he 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
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
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.
“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
The pair believe that the concrete method was
used only for the stones on the higher levels of the Pyramids.
There are some 2.5 million stone blocks on the Cheops Pyramid.
The 10-tonne granite blocks at their heart were also natural,
they say. The professors agree with the “Davidovits theory” that
soft limestone was quarried on the damp south side of the Giza
Plateau. This was then dissolved in large, Nile-fed pools until
it became a watery slurry.
Lime from fireplace ash and salt were mixed
in with it. The water evaporated, leaving a moist, clay-like
mixture. This wet “concrete” would have been carried to the site
and packed into wooden moulds where it would set hard in a few
days. Mr Davidovits and his team at the Geopolymer Institute at
Saint-Quentin tested the method recently, producing a large
block of concrete limestone in ten days.
New support for their case came from Guy
Demortier, a materials scientist at Namur University in Belgium.
Originally a sceptic, he told the French magazine that a decade
of study had made him a convert: “The three majestic Pyramids of
Cheops, Khephren and Mykerinos are well and truly made from
The concrete theorists also point out
differences in density of the pyramid stones, which have a
higher mass near the bottom and bubbles near the top, like
old-style cement blocks.
Opponents of the theory dispute the
scientific evidence. They also say that the diverse shapes of
the stones show that moulds were not used. They add that a huge
amount of limestone chalk and burnt wood would have been needed
to make the concrete, while the Egyptians had the manpower to
hoist all the natural stone they wanted.
The concrete theorists say that they will be
unable to prove their theory conclusively until the Egyptian
authorities give them access to substantial samples.
How the Egyptians really built a Pyramid