As the title suggests. If roman concrete supposedly has the capabilities to mend tiny cracks via chemical reaction, why isn’t it used with modern reinforcements to seal the pathways to the steel beams to protect it from oxygen and elements and prevent corrosion? Are there any major downsides to hot-mixed concrete, is it not as good as the studies make it out to be, or is it simply not viable due to cost and manufacturing process/storage requirements?
As others have mentioned roman concrete isn’t as great as many people like to pretend. It is good, but we have long since surpassed it.
Also, rebar reinforced concrete ultimately has a life span because of corrosion of the rebar, which while you can reduce the corrosion, you will never eliminate it. The only concrete you will see standing 500 years from now is unreinforced concrete in favorable conditions which isn’t nearly as strong as reinforced and requires specific designs like archs to use and requires more concrete overall which is more expensive.
Most reinforced concrete is expected to be compromised after 50 years without annual inspections to verify its integrity, and after 100 years it will almost all be trash. But it was built with the engineers knowing that from the start.