The 3 pyramids near Giza in Egypt were built 5,000 years ago but there is still a mystery how they were built.
The prevailing theory of most Egyptologists is, although there is no written or any other evidence, that the big stones, each 2.5 tons weight which construct the pyramids were carved in far quarries, hauled to the pyramid site and lifted to place on the pyramid.
Such theory set the following questions:
1. The Egyptians had no Iron tools, only Copper and Bronze tools
which were too soft and not suitable to carve the big stones. More to say, the joints between blocks were so accurate that a human hair could not be passed in between. Such could not be achieved by stone carving or chiseling with copper or bronze tools.
2. The wheel was not existed in Egypt at that time. How they hauled the big stones (2,300,00 stones of 2.5 tons each) from the far away quarries to the pyramid site.
3. Crane pulleys we not existed at that time. How could the Egyptians lift the stones up to the height of 100-150 meters.
In 1980, a French materials scientist Joseph Davidovitz proposed a new controversial theory:
The big stones were casted at sight, on the pyramid, using stone size molds and Geopolymer concrete with as a Silicon non-organic polymer. He suggested that the geopolymer was produced by mixing of crushed limestone, clay, water, and lime. Later a different geopolymer compositions were proposed but the proposal in general remained unchanged. The Egyptians casted the stones at site.
This proposal could explain how pyramids were built where no wheels and no pulley blocks were existed, as well as the accuracy of joints.