November 30, 2006
Scientist Says Concrete Was Used in Pyramids
By JOHN NOBLE WILFORD
In new research on the Great Pyramids of Giza, a scientist says he
has found more to their construction than cut natural limestone. Some
original parts of the massive structures appear to be made of
concrete blocks.
If true, historians say, this would be the earliest known application
of concrete technology, some 2,500 years before the Romans started
using it widely in harbors, amphitheaters and other architecture.
Reporting the results of his study, Michel W. Barsoum, a professor of
materials engineering at Drexel University, in Philadelphia,
concluded that the use of limestone concrete could explain in part
how the Egyptians were able to complete such massive monuments,
beginning around 2550 B. C. They used concrete blocks, he said, on
the outer and inner casings and probably on the upper levels, where
it would have been difficult to hoist carved stone.
“The sophistication and endurance of this ancient concrete technology
is simply astounding,” Dr. Barsoum wrote in a report in the December
issue of The Journal of the American Ceramic Society.
Dr. Barsoum and his co-workers analyzed the mineralogy of samples
from several parts of the Khufu pyramid, and said they found mineral
ratios that do not exist in any of the known limestone sources. From
the geochemical mix of lime, sand and clay, they concluded, “the
simplest explanation” is that it was cast concrete.
Dr. Barsoum, a native of Egypt, said in an interview that he expected
his interpretation to be controversial — and it already is.
Zahi Hawass, secretary-general of antiquities in Egypt and director
of the Giza Pyramids excavations, said in an e-mail message, “The
idea that concrete was used is unlikely and completely unproven.”
Noting that the pyramids have been restored and reinforced many times
with the extensive use of concrete, Dr. Hawass said, “I would ask Dr.
Barsoum the question: where did he get the samples he is working
with, and how can he show that the samples are not taken from areas
that have been restored in modern times?”
Most Egyptologists think the pyramids were built with limestone
blocks that were cut to shape in nearby quarries using copper tools.
The blocks were then hauled to the pyramid sites, lifted up ramps and
hoisted into place with the help of wedges and levers.
But a geologist and another materials scientist, who were familiar
with the research, said that Dr. Barsoum was a careful and reputable
scientist and that his work should be seriously considered.
“I don’t know whether he’s right or wrong,” said Sheldon Wiederhorn,
an engineer at the National Institute of Standards and Technology, in
Rockville, Md., and associate editor of the ceramic society’s
journal. “He makes a case that’s convincing, and I think his view
should be heard.”
David Walker, a Columbia geologist who has read the report, said that
the microscopic examination of the blocks “certainly revealed things
you wouldn’t expect to find in normal limestone.”
In the journal report, Dr. Barsoum and his co-authors, Adrish Ganguly
of Drexel and Gilles Hug of the National Center for Scientific
Research in France, wrote: “We hereby acknowledge that nature is
quite resourceful and could have — however unlikely — produced all
the microstructures examined herein. We believe, however, that our
work presents enough evidence to entertain the possibility that
crucial parts of the Great Pyramids are indeed made of reconstituted
limestone; only more research will tell.”
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Copyright 2006 The New York Times Company
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