JPH059760A - Reinforcing bar inhibiting formation of rust - Google Patents

Abstract

PURPOSE:To inhibit the formation of rust on reinforcing bars without deteriorating the adhesive property of the bars to concrete because the bars are liable to rust under the influence of rain water and underground water over a long period of time during and after construction and lower the strength of a building with the lapse of time. CONSTITUTION:Reinforcing bars are coated with resin based on epoxy resin and then aminosilane, epoxysilane or isocyanatosilane is applied to the coated bars to obtain reinforcing bars considerably inhibiting the formation of rust and not deteriorating adhesive property to concrete.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Reinforcing bars have been widely used as core materials for all reinforced concrete structures, and concrete itself exerts compressive strength and bending strength, as well as its tensile strength. It is well known that they are responsible. However, as its name implies, it is a material containing iron as its main component, so it easily rusts significantly during construction due to water such as rainwater, groundwater, or dew condensation, and even after being embedded in a concrete skeleton for a long time. Over the course of the gradual neutralization of the concrete frame, rust is generated at the same time, causing not only the decrease in the tensile strength of itself but also the peeling and cracking of the concrete. Due to the acid rain in question,
It is feared that it will be further promoted. In view of such a current situation, the present invention provides a reinforcing bar that is inexpensive and effectively suppresses rusting.

[0002]

2. Description of the Related Art Reinforcing bars are traditionally said to be extremely rusty, and their use and construction are mainly due to the process management, such as quick concrete injection work when the weather is fine. However, in large buildings such as bridges, every time it rains, emergency measures such as covering the exposed structure of the reinforcing bars with sheets are also being implemented. After the construction is completed, the reinforcing bars are covered with concrete that is strongly alkaline, so rust does not progress for the time being and can remain stable, but concrete does not have carbon dioxide gas in the air or acid rain as described above. The rust gradually progresses because it is gradually neutralized by the action of. To prevent such a phenomenon,
Reinforcing bars coated with various synthetic resins have been devised. In particular, epoxy resin has good adhesiveness to metals, effectively prevents rust, has moderate flexibility, and exhibits chemical stability to withstand the strong alkali of concrete. It is also being done. However, since these organic resins including epoxy resin generally have poor adhesion to concrete, the adhesion of coated reinforced concrete to concrete is poor, and when the original strength of reinforced concrete cannot be obtained, or when the covering thickness is large. In thin parts, concrete may come off from the skeleton.

[0003]

Under the circumstances described above, the appearance of a reinforcing bar which is covered with an organic resin to suppress the generation of rust and which can be well bonded to concrete has been awaited.

[0004]

Means for Solving the Problems The inventors of the present invention applied a silane coupling agent of a certain kind to a reinforcing bar coated with an epoxy resin and dried it to obtain an anticorrosive effect and an adhesive property to concrete. The present invention has been found to be significantly improved, and the present invention has been achieved. The configuration of the present invention will be described in detail below. For details of the quality of the reinforcing steel to be used for reinforcing the concrete frame as a steel material, see JIS G3101 and JIS G31.
07, JISG3110, JISG3112, JISG
3117, JISG3521, or JISG353
2 and the quality of the reinforcing bars constituting the present invention shall comply with this. Although the size and shape are not particularly specified, in general, bar steel and deformed round steel, which are already described in the above JIS standard, are widely spread,
The diameter is 9 to 28 when the cross section is considered to be a perfect circle.
The range of mm is suitable in terms of ease of handling and strength. As the resin that should cover the rebar, it has adequate adhesion to the rebar, moderate flexibility that can withstand light bending, chemical stability that can withstand a concrete atmosphere that is a strong alkali, and above all, the effect of preventing rust from the rebar. An epoxy resin is used exclusively because it satisfies all of these conditions and is reasonably priced. There are many types of epoxy resins, such as phenol novolac type, EPbis type, etc. Furthermore, they are classified into cross-linking reaction curing type and lacquer type depending on the difference in the film formation process.
Any epoxy resin can be selected as long as it does not impair the properties matching the above-mentioned conditions such as the adhesiveness with the reinforcing bar. Especially, when the EP-bis type epoxy resin having a number average molecular weight of 1,000 to 7,000 is combined with a curing agent, the best properties are exhibited. Examples of the curing agent include aminoplast, polyisocyanate, blocked polyisocyanate, polybasic acid, polybasic acid anhydride, polyacid base, amino group-containing silane coupling agent, and the like.
When any of aminoplast, blocked polyisocyanate, polybasic acid, and polybasic acid anhydride is used as the curing agent, heating is required for crosslinking and curing, but polyisocyanate, polyacid group, amino group When any of the contained silane coupling agents is used, crosslinking and curing can be performed even at room temperature. If the amount of the curing agent added is too small, a sufficiently cured film may not be obtained, but if it is too large, the film will become brittle, and the epoxy resin will have good adhesiveness and rust to the reinforcing bars originally possessed by the epoxy resin. It is also possible that the effect of preventing Therefore, the addition amount of these curing agents is 100% epoxy resin.
5 to 50 parts by weight relative to parts by weight, especially 10
A range of up to 35 parts by weight is preferred. In addition to the above epoxy resin and curing agent, pigments, defoaming agents, surface smoothing agents, thickening agents, curing accelerating catalysts and the like can be added as needed. It is preferable to add well-known and commonly used anticorrosion pigments such as red, lead chromate, zinc chromate, and zinc phosphomolybdate from the viewpoint of suppressing rusting of the reinforcing bar, and the addition amount is 0 with respect to 100 parts by weight of the epoxy resin. The range of 30 to 30 parts by weight is suitable, and the range of 3 to 15 parts by weight is more preferable. Then, the mixture containing the epoxy resin as a main component is subjected to powder coating or a solution having a non-volatile content of 5 to 70% by weight with an organic solvent, and then spray coating or dipping, or by a known conventional coating method such as a flow coater. After being applied to the reinforcing bars, it is formed into a film to cover the reinforcing bars by appropriately drying at room temperature or by heating and drying. When a water-soluble or emulsion type epoxy resin is used, water is used as a diluting solvent. The film thickness is 5 to 200 microns, especially 10 to 15
A range of 0 micron is suitable. Next, a silane coupling agent is applied to the reinforcing bar coated with the epoxy resin and dried, but as the silane coupling agent to be provided,
One or a mixture thereof selected from epoxysilane, aminosilane and isocyanatesilane. However, when aminosilane and isocyanatesilane are mixed, they react instantaneously, so it is impossible to mix both. The epoxysilane may be a compound having an epoxy ring at one end of the molecule and an alkoxysilyl group at the other end, and examples thereof include 3-glycidoxypropyltrimethoxysilane and 3.4-glykydoxycyclohexyltrimethylsilane. Etc. The aminosilane may be a compound having an amino group, preferably an aliphatic amino group, at one end of the molecule and an alkoxysilyl group at the other end, and examples thereof include 3-aminopropyltriethoxysilane and N.
Examples include-(2-aminoethyl) -3-aminopropyltrimethoxysilane. Isocyanate silane is
A compound having an isocyanate group at one end of the molecule and an alkoxysilyl group at the other end may be used, and examples thereof include 3-
Isocyanate propyl trimethoxy silane, 3-isocyanate propyl trimethoxy silane, etc. are mentioned. When these silane coupling agents are used as they are or after they are appropriately diluted with an organic solvent and applied on a reinforcing bar coated with an epoxy resin, and dried and fixed, a reinforcing bar according to the present invention can be obtained. The coating amount of the silane coupling agent may be very small, 20 mg / m on the surface of the reinforcing bar in terms of silicon atoms.
^{If two} or more are attached, the expected effect can be obtained.

[0005]

[Effect] Epoxy resin forms a strong hydrogen bond with the hydroxyl group on the iron surface, and since there is little shrinkage during curing film formation, this is a cause of good adhesion to iron and the effect of preventing rust. However, the surface after curing is hydrophobic and has a marked lack of affinity with hydrophilic concrete. Therefore, it is considered that adding a silane coupling agent to increase the affinity with the concrete is effective for increasing the adhesiveness with the concrete. Conventionally, various attempts have been made to add a silane coupling agent to an epoxy resin, but in this case, the silane coupling agent tends to be easily adsorbed by the iron surface, and the concrete on the surface after the epoxy resin has hardened. It had almost no effect on the affinity with. Even immediately after curing of the epoxy resin, since many unreacted functional groups due to the epoxy resin and the curing agent such as chrysidyl group, hydroxyl group, amino group, and isocyanate group are left, these unreacted functional groups and the surface By applying a silane coupling agent capable of chemically bonding with and fixing it, and by orienting an alkoxysilyl group having a high affinity for concrete on the surface, the affinity of the epoxy resin film surface with concrete can be remarkably enhanced.

[0006]

[Examples] 100 g of an epoxy resin "Epicoat 1004" (produced by Shell Co., Netherlands) is used as a curing agent as an aminoplast, that is, "Simel 370" (product of Mitsui Toatsu Chemicals, Inc.) which is methyl etherified methylol melamine. At the same time, it was dissolved in a solvent composed mainly of toluene and methyl cellosolve to obtain a mixture having a nonvolatile content of 50% by weight. Small round steel for reinforcing bars (standard SD30A nominal diameter D10)
This mixture was applied to and dried at 160 ° C. for 30 seconds to obtain an epoxy resin-coated rebar. Next, isocyanate silane, ie, 3-isocyanatepropyltrimethoxysilane "KBM9001" (produced by Shin-Etsu Chemical Co., Ltd.) was made into a 5% solution with a solvent mainly containing xylene, and then applied to the above epoxy resin-coated reinforcing bars. It was dried with warm air to obtain the reinforcing bar of the example. The surface silicon concentration of this product was about 40 mg / m ² . Separately, uncoated small round steel for reinforcing bars and reinforcing bars which were not further processed at the stage of coating with epoxy resin were prepared, and the former was Comparative Example 1 and the latter was Comparative Example 2. The above-mentioned Example, Comparative Example 1,
When the three members of Comparative Example 2 were simultaneously subjected to an adhesion test with concrete and a corrosion resistance test under a salt water atmosphere, the Example showed the same adhesiveness with Concrete as Comparative Example 1,
In addition, it exhibited a good rust inhibiting effect, which is slightly superior to that of Comparative Example 2. Incidentally, in the adhesion test, Comparative Example 2 showed no adhesion to concrete at all, and in the corrosion resistance test in a salt water atmosphere, only Comparative Example 1 showed rapid and easy rusting.

[0007]

INDUSTRIAL APPLICABILITY According to the present invention, since it is possible to provide a reinforcing bar which suppresses rust generation at a relatively low cost and without causing a decrease in adhesion with a concrete skeleton as in the conventional method, the strength of a reinforced concrete structure can be provided. It is considered that the life of the reinforced concrete structure can be effectively extended and the deterioration of the reinforced concrete structure can be effectively prevented with the progress of neutralization of concrete due to acid rain or the like. Moreover, it is considered that the work can be carried out even under rainy weather without considering rusting, which contributes to a significant rationalization of the process.

Claims (2)

[Claims] 1. A reinforcing bar characterized in that the surface is first coated with a resin containing an epoxy resin as a main component, and then a silane coupling agent is applied and dried and fixed. 2. The reinforcing bar according to claim 1, wherein one kind or a mixture thereof selected from aminosilane, epoxysilane and isocyanatesilane is used as the silane coupling agent.