Extrait de l' Oxford Encyclopedia of Ancient Egypt, tome III.Texte de l'égyptologue tchèque Miroslav Verner, auteur de The Pyramids: The Mystery, Culture, and Science of Egypt's Great Monuments, Grove Press, octobre 2001
"As far as structure and construction methods are concerned, research has shown that each pyramid has two basic parts (aside from the substructure). These are a core and a casing, which could both be built in various ways. The core was usually made of poorer quality, very roughly worked limestone or mud bricks, while the casing was always constructed from very high quality white limestone.
The core of the Step Pyramid is made of limestone ashlars (square-cut blocks) placed in layers inclined inward so that the resulting pressure is directed toward the center of the building. The core of the Great Pyramid is constructed in a combination of compact stone masonry placed in accretion layers and probably also chambers filled with sand.
In the fifth dynasty, the cores were built in horizontal layers of coarse stone blocks, with careful construction only on the outside ; the inside was filled with waste material. There followed a period in which cores were made from small irregular pieces of stone stuck together with clay lime mortar. From the twelfth dynasty, there was the adoption of core construction using mud bricks, with a skeleton of limestone walls radiating from the vertical axis of the pyramid.
It is believed that the casing was usually constructed at the same time as the core, but this was not the case with some pyramids, such as those of Sneferu in Meidum or Neferirkare Kakai's.
No detailed answer can yet be given to the question of the engineering construction of the Egyptian pyramids. For that, it would be necessary to take them apart, investigate them fully, and put them together again, since research has shown that no universal method existed. Instead, at different times and at different places, pyramids were made using various materials and plans.
Even in antiquity, authors were suggesting two basic methods : the use of wooden machines (suggested by Herodotus) or the use of ramps (suggested by Diodorus Siculus). It is likely that the pyramids were built up to approximately half their projected height (perhaps 80 percent of the volume of masonry), mainly by using a system of ramps, part of which would be integrated into the core. In the next phase, more use was probably made of simple machines wooden levers, rollers, stone false pulleys, ropes, and so on.
It has been estimated that the total work force in the construction of the Great Pyramid, including provisioning, quarries, and transport of materials, was perhaps thirty-five thousand people. In the building of small pyramids such as those of the fifth dynasty, fewer than ten thousand may have been employed.
Both textual and graphic evidence show that haulage was accomplished either by gangs of men or by teams of oxen. The work, from the quarrying of stone to the completion of the casing, was perfectly organized. The degree of coordination of individual tasks and the skill and productivity of the stoneworking were extraordinary. These may be the simplest secrets of the pyramid builders, but perhaps the greatest."