Why is calcium carbonate used as a building material

Calcium Carbonate is very cheap to produce in bulk and has some properties that can be favorable for building a house. That being said, im guessing you got this question from the acid rain post with calcium carbonate. Many things will break down in contact with an acidic substance but it will take a very long time in the case of acid rain (because it is dilute)

Because it is used for building - making concrete and cement - and the manufacture of glass, steel and iron.