what did egyptians use as cement to keep the big stones in place to make the pyramids?
None at all, I've been to the Pyramids in Cairo, the size of the blocks mean that cement or any type of bonding isn't needed.
They are not cemented at all. Each block weighs about 20 tons, and just sits there. They are not bricks! They are huge and don't need to be held in place. Most ancients used cut stone, which would sit there because of size and fit, not cement for large buildings. They did have bricks though. They may have had cement, or may have used mud, like adobe. Cement was known to the Romans. Most of the Colosseum is Cement- actually, concrete.
