Pyramids were built with concrete rather than rocks, scientists claim

This would explain many of the architectural difficulties that were overcome by the Egyptian's.

The Ancient Egyptians built their great Pyramids by pouring concrete into blocks high on the site rather than hauling up giant stones, according to a new Franco-American study.

The research, by materials scientists from national institutions, adds fuel to a theory that the pharaohs’ craftsmen had enough skill and materials at hand to cast the two-tonne limestone blocks that dress the Cheops and other Pyramids.

Despite mounting support from scientists, Egyptologists have rejected the concrete claim, first made in the late 1970s by Joseph Davidovits, a French chemist.

The stones, say the historians and archeologists, were all carved from nearby quarries, heaved up huge ramps and set in place by armies of workers. Some dissenters say that levers or pulleys were used, even though the wheel had not been invented at that time.
Until recently it was hard for geologists to distinguish between natural limestone and the kind that would have been made by reconstituting liquefied lime.

But according to Professor Gilles Hug, of the French National Aerospace Research Agency (Onera), and Professor Michel Barsoum, of Drexel University in Philadelphia, the covering of the great Pyramids at Giza consists of two types of stone: one from the quarries and one man-made. Read More.