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Making cement releases carbon dioxide in the conversion of flimsy calcium carbonate to sturdy calcium oxide by roasting it. Reversing the process by injecting

Making cement releases carbon dioxide in the conversion of flimsy calcium carbonate to sturdy calcium oxide by roasting it. Reversing the process by injecting carbon dioxide in curing cement is turning sturdy calcium oxide into flimsy calcium carbonate. Every pound of CO2 you sequester this way necessitates multiple pounds of CO2 released elsewhere to get that oxide to your construction site (production + transportation). The economics and carbon footprint are similar to corn ethanol- attractive and green if you pay no attention to the total balance. A corn belt politician I’d expect this from. IEEE should know better.

Y_Y 3y ago
I'm surprised a publication aimed at professional engineers thinks it could get away with a sleight of hand like that.
- mchannon 3y ago
  I doubt it's intentional. It's just the modern day equivalent of a perpetual motion machine or a "machine that makes water out of air" (dehumidifier). This particular subject matter area falls in a blind spot where electrical, chemical, and environmental engineering meet, and nobody gets rich pulling the rug out like I just did. I write about this in my book Fat Gas. Plenty of modern-day snake oil salesmen out there.
  - anon4242 3y ago
    > a "machine that makes water out of air" Isn't that just your typical air-con unit?
    - mchannon 3y ago
      Exactly. But you will find dozens of examples in a google search of people who somehow think they've solved the world's water woes by collecting condensate off a disassembled A/C or dehumidifier, and ignorant uncritical news reporters buying it hook line and sinker. Collected funding, even had a whole embarrassing incident at Cal involving the freshman engineering class a few years ago. There is definitely a need for clean water out of air, but it's got some subtle limitations: you don't need it when it's already raining, and the further you get from that condition, the less well dehumidifiers work in terms of gallons produced per kwh consumed. Below 50% RH, you're getting bupkis for condensate. Most of that energy is spent cooling off air but not quite cold enough to get it to leave its moisture behind. Here's an easy thought experiment next time you run across one of these "inventions". If a cubic foot of air at 40% humidity contains .24 mL (sorry for mixed units) of water, give them the benefit of the doubt and say their setup is 100% efficient for pulling every last molecule of water out of air. and it runs on a 28cfm computer case fan. How many gallons per hour would that be? 0.1. The reason these suck is not that they don't work in dry conditions (though they don't), but that they don't move enough air to be useful.
ZeroGravitas 3y ago
They covered a few products and techniques. Which one specifically are you talking about? The CarbiCrete one for example uses CO2 to cure the concrete, but doesn't use cement. https://www.sciencedirect.com/science/article/abs/pii/S0959652616311374 https://www.sciencedirect.com/science/article/abs/pii/S09596... > steel slag has shown the potential to replace cement as an alternative binder if carbonation activation is performed.
- mchannon 3y ago
  Since Elsevier is hiding the meat in that journal article, I can only go off what I read, but it looks identically flawed. • Compressive strength of normal concrete: 25-50MPa • Compressive strength of their slag concrete with 2h CO2 added: 12MPa • Compressive strength of their slag concrete with 24h CO2 added: 24.3MPa My takeaway: Using slag instead of cement = good idea. Using slag OR cement plus CO2 = bad idea.
  - Faaak 3y ago
    BTW: You can access most scientific articles through sci-hub: https://sci-hub.ru/https://www.sciencedirect.com/science/article/abs/pii/S0959652616311374 https://sci-hub.ru/https://www.sciencedirect.com/science/art...
  - digging 3y ago
    I'm following as a layperson, can you explain how to reach your takeaway from the bullets presented? It seems like #3 is almost identical to low-end normal concrete, so "good idea". Not sure what "24h" vs "2h" refers to though.
  - Beltiras 3y ago
    Difference is that compressive strength generally decreases over time. Here we have a product where it increases over time. Changes the equation on how you build and maintain it.
  - deleted 3y ago
    [deleted]
henearkr 3y ago
In this new process, it's not the cement (by its classical definition) that is cured by the CO2 in the air, it's the calcium-enriched biochar. Thus the cement part is still sturdy, and the biochar part avoids making it flimsy because this calcium treatment enhances its binding with the cement. It looks like the main problem with previous experiments with biochar added in cement was that the biochar did not bind well, making a crumbling result, but this article is about solving precisely that.
- mchannon 3y ago
  The article claims "[t]his calcium carbonate strengthens the biochar" but this runs counter to my understanding and I'd like to see some numbers, particularly versus alkalized biochar that is never exposed to CO2. How important is binding in compression (which is what concrete is used for)? Not very. Carbonate doesn't strengthen, it weakens. And if forming carbonate in biochar strengthens versus standard biochar, I would imagine forming oxide in biochar would strengthen even more.
  - henearkr 3y ago
    No, the full quote is "This calcium carbonate strengthens the biochar and helps it bind better with cement, giving strong concrete." The binding part is very important. It holds grains between them. For example that's the difference between a hard granite and a crumbly, sandy granite rock (that's called "decomposed granite"). It's day and night. And I also believe them that the treated biochar is stronger than the untreated one. Maybe if the same process was used to treat the cement itself it would be a disaster, but here that's not the case. What do you mean "forming oxide in biochar"?? The oxide of biochar is CO2. Are you trying to make fun of me heh...
    - mchannon 3y ago
      Calcium hydroxide is an extremely weak base in practice, and wouldn't oxidize carbonaceous materials if your life depended on it. But I could see it depositing in biochar as Calcium Oxide. A physical mixture, not a chemical reaction, is what I meant.
blurbleblurble 3y ago
Why does it have to be either or? Aren't there plenty of use cases for the concrete with less compressive strength? Stuff like floors and walls of smaller buildings could be perfectly fine with the 25 MPa, couldn't they? Patios? Foundations of smaller buildings? If there's a good amount of stuff that doesn't need the higher compressive strengths, I'd think there could be some decent potential to offset with this stuff. Applications that really need higher strength wouldn't need to use this carbonized stuff.
- lostlogin 3y ago
  For some of those scenarios, couldn’t concrete be abandoned altogether? Wooden building work pretty well, though forestry has plenty of its own problems (see New Zealand and it’s series of slash disasters).
  - readthenotes1 3y ago
    China, by far the largest user here, builds very tall vacant buildings with concrete. Wood can only take you so high
    - hinkley 3y ago
      With manufactured beams it can take you higher than you think, but building codes need to be adjusted.
  - blackflame7000 3y ago
    [dead]
  - peterashford 3y ago
    Slash is an issue of bad practices. It's fixable with better management and isn't an inherient feature of forestry
- tristor 3y ago
  There's need, and there's expect. Unless you expect every homeowner or other property owner to do expensive and destructive testing prior to a reconfiguration, remodel, or bringing in heavy semi-stationary loads onto their property, it's somewhat critical that concrete behave like concrete regardless of its initial use case. A simple example is in my previous home when I had a section of the master bedroom closet partially walled around a Class C TL-30 rated firesafe, and the room partially reconstructed with ballistic armor in the walls and a vault door, to turn it into a safe room for valuables + home protection. The safe had a weight of nearly 9000 pounds in a footprint of 64 by 30 inches on the floor. I was only able to do this because the house was a slab on grade construction and we knew the footing depth and slab thickness of the concrete would handle the weight. If this had been some sort of "eco concrete" it would have cracked and eventually failed under that weight, and we would not have known this because the slab thickness would have been the same. P.S.: Since everyone always asks because it's hard to find actual safes (most "safes" are garbage RSCs), it was custom built by a local safe-maker and expect to pay $$$$$. The safe I had installed was $35k, and that didn't include the room tearout/rebuild or the vault door, just the freestanding safe that went into the room.
Mystery-Machine 3y ago
Transportation can be carbon neutral. So you can remove that from equation. At least there are many ways people are trying to reduce transportation carbon emissions to as close to zero as possible.
- moffkalast 3y ago
  It can be. But is it? Will it be any time soon? Isn't the Tesla Semi the only EV truck on the market and isn't being produced in any major quantities yet? It'll probably be decades before any of those reach your average concrete production site where they're still using trucks from the 90s.
  - zardo 3y ago
    > Isn't the Tesla Semi the only EV truck on the market. At this point, I don't think anyone that makes a heavy duty truck doesn't sell an EV version. Volvo started selling an EV concrete mixer this year.
  - vel0city 3y ago
    There are many truck manufacturers shipping trucks today. The Teslas that Frito Lay received weren't their first EV trucks, they had been operating EV trucks before they received the Teslas. https://www.teslarati.com/daimler-freightliner-ecascadia-penske-deliveries/ https://www.teslarati.com/daimler-freightliner-ecascadia-pen... https://afdc.energy.gov/case/404 https://afdc.energy.gov/case/404
    - throwawaylinux 3y ago
      Even if you buy carbon neutral electricity, increasing the demand for it will end up increasing carbon positive electricity production (in the large scheme of things). And we'll ignore carbon to manufacture the truck and create and maintain the roads, warehouses, and other transport infrastructure.
      - vel0city 3y ago
manojlds 3y ago
Could you give some links on claim on ethanol mixing not being a great alternative?
- mchannon 3y ago
  First one's on me, the rest you can pay for, or google: https://e360.yale.edu/features/the_case_against_ethanol_bad_for_environment https://e360.yale.edu/features/the_case_against_ethanol_bad_...
rch 3y ago
I don't immediately see any claims that this material is fit for all purposes regular concrete would be. The first application that comes to mind for me is an alternative to styrofoam-fill insulating concrete forms. Biochar sounds like an improvement vs even waste diverted styrofoam.
cultureswitch 3y ago
Why do you write like Yoda?
xchip 3y ago
Spot on, and add you say, IEEE should know better
krick 3y ago
Weird to assume IEEE or any other large enough organization that has people being paid money to write posts on the internet (i.e. PR dept) is somehow different from "corn belt politicians" and won't be pushing the same agenda. The main point of doublethink is that people that are not good at it, are not allowed to speak publicly anyway, so it's kinda besides the point if some random engineer has problems evaluating how come that worse concrete is better concrete.

Y_Y 3y ago

I'm surprised a publication aimed at professional engineers thinks it could get away with a sleight of hand like that.

mchannon 3y ago
I doubt it's intentional. It's just the modern day equivalent of a perpetual motion machine or a "machine that makes water out of air" (dehumidifier). This particular subject matter area falls in a blind spot where electrical, chemical, and environmental engineering meet, and nobody gets rich pulling the rug out like I just did. I write about this in my book Fat Gas. Plenty of modern-day snake oil salesmen out there.
- anon4242 3y ago
  > a "machine that makes water out of air" Isn't that just your typical air-con unit?
  - mchannon 3y ago
    Exactly. But you will find dozens of examples in a google search of people who somehow think they've solved the world's water woes by collecting condensate off a disassembled A/C or dehumidifier, and ignorant uncritical news reporters buying it hook line and sinker. Collected funding, even had a whole embarrassing incident at Cal involving the freshman engineering class a few years ago. There is definitely a need for clean water out of air, but it's got some subtle limitations: you don't need it when it's already raining, and the further you get from that condition, the less well dehumidifiers work in terms of gallons produced per kwh consumed. Below 50% RH, you're getting bupkis for condensate. Most of that energy is spent cooling off air but not quite cold enough to get it to leave its moisture behind. Here's an easy thought experiment next time you run across one of these "inventions". If a cubic foot of air at 40% humidity contains .24 mL (sorry for mixed units) of water, give them the benefit of the doubt and say their setup is 100% efficient for pulling every last molecule of water out of air. and it runs on a 28cfm computer case fan. How many gallons per hour would that be? 0.1. The reason these suck is not that they don't work in dry conditions (though they don't), but that they don't move enough air to be useful.

ZeroGravitas 3y ago

They covered a few products and techniques. Which one specifically are you talking about? The CarbiCrete one for example uses CO2 to cure the concrete, but doesn't use cement. https://www.sciencedirect.com/science/article/abs/pii/S0959652616311374 https://www.sciencedirect.com/science/article/abs/pii/S09596... > steel slag has shown the potential to replace cement as an alternative binder if carbonation activation is performed.

mchannon 3y ago
Since Elsevier is hiding the meat in that journal article, I can only go off what I read, but it looks identically flawed. • Compressive strength of normal concrete: 25-50MPa • Compressive strength of their slag concrete with 2h CO2 added: 12MPa • Compressive strength of their slag concrete with 24h CO2 added: 24.3MPa My takeaway: Using slag instead of cement = good idea. Using slag OR cement plus CO2 = bad idea.
- Faaak 3y ago
  BTW: You can access most scientific articles through sci-hub: https://sci-hub.ru/https://www.sciencedirect.com/science/article/abs/pii/S0959652616311374 https://sci-hub.ru/https://www.sciencedirect.com/science/art...
- digging 3y ago
  I'm following as a layperson, can you explain how to reach your takeaway from the bullets presented? It seems like #3 is almost identical to low-end normal concrete, so "good idea". Not sure what "24h" vs "2h" refers to though.
- Beltiras 3y ago
  Difference is that compressive strength generally decreases over time. Here we have a product where it increases over time. Changes the equation on how you build and maintain it.
- deleted 3y ago
  [deleted]

henearkr 3y ago

In this new process, it's not the cement (by its classical definition) that is cured by the CO2 in the air, it's the calcium-enriched biochar. Thus the cement part is still sturdy, and the biochar part avoids making it flimsy because this calcium treatment enhances its binding with the cement. It looks like the main problem with previous experiments with biochar added in cement was that the biochar did not bind well, making a crumbling result, but this article is about solving precisely that.

mchannon 3y ago
The article claims "[t]his calcium carbonate strengthens the biochar" but this runs counter to my understanding and I'd like to see some numbers, particularly versus alkalized biochar that is never exposed to CO2. How important is binding in compression (which is what concrete is used for)? Not very. Carbonate doesn't strengthen, it weakens. And if forming carbonate in biochar strengthens versus standard biochar, I would imagine forming oxide in biochar would strengthen even more.
- henearkr 3y ago
  No, the full quote is "This calcium carbonate strengthens the biochar and helps it bind better with cement, giving strong concrete." The binding part is very important. It holds grains between them. For example that's the difference between a hard granite and a crumbly, sandy granite rock (that's called "decomposed granite"). It's day and night. And I also believe them that the treated biochar is stronger than the untreated one. Maybe if the same process was used to treat the cement itself it would be a disaster, but here that's not the case. What do you mean "forming oxide in biochar"?? The oxide of biochar is CO2. Are you trying to make fun of me heh...
  - mchannon 3y ago
    Calcium hydroxide is an extremely weak base in practice, and wouldn't oxidize carbonaceous materials if your life depended on it. But I could see it depositing in biochar as Calcium Oxide. A physical mixture, not a chemical reaction, is what I meant.

blurbleblurble 3y ago

Why does it have to be either or? Aren't there plenty of use cases for the concrete with less compressive strength? Stuff like floors and walls of smaller buildings could be perfectly fine with the 25 MPa, couldn't they? Patios? Foundations of smaller buildings? If there's a good amount of stuff that doesn't need the higher compressive strengths, I'd think there could be some decent potential to offset with this stuff. Applications that really need higher strength wouldn't need to use this carbonized stuff.

lostlogin 3y ago
For some of those scenarios, couldn’t concrete be abandoned altogether? Wooden building work pretty well, though forestry has plenty of its own problems (see New Zealand and it’s series of slash disasters).
- readthenotes1 3y ago
  China, by far the largest user here, builds very tall vacant buildings with concrete. Wood can only take you so high
  - hinkley 3y ago
    With manufactured beams it can take you higher than you think, but building codes need to be adjusted.
- blackflame7000 3y ago
  [dead]
- peterashford 3y ago
  Slash is an issue of bad practices. It's fixable with better management and isn't an inherient feature of forestry
tristor 3y ago
There's need, and there's expect. Unless you expect every homeowner or other property owner to do expensive and destructive testing prior to a reconfiguration, remodel, or bringing in heavy semi-stationary loads onto their property, it's somewhat critical that concrete behave like concrete regardless of its initial use case. A simple example is in my previous home when I had a section of the master bedroom closet partially walled around a Class C TL-30 rated firesafe, and the room partially reconstructed with ballistic armor in the walls and a vault door, to turn it into a safe room for valuables + home protection. The safe had a weight of nearly 9000 pounds in a footprint of 64 by 30 inches on the floor. I was only able to do this because the house was a slab on grade construction and we knew the footing depth and slab thickness of the concrete would handle the weight. If this had been some sort of "eco concrete" it would have cracked and eventually failed under that weight, and we would not have known this because the slab thickness would have been the same. P.S.: Since everyone always asks because it's hard to find actual safes (most "safes" are garbage RSCs), it was custom built by a local safe-maker and expect to pay $$$$$. The safe I had installed was $35k, and that didn't include the room tearout/rebuild or the vault door, just the freestanding safe that went into the room.

Mystery-Machine 3y ago

Transportation can be carbon neutral. So you can remove that from equation. At least there are many ways people are trying to reduce transportation carbon emissions to as close to zero as possible.

moffkalast 3y ago
It can be. But is it? Will it be any time soon? Isn't the Tesla Semi the only EV truck on the market and isn't being produced in any major quantities yet? It'll probably be decades before any of those reach your average concrete production site where they're still using trucks from the 90s.
- zardo 3y ago
  > Isn't the Tesla Semi the only EV truck on the market. At this point, I don't think anyone that makes a heavy duty truck doesn't sell an EV version. Volvo started selling an EV concrete mixer this year.
- vel0city 3y ago
  There are many truck manufacturers shipping trucks today. The Teslas that Frito Lay received weren't their first EV trucks, they had been operating EV trucks before they received the Teslas. https://www.teslarati.com/daimler-freightliner-ecascadia-penske-deliveries/ https://www.teslarati.com/daimler-freightliner-ecascadia-pen... https://afdc.energy.gov/case/404 https://afdc.energy.gov/case/404
  - throwawaylinux 3y ago
    Even if you buy carbon neutral electricity, increasing the demand for it will end up increasing carbon positive electricity production (in the large scheme of things). And we'll ignore carbon to manufacture the truck and create and maintain the roads, warehouses, and other transport infrastructure.
    - vel0city 3y ago

manojlds 3y ago

Could you give some links on claim on ethanol mixing not being a great alternative?

mchannon 3y ago
First one's on me, the rest you can pay for, or google: https://e360.yale.edu/features/the_case_against_ethanol_bad_for_environment https://e360.yale.edu/features/the_case_against_ethanol_bad_...

rch 3y ago

I don't immediately see any claims that this material is fit for all purposes regular concrete would be. The first application that comes to mind for me is an alternative to styrofoam-fill insulating concrete forms. Biochar sounds like an improvement vs even waste diverted styrofoam.

cultureswitch 3y ago

Why do you write like Yoda?

xchip 3y ago

Spot on, and add you say, IEEE should know better

krick 3y ago

Weird to assume IEEE or any other large enough organization that has people being paid money to write posts on the internet (i.e. PR dept) is somehow different from "corn belt politicians" and won't be pushing the same agenda. The main point of doublethink is that people that are not good at it, are not allowed to speak publicly anyway, so it's kinda besides the point if some random engineer has problems evaluating how come that worse concrete is better concrete.