JP4381357B2 - Method for increasing the adhesion of steel - Google Patents

Description

 The present invention relates to a method for improving the adhesion characteristics between a steel material such as a reinforcing bar, a steel frame, and an anchor member of a concrete structure and concrete.

  In a concrete structure such as reinforced concrete or steel reinforced concrete, a method of providing irregularities on the surface of the steel material is generally used in order to enhance the adhesion characteristics of the steel material such as the reinforcing steel, the steel frame, and the anchor member.

Further, for example, as shown in Patent Document 1, a technique is also disclosed in which a polymer cement layer is formed between a reinforcing bar surface and concrete, and the adhesion characteristics of the reinforcing bar and concrete are improved by the effect of the polymer cement layer. .
When a tensile force acts on the reinforcing bar, the force is transmitted to the polymer cement layer 4 shown in FIG. 4 due to the adhesion force and the like, and further, the force is transmitted to the concrete 3 due to shear deformation and compression deformation generated in the polymer cement layer 4. Is done. At this time, since the interface between the polymer cement layer 4 and the concrete 3 has an uneven shape as a whole, the tensile force is transmitted to the concrete 3 on average (see, for example, Patent Document 1). .

In addition, a technique is also disclosed in which an adhesive layer such as a water-reactive epoxy resin, an ethylene sac resin, or a rubber latex polymer mortar is provided on the surface of the reinforcing bar, and the adhesion performance is enhanced by the interposition of the adhesive layer (for example, Patent Documents). 2).
JP-A-10-152940 JP-A 64-090366

  However, in the method of interposing the polymer cement layer and the adhesive layer described in Patent Documents 1 and 2, when a tensile force acts on the reinforcing bar, the friction force at the interface between each layer and the reinforcing bar and the interface between each layer and the concrete Stress is transmitted from the reinforcing bars to the concrete. Therefore, it can be said that the adhesive force between the concrete and the reinforcing bar depends on the frictional force at both interfaces. Since the area of the interface cannot be enlarged so much, there is a limit to increasing the adhesion strength between the reinforcing steel and the concrete by increasing the frictional force.

  Then, this invention makes it a subject to further raise the adhesion strength of the steel material surface and concrete.

In order to solve the above-described problems, the present invention arranges an additive having the performance of making concrete dense around a steel material embedded in a concrete structure, and casts the concrete around the additive. The concrete around the steel material was made solid, and the adhesion performance between the concrete and the steel material was enhanced by the solidification.
If it does in this way, the concrete around steel materials will become solid by the effect of an additive, and the surrounding concrete will become easy to adhere to steel materials integrally. For this reason, the adhesion strength between the concrete and the steel surface can be increased. Here, being solid means that the additive and the unreacted calcium in the concrete are bonded and hardened by the pozzolanic effect. This effect improves the adhesion performance between the steel material and the concrete.

  As the additive, silica fume, blast furnace slag, fly ash, ceramic powder such as alumina, or glass powder can be employed.

  Further, short fibers of inorganic or organic material may be disposed around the steel material instead of the additive, and concrete may be placed around the steel material. Inorganic or organic short fibers arranged around the steel material can make the concrete dense, and can exert the same effect as the additive.

  In the present invention, since the concrete around the steel material is made dense, the adhesion strength between the steel material surface and the concrete can be increased.

  One embodiment is described below. FIG. 1 shows the surface of a deformed reinforcing bar 1 provided with knots 2 at a predetermined interval, by applying an additive 5 that increases the adhesion performance between the concrete and the deformed reinforcing bar 1 by making the concrete dense. This shows a state in which concrete is laid.

In this embodiment, a siliceous admixture is used as the additive 5. The siliceous admixture is effective in improving the strength, erosion resistance, and water tightness by mixing siliceous materials such as blast furnace slag and fly ash. This utilizes the reactivity (pozzolanicity) with calcium hydroxide generated by the hydration reaction of cement.
In addition to this, for example, silica fume, blast furnace slag, fly ash, ceramic powder such as alumina, or glass powder can be used as the additive 5. In the case of using any additive 5, the effect of the additive 5 can make the concrete 3 dense and exert an effect of enhancing the adhesion between the deformed reinforcing bar 1 and the concrete 3. If the adhesion between the deformed reinforcing bar 1 and the concrete 3 is increased, it is possible to prevent cracks generated in the concrete structure or to improve the proof stress of the structure.
Further, according to the above method, it is not necessary to knead the additive so that the additive spreads over the entire concrete as in the conventional case, so that the effect of enhancing the adhesion force can be exhibited with a very small amount.
Note that when the additive 5 is disposed, an adhesive layer or the like as in the conventional example may be provided so that the additive 5 is easily fixed around the deformed reinforcing bar 1. In the case of providing an adhesive layer or the like, for example, when the additive 5 is a powder, the surface of the particles of the powder may be coated with an adhesive, or a water-soluble adhesive may be applied to the steel surface. After thinly applying, an additive may be arranged directly around the steel material. In this case, the additive 5 is easily fixed around the deformed reinforcing bar 1 due to the effect of the coated adhesive. These adhesives may be used to such an extent that the additive 5 does not fall off when placing concrete.

  Further, as a means for arranging the additive 5, a mode in which the additive 5 is applied by a technique such as brushing, spraying or dobbing is conceivable. In addition, a sheet impregnated with the additive may be deformed. You may wind around the predetermined position of the reinforcing bar 1. The sheet is preferably soluble in the concrete 3.

Further, as another embodiment, a structure in which a fibrous reinforcing material made of inorganic or organic short fibers is arranged on the surface of a steel material and concrete is cast around it can be adopted.
According to this technique, the concrete around the reinforcing bar can be made dense by the reinforcing effect of the inorganic or organic material short fibers, and the effect of enhancing the adhesion between the deformed reinforcing bar and the concrete can be exhibited. If the adhesion between the deformed reinforcing bar and the concrete increases, it is possible to prevent cracks generated in the concrete structure or to improve the proof stress of the structure.

  The additive 5 and the fibrous reinforcing material made of short fibers of inorganic or organic materials can be applied to all steel materials used in concrete structures, for example, reinforcing bars, steel frames, anchor members, etc. It is good to use it for steel materials near places where cracks are a problem, such as reinforcements for lap joints and beam-column joints and reinforcements around beam through holes.

Experimental example

The following experiment was conducted to determine how much the adhesion performance between the deformed reinforcing bar and the concrete is increased by arranging the additive around the deformed reinforcing bar.
In the experiment, the load when the deformed reinforcing bar shown in FIG. 3 was pulled out in the direction of the arrow in the figure and the axial displacement of the deformed reinforcing bar were measured. The experimental results are shown in FIG.
Additive 1 uses fly ash, and additive 2 uses alumina.

The principal part expanded sectional view of one embodiment Graph showing the relationship between load and displacement in the experimental example The figure which shows the situation where a deformed reinforcing bar is pulled out from concrete in an experimental example Main section enlarged sectional view of the conventional example

Explanation of symbols

1 Deformed bar (steel)
2 Node 3 Concrete 4 Polymer cement layer 5 Additive

Claims (2)

After applying a water-soluble adhesive to the surface of the steel material 1 embedded in the concrete structure, an additive material 5 having the ability to solidify the concrete is placed around the steel material 1 and the concrete 3 is placed around the steel material 1 By doing so, the concrete 3 surrounding the steel material 1 is made dense, and the adhesion performance between the concrete 3 and the steel material 1 is enhanced by making the concrete 3 solid.   The method for enhancing the adhesion of steel materials according to claim 1, wherein the additive 5 is ceramic powder such as silica fume, blast furnace slag, fly ash, alumina, or glass powder.

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