PURPOSE: To inhibit the deterioration of bending strength with the lapse of time and to attain extremely high early strength by mixing fine powder of water granulated blast furnace slag with fine powder of Al ash subjected to hydroxylation treatment and an aq. soln. of water glass or fine powder of solidified water glass.

CONSTITUTION: Fine powder of water granulated blast furnace slag is mixed with 5-20% fine powder of Al ash consisting of 50-70% Al2O3, 5-10% SiO2, 5-10% metallic Al, 3-6% C and other impurities and subjected to hydroxylation treatment by immersion in water and fine powder of cement (clinker) is added to the mixture by 15% of the amt. of the Al ash powder to an amt. nearly equal to the amt. of the powder as required. An aq. soln. of water glass or fine powder of solidified water glass is then added to the mixture and mixed.