A process for converting gypsum into precipitated calcium carbonate including reacting a mixture comprising gypsum and a seed, a mineral acid, or both with at least one carbonate source, whereby precipitated calcium carbonate is produced in the form of calcite and/or aragonite directly without conversion from a vaterite polymorph. Also, a process for converting gypsum into precipitated calcium carbonate including providing a mixture comprising i) gypsum ii) a seed, a mineral acid, or both iii) at least one additive selected from the group consisting of ammonium sulfate, an organic acid, or an iron material, and reacting the mixture with at least one carbonate source to produce precipitated calcium carbonate in the form of vaterite. The precipitated calcium carbonates having desired and unique composition, polymorph and crystal size characteristics formed by these processes.

There is provided a method for manufacturing a porous material including a calcium carbonate, the method including a digestion carbonation process of causing digestion and carbonation of a porous material including a calcium oxide in a presence of water under a flow of a gas including carbon dioxide.

The present invention is directed to a process for producing an aqueous suspension of precipitated calcium carbonate, wherein a milk of lime is prepared by mixing water, a calcium oxide containing material, at least one water-soluble polymer having a molecular weight M.sub.w in the range from 200 to 6500 g/mol, and at least one slaking additive, and subsequently, the milk of lime is carbonated to form an aqueous suspension of precipitated calcium carbonate.

Use, as an opacifier, of precipitated calcium carbonate particles at least partially in the form of nano fibers or nanochain like agglomerates constituted by at least two interconnected primary particles.

The present invention is directed to a process for producing precipitated calcium carbonate with improved resistance to structural breakdown, wherein the milk of lime is carbonated in the presence of at least one gas other than carbon dioxide, or the carbonation is carried out in the presence of a static gas bubble comminution unit as well as to precipitated calcium carbonate obtained by such a process.

The invention is directed to compositions, tools and methods for the manufacture of construction materials, masonry, solid structures and compositions to facilitate dust control. More particularly, the invention is directed to the manufacture of bricks, masonry and other solid structures using small amount of aggregate material that is pre-loaded with spores and/or vegetative bacterial cells.

The present invention relates to the use of a depolymerized carboxylated cellulose solution for preparing an aqueous Precipitated Calcium Carbonate (PCC) slurry by slaking a material containing calcium oxide in water, followed by carbonation of the milk of lime thus obtained. The depolymerized carboxylated cellulose solution has a solid content of 25 wt. % to 40 wt. %, based on the total weight of the solution and a molecular weight of between 10 000 g/mol to 40 000 g/mol.

The present invention is directed to a process for producing an aqueous suspension of precipitated calcium carbonate, wherein a milk of lime is prepared by mixing water, a calcium oxide containing material, at least one water-soluble polymer having a molecular weight M.sub.w in the range from 200 to 6500 g/mol, and at least one slaking additive, and subsequently, the milk of lime is carbonated to form an aqueous suspension of precipitated calcium carbonate.

The present invention relates to a process for producing an aqueous suspension of precipitated calcium carbonate, wherein a depolymerized carboxylated cellulose is added during lime slaking. Furthermore, the present invention relates to an aqueous suspension of calcium carbonate and a precipitated calcium carbonate obtained by said process as well as the use thereof.

The present invention relates to a process for preparing an aqueous suspension comprising precipitated calcium carbonate. The invention further relates to an aqueous suspension comprising precipitated calcium carbonate as well as a partially dewatered or essentially completely dried precipitated calcium carbonate obtainable by the process and the use of the aqueous suspension comprising precipitated calcium carbonate and/or the partially dewatered or essentially completely dried precipitated calcium carbonate in paper making, paper coating, plastic, agricultural, adhesives, sealants and/or paint applications.