[inglor_cz]

We can prolong life of small concrete structures if no rebar is used. Without rebar, concrete cannot tolerate high loads, but its lifespan is dramatically increased, from a few decades to potentially millennia. It is, after all, a kind of artificial stone.

Concrete without rebar can be used for construction of small buildings and those would last a long, long time. Much longer than anything made of timber. A 20-generation home of sorts. Remember that once the timber rots away or is burnt, the trapped carbon gets released again.

[Theodores]

I think your last point is well known.

Let's grow more trees and go back to buildings made of wood isn't commonly suggested though.

In the UK wood is historically used for floors, doors and windows. The rest was stone until canals and trains enabled brick to be used. With roads came concrete.

[vondur]

I’m wonder if Roman structures used any rebar or something similar?

[inglor_cz]

Nope. That seems to be one of the reasons why they are so sturdy. Nothing susceptible to rusting inside.

Some Roman concrete piers have actually hardened further through the constant action of the waves, so they are now harder than they were in antiquity.