrete more sustainable

#20

Post by axus »

high_5 wrote: post #17
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…

Imagine the shock for those poor bastards then: https://en.wikipedia.org/wiki/Ponte_Morandi#Collapse 51 years.

Or these guys https://en.wikipedia.org/wiki/Surfside_condominium_collapse

42 years... and some poor maintenance

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