Egyptian Pyramid Construction TechniquesIntroductionThe Pyramids of Egypt are among the largest structures ever built[1] and constitute one of the most potent and enduring symbols of Ancient Egyptian civilization. Most were built during the Old and Middle Kingdom periods.[2] Most of them took about 27 years to build. In Ancient Egypt, a pyramid was referred to as mer, literally "place of ascendance." The Great Pyramid of Giza is the largest in Egypt and one of the largest in the world. Until Lincoln Cathedral was built in 1300 A.D., it was the tallest building in the world. The base is over 52,600 square meters in area. The Pyramid of Giza is one of the Seven Wonders of the World, and the only one of the seven to survive into modern times. The Ancient Egyptians capped the peaks of their pyramids with gold and covered their faces with polished white limestone, though many of the stones used for the purpose have fallen or been removed for other structures. Historic developmentBy the time of the early dynastic period of Egyptian history, the pyramids were built by the horde, buried in bench-like structures known as mastabas.[3][4] The first historically documented Egyptian pyramid is attributed to the architect Imhotep, who planned what Egyptologists believe to be a tomb for the pharaoh Djozer. Imhotep may have been the first to conceive the notion of stacking mastabas on top of each other — creating an edifice comprised of a number of "steps" that decreased in size towards its apex. The result was the Step Pyramid of Djozer — which was designed to serve as a gigantic stairway by which the soul of the deceased pharaoh could ascend to the heavens. Such was the importance of Imhotep's achievement that he was deified by later Egyptians.[5] The most prolific pyramid-building phase coincided with the greatest degree of absolutist pharaonic rule. It was during this time that the most famous pyramids, those near Giza, were built. Over time, as authority became less centralized, the ability and willingness to harness the resources required for construction on a massive scale decreased, and later pyramids were smaller, less well-built and often hastily constructed. Long after the end of Egypt's own pyramid-building period, a burst of pyramid-building occurred in what is present-day Sudan, after much of Egypt came under the rule of the Kings of Napata. While Napatan rule was brief and ceased in 661 BC, the Egyptian influence made an indelible impression, and during the later Sudanese Kingdom of Meroe (approximately in the period between 300 BC–AD 300) this flowered into a full-blown pyramid-building revival, which saw more than two hundred indigenous, but Egyptian-inspired royal pyramid-tombs constructed in the vicinity of the kingdom's capital city. Pyramid symbolismThe shape of Egyptian pyramids is thought to represent the primordial mound from which the Egyptians believed the earth was created. The shape is also thought to be representative of the descending rays of the sun, and most pyramids were faced with polished, highly reflective white limestone, in order to give them a brilliant appearance when viewed from a distance. Pyramids were often also named in ways that referred to solar luminescence. For example, the formal name of the Bent Pyramid at Dahshur was The Southern Shining Pyramid, and that of Senwosret at el-Lahun was Senwosret is Shining. While it is generally agreed that pyramids were burial monuments, there is continued disagreement on the particular theological principles that might have given rise to them. One theory is that they were designed as a type of "resurrection machine"[6] The Egyptians believed the dark area of the night sky around which the stars appear to revolve was the physical gateway into the heavens. One of the narrow shafts that extends from the main burial chamber through the entire body of the Great Pyramid points directly towards the center of this part of the sky. This suggests the pyramid may have been designed to serve as a means to magically launch the deceased pharaoh's soul directly into the abode of the gods. All Egyptian pyramids were built on the west bank of the Nile, which as the site of the setting sun was associated with the realm of the dead in Egyptian mythology.[7] Number and location of pyramidsThe number of pyramid structures in Egypt today is reported by most sources as being between 81 and 112, with a majority favoring the higher number. In 1842 Karl Richard Lepsius made a list of pyramids, in which he counted 67, but more have been identified and discovered since his time. The imprecise nature of the count is related to the fact that as many smaller pyramids are in a poor state of preservation and appear as little more than mounds of rubble, they are only now being properly identified and studied by archaeologists. Most are grouped in a number of pyramid fields. Construction DatesThe following table lays out the chronology of the construction of most of the major pyramids mentioned here. Each pyramid is identified through the pharaoh who ordered it built, their approximate reign and its location.
Notes & References
Construction TechniquesEgyptian pyramid construction techniques are a matter of much speculation. Many theories about how the Egyptian pyramids were built have been developed and published, and new theories are still being created, but there is not yet any real consensus in the scientific world. One factor that almost all agree on is that construction techniques developed over time; the earliest pyramids were built in different ways than the later ones. Most construction theories are based on the idea that the pyramids were built by moving huge stones from a quarry and somehow dragging and lifting them into place. The disagreements center on the method by which the stones were conveyed and placed. There is, however, one other theory that is based on the "stones" being manufactured in-place from a kind of "limestone concrete". In addition to the many theories as to the techniques involved, there are also disagreements as to the kind of workforce that was used. One theory, suggested by the Greeks, posits that slaves were forced to work until the pyramid was done. A more widely accepted theory in the modern era, however, suggests that the Great Pyramid of Egypt was built by hundreds of skilled workers who camped near the pyramids and worked for a salary or as a form of paying taxes until the construction was completed. Historical considerationsThird and Fourth DynastiesDuring the earliest period, pyramids were constructed wholly of stone. Locally quarried limestone was the material of choice for the main body of these pyramids, while a higher quality of limestone quarried at Tura (near modern Cairo) was used as the outer casing. Granite, quarried near Aswan, was used to construct some architectural elements, including the porticulis (a type of gate) and the roofs and walls of the burial chamber. Occasionally, granite was used in the outer casing as well, such as in the pyramid of Menkaure. In the early pyramids, the layers of stone (called courses) forming the pyramid body were laid sloping inwards; however, this configuration was found to be less stable than simply stacking the stones horizontally on top of each other. The Bent Pyramid at Dahshur represents the transition between these two building techniques; its lower section is built of sloping courses, while in its upper section the stones are laid horizontally. Middle Kingdom and onwardDuring the Middle Kingdom, pyramid construction techniques changed again. Most pyramids built at this time were little more than mountains of mud brick encased in a veneer of polished limestone. In several cases, later pyramids were built on top of natural hills to further reduce the volume of material needed in their construction. The materials and methods of construction used in the earliest pyramids have ensured their survival in a generally much better state of preservation than is the case with the pyramid monuments of later pharaohs. Construction method theoriesBuilding the pyramids from quarried stonesOne of the major problems faced by the early pyramid builders was the need to move huge quantities of rock. While 80 men can drag a 2.5-ton block of stone on a sled, as depicted in carvings in some later Egyptian tombs, this brute-force method was not very efficient. Dr R H G Parry[1] has suggested a method for rolling the stones, using a cradle-like machine that had been excavated in various New Kingdom temples. Four of those objects could be fitted around a block so it could be rolled easily. Experiments done by the Obayashi Corporation, with concrete blocks 0.8 m square by 1.6 m long and weighing 2.5 tons, showed how 18 men could drag the block over a 1-in-4 incline ramp, at a rate of 18 meters per minute. Vitruvius in De architectura[2] described a similar method for moving irregular weights. While it is unknown if the Egyptians used this method, the experiments show it could have worked. While Egyptologists maintain this, and indeed the pyramids were mostly made of 2.5 ton blocks, there were the 15-ton and the few 70-ton blocks that they do not mention. As the stones forming the core of the pyramids were roughly cut, especially in the Great Pyramid, the material used to fill the gaps was another problem. Huge quantities of gypsum and rubble were needed. The filling has almost no binding properties, but it was necessary to stabilize the construction. To make the gypsum mortar, it had to be dehydrated by heating, and this required a lot of wood. The findings of the David H. Koch Pyramids Radiocarbon Project[3] suggest that Egypt had to strip its forest and scrap every bit of wood it had to build the pyramids of Giza. When the project tried to date several pyramids using the carbon extracted from the filling in the pyramids' core, they found the dates spanned almost 300 years, implying that old wood was used for some parts of the pyramids. This was seen only in the Old Kingdom pyramids, especially from Djoser to Menkaure. This could mean that later pyramids were built smaller out of necessity, due to the severely depleted state of Egypt's forest resources. There is good information concerning the location of the quarries, tools used to cut stone, transportation of the stone to the monument, leveling the foundation, and leveling the subsequent tiers of the developing superstructure. Workmen used copper chisels, drills, and saws to cut softer stone, such as most of the limestone. The harder stones, such as granite, granodiorite, syenite, and basalt, could not be cut with copper tools alone; instead they were worked with time consuming methods like pounding with dolerite, drilling, and sawing with the aid of an abrasive, like quartzite sand. Blocks were transported by sledge lubricated by water. Leveling the foundation was accomplished by the use of water filled trenches. The writings of Herodotus and Diodorus SiculusThe unknowns of pyramid construction revolve around the question of how the blocks were moved up the superstructure. There is no known accurate historical or archaeological evidence that definitively resolves this question. Therefore, most discussion on construction methods involves functional possibilities that are supported by limited historical and archaeological evidence. Historical accounts for the construction of the Egyptian pyramids do little to point directly to definitive methods to lift the blocks; yet most Egyptologists refer to these accounts when discussing this portion of pyramid construction. The first historical accounts of the construction of these monuments come centuries after the era of pyramid construction, by Herodotus in the 5th century BC and Diodorus Siculus in the 1st century BC. Herodotus' account states:[4]
Diodorus Siculus' account states:[5]
Both Herodotus' and Diodorus Siculus' writings are known to contain gross errors of fact and Siculus is routinely accused of borrowing from Herodotus. Herodotus' description of slave labor is one of the most persistent myths of the construction process, and Diodorus Siculus' description of the shipment of the stone from Arabia is wildly incorrect. Since both accounts are known to be both false and true, it is impossible to select either technique from historical documents. However, these documents do give credit to both the levering and ramp methods. Various kinds of ramps - theories of Mark Lehner and others
Most Egyptologists acknowledge that ramps are the most tenable of the methods to raise the blocks, yet they acknowledge that it is an incomplete method which needs to be supplemented by another device. The method most accepted for assisting ramps is levering [6] (Lehner 1997: 222). The archaeological record gives evidence of only small ramps and inclined causeways, not something that could have been used to construct even a majority of the monument. To add to the uncertainty, there is considerable evidence demonstrating that non-standardized or ad hoc construction methods were used in pyramid construction (Arnold 1991: 98 [7], Lehner 1997: 223). Therefore, there are many proposed ramps and there is a considerable amount of discrepancy regarding what type of ramp was used to build the pyramids.[8] One of the widely discredited ramping methods is the large straight ramp, and it is routinely discredited on functional grounds for its massive size, lack of archaeological evidence, huge labor cost, and other problems (Arnold 1991: 99, Lehner 1997: 215, Isler 2001: 213[9] However, the large straight ramp, seen in the picture above, is the only ramp design that can effectively build the entire monument. Other ramps serve to correct these problems of ramp size, yet either run into critiques of functionality, limited archaeological evidence, or the inability to construct the entire monument, mostly due to the limited space available at the top of the monument. There are zig-zagging ramps, Straight ramps utilizing the incomplete part of the superstructure (Arnold 1991), Spiraling ramps supported by the superstructure and spiraling ramps leaning on the monument as a large accretion are proprosed. Mark Lehner speculated that a spiraling ramp, beginning in the stone quarry to the southeast and continuing around the exterior of the pyramid, may have been used. The stone blocks may have been drawn on sleds along the ramps lubricated by water or milk.[10] Yet each of these ramps are criticized for their inability to construct the entire monument. In other words, ramping methods work fine for most of the superstructure, but cannot create the top or the entire monument. Levering methods are considered to be the most tenable solution to complement ramping methods, partially due to Herodotus' description; and partially to the Shadoof; an irrigation device first depicted in Egypt during the New Kingdom, and found concomitantly with the Old Kingdom in Mesopotamia. In Lehner's (1997: 222) point of view, levers should be employed to lift the top 3% of the material of the superstructure. It is important to note that the top 4% of this material comprises 1/3rd of the total height of the monument. In other words, in Lehner's view, levers should be employed to lift a small amount of material and a great deal of vertical height of the monument. In the milieu of levering methods, there are those which lift the block incrementally, as in repeatedly prying up alternating sides of the block and inserting a wooden or stone shims to gradually move the stone up one course; and there are other methods that use a larger lever to move the block up one course in one lifting procedure. Since the discussion of construction techniques to lift the blocks attempts to resolve a gap in the archaeological and historical record with a plausible functional explanation, the following examples by Isler, Keable, and Hussey-Pailos [11] list experimentally tested methods. Isler's method (1985, 1987) is an incremental method and, in the Nova experiment (1992), used wooden shims or cribbing. Isler [12] was able to lift a block up one tier in approximately one hour and 30 minutes. Peter Hodges’ and Julian Keable’s[13] method is similar to Isler's method and instead small manufactured concrete blocks as shims, wooden pallets, and a pit where their experimental tests were performed. Keable was able to perform his method in approximately 2 minutes. Scott Hussey-Pailos's (2005) method [11] uses a simple levering device to lift a block up course in one movement. This method was tested with materials of less strength than historical analogs (tested with materials weaker than those available in ancient Egypt), a factor of safety of 2, and lifted a 2500 pound block up one course in under a minute. This method is presented as a levering device to work complimentary with Mark Lehner's idea of a combined ramp and levering techniques. Theories of Ron WyattIn the late 1970s, biblical researcher Ron Wyatt claimed to have discovered a working levered machine inspired by the Egyptian glyph used to indicate the act of building. In 1979, Royal Jordanian Airlines flew his materials to Egypt and Wyatt demonstrated his machines on an actual pyramid. [14] Jean-Pierre Houdin's "internal ramp" theoryA recent (2006) construction theory for the Great Pyramid presented by French architect Jean-Pierre Houdin involves the use of an "internal ramp" for the top 70% of the structure.[15] A simplified way of thinking of this method is that the upper part of the pyramid was built "inside out". Houdin and a team of engineers used computer-aided design technology to test and refine the theory, which according to Houdin makes his theory the only one "proven" to be a viable technique.[16] Houdin has written a book about his theory: Khufu: The Secrets Behind the Building of the Great Pyramid.[17] The use of wind powerIt has also been suggested that Egyptians might have moved the stones with wind power, relying on kites and pulleys rather than huge numbers of slaves. On June 23, 2001, Caltech aeronautics professor Mory Gharib and a small team of undergraduates working in the California desert raised a 6900 lb (3.1 tonne), 3 metre tall obelisk into a vertical position in 22 mph (35 km/h) winds in under 25 seconds. They used only a kite, a pulley system, and a support frame to demonstrate that wind power can be harnessed to create large lifting forces. Maureen Clemmons first thought of this idea after seeing an image in Smithsonian of some men raising an obelisk. Clemmons also found a frieze that showed an unidentifiable wing pattern directly above some men and possible ropes.[18] Limestone concrete theoryMaterials scientist Joseph Davidovits has posited that the blocks of the pyramid are not carved stone, but mostly a form of limestone concrete and that they were "cast" as with modern cement.[19] According to this theory, soft limestone with a high kaolinite content was quarried in the wadi on the south of the Giza Plateau. The limestone was then dissolved in large, Nile-fed pools until it became a watery slurry. Lime (found in the ash of cooking fires) and natron (also used by the Egyptians in mummification) was mixed in. The pools were then left to evaporate, leaving behind a moist, clay-like mixture. This wet "concrete" would be carried to the construction site where it would be packed into reusable wooden moulds and in a few days would undergo a chemical reaction similar to the "setting" of cement. New blocks, he suggests, could be cast in place, on top of and pressed against the old blocks. Proof-of-concept tests using similar compounds were carried out at a geopolymer institute in northern France and it was found that a crew of ten, working with simple hand tools, could build a structure of fourteen, 1.3- to 4.5-ton blocks in a couple of days.[20] He claims he found hieroglyphic texts stating they used this technology. Davidovits' method is not accepted by the academic mainstream. His method deals only with limestone, and not with granite stones weighing well over 10 tons, which he says were carved. Geologists have heavily scrutinized Davidovits results and concluded that his came from natural limestone quarried in the Mokattam Formation.[21] However, Davidovits alleges that the bulk of soft limestone is coming from the same natural Mokkatam Formation quarries found by geologists, and insists that ancient Egyptians used the soft marly layer instead of the hard one to re-agglomerate stones, which some geologists disagree. Davidovits' theory recently gained support from Michel Barsoum, a researcher in the field of ceramics.[22] Michel Barsoum and his colleagues at Drexel University published their findings supporting Davidovit's theory in the Journal of the American Ceramic Society in 2006.[23] Portable wooden ramps theoryFrank Steiger, an amateur scientist, has an interesting theory:
Even though it is generally conceded that a single straight mud rubble ramp to the top of one of the larger pyramids is simply not possible, it is still illustrated in many web pages. The gigantic size and the labor and materials necessary to construct and remove such a ramp effectively rule it out of consideration. The only practical method of raising and placing the stone blocks is the use of portable wooden ramps on each of the four sides of the pyramid. Photographs of the larger pyramids reveal that the stone blocks were placed in uniform horizontal steps. During construction, the outermost course of stone blocks was temporarily omitted in order to provide room for the wooden ramps. As each layer was completed, the topmost ramp was moved upward, with the lower ramps following in succession to form a continuous queue of stone blocks moving on the ramps to the placement level. Upon reaching the top, the angular facing blocks were placed from the top down. The angular blocks alternated with the final rectangular blocks to fill the space previously omitted to provide for the wooden ramp. As each row of angular facing blocks was placed, the wooden ramps were moved down in a stepwise progression. This required careful planning to ensure that upon reaching the top, the queue then consisted of angular facing blocks alternating with rectangular blocks. Complete details on how the blocks and ramps had to be moved to accomplish this are available in http://www.fsteiger.com/Pyramid.html References
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