alt Hacker News> The only thing is, it requires maintainance, which is why Portland cement has taken over the world.
What kind of maintenance and why did roman cement survive without it? Or are we simply looking at ancient survivorship bias where the surviving roman concrete structures survived through the lime cycle without maintenance until it was no longer required?
I mentioned elsewhere that time taken for setting is also a major factor for why Portland cement is preferred.
Maintenance is probably less of a factor but it also depends on the use case. Take what I have to say with a grain of salt. Lime is a living material that slowly converts lime to limestone. For some use cases, the lime needs to be replenished often through applying lime wash on the plaster of external walls or wet interior walls.
As for load bearing walls or regular interior plaster walls I'm not sure there is much maintenance you can do and they are fairly durable.
As far as I know Portland cement sets faster and is a stronger but has a life span of decades and does not lend itself to be repaired or replenished.
I'd like to also convey some vibes I have about this topic as follows. Imagine having a 2 storey family home made of concrete that you want passed on for many generations. In 50-75 years, repairs/upgrades would require a lot of demolition as concrete with rebar is very strong. Much of the old material is trashed and hard to recycle. A similar house made of lime based products and some stone and wood would lend itself more easily for similar repairs and seamless upgrades and can maintain the same aesthetic look for longer. It feels like lime based products are appropriately strong and suitable for the smaller scale. The old material can be treated like any old dirt or rubble and is less polluting.