Are Pyramids Made Out Of Concrete, as Joseph Davidovits claimed? This page on wikipedia: http://en.wikipedia.org/wiki/Joseph_Davidovits presents a short bio of Davidovits and his theory about how pyramids were built. According to this theory, the ancient Egyptians would have used a kind of concrete instead of carving huge blocks of stone. For our modern times, this might still be an very attractive technology since the current cement industry generates huge quantities of CO2 in the athmosphere while it seems that the ancient Egyptians technology requires no fuels and needs no decarbonation of limestone. But is this theory reliable? And how would it be possible to produce such concrete on a large scale? And what are the basic principles finally?