Were pyramids cast-in-place concrete?

According to a report, researchers are exploring a new controversial theory, which suggests that the great pyramids of Giza may have been cast in place of concrete, rather than quarried and moved into position. The theory is being tested by researchers from Massachusetts Institute of Technology in the US.

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. Now, in order to help identify blocks that were cast rather than quarried, MIT students 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. According to Linn Hobbs, co teacher of the pyramid-building class at MIT, "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."

At least 90% 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 and natron (sodium carbonate), according to the research. The research also said that 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. Your comment?