JP2812850B2 - How to adjust the adhesion between concrete and embedded steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the adhesive force between a hardened concrete body and a steel material embedded therein.

[0002]

BACKGROUND OF THE INVENTION The present invention provides a method for increasing or decreasing the adhesion between hardened concrete and steel buried inside such as reinforcing steel, pretensioned or posttensioned steel or steel wire. A) an electrochemical treatment of hardened concrete for conditioning; Heretofore, there has been no known method of controlling and changing the adhesion between hardened concrete and steel / concrete on site, and thus the above-described method has been impossible.

[0003]

SUMMARY OF THE INVENTION It is a feature of the present invention that the condition of the steel / concrete bond surface in a hardened concrete structure can be adjusted in order to enhance the filling at the contact surface. Due to the accumulation of breathing water on the steel surface during the initial hardening period of the concrete, or insufficient compaction of the concrete during the pouring operation, the filling of the bonding surface between the reinforcing embedded steel or the tension member is often poor. Complete. As a result of insufficient filling at the steel / concrete adhesion surface, water leakage occurs in a structure where water pressure is applied, neutralization of the concrete surface around the steel material, and corrosion of the steel material.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a distributed electrode, wherein the internally buried steel material is used as the negative electrode and is located at a predetermined distance from the steel material, usually located on the outer surface of concrete. It is based on the discovery that during electrochemical treatment of concrete using the body as a positive electrode, the adhesion between the buried steel and the surrounding concrete changes significantly as a result of the action of the charge. At the initial stage of the treatment, the adhesive force continuously decreases to a level lower than the initial value, but with continued treatment, the adhesive force continuously increases significantly. The variation value of the adhesive force is
It has been found that certain types of concrete are predictable and reproducible. Thus, by creating a data reference value for the relationship between a given treatment time and the effect of the adhesion between steel / concrete, a predictable adjustment of such adhesion in an existing structure is made possible.

[0005] For example, when a reinforcing steel material fixed at both ends is used, it is desired to increase the adhesive force at the adhesive surface between the steel material and the concrete. Prior art electrochemical treatment of reinforced concrete is well known, with the internal steel being connected as a negative pole and the external distributed electrode being used as a positive pole. Such an example is described in U.S. Pat. No. 4,832,903 to Benesland et al.
No. However, such prior art methods are intended for use, for example, in the rehabilitation of chloride-contaminated concrete structures, or even concrete structures that are even corroded, even with embedded steel. Although the technical method of the present invention can be used in connection with corroded concrete, the treatment method of the present invention is not a method for rehabilitation treatment, but controls the adhesive force on the steel / concrete adhesive surface. It is intended to be adjusted. In the method of the present invention, the processing state and control parameters are completely different from those of the rehabilitation treatment.

Thus, according to the present invention, a hardened concrete body and a reinforcing steel material embedded therein and / or
A method for adjusting the adhesive force between a pretensioned or posttensioned steel material, comprising: (a) providing a DC voltage source; and (b) connecting a negative pole of the voltage source to the internally buried steel material. (C) creating distributed electrode means coupled to the concrete body; (d) connecting the dispersed electrode means to the positive pole of the voltage source; and (e) connecting steel / concrete. The strength, indicating the continuous relationship between the total current amount of the steel material and the buried steel material unit flowing between the dispersed electrode means, a reference value data that can be applied to the concrete body, if necessary, first created (F) driving the voltage source to provide a surface area of one square meter of the buried steel material between the buried steel material and the disposed electrode means.
A step of or current flows for from 0.1 to 10 amps, (g) the total charge per unit of the steel material, when creating the data reference value becomes the calculated value,
A step of terminating the entire process when a predetermined adjustment value of the adhesion between the embedded steel material and the concrete has been reached.

For a more complete understanding of the above and other features and objects of the present invention, reference is made to the following detailed description of the preferred embodiment of the invention and the accompanying drawings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, steel / concrete adhesion is achieved by passing an electric current between the buried steel and a distributed electrode set on the concrete surface at a distance from the steel. FIG. 1 shows a typical model for accomplishing that purpose. Shown at 10 in FIG. 1 is a reinforced (or pre-tensioned or post-tensioned) concrete structure. The concrete body shown in the figure is reinforced by a plurality of reinforcing steel materials 12 buried in concrete and surrounded by concrete.

The negative pole of the DC voltage power source G is
2, the positive electrode is connected to the dispersion electrode 13, and the electrode 13 is made of a conductive metal net such as steel or titanium. In the illustrated configuration, the electrode 13 is
The electrolyte carrier 14 buried in the casing 4 is formed of, for example, an aqueous solution or a cellulose pulp fiber moistened with an electrolytic solution. If cellulose pulp fibers are used, they are usually sprayed onto the outer surface 15 of the concrete 11 to form two layers. Since the fibrous material is applied to the concrete surface by itself, it can be spread on vertical and downward surfaces. As shown in FIG. 1, after the first layer is formed by spraying, the mesh electrode 13 is laid, and the second layer of the fiber material is formed on the upper surface of the mesh electrode.

In the present invention, the form of the dispersion electrode is not particularly specified. The electrode 13 may be immersed in a liquid or buried in a porous material or cloth containing water, as long as the material of the concrete and the orientation of the surface permit. Similarly, the concrete surface can be covered with a conductive layer (or a conductive thin film can be directly applied). What is drastically necessary to achieve the object of the present invention is to equip an electrode arranged in a predetermined area in order to pass a constant current between the internal buried steel material 12 and its counter electrode.

The power supply capacity of the power supply G is not particularly important.
However, in actual operation, 40V or less,
It is desirable to be able to supply a DC voltage of usually 5 to 40 V, preferably adjustable. For safety, 40 volts is a suitable upper limit. Also, the device preferably has a current capability capable of supplying a current of 0.1 to 10 amps per square meter of surface area of the buried steel material in the work area, typically 0.5 to 10 amps.

FIG. 2 shows the adhesion of steel / concrete in MPa relative to the total charge applied to the buried steel in ampere-hours per square meter of steel surface area.
The value in (megapascal) units is represented by a curve. FIG.
The solid line indicates the average value of the concrete with the standard composition. Dotted lines above and below the solid line show typical deviation value curves from the average value.

As can be seen from FIG. 2, in the first step of the method of the present invention, that is, until the time when the electric current is supplied at 4000 to 5000 amp. The adhesive force between them is reduced. As shown, the initial adhesive force was approximately 1.8 MPa, but gradually increased from 0.6 to 0.7 MPa.
a, at which time the current supply is approximately 4300 amps per square meter of steel surface area.

Then, as the current supply between the buried steel material and the dispersed electrode is further continued, the adhesive force between the buried steel material and the surrounding concrete starts to increase. Further, as the amount of current is increased, the adhesive force dramatically exceeds the initial value and eventually reaches the maximum value. In the graph of FIG. 2, the maximum value of the adhesive force is about 5.7 MPa around 12,000 amp-hours per square meter of steel surface area.

After the adhesive force reaches its maximum value, it starts to decrease again even if the current supply is continued. However, ultimately, the adhesive force becomes substantially horizontal, and is approximately 14,000 to 14,000 square meters of steel material surface area.
Relatively stable at currents in the range of 15000 amps-hours. Generally, there is no reason to perform a treatment that exceeds the maximum adhesion value. In fact, such processing is only a loss.

The graph of FIG. 2 is shown as a curve based on actual measurements from a concrete of average quality.
Similar data reference values can be obtained for concrete of any composition, but the curve values in FIG. 2 are suitable for most practical processes. From Fig.2, to reduce the adhesive force between the buried ordinary steel and the surrounding ordinary concrete,
7000 amps / hour per square meter of steel surface area
Or less, preferably between 2000 and 6000 ampere-hours, and in order to increase the adhesion, the steel
7000-15000 amps per square meter
A hour , preferably 8000 to 12000 amps
It can be seen that it is only necessary to supply the amount of charge over time .

In the method of the present invention, at the time when the treatment is performed so that the adhesive force exceeds the initial value, the adhesive surface between the steel material and the concrete or the gap between the concrete around the steel material and the concrete is removed by the electrochemical reaction on the steel material surface. Has been observed to be full of material produced by These materials are considered to be mixtures of various compounds including calcium hydroxide and calcium carbonate. The filling of the gap with this chemically reactive compound in any case renders the attachment surface impermeable and hermetically sealed.

It is an object of the present invention to be the first method to achieve a remarkable and unexpected effect that allows the steel / concrete adhesion to be adjusted in-situ in a hardened concrete structure. For example, it is desirable to increase the mutual adhesion in standard double-ended steel embedded in ordinary concrete structures. Data reference values for ordinary concrete compositions are easily created and can be applied to most types of concrete. In the case of detailed structures and / or unique concrete structures, a series of simple tests can be performed to set the data reference values for that particular concrete. The data reference values can be applied to a special structure using a specific composition, and are used for controlling the configuration.

In addition to accurately controlling and adjusting the steel / concrete adhesion described above, the method of the present invention provides an effective sealing of the steel / concrete adhesion surface to prevent ingress of moisture and ambient air. Also available. The filling action is
This is the effect of sedimentation of reaction products at the steel / concrete attachment surface and the surrounding concrete gaps, which makes the concrete in that area almost impervious to external liquids and gases.

The method of the present invention can be easily and economically applied or utilized with conventional techniques and equipment. For example, as a general-purpose example, if the external electrode means is provided on the outer surface of the structure, it can be washed or removed after the treatment is completed. The embodiment of the invention described above is a preferred example and it goes without saying that changes can be made without departing from the scope of the appended claims. The following describes some preferred embodiments of the present invention.

(1) Adhesive force between steel and concrete;
First, a data reference value applicable to a concrete body, which indicates a continuous relationship between the total current of the buried steel unit flowing between the steel material and the distributed electrode means, is prepared, and the total charge per unit of the steel material is calculated. 2. A time point when the amount reaches a predetermined adjustment value of the adhesive force between the buried steel material and the concrete, is known from a value calculated from the data reference value.
The described method.

(2) The data reference value indicates a continuous relationship between the total amount of applied current per unit in the surface area of the buried steel material and the adhesive force between the steel material and the concrete. The method of claim 1. (3) The process is completed when the total current applied to the buried steel material reaches a value that reduces the adhesive force between the steel material and the concrete by a predetermined amount. Item 7. The method according to Item 1.

(4) The processing is terminated when the total amount of current applied to the buried steel material reaches a value that increases the adhesive force between the steel material and the concrete by a predetermined amount. The method according to claim 1, wherein (5) The voltage supply is capable of supplying a DC voltage of about 40 volts or less, and supplies about 0.1 to about 10 amps per square meter of the surface area of the buried steel during processing. The method of claim 1, wherein:

(6) (a) The buried steel material is constituted by a reinforcing member which is not subjected to a tensile force, and (b) the treatment increases the adhesive force between the reinforcing member and the concrete. The method of claim 1, wherein the method is controlled. (7) The treatment is carried out sufficiently continuously so as to fill the adhesion surface between the steel material and the concrete by filling the gap of the surrounding concrete with a product of electrochemical action. The method according to the above (4).

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a concrete structure showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the treatment time of the present invention and the effect of the adhesive force between concrete and steel embedded therein.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Reinforced concrete structure 11 ... Concrete 12 ... Strong steel material 13 ... Electrode 14 ... Electrolyte carrier 14 15 ... Outer surface

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E04G 23/02

Claims (1)

(57) [Claims] 1. A hardened concrete body and a reinforcing steel material embedded therein and / or a pretension or post
A method of adjusting the adhesive force between a tension steel and a steel material, comprising: (a) providing a DC voltage source; and (b) connecting a negative pole of the voltage source to the internal buried steel material. c) creating dispersed electrode means coupled to the concrete body; (d) connecting the dispersed electrode means to a positive pole of the voltage source; and (e) driving the voltage source to bury the embedded steel material. A surface area of one square meter of the buried steel material between
A step of or current flows from 0.1 to 10 amps, the total processing upon reaching a predetermined adjustment value adhesion between (f) the total charge per unit of the steel product and the embedded steel concrete And c. Ending the step of adjusting the adhesive force between the concrete and the buried steel material.