The unit weight of the Reinforced concrete is 25 Kn/cu.m i.e., if u cast a concrete cube of dimensions 1m width, 1m breadth and 1m depth, this cube weighs 2500 kg.
Concrete is very strong in compression but weak in tension. RCC is concrete with reinforcing steel bars in it. Steel is a really good material in tension. Steel carries the tensile load and thus RCC...
RCC is able to withstand heavy loads - compression from the concrete, tension from the rebar - , it is relatively cheap and easy to fashion into custom shapes even on site.
apply Ld/db = 3/40 (rad f'c/fy) * (Alpha*beta*gamma*lamda) / ([C + Ktr]/db) Check ACI 318-08 Eq 12-1. It was developed by some smart south African dude. Enjoy....