Abstract: A mixing device (1) having at least two concentric tubular elements (2, 3) including an outer tubular element (2) and an inner tubular element (3) inside the outer tubular element, the outer tubular element and the inner tubular element each supplying a liquid (5) or solid products to be mixed together, and a helical member (4) disposed for rotational movement inside the outer tubular element for entrainment of the liquid (5) or solid products, the helical member surrounding the inner tubular element, the outer tubular element including at least one inlet orifice (6a) for introducing the liquid (5) or solid products into the outer tubular element to be entrained by the helical member, and an outlet orifice (7) for delivering a mixture (9) of the liquid and solid products (5, 8) outside the outer tubular element, the inner tubular element (3) having an open end terminating inside the outer tubular element (2) downstream of the inlet orifice (6a) and upstream of the outlet orifice (7), wherein the mixture (9) i

Abstract: Compound concrete composition for the manufacture of moulds, comprising: (1) a binder which comprises an alkaline-earth mineral substance, a constituent made up of fine particles of a compound other than an oxide, 90% of which have a particle size of between 1 and 150 .mu.m with a median diameter of between 3 and 20 .mu.m, these fine particles comprising particles of a substance which has a thermal conductivity higher than approximately 30 W/mK, chosen from silicon carbides, silicon carbonitrides, silicon nitrides, boron carbides, titanium carbides and tungsten carbides and a constituent made up of ultrafine particles at least 70% of which have a particle size smaller than 1 .mu.m with a median diameter of between 0.3 and 0.8 .mu.m, (2) water optionally with the addition of a dispersant, and (3) fillers comprising metal granulates and metal fibres, wherein the water/binder ratio is lower than 0.20 and the concrete composition has a thermal conductivity at 200.degree. C.

Abstract: According to the invention a pozzolan is selected which exhibits a capacity for fixing lime during the Chapelle test at 90.degree. C. greater than 700 mg of CaO per gram of pozzolan, a capacity for fixing lime during the Chapelle test at 50.degree. C. greater than 200 mg of CaO per gram of pozzolan and a ratio of the quantity of CaO fixed during the 50.degree. C. Chapelle test to the specific surface area of the pozzolan which is greater than about 10 mg of CaO per square meter of pozzolan. The composite material obtained is used in construction to produce facade elements, for example, which have improved resistance to aging.

Abstract: A process for producing reinforced cementitious compositions in which the following constituents are mixed in the aqueous phase in the following order: about 35-55 parts by weight of water mixed with about 3-12 parts of a polymer, by weight of dry polymer; up to about 5 parts of a water-reducing auxiliary agent and/or a liquifying agent; from about 15-30 parts of metakaolin; from about 50-120 parts of silica sand; and about 100 parts of cement. Continuous mixing is maintained until a homogeneous, thixotropic paste is obtained. Then between 2 and 15% by weight of alkaline-resistant glass fibers, relative to the weight of the paste, is introduced into the paste. The product produced by this method is particularly suitable for use as a mortar or paste which may be easily sprayed upon vertical surfaces and as hydraulic concretes, resistant to the effects of weather and aging.