By JOHN NOBLE WILFORD Published: November 30, 2006 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.
Skip to next paragraph 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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