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While it's interesting to explore ancient concrete, actually scalable improvements of concrete production will be made elsewhere. For instance HeidelbergCement

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 production process.

culi 3y ago
I tried looking it up but don't fully understand. What exactly is the OxyCal hybird process?
- semi-extrinsic 3y ago
  It's their name for combining oxyfuel combustion with amine capture. Oxyfuel is where you feed the combustion process using pure oxygen mixed with exhaust gas, instead of air. Since you're not pulling in all that nitrogen gas from the air, the exhaust is much richer in CO2, which is then easier to catch. Amine capture is where you use an amine solvent liquid that is sprayed as droplets into a large column, where the droplets fall down and absorb CO2 into the liquid, while the exhaust gas flows up and leaves the column free from CO2. Then the liquid that collects at the bottom is moved to a stripper cylinder, where the liquid is heated up and the CO2 is released as pure gas. Specifically for the cement process, using both of these technologies together, it turns out you can do some cool process integration where the byproduct of one is the requirement of the other, and vice versa, so you can make the whole setup a lot cheaper in both CAPEX and OPEX.
willmadden 3y ago
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.
- semi-extrinsic 3y ago
  You are correct that reinforced concrete will corrode, generally the service life of reinforced concrete is around 50 years if no special measures are taken. This is because the initial alkalinity of the concrete, which protects the steel, will be neutralized over time. This is the same for modern and for Roman concrete. But many methods are available both to extend life, and to monitor the health of reinforced concrete. The failures that do occur are typically due to negligent maintenance. The Romans didn't use steel reinforcement, of course, they just used massive concrete structures. We can do the same today, but it would mean no skyscrapers, no long span bridges, etc. To be able to build the Pantheon, at 43 meters height, they used walls with a thickness going from 6.4 meters at the base down to just 1.2 meters at the top. In addition they reduced the density of the concrete by almost 50% towards the top, by using very light aggregates. In comparison the Burj Khalifa at 828 meters heigt has less than a tenth of the wall thickness at the base, just 0.6 meters of reinforced concrete wall thickness in the hexagonal frame.
  - willmadden 3y ago
    I'm more interested in using concrete for normally sized structures with greater longevity. The Pantheon has stood for 1,900 years. I doubt Burj Khalifa will last much more than 100 years. Roman concrete is far more durable than modern concrete, reinforced or otherwise. Roman concrete self-heals cracks. They think they've figured out why, quicklime: https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106 https://news.mit.edu/2023/roman-concrete-durability-lime-cas... The theory is that the Romans hot-mixed their concrete with quicklime. As soon as tiny cracks start to form within the concrete, the cracks travel to lime clasts. The lime then reacts with water, creating a calcium-saturated solution. That solution then recrystallizes as calcium carbonate, sealing the cracks and strengthening the concrete. The concrete is cheap. They are going to commercialize a modern formulation. One to watch.
greenpresident 3y ago
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.

culi 3y ago

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

semi-extrinsic 3y ago
It's their name for combining oxyfuel combustion with amine capture. Oxyfuel is where you feed the combustion process using pure oxygen mixed with exhaust gas, instead of air. Since you're not pulling in all that nitrogen gas from the air, the exhaust is much richer in CO2, which is then easier to catch. Amine capture is where you use an amine solvent liquid that is sprayed as droplets into a large column, where the droplets fall down and absorb CO2 into the liquid, while the exhaust gas flows up and leaves the column free from CO2. Then the liquid that collects at the bottom is moved to a stripper cylinder, where the liquid is heated up and the CO2 is released as pure gas. Specifically for the cement process, using both of these technologies together, it turns out you can do some cool process integration where the byproduct of one is the requirement of the other, and vice versa, so you can make the whole setup a lot cheaper in both CAPEX and OPEX.

willmadden 3y ago

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.

semi-extrinsic 3y ago
You are correct that reinforced concrete will corrode, generally the service life of reinforced concrete is around 50 years if no special measures are taken. This is because the initial alkalinity of the concrete, which protects the steel, will be neutralized over time. This is the same for modern and for Roman concrete. But many methods are available both to extend life, and to monitor the health of reinforced concrete. The failures that do occur are typically due to negligent maintenance. The Romans didn't use steel reinforcement, of course, they just used massive concrete structures. We can do the same today, but it would mean no skyscrapers, no long span bridges, etc. To be able to build the Pantheon, at 43 meters height, they used walls with a thickness going from 6.4 meters at the base down to just 1.2 meters at the top. In addition they reduced the density of the concrete by almost 50% towards the top, by using very light aggregates. In comparison the Burj Khalifa at 828 meters heigt has less than a tenth of the wall thickness at the base, just 0.6 meters of reinforced concrete wall thickness in the hexagonal frame.
- willmadden 3y ago
  I'm more interested in using concrete for normally sized structures with greater longevity. The Pantheon has stood for 1,900 years. I doubt Burj Khalifa will last much more than 100 years. Roman concrete is far more durable than modern concrete, reinforced or otherwise. Roman concrete self-heals cracks. They think they've figured out why, quicklime: https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106 https://news.mit.edu/2023/roman-concrete-durability-lime-cas... The theory is that the Romans hot-mixed their concrete with quicklime. As soon as tiny cracks start to form within the concrete, the cracks travel to lime clasts. The lime then reacts with water, creating a calcium-saturated solution. That solution then recrystallizes as calcium carbonate, sealing the cracks and strengthening the concrete. The concrete is cheap. They are going to commercialize a modern formulation. One to watch.

greenpresident 3y ago

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.