Effect of Crystal-shaped Additives of Precipitated Calcium Carbonate on the Whiteness of Modified Fly Ash and Hand Sheets

Fly ash was modified using calcium oxide and carbon dioxide. The morphology of precipitated calcium carbonate was controlled by adding different crystal-shape-forming additives. Effects of sodium hexametaphosphate, zinc chloride, sodium tetraborate decahydrate, and aluminium chloride on the crystal shape of precipitated calcium carbonate were studied. The effects of crystal-shaped additives of precipitated calcium on the whiteness of modified fly ash and hand sheets were analyzed. The results showed that the addition of ZnCl2 (0.35%) can play a role in coating fly ash well. The coating effect of the acicular, chain, and lamellar precipitated calcium carbonate on the surface of fly ash was slightly less effective than that of globular crystals.