The present invention relates to the use of a combination of block polymers and particular compositions in a fluid injected under pressure into an oil-bearing rock, where: the fluid comprises solid particles and/or is brought into contact with solid particles within the oil-bearing rock following the injection thereof, the combination comprises (i) a polymer comprising: —a first block that is adsorbed on at least a portion of the particles; and —a second block, having a composition different from that of the first, and having a weight-average molecular weight of greater than 10 000 g/mol, for example greater than 100 000 g/mol, and that is soluble in the fluid; (ii) particles suitable for providing a gas barrier effect, preferably a latex and/or silica particles.

The present invention relates to the use of a combination of block polymers and particular compositions in a fluid injected under pressure into an oil-bearing rock, where: the fluid comprises solid particles and/or is brought into contact with solid particles within the oil-bearing rock following the injection thereof, the combination comprises (i) a polymer comprising: —a first block that is adsorbed on at least a portion of the particles; and —a second block, having a composition different from that of the first, and having a weight-average molecular weight of greater than 10 000 g/mol, for example greater than 100 000 g/mol, and that is soluble in the fluid; (ii) particles suitable for providing a gas barrier effect, preferably a latex and/or silica particles.

A set control composition for cementitious systems comprises (a) an amine-glyoxylic acid condensate, and (b) at least one of (i) a borate source and (ii) a carbonate source. The carbonate source is selected from inorganic carbonates having an aqueous solubility of 0.1 gL.sup.−1 or more, and organic carbonates. The set control composition improves workability of cementitious systems for prolonged periods of time without compromising early compressive strength. Due to the retarding action of the set control composition, the dosage of dispersant(s) necessary to obtain a desired flowability of the cementitious system can be reduced.

A set control composition for cementitious systems comprises (a) an amine-glyoxylic acid condensate, and (b) at least one of (i) a borate source and (ii) a carbonate source. The carbonate source is selected from inorganic carbonates having an aqueous solubility of 0.1 gL.sup.−1 or more, and organic carbonates. The set control composition improves workability of cementitious systems for prolonged periods of time without compromising early compressive strength. Due to the retarding action of the set control composition, the dosage of dispersant(s) necessary to obtain a desired flowability of the cementitious system can be reduced.

An embodiment according to the present invention provides a dental gypsum powder including a hemihydrate gypsum and a water-reducing agent, wherein the mass ratio of the water-reducing agent to the hemihydrate gypsum is 0.1 to 1%, the content of particles having a particle diameter of 10 μm or less is 15 to 35 volume %, the content of particles having a particle diameter of 20 μm or less is 40 to 55 volume %, and the content of particles having a particle diameter of 30 μm or less is 55 to 75 volume %.

An embodiment according to the present invention provides a dental gypsum powder including a hemihydrate gypsum and a water-reducing agent, wherein the mass ratio of the water-reducing agent to the hemihydrate gypsum is 0.1 to 1%, the content of particles having a particle diameter of 10 μm or less is 15 to 35 volume %, the content of particles having a particle diameter of 20 μm or less is 40 to 55 volume %, and the content of particles having a particle diameter of 30 μm or less is 55 to 75 volume %.

A process for producing foamed concrete includes introducing air pores into aqueous concrete compositions by one or more air pore formers and/or by introducing air. The aqueous concrete compositions are based on one or more foam stabilizers, one or more protective colloid-stabilized polymers of ethylenically unsaturated monomers in the form of aqueous dispersions or water-redispersible powders, 30% to 95% by weight of cement, based on the dry weight of the components for production of the concrete compositions, optionally one or more fillers, and optionally one or more additives.

A process for producing foamed concrete includes introducing air pores into aqueous concrete compositions by one or more air pore formers and/or by introducing air. The aqueous concrete compositions are based on one or more foam stabilizers, one or more protective colloid-stabilized polymers of ethylenically unsaturated monomers in the form of aqueous dispersions or water-redispersible powders, 30% to 95% by weight of cement, based on the dry weight of the components for production of the concrete compositions, optionally one or more fillers, and optionally one or more additives.

A retarder mixture for oil and gas well cementing includes a lignosulfonate compound and at least one hydrolyzed carbohydrate. A method includes blending the retarder mixture and a cement precursor to form a cement precursor mixture and introducing water into the cement precursor mixture to form a cement mixture. The cement mixture is pumped down a well and cures to form a cement sheath containing the cement precursor and the retarder mixture.

A retarder mixture for oil and gas well cementing includes a lignosulfonate compound and at least one hydrolyzed carbohydrate. A method includes blending the retarder mixture and a cement precursor to form a cement precursor mixture and introducing water into the cement precursor mixture to form a cement mixture. The cement mixture is pumped down a well and cures to form a cement sheath containing the cement precursor and the retarder mixture.