Alumina-modified colloidal silica nanoparticles mitigate Alkali Silica Reaction (ASR) in cementitious compositions. Additives containing the nanoparticles are used in methods of reducing ASR in concrete and to form cementitious compositions. Cementitious products, such as concrete, made by these methods are described herein.

To provide a means capable of suppressing the generation of gelation at the time of or after the addition of a silane coupling agent in the production of a cationically modified silica including modifying a silica raw material with a silane coupling agent. The present invention is a method for producing a cationically modified silica, including: mixing a silica raw material having a negative zeta potential with a silane coupling agent having an amino group or a quaternary cationic group; and reacting the silica raw material with the silane coupling agent to obtain a cationically modified silica, in which the cationically modified silica satisfies the following relational expression (1):
X<Yrelational expression (1) in the relational expression (1), X is a pH value at which an isoelectric point is shown in the cationically modified silica, and Y is a pH value of the cationically modified silica.

To provide a means capable of suppressing the generation of gelation at the time of or after the addition of a silane coupling agent in the production of a cationically modified silica including modifying a silica raw material with a silane coupling agent. The present invention is a method for producing a cationically modified silica, including: mixing a silica raw material having a negative zeta potential with a silane coupling agent having an amino group or a quaternary cationic group; and reacting the silica raw material with the silane coupling agent to obtain a cationically modified silica, in which the cationically modified silica satisfies the following relational expression (1):
X<Yrelational expression (1) in the relational expression (1), X is a pH value at which an isoelectric point is shown in the cationically modified silica, and Y is a pH value of the cationically modified silica.

The present invention relates to a method of preparing an aerogel blanket in which, a surface of a base material for a blanket is activated and roughness and porosity of the surface of the base material for a blanket are increased to increase adhesion performance of a silica aerogel by inducing etching of a surface of a base material for a blanket using an acidic solution, and mechanical flexibility is increased and the generation of dust is minimized by further performing a gel deformation process of introducing cracks into the aerogel, and a low-dust and high-insulation aerogel blanket prepared according to the present invention.

The present invention relates to a method of preparing an aerogel blanket in which, a surface of a base material for a blanket is activated and roughness and porosity of the surface of the base material for a blanket are increased to increase adhesion performance of a silica aerogel by inducing etching of a surface of a base material for a blanket using an acidic solution, and mechanical flexibility is increased and the generation of dust is minimized by further performing a gel deformation process of introducing cracks into the aerogel, and a low-dust and high-insulation aerogel blanket prepared according to the present invention.

A gas separation membrane containing a matrix resin and hyperbranched polymer- or dendrimer-bound, heteromorphous shaped silica nanoparticles, which are formed of heteromorphous shaped silica nanoparticles having surfaces onto which a hyperbranched polymer or a dendrimer is chemically added.

A gas separation membrane containing a matrix resin and hyperbranched polymer- or dendrimer-bound, heteromorphous shaped silica nanoparticles, which are formed of heteromorphous shaped silica nanoparticles having surfaces onto which a hyperbranched polymer or a dendrimer is chemically added.

A process for producing a charge-reversed aqueous silica sol includes: (a) providing a slurry of an acidic cation-exchange solid in an aqueous liquid; (b) providing a starting aqueous silica sol with an alkaline pH and including a monovalent cation(s); (c) contacting the slurry with the starting sol; (d) separating the acidic cation-exchange solid from the mixture (c) to leave a decationised aqueous silica sol with an acidic pH and a reduced monovalent cation(s) content compared to the starting sol; and (e) contacting the decationised sol with a compound(s) including a modifying element(s) that can adopt a +3 or +4 oxidation state to produce a charge-reversed aqueous silica sol whose silica particles include the modifying element(s) on their surface. The S-value of the starting sol is from about 10 to about 50%, and the surface area of colloidal silica particles in the starting sol is at least about 500 m.sup.2 g.sup.1.

A process for producing a charge-reversed aqueous silica sol includes: (a) providing a slurry of an acidic cation-exchange solid in an aqueous liquid; (b) providing a starting aqueous silica sol with an alkaline pH and including a monovalent cation(s); (c) contacting the slurry with the starting sol; (d) separating the acidic cation-exchange solid from the mixture (c) to leave a decationised aqueous silica sol with an acidic pH and a reduced monovalent cation(s) content compared to the starting sol; and (e) contacting the decationised sol with a compound(s) including a modifying element(s) that can adopt a +3 or +4 oxidation state to produce a charge-reversed aqueous silica sol whose silica particles include the modifying element(s) on their surface. The S-value of the starting sol is from about 10 to about 50%, and the surface area of colloidal silica particles in the starting sol is at least about 500 m.sup.2 g.sup.1.

There is provided a production method of a chain silica particle dispersion. This production method includes a dispersion preparation step of hydrolyzing alkoxysilane in the presence of ammonia to prepare a silica particle dispersion, an ammonia removal step of removing the ammonia from the silica particle dispersion such that an ammonia amount relative to silica contained in the silica particle dispersion is 0.3% by mass or less, and a hydrothermal treatment step of hydrothermally treating the silica particle dispersion having a silica concentration of 12% by mass or more, from which the ammonia has been removed, at a temperature of not lower than 150 C. and lower than 250 C. An abrasive including such chain silica particles is high in polishing rate and excellent in polishing properties.