[quote]Varqanir wrote:
Zap Branigan wrote:
Actually the pyramids were likely build with a prehistoric form of concrete and cast in place.
No, we’re pretty sure that the pyramids were built of limestone blocks quarried near Giza.
and the area certainly did not have the food to feed all the slaves that most people think built them.
You’re kidding, right?
Egyptian agriculture was the best in the world at the time. The annual flooding of the Nile gave the Nile valley some of the most fertile soil in the ancient world, and the wealth of the Empire was built on the surpluses of grain that they were able to grow.[/quote]
Not according to an engineering study and chemical anaysis I read a few years ago in an enginering magazine.
Edit:
Here is what I found on-line.
http://web.mit.edu/newsoffice/2008/pyramid-tt0402.html
Gathering ‘concrete’ evidence
MIT class explores controversial pyramid theory with scale model
David Chandler, MIT News Office
April 2, 2008
Even though they are among the best-known structures on Earth, the pyramids of Egypt may still hold surprises. This spring, an MIT class is testing a controversial theory that some of the giant blocks that make up the great pyramids of Giza may have been cast in place from concrete, rather than quarried and moved into position.
In order to help identify blocks that were cast rather than quarried, students in the class, Materials in Human Experience (class 3.094), are assembling a small pyramid using a combination of both kinds of material. They will then use techniques such as microscopic imagery and chemical analysis to look for signs that might provide ways of telling the difference on samples from the Great Pyramid itself.
While many people think of concrete as a recent material, in fact the Romans used a version made from volcanic ash and lime extensively for most of their famous buildings, including the Pantheon. But although the idea that the Egyptians may have used a kind of concrete in building the pyramids was first suggested in the 1930s, with a specific material that could have been used proposed in 1988, so far there has been no proof and the idea has remained mired in controversy.
Contentious subject
In fact, the very idea has been so controversial that “you can’t get research funding, and it’s difficult to get a paper through peer review,” says Linn Hobbs, professor of materials science and engineering and professor of nuclear science and engineering at MIT and coteacher of the pyramid-building class.
Hobbs says that actually building a small-scale model of the pyramid using the materials and methods the Egyptians may have used is far more than just an educational exercise for the students. “Like any other investigation of ancient technologies, you can only get so far by speculating, and even only so far by looking at evidence. To go the rest of the way, you have to do the thing yourself. You have to get acquainted with the materials.”
Speculating on materials
The materials and know-how needed to cast the pyramids’ giant 2-1/2 ton blocks in place, rather than quarrying and moving blocks of solid limestone, was definitely available to the Egyptians, Hobbs explains. At least 90 percent of the material would have consisted of powdered limestone, and Egyptian limestone is especially fragile and can easily be reduced to finely divided sludge simply by soaking it in water. The rest–the binder or cement–could have been made from materials they were known to have had and used for other purposes.
The binder, known as a geopolymer, could have been made from lime, kaolinite (a kind of clay), a fine silica (such as diatomaceous earth) and natron (sodium carbonate). The same ingredients were used by the Egyptians to make self-glazing pottery ornaments, a material called Egyptian faience, and well known to archeologists. When fired at high temperature, the material produces a rich blue glaze on the surface. But if left for days or weeks at room temperature, it self-cures into a rock-hard material that could have provided a binder for cementing the disaggregated limestone together into cast blocks.
Hobbs suggests that some ancient craftsman may have inadvertently left some faience material unfired, and discovered by accident the hard material that resulted. In building pyramids, especially the higher layers as the structure grew, casting blocks in place would have been a far easier task than carving them to precise sizes and shapes and then moving them up long earthen ramps into their final positions – a process that has never been described or pictured in any of the vast number of Egyptian texts and murals that have been found.
Like Silly Putty and Jell-O
While wet, the consistency of the material is quite different from modern Portland cement, Hobbs says. “It’s like something between mortar and Jell-O. When you try to pack it, it kind of ripples,” he says. “It’s rather like Silly Putty.”
But the unusual material has a significant advantage: It doesn’t shrink when it sets. “With most cements, you worry about shrinkage,” Hobbs says, but not with this kind.
The class has been experimenting with different proportions and variations in ingredients for the geopolymer, to see which produces the strongest, most durable and limestone-like results. “This is not a cookbook class,” Hobbs explains–he and the students are figuring things out as they go along.
An agnostic in search of answers
Hobbs is not pushing the cast-block theory, which was first advanced by French materials chemist Joseph Davidovits, who invented (or perhaps reinvented) the geopolymer formula. Hobbs calls himself an agnostic on the matter, but thinks that it is a theory that deserves serious study and investigation.
“My own take is, they probably did both–cut some and cast some,” he says.
“It’s not science unless we formulate hypotheses that can be proved or disproved,” he says. He hopes the class will produce a scientific paper detailing how the question could be resolved more definitively through microscopic and microchemical analysis. “It’s good that the students can see a real scientific controversy being addressed in productive ways.”
http://dsc.discovery.com/news/2006/12/08/pyramids_arc.html?category=archaeology&guid=20061208120000
Were the Pyramids Made With Concrete?
Rossella Lorenzi, Discovery News
type size: [A] [A] [A]
Dec. 8, 2006 �?? Concrete was poured to build the Great Pyramids about 5,000 years ago, according to controversial research, which suggests the ancient Egyptans predated the Romans by thousands of years as the inventors of concrete.
Michel Barsoum, professor of materials engineering at Drexel University in Philadelphia, and colleagues report in the current issue of the Journal of the American Ceramic Society that the pyramids were constructed with a combination of carved stones and blocks of limestone-based concrete.
The study, drawn on a research made in the mid-1980s by the French materials scientist, Joseph Davidovits, consists of a detailed examination of samples taken from the pyramids and their vicinity.
The aim was to determine whether the pyramid materials are natural or synthetic.
“Davidovits proposed that the pyramid blocks were cast in situ, with a wet mix of limestone particles and a binder, tamped into molds,” wrote the researchers.
In time, the French scientist claimed, the wet mix hardened into a concrete that featured the appearance and properties of native limestone.
But Davidovits�?? theory lacked hard evidence and was widely rejected by the Egyptologist community.
The longstanding belief is that the pyramids were built with blocks of limestone carved from nearby quarries. The blocks were cut to shape using copper tools, transported to the pyramid site and then hauled up huge ramps and set in place using wedges and levers.
Using scanning and transmission electron microscopy, Barsoum and his co-workers, Gilles Hug of the French National Aerospace Research Agency, and Adrish Ganguly of Drexel University, analyzed and compared the mineralogy of a number of pyramid samples with six different limestone samples from their vicinity.
They found that pyramid samples featured mineral ratios that did not exist in any known limestone sources.
“The most convincing argument is the presence of amorphous SiO2 (silica),” Barsoum told Discovery News. “In sedimentary rocks, the SiO2 is almost always crystalline.”
He also noted that some samples of calcite and dolomite taken from pyramid samples featured water molecules trapped inside �?? again, he said, this is not a phenomenon found in nature.
The researchers believe that a limestone concrete, called a geopolymer, was used for, at most, 20 percent of the blocks �?? in the outer and inner casings and in the upper parts of the pyramids.
Davidovits, himself, tested a limestone-based concrete recipe at the Geopolymer Institute at Saint-Quentin.
He concluded that diatomaceous earth (a soil formed by the decay of tiny organisms called diatoms), dolomite and lime were mixed in water to produce a clay-like mixture. This was what the ancient Egyptians would have poured into wooden moulds at Giza to obtain concrete blocks in a few days.
Indeed, with this recipe, Davidovits produced a large concrete limestone block in ten days.
The researchers point out that pouring concrete would have spared the ancient builders from using steep ramps to push stones to the summit of the pyramids.
Zahi Hawass, chief of Egypt’s Supreme Council of Antiquities, dismissed the theory as “unlikely.”
He noted that concrete was widely used at the pyramids in modern restoration work, suggesting that team may have taken samples from these modern cuts.
But Barsoum rejected such criticism.
“I would have to be a complete and utter fool to confuse Portland cement to what we saw,” he said.
David Walker, a Columbia University geologist, said that Barsoum and colleagues have a strong case when considering the mineralogical constitution of the block chips they examined.
“Both sides in this controversy have good points. Some blocks are definitely natural and some are not,” Walker said, adding that the mystery over how the ancient Egyptians may have poured concrete is “all the more intriguing.”
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.
