[kibwen]

Only if you take out the rebar. Concrete is porous, water penetrates to the rebar inside, the rebar rusts and expands, cracking the concrete. But if you remove the rebar, you remove much of the tensile strength of the structure, which means you need to use way more concrete to compensate (via the sheer compressive force of its own weight).

[elzbardico]

What about those new materials for rebar? Like fiberglass? What do you think of them?

[bombela]

Not the parent. My understanding is metal rebar is the cheapest. You need a lot of rebar in modern concrete construction.