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A construction management study (testing) carried out by the firm Daniel, Mann, Johnson, & Mendenhall in association with Mark Lehner and other Egyptologists, estimates that the total project required an average workforce of 14,567 people and a peak workforce of 40,000. Without the use of pulleys, wheels, or iron tools, they used critical path analysis to suggest the Great Pyramid was completed from start to finish in approximately 10 years. Their study estimates that the number of blocks used in construction was between 2-2.8 million (an average of 2.4 million), but settles on a reduced finished total of 2 million after subtracting the estimated area of the hollow spaces of the chambers and galleries. Most sources agree on this number of blocks somewhere above 2.3 million.Their calculations suggest the workforce could have sustained a rate of 180 blocks per hour (3 blocks/minute) with ten hour work days for putting each individual block in place. They derived these estimates from modern third-world construction projects that did not use modern machinery, but conclude it is still unknown exactly how the Great Pyramid was built.
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.
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.
'Egyptian workmen went to outcrops of relatively soft limestone, disaggregated it with water, then mixed the muddy limestone (including the fossil-shells) with lime and tecto-alumino-silicate-forming materials (geosynthesis) such as kaolin clay, silt, and the Egyptian salt natron (sodium carbonate).
The limestone mud was carried up by the bucketful and then poured, packed or rammed into molds (made of wood, stone, clay or brick) placed on the pyramid sides. This re-agglomerated limestone, bonded by geochemical reaction (called geopolymer cement), thus hardened into resistant blocks.
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 concrete.”
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 concrete stones.” [
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.
Advanced technology plays no part in the production of geopolymers. This is the most basic prerequisite if the theory is to be feasible. An individual of the Stone Age could produce geopolymers if he or she astutely applied the knowledge that comes from intelligent, repeated observation and experimentation with substances found in the environment.
... suitable ingrediants were available in quantites of millions of tons. Mud from the Nile River contains alumina and is well suited for low-temperature mineral synthesis. The natron salt is extraordinarily abundant in the deserts and lakes. Natron reacts with lime and water to produce casustic soda, the main ingreient for alchemically making stone. An abundance of lime would have been available by calcining limestone in simple hearths. In ancient times, the Sinai mines were rich in deposits of turquoise and chrysocolla, needed for the production of synthetic zeolites. The mines also contained the arsenic minerals of olivenite and scorodite, needed to produce rapid hydraulic setting in large concrete blocks.
Source: "The Pyramids - An Enigma Solved" - Davidavits - pp69-70
Originally posted by Merriman Weir
This is interesting but I'm not wholly sure what the angle is exactly. Is it that it's now confirmed or is that the idea of Egyptians using 'concrete' is new? Hasn't this explanation been posited for a long time now?
It's been long known that the Romans also used similar techniques in what's often called the Concrete Revolution and they got quite clever with it too: the dome of the Pantheon &c.
Originally posted by grover
reply to post by Merriman Weir
The Romans supposedly developed concrete in and around 200 BC. If this hypothisis is correct then it would predate the Romans by over 2000 years.
BTW I am giving you a star for this thread.
[edit on 27-9-2009 by grover]
Originally posted by abecedarian
Thanks for the great read.
As for your idea about casting, perhaps a sand or similar mold was made and the material was poured around it. Then after firing, water could be used to wash the sand out. A similar process is used to cast engine blocks.
Originally posted by grover
reply to post by Iamonlyhuman
There were several "dark ages" between the building of the pyramids and the Romans...
specifically there were 3 periods between the old kingdom...the middle kingdom and the new kingdom in which apparently the whole social order of ancient Egypt broke down.
Just like the dark age between the Mycenaean (Achaean) and the the people we know as the Greeks...much was lost in those centuries.