Abstract: The invention relates to molding a right cylindrical body from a settable loose granular composition in a mold cavity, in which a mold cavity (4) is fed with successive charges of the composition in the loose state and each new charge is thrust by means of thrust surfaces (11) into the surface S of the molded composition in order to cause the new charge and the molded composition to interpenetrate in such a manner as to densify the molded composition. The invention is applicable to making a pipe, in particular out of a cement composition.

Abstract: The invention relates to molding a right cylindrical body from a settable loose granular composition in a mold cavity, in which a mold cavity (4) is fed with successive charges of the composition in the loose state and each new charge is thrust by means of thrust surfaces (11) into the surface S of the molded composition in order to cause the new charge and the molded composition to interpenetrate in such a manner as to densify the molded composition. The invention is applicable to making a pipe, in particular out of a cement composition.

Abstract: A concrete includes organic fibers, dispersed in a cement matrix. The cement matrix includes elements having predetermined particle sizes. The organic fibers have predetermined lengths and diameters. The behavior of the concrete is improved both with respect to the occurrence of minute cracks and the propagation of large cracks as a result of a synergistic effect between the cement matrix and the organic fibers.

Abstract: The invention concerns a concrete obtained by mixing with water, cement, granular elements, elements with puzzolanic reaction, constituents capable of improving the toughness of the matrix, metal fibers and at least a dispersing agent, in specified conditions and proportions. Said concrete has improved properties compared to prior art concrete comprising metal fibers.

Abstract: Cementation slurries well suited for encasing reinforcing elements therefor, for example prestressed steel cable, while reducing the risk of embrittlement thereof, contain from about 1.5% to 3% by weight of homogenizing and exudation-reducing hydrophilic particulates (e.g., precipitated silica particles) that are inert in respect of liquids, have a specific surface area of greater than about 200 m.sup.2 /g and which are fragmentable during mixing and/or injection into multiple fragments having particle sizes ranging from about 5 to 300 nanometers.

Abstract: A process for spraying concrete or mortar, by a dry route or by a wet route, in order to produce on a surface a layer of concrete or of mortar. Just before or at the time of spraying, an aqueous suspension (A) of silica and of an aluminum compound chosen from aluminum sulphate, basic aluminum sulphates, alums and mixtures thereof is added to the concrete or mortar. The aqueous suspension (A) has a pH lower than 4, a solids content of between 10 and 50% by weight, and, after a period at rest of 48 hours, is in the form of a gel which is reversible under low shear. The aqueous suspension (A) is effective for increasing the thickness of the sprayed layer and reducing rebound of the concrete or mortar sprayed onto the surface.

Abstract: Cementation slurries well suited for encasing reinforcing elements therefor, for example prestressed steel cable, while reducing the risk of embrittlement thereof, contain from about 1.5% to 3% by weight of homogenizing and exudation-reducing hydrophilic particulates (e.g., precipitated silica particles) that are inert in respect of liquids, have a specific surface area of greater than about 200 m.sup.2 /g and which are fragmentable during mixing and/or injection into multiple fragments having particle sizes ranging from about 5 to 300 nanometers.

Abstract: A method and composition for preparing concrete elements comprising the steps of mixing a composition comprising the following components expressed in parts by weight (p):a) 100 p of Portland cement;b) 30 p to 100 p or better 40 p to 70 p of fine sand having a grain size of at least 150 micrometers;c) 10 p to 40 p or better 20 p to 30 p of amorphous silicon having a grain size of less than 0.5 micrometers;d) 20 p to 60 p or better 30 p to 50 p of ground quartz having a grain size of less than 10 micrometers;e) 25 p to 100 p, or better 45 p to 80 p of steel wool;f) a dispersing agent;g) 13 p to 26 p or better 15 p to 22 p of water; and after setting, curing the concrete at a temperature of 250.degree. C. or higher, for a length of time sufficient to transform cement hydration products into crystalline hydrates of the xonotlite type; thus eliminating substantially all of the free water and at least the main part of the adsorbed and chemically bonded water.