Feedback archive → Feedback 2013

Building the ancient pyramids of Giza

Wikimedia commons/kallerna

Paul v.L. from the Netherlands writes in response to How did they build the Great Pyramid?—an architect’s proposal:

Wikimedia Commons/Diego Delso

Article author Trevor Harris replies:

Davidovits proposal on polymer concrete

I certainly see the merit in the technology and believe the ancients had access to this information. Ancient Rome built structures with remarkable concrete properties e.g. Pantheon. (This information still comes down from Noah’s intelligent family).

There are technical reasons why I do not fully accept his theory for the construction system. However, I am very open to supporting his explanation for the incredible precision in the casing stones being cast concrete.

1. His proposal requires an army of humans climbing massive staircases up the whole height with bags of heavy mortar. In the hot sun such workers would be exhausted by the time they reach the top. Not to mention the setting time when slurry starts to set. If the mixing was done at the higher level as shown in his videos then large amount of water have to be carried/pumped to the high level.
2. His simplistic video may work at a low level site to form some simple structure but as the structures rises the logistics becomes massive. The idea of masses or workers tamping down each section of stone consistently as the structure rises as well as all the cartage by hand is a challenge in logistics.
3. The ramming technique shows a simple rectangular mould where tamping of the mix is easy. The casing stones are not rectangular blocks but have sloping sides with obtuse angles. This requires a more refined design of formwork and more quality control on the mix and the compaction. If it can be proven categorically that the casing stones are polymer concrete (and I am open to that) then I would suggest that these stones are still cast on the ground and taken up the ramp and placed with the incredible precision required.
4. A slight variation to the above is that the blocks are placed in staggered formation around the perimeter with gaps between. Then infill blocks are cast between these blocks producing the close tolerances at the joins and the smeared mortar described in some accounts. This would require a mixing station in the centre of each platform layer.
5. The evidence still seems to support that the majority of the core blocks are from the quarry of the Giza plateau. Quarry marks can be seen on the stones. The other interesting feature is the incredible variation in all the stones of the pyramid. Both the course thickness and the size and position in locations. This does not point to a multiple mass productions from standardized form boards. However on this point if it can be proven they are cast I would still propose the ramp/lifters proposal as the most logical way to construct it
6. The slight indentation of each casing stone—they are not in an exact straight line shows they were very carefully positioned with accurate sight lines. This is difficult to do with external formwork being used for each block

The need for a ramp

1. His proposal does not explain the raising and placing of the largest stones in the pyramid. These are the massive granite relieving stones that weigh up to 63 tonne (70 tons). These are located above the King’s Chamber about 64 metres above the ground. Dense granite is not made by casting techniques. This requirement to get large stones to a high position is an important factor in the ramp proposal
2. The ramp proposal gives a large working platform near the construction zone
3. My proposal for the massive ramp was the maximum position to get the large relieving stones easily into place. However this ramp is quite large. A smaller ramp could be considered—say 35–40 metres high which would mean the largest stones would have to be hoisted 25–30 metres for the last section. Not impossible with inclined ramps, pulleys and animals.

Time frame

1. Any proposal requires a rapid rate of construction. The idea of curing times and allowing blocks to dry before casting the next block slows down the rate.
2. The ramp/lifters gives a maximum rate of placing and working on a number of positions at the same time

Summary

1. I am open to the possibility of the casing stones being cast concrete. However I believe they would be created in very controlled conditions on the ground before being dragged in frames up to site.
2. The largest stones placement is not explained by the Davidovits proposal.
3. A reduced ramp can be considered if the largest stones are placed by some lifting technique for 20–30 metres.
4. My basic proposal as presented for the construction of the pyramids still stands and meets all the logistical and alignment controls required.

Trevor Harris