...Barsoum now believes he has discovered the actual recipe used to construct the pyramids in Egypt.
Start with pool of water and then add:
Quicklime (widely available in stores, but you could make your own by heating limestone to 900 degrees C.)
Mix and wait a few days to allow water to evaporate
At this point the limestone ‘mud’ is placed in earthbags or wood forms. Dr. Barsoum says sand was not used because it does not dissolve and so it’s not part of the chemical ‘glue’ that binds the other materials together.
Instead of course we'd put the mud in forms for casting cores