Method of preparing alkali-activated cement by stepwise calcination with sodium chloride

A method of preparing an alkali-activated cement by stepwise calcination with sodium chloride, comprising:

• (1) mixing a sodium chloride, a silicate and a carbonate followed by grinding to obtain a raw material powder;
• (2) sequentially subjecting the raw material powder to a first calcination at 850-1050° C., a second calcination at 1240° C. or more and cooling to obtain a clinker;
• and
• (3) mixing the clinker with an alkali to produce the alkali-activated cement, wherein the alkali is sodium hydroxide, potassium hydroxide or a combination thereof;
• wherein a mixture of the silicate and the carbonate is adapted to produce a residue comprising SiO2, Al2O3, CaO, and MgO after oxidative calcination at 950±25° C.;
• a total weight of SiO2, Al2O3, CaO, and MgO accounts for 90.0% or more by weight of the residue;
• SiO2 accounts for 31.0-47.0% by weight of the residue;
• Al2O3 accounts for 12.4-18.0% by weight of the residue;
• CaO accounts for 21.3-46.3% by weight of the residue;
• and MgO accounts for 0-16.2% by weight of the residue;
• in the step (1), the sodium chloride is 8.0-20.0% by weight of the residue;
• and
• in the step (3), a weight of the alkali is calculated as follows:
• (a weight of NaOH+0.713×a weight of KOH)/a weight of the clinker=(0.5-3.0)%.