Joseph Davidovits (1935- ) is a French scientist who has worked on geopolymers since the 1970s. which can be used to create cement that is economically and ecologically superior to Portland cement.
In the late 1970s, Professor Davidovits shook the world of Egyptology with his claim that some of the blocks used to build the Great Pyramid had been cast rather than carved(a)(e)! This generated a debate that has rumbled on over the past four decades(c). Professor Michel Barsoum supports Davidovits(g), Professor Linn Hobbs of MIT is ambivalent(h), while geologist Dipayan Jana is strongly opposed(i).
>In 2020, Davidovits published a rebuttal of arguments put forward by Jena and others, ensuring the continuance of the controversy for some time to come(k).<
Not content with upsetting Egyptologists Davidovits has now annoyed archaeologists at other sites with his more recent claims that casting and not carving had also been used at Tiwanaku and Puma Punku in Bolivia(b) as well as on Easter Island(d)! This proposed connection between the Easter Island moai and South America is explained in an interesting video from Davidovits(j).
I have always been cautiously sympathetic towards Davidovits’ geopolymer theories, However, when I read of his claim that the Easter Island statues were also made with artificial stone, my doubts grew. I consulted my well-thumbed paperback copy of Thor Heyerdahl‘s Aku-Aku  and found images between pages 112 and 113 showing unfinished giant moai in a quarry still with the back part of the statues to be cut free from the rock. The stone tools used for the sculpting of the giants still lay nearby. I am now waiting for Davidovits to comment on Stonehenge!
Furthermore, the claim of casting rather than carving, implies the use of moulds, something that I have never seen represented on the walls of any of the tombs or temples of Egypt nor have the physical remains of any such moulds been found. Compounding this is the fact that sites identified by Davidovits as having used artificial stone, particularly Egypt and Easter Island, suffered from a dearth of suitable timber for making moulds!
Davidovits has also published a short series of ebooks concerning the Bible and Egypt(f).
(k) (PDF) Giza Pyramids and Geopolymer Limestone: Deep Misleading analysis on the “Lauer Sample” by petrologists and geologists. A rebuttal of the articles published by Dipayan Jana and others (researchgate.net) *