"Major efforts were dedicated to greenhouse CO2 mitigation with the development of low CO2 geopolymer cements. My research... started in 1990 at Penn-State University... The production of 1 tonne of kaolin based-geopolymeric cement generates 0.180 tonnes of CO2, from combustion carbon-fuel, compared with... Portland cement... six times less. Fly ash based-geopolymeric cement... up to nine times less than Portland..."
January 1, 1970
https://en.wikiquote.org/wiki/Joseph_Davidovits