Plastic and nonmetallic article shaping or treating: processes – Forming stressed concrete articles
Reexamination Certificate
2000-04-25
2002-05-14
Dawson, Robert (Department: 1712)
Plastic and nonmetallic article shaping or treating: processes
Forming stressed concrete articles
C428S418000, C523S454000, C523S455000, C523S456000, C528S091000, C528S093000
Reexamination Certificate
active
06387310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermosetting resin composition for prestressed concrete tendon used for anti-rust and anti-corrosion of a tendon that is used in a post-tension technique of a prestressed concrete, the composition being used also for integral bonding of the tendon and concrete, and the invention also relates to a use method thereof and a prestressed concrete tendon using the composition.
2. Description of the Related Art
A post-tension technique of a prestressed concrete is a technique in which prior to pouring a concrete, a metal- or resin-made sheath having inserted therein a tendon such as PC steel material (PC steel wire, PC steel twisted wire, PC steel rod or the like) is arranged for reinforcement in a concrete form, a concrete is poured into the concrete form, the tendon is strained after the concrete is set, and a cement milk or the like is poured into a space between the sheath and the tendon for the purpose of anti-rust and anti-corrosion of the tendon and also adhesion and integral bonding of the tendon and concrete.
However, in this conventional technique, works of inserting the tendon in the sheath and pouring a cement milk are complicated works and require much time and labor. Further, because a space between the tendon and the sheath is very narrow, filling the space with the concrete milk tends to be incomplete. Japanese Patent Application Laid-Open No. Sho 64-31873 proposes a technique of previously filling a curable composition in a space between a sheath and a tendon. Since in this technique, a curable composition is previously filled in a space between a sheath and a tendon, the space between the sheath and the tendon is completely filled. As a result, improvement in reliability and labor saving in a work site can be achieved.
However, it has been found that there is the following disadvantage in a large-sized concrete structure. Heat of hydration reaction generated in solidifying a concrete accumulates in the structure and a certain portion may reach a high temperature of 80° C. or higher. As a result, if a tendon is arranged for reinforcement in the large-sized structure by applying the above conventional technique, the curable composition filling the space between the sheath and the tendon hardens during the period between a period that a temperature exceeding 80° C. is maintained and a period of the subsequent natural cooling. Then when trying to strain the tendon, it is no longer possible to strain the tendon. Furthermore, it was found that the degree of accumulation of heat of hydration reaction generated in solidifying a concrete differs, and the peripheral temperatures of the tendon differ depending on the place, because the concrete structure in which the tendon is arranged, has a non-uniform thickness and the tendon hangs down when the concrete structure in which tendon is arranged, is long in size.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a thermosetting resin composition for prestressed concrete tendon, having the desired performances such that, even if a heat storage temperature in the concrete structure elevates from 30 to 85° C. or higher, particularly a temperature reaching 95° C., due to heat of hydration reaction in setting a concrete and this temperature is maintained until the completion of the reaction, the composition does not harden thereby being capable of straining the tendons after setting the concrete, and the composition including the site of 30° C. or lower where there is substantially no partial heat storage due to heat of hydration reaction in solidifying the concrete, hardens after the passage of the prescribed time under spontaneous environmental temperature after the subsequent natural cooling, thereby achieving anti-rust and anti-corrosion of the tendons and also adhesion and integral bonding of the tendons and the concrete.
A second object of the present invention is to provide a use method of the thermosetting resin composition for prestressed concrete tendon, which can obtain a prestressed concrete structure having a desired performance by a post-tension technique using the thermosetting resin composition for prestressed concrete tendon.
A third object of the present invention is to provide a prestressed concrete tendon which is effective to obtain a concrete structure having the desired performances such that the composition does not harden, even if a heat storage temperature in the concrete structure elevates from 30 to 85° C. or higher, particularly a temperature reaching 95° C., due to heat of hydration reaction in setting a concrete and this temperature is maintained until the completion of the reaction, the composition does not harden thereby being capable of straining the tendons after setting the concrete, and the composition including the site of 30° C. or lower where there is substantially no partial heat storage due to heat of hydration reaction in solidifying the concrete, hardens after the passage of the prescribed time under spontaneous environmental temperature after the subsequent natural cooling, thereby achieving anti-rust and anti-corrosion of the tendons and also adhesion and integral bonding of the tendons and the concrete by using the thermosetting resin composition for prestressed concrete tendon.
According to the present invention, there is provided a thermosetting resin composition for prestressed concrete tendon, comprising an epoxy resin, a latent hardener and a hardening accelerating diluent, the composition characterized by being previously heat treated at a temperature of 40 to 140° C. The present invention further provides a use method of the thermosetting resin composition for prestressed concrete tendon, characterized in that the time of from pouring of concrete to straining of the tendon is 7 days or longer and the time of from pouring of concrete to hardening of the thermosetting resin composition is within 350 days.
Further, according to the present invention, there is provided the use method of the thermosetting resin composition for prestressed concrete tendon, characterized in that a maximum heat storage temperature due to hydration reaction of concrete is 80° C. or higher, particularly 80 to 95° C.
The present invention also provides a prestressed concrete tendon using the thermosetting resin composition for prestressed concrete tendon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is described in detail below regarding a thermosetting resin composition for prestressed concrete tendon (hereinafter referred to as a “composition of the present invention”), its use method and a prestressed concrete tendon using the composition of the present invention.
The composition of the present invention comprises an epoxy resin, a latent hardener and a hardening accelerating diluent as the essential components.
The epoxy resin which is one of the essential components in the composition of the present invention is a liquid resin having two or more epoxy groups in one molecule. Examples of the epoxy resin include polyglycidylated-products of polyhydric phenols such as 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl) ethane, bis(4-hydroxyphenyl)methane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, hydroquinone and resorcin.
The epoxy resin is preferably a resin purified such that a hydrolyzable chlorine content therein is reduced to less than 0.07% by weight, preferably 0.05% by weight, and particularly preferably 0.03% by weight. In the present invention, if the latent hardener described hereinafter is reacted with chlorine, hardening time prolongs. Therefore, it is advantageous that the content of the hydrolyzable chlorine is smaller.
Besides the epoxy resins listed above, other epoxy resins can be used in the composition of the present invention for the purpose of, for example, controlling a viscosity of the composition. Examples of the other epoxy resin that can be used include polyglycidylated products of polyhydric alcohols such as ethylen
Hirata Seiichiro
Iizuka Hiroshi
Kobayashi Toshio
Ohnisi Mutsuhiko
Ahlward D.
Birch & Stewart Kolasch & Birch, LLP
Dawson Robert
Mitsui Chemicals Inc.
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