Are the Pyramids Made from Concrete Blocks?

Material scientists are renewing claims that the great pyramids at Giza were partly made from cement-like blocks:

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.

“There’s no way around it. The chemistry is well and truly different,” Professor Hug told Science et Vie magazine. Their study is being published this month in the Journal of the American Ceramic Society.

The pair used X-rays, a plasma torch and electron microscopes to compare small fragments from pyramids with stone from the Toura and Maadi quarries.

They found “traces of a rapid chemical reaction which did not allow natural crystalisation . . . The reaction would be inexplicable if the stones were quarried, but perfectly comprehensible if one accepts that they were cast like concrete.”