Abstract: A cementitious product is produced from a combination of two groups of materials: the first group consisting of lime of Portland cement or Linfan (which is defined as a thermally cracked shell of calcium sulfate surrounding a core of lime) or Linvein (a lime particle coated with cracked calcium carbonate); and a second material consisting of thermally cracked fly ash which is cracked by thermally quenching such finely divided particulate material from an elevated temperature at least above 300.degree. C. and preferably higher than 450.degree. C. to ambient or below ambient temperatures.The two materials are blended together. They are mixed with water, placed in a form, and then allowed to cure. Filler materials can also be used in the form of sand, gravel, and other aggregates, depending upon the strength and compositional characteristics desired in the final product.