Actually, in Edmonton, most high-rise construction is reinforced concrete (more available and therefore usually less expensive than steel). Concrete and steel have nearly identical coefficients of expansion and so they are interchangeable in construction projects. Structural concrete is most often reinforced with steel reinforcement bars (rebars) -- I say most often because modern construction is experimenting with other fibres for reinforcement (carbon nanotubes, various plastic fibres, etc.). The advantages of steel relate primarily to the speed of erection and savings in labour and forming costs; concrete, material-wise is much cheaper. It is actually a good thing for construction -- one industry seems to effectively keep the other honest.