Abstract: This invention relates to an aqueous suspension including a mixture of at least one aqueous suspension of precipitated silica and of at least one latex, in which the said aqueous suspension of precipitated silica has a solids content of between 10 and 40% by weight, has a viscosity lower than 4×10−2 Pa s at a shear of 50 s−1 and, after centrifuging at 7500 revolutions per minute for 30 minutes, produces a supernatant containing more than 50% of the weight of the silica initially in suspension.

Abstract: The present invention relates to an aqueous suspension comprising: A) silica and/or alumina particles, and B) a compound of overall formula (I): Al(OH)a(SO4)b(SiOx)c(Y)d  (I)  with: a between 0.1 and 2, b between 0.3 and 1.5, c between 0 and 0.1, d greater than 0.05, Y chosen from alkali metals and alkaline earth metals, x between 2 and 4, and its derivatives, the said compound (B) being present in the suspension at a concentration of at least 1.65 mol/l, expressed as moles of aluminium issued from the said compound. Another subject-matter of the invention is a process useful for the preparation of the said suspension and its use in the field of cement pastes, mortars and concretes and in particular as setting and hardening accelerating agent for cements.

Abstract: An aqueous suspension is provided including a mixture of at least one aqueous suspension of precipitated silica and of at least one latex, in which the aqueous suspension of precipitated silica has a solids content of between 10 and 40% by weight, has a viscosity lower than 4×10−2 Pa s at a shear of 50 s−1 and, after centrifuging at 7500 revolutions per minute for 30 minutes, produces a supernatant containing more than 50% of the weight of the silica initially in suspension. This suspension can be employed in compositions based on an inorganic binder and in concrete compositions.

Abstract: This invention relates to an aqueous suspension including a mixture of at least one aqueous suspension of precipitated silica and of at least one latex, in which the said aqueous suspension of precipitated silica has a solids content of between 10 and 40% by weight, has a viscosity lower than 4×10−2 Pa s at a shear of 50 s−1 and, after centrifuging at 7500 revolutions per minute for 30 minutes, produces a supernatant containing more than 50% of the weight of the silica initially in suspension.

Abstract: Silicas in the form of powder and substantially spherical beads or granules are characterized by a CTAB specific surface of 140 and 240 m2/g a high ultrasonic disaggregation factor, an average diameter, which is small after ultrasonic disaggregation, and optionally, a porous distribution, the porous volume formed by the pores with a diameter of 175 to 275 Å being less than 50% of the porous volume formed by the pores with diameters of 400 Å or less. The silicas may be used as reinforcing fillers for elastomers.

Abstract: A mechanically strong, vulcanized elastomeric matrix having an effective amount of a reinforcing filler material homogeneously dispersed and distributed therethrough, the reinforcing filler material comprising finely divided precipitated silica particulates and the precipitated silica particulates deriving from a powder having a CTAB specific surface ranging from 100 to 140 m2/g, a median diameter &phgr;50, after ultrasonic disintegration, less than 2.8 &mgr;m, exhibiting an ultrasonic disintegration factor FD greater than 3 ml, having a BET specific surface ranging from 100 to 200 m2/g, having a mean particle size greater than 15 &mgr;m, a packing density in the tamped state of at least 0.17, and a DOP oil uptake ranging from 150 to 400 ml/100 g.

Abstract: Silicas in the form of powder and substantially spherical beads or granules are characterized by a CTAB specific surface of 140 and 240 m2/g a high ultrasonic disaggregation factor, an average diameter, which is small after ultrasonic disaggregation, and optionally, a porous distribution, the porous volume formed by the pores with a diameter of 175 to 275 Å being less than 50% of the porous volume formed by the pores with diameters of 400 Å or less. The silicas may be used as reinforcing fillers for elastomers.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a BET specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a zinc content of between 1 and 5% by weight, and by the fact that the number N of stearic acid molecules consumed per nm.sup.2 of silica surface, when stearic acid is reacted with this silica in xylene for 2 hours at 120.degree. C., is at least 1. The invention also relates to the use of the said silicas as reinforcing fillers for elastomers, especially for improving their rheological properties.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a pore distribution such that the pore volume consisting of the pores whose diameter is between 175 and 275 .ANG. represents less than 50% of the pore volume consisting of the pores of diameters smaller than or equal to 400 .ANG., a zinc content of between 1 and 5% by weight and by the fact that the number N of molecules of stearic acid consumed per nm.sup.2 of silica surface, when stearic acid is reacted with the said silica in xylene for 2 hours at 120.degree. C., is at least 1.

Abstract: The invention relates to aqueous suspensions of precipitated silica and of aluminum sulphate which have a pH lower than 4 and a solids content of between 10 and 50% by weight and which, after a period at rest of 48 hours, are in the form of a gel. The gel is reversible under low shear. The invention also relates to processes for the preparation of these suspensions and to their uses, especially in the field of cement mixes, mortars and concretes.

Abstract: Precipitated silica particulates suited for homogeneous incorporation, dispersion and distribution within vulcanized elastomeric matrices reinforced therewith can be formed as either a powder, substantially spherical beads, or granulates. The silica particulates have a CTAB specific surface ranging from 100 to 140 m.sup.2 /g, a median diameter .phi..sub.50, after ultrasonic disintegration, less than 2.8 .mu.m, an ultrasonic disintegration factor F.sub.D greater than 3 ml, a BET specific surface ranging from 100 to 200 m.sup.2 /g, a mean particle size greater than 15 .mu.m when formed as a powder, at least 80 .mu.m when formed a s substantially spherical beads, and at least 1 mm when formed as a granulate, a packing density in the tamped state of at least 0.17, and a DOP oil uptake ranging from 150 to 400 ml/100 g.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a BET specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a zinc content of between 1 and 5% by weight, and by the fact that the number N of stearic acid molecules consumed per nm.sup.2 of silica surface, when stearic acid is reacted with this silica in xylene for 2 hours at 120.degree. C., is at least 1. The invention also relates to the use of the said silicas as reinforcing fillers for elastomers, especially for improving their rheological properties.

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: Novel silicas in the form of powder and spherical beads or granules. The silicas are characterized by having a specific CTAB surface of 100-140 m.sup.2 /g, a small median diameter, following disaggregation by ultrasound means, and optionally, a porous distribution so that the porous volume occupied by the pores whose diameter is 175-275 .ANG. is less than 55% of the porous volume occupied by the pores having diameters of 400 .ANG. or less. The invention also concerns a method for the preparation of said silicas and their use as reinforcing fillers for elastomers.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a pore distribution such that the pore volume consisting of the pores whose diameter is between 175 and 275 .ANG. represents less than 50% of the pore volume consisting of the pores of diameters smaller than or equal to 400 .ANG., a zinc content of between 1 and 5% by weight and by the fact that the number N of molecules of stearic acid consumed per nm.sup.2 of silica surface, when stearic acid is reacted with the said silica in xylene for 2 hours at 120.degree. C., is at least 1.

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: The invention concerns a process and apparatus for electrochemical measurement of the concentration of oxide ions dissolved in a bath based on molten halides. The process is based on impedance measurement at a low current and a low overvoltage, between an indicator electrode, a reference electrode and a counter electrodes. The real value Z.sub.r of the impedance is determined for two frequencies, a low frequency Zr(B) (such as 15-25 Hz) and a high frequency Zr(H) (such as 10-100 kHz); the inverse of the concentration of oxide ions is a linear function of the difference between Zr(B) and Zr(H). This method has a high level of accuracy in the low ranges of concentration of oxide ions.