Nissan Chemical Industries Limited

Takahiro Hori

Masamichi Obitsu

Yuriko Sakaguchi

Yuji Nakamura

Toyoji Koinuma

Makoto Takakura

Akio Kitagawa

A hardened cement-based mass having a corrosive metallic material embedded therein, or containing an aggregate reactive with an alkaline substance, is impregnated with an aqueous solution containing 1 to 50% by weight of a dissolved nitrite of an alkali metal or alkaline earth metal and 0.01 to 20% by weight of a dissolved organic silicon compound such as sodium methylsiliconate or potassium methylsiconate, or a dissolved or emulsified polymer thereof, or with a solution prepared by using an aliphatic alcohol having 1 to 3 carbon atoms, and containing 1 to 50% by weight of a dissolved nitrite of an alkali metal or alkaline earth metal and 0.01 to 20% by weight of an dissolved organic silicon compound such as methyltrimethoxysilane or ethyltrimethoxysilane, or a dissolved polymer thereof, and is allowed to dry in the air. Alternatively, the mass is coated with an unsolidified cement paste, mortar or concrete containing 1 to 25% by weight of a nitrite of an alkali metal or alkaline earth metal and 0.01 to 20% by weight of an organic silicon compound such as sodium or potassium methylsiliconate, or a polymer thereof, based on the weight of the cement which, e.g., the cement paste contains, and, e.g., the cement paste is allowed to harden in the air.

Method of preventing the deterioration of a hardened cement-based mass

The invention is a method for preventing a hardened cementitious material from deteriorating or for repairing a deteriorated cementitious material, and more particularly to such method for the hardened cementitious material comprising metal materials to be corroded by a salt content and cause alkali-aggregate. It is characterized by applying a cement paste, mortar or concrete added with 1-25 weight % lithium nitride relative to the cement content so as to cover the surface of hardened cementitious material.

Method for preventing hardened cementitious material from deteriorating

An aqueous solution of 1-30 weight % alkali metal silicate and 0.005-10 weight % nitrite is stable and well permeable into hardened cementitious material. When applying said aqueous solution on the surface of hardened cementitious structure having metallic armatures embedded therein, it is possible not only to form surface layer improved in compactness, strength, hardness, waterproofing and weathering for preventing deterioration thereof and repair deteriorated cementitious material but also to prevent said metallic armatures from rusting.

An agent and method for modifying a surface layer of hardened cement structures or substrates with use of the agent which comprises in a specified ratio of an alkali silicate solution and a sodium naphthalenesulfonate-formaldehyde condensate. Said agent has an excellent stability and a remarkable permeability into the cement structure to form a deeper strengthened surface layer thereon.

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Funabashi, Japan

Takahiro Hori