Compositions: coating or plastic – Materials or ingredients – Additive materials for inorganic cements which contain a...
Patent
1998-08-10
2000-12-12
Green, Anthony
Compositions: coating or plastic
Materials or ingredients
Additive materials for inorganic cements which contain a...
106 1832, 106727, 106808, 524183, 524185, A01N 5502, C04B 2412, C04B10367
Patent
active
061592811
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a deterioration inhibitor for concrete or mortar which inhibits and/or kills sulfur oxidizing bacteria and to a method of inhibiting the deterioration of concrete or mortar which uses the deterioration inhibitor. More particularly, the present invention relates to a deterioration inhibitor for concrete or mortar and to a method of inhibiting the deterioration of concrete or mortar which are preferably used for concrete or mortar structures in sewerage systems or the like.
BACKGROUND ART
In recent years, deterioration of concrete structures in sewerage systems or the like in Japan has been reported frequently. Deterioration occurs not only in Japan but also in other countries and has been reported in Australia, Egypt, South Africa, the U.S., and the like. Because it costs a large amount of money to build sewerage systems or the like, it is important to take appropriate measures against the deterioration of concrete so as to enable the system effectively to function over a long time.
It is known that the deterioration of concrete is caused by two types of microorganisms, i.e., sulfate reducing bacteria and sulfur oxidizing bacteria such as the genus Thiobacillus or the like. In the process of the deterioration of concrete by these microorganisms, firstly, sulfate in sewage (normally, the concentration of sulfate in sewage is within the range of 20 to 40 mg/l) is reduced by the sulfate reducing bacteria under anaerobic conditions and hydrogen sulfide is thereby generated. Next, the hydrogen sulfide is absorbed by water on the concrete wall surface and is oxidized by sulfur oxidizing bacteria under aerobic conditions. Sulfuric acid is thereby generated. Calcium in the concrete is changed to calcium sulfate (plaster) by the generated sulfuric acid. In this way, the concrete becomes fragile (deteriorates).
Among the aforementioned two types of microorganisms, the sulfur oxidizing bacteria is considered to be the main cause of the deterioration of concrete. Various methods have been proposed for inhibiting the change of hydrogen sulfide to sulfuric acid by the sulfur oxidizing bacteria.
One of these methods is a method of reducing the concentration of hydrogen sulfide which is a substrate for sulfur oxidizing bacteria. For example, methods are known in which air or oxygen is injected into sewage to oxidize hydrogen sulfide before the hydrogen sulfide is absorbed by water on the concrete wall surface, and to suppress the activity of the anaerobic sulfate reducing bacteria so that the generation of hydrogen sulfide is reduced. Among these methods, the method of injecting air into the sewage is a relatively simple method. However, in this method, the injected air may affect the equilibrium between the gas and liquid of the hydrogen sulfide such that the amount of hydrogen sulfide diffused in the air is larger than that in a case in which air is not injected. Further, hydrogen sulfide can be oxidized more effectively in the method of injecting oxygen into the sewage than in the method of injecting air. However, there is a drawback in that the cost of the method is high.
Another inhibiting method is a method of adding a large amount of chlorine, hydrogen peroxide, potassium permanganate, or a metallic salt whose metal is iron, zinc, lead, copper, or the like into sewage so that the hydrogen sulfide within the sewage bonds therewith. Further, Japanese Patent Application Laid-Open (JP-A) No. 7-70561 discloses a method of inhibiting the deterioration of concrete in which a water-soluble quinone derivative is added into sewage to oxidize hydrogen sulfide and to suppress the activity of the anaerobic sulfate reducing bacteria. However, since the material added into the sewage disappears as it flows, these methods are not effective and are expensive.
Moreover, a method of inhibiting the deterioration of concrete is known in which sulfur oxidizing bacteria is killed by mixing an antibacterial agent, which is an organic compound, with concrete. However, the antibacterial ag
REFERENCES:
patent: 5435846 (1995-07-01), Tatematsu et al.
Enokida Toshio
Tamano Michiko
Tanaka Reiko
Uchida Hiromi
Green Anthony
Toyo Ink Manufacturing Co. Ltd.
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