Aqueous slurry of precipitated calcium carbonate and ground calcium carbonate in combination

A method for the preparation of an aqueous slurry of calcium carbonate particles which comprises the steps of:

• (a) subjecting an aqueous slurry or a dehydrated wet cake of precipitated calcium carbonate particles containing an admixture of a viscosity-reducing agent having a solid concentration in the range from 25 to 75% by weight to a primary dispersing treatment by using a mixer so that the calcium carbonate particles have a median diameter in the range from 0.2 to 3.0 Jim and the slurry has a viscosity not exceeding 1000 centipoise at 25.degree. C.;
• (b) admixing the aqueous slurry of (a) with dry-ground calcium carbonate particles having a median diameter in the range from 1.5 to 30.0 .mu.m in such an amount that the weight proportion of the precipitated calcium carbonate to the ground calcium carbonate is in the range from 20:80 to 80:20 and the solid concentration of the resulting aqueous slurry is in the range from 60 to 85% by weight;
• (c) subjecting the aqueous slurry of (b) to a secondary dispersing treatment by using a mixer so that the slurry has a viscosity not exceeding 1000 centipoise at 25.degree. C.;
• and
• (d) subjecting the aqueous slurry of (c) to a tertiary dispersing treatment in a sand grinding mill so that the median diameter of the calcium carbonate particles is in the range from 0.2 to 2.0 .mu.m.