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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

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.

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.