Abstract: This invention relates to a lightened gas-impermeable cement grout which comprises hydraulic cement, water, silica fumes in an amount of from about 5 to about 65 weight % based on the weight of the cement, and at least one polyethylene imine having a molecular weight of between about 600,000 and about 1,000,000 in an amount of from about 1 to about 25% weight % based on the weight of the water.

Abstract: The invention concerns a compound cement containing cement and a blast-furnace slag, more particularly for bore holes.This compound cement is characterized in that it comprises the following components:a Portland cement presenting, by weight, a magnesium oxide content of max. 6%, a sulphur trioxide content of max. 3%, an insoluble residue of max. 0.75%, a tricalcium silicate content between 48 and 65%, a tricalcium aluminate content of max. 3%, a total amount formed by the amount of tetracalcium aluminoferrite, plus the amount of dicalcium ferrite, plus two times the amount of tricalcium aluminate which is at most equal to 24%, and a total amount of alkalies, calculated as sodium oxide equivalents, of max. 0.75%.and a ground blast-furnace slag with a vitrification rate of 90 to 100%;these two components presenting a similar mesh size, comprised between 2,800 and 3,000 cm.sup.2 /g, and being mixed together in the following wt-% proportion: 50 to 10% of Portland cement and 50 to 90% of ground slag.

Abstract: Hydraulic cement composition with delayed setting, intended to be employed in an environment which may be under extreme temperature, pressure and salinity conditions, the composition being characterized in that it incorporates(a) a saline or nonsaline aqueous liquid phase,(b) at least one hydraulic cement,(c) a setting-retarder adjuvant preserving and/or improving the rheological properties, a water-soluble copolymer resulting from the copolymerization of ethylenic acids, acrylamides and ethylenic esters of phosphoric acid.