There are a lot of ways you can strengthen or modify concrete so it's more resistant to decay. Every concrete company has several. The builder just has to specify what they want in the mix, and pay a bit more. They go right in the concrete truck and get mixed in on the way to the job site. It's amazing how much better they can make it than the cheapest patio slab concrete. They can also add calcium nitrite, to eliminate rebar corrosion from chlorides in the concrete.

I wonder if they can use other materials for rebar, that can't corrode. Like carbon fiber.

We're flying electric helicopters on Mars yet you can't turn on your clothes dryer in Texas. That's because scientists are in charge of Mars, and Republicans are in charge of Texas.