JP2021170038A - Evaluation test method for reinforcing bar corrosion associated with cracks in concrete columns - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dramatically improve the efficiency of an evaluation test by establishing a test method using a small simple test piece which enables an inexpensive and simple evaluation test and making it possible to accurately control the crack width due to a load in micron units. Provided is an evaluation test method for reinforcing bar corrosion associated with a crack in a concrete column, which can be improved. According to the present invention, a cutting step S1 of cutting out a concrete piece containing at least one reinforcing bar from a concrete pillar as a specimen and a portion of the cut out specimen other than the planned surface on which a predetermined crack is generated are sealed. Observation of the sealing step S2 of sealing with a stopper, the crack introducing step S3 of installing the specimen on a pedestal and generating cracks on the surface other than the portion sealed with the sealing material, and observing the crack width of the specimen. While carrying out, it has an exposure step S4 for exposing the specimen for a predetermined period of time, and a disassembly confirmation step S5 for disassembling the specimen after exposure and confirming the progress of neutralization of the concrete material and the corrosion status of the reinforcing bar. It is characterized by that. [Selection diagram] FIG. 9

Description

The present invention relates to an evaluation test method for reinforcing bar corrosion associated with cracks in concrete columns for clarifying the correlation between the width of cracks (cracks) in concrete columns and the degree of corrosion of reinforcing bars in, for example, power distribution equipment.

Generally, when a crack occurs in a concrete column and the internal reinforcing bar is exposed, the reinforcing bar is corroded and rusted, and there is a risk that the performance of the concrete column itself is adversely affected.

Therefore, in order to elucidate the correlation between the width of cracks in concrete columns and the degree of corrosion of reinforcing bars, conventionally, for example, the concrete columns themselves, which are actual structures with a length of 14 m or the like, are used with heavy machinery. By building and applying a design load to introduce cracks (cracks), exposing them for a predetermined period of time, and then disassembling them, the width of the cracks and the corrosion status of the reinforcing bars were confirmed.

Further, conventionally, as disclosed in Patent Document 1, a pre-crack can be introduced into a test piece of a brittle material such as ceramics, concrete, rock, etc., and the length of the pre-crack can be controlled. A crack introduction device and a pre-crack introduction method have been proposed.

That is, this pre-crack introduction device introduces a pre-crack into the test piece by applying a tensile force loading means for applying a tensile force to the test piece and a compressive load on the test piece in a direction orthogonal to the direction in which the tensile force acts. When introducing a pre-crack into a test piece, the test piece is pre-cracked by applying a tensile force to the test piece with a tensile force loading means while a compressive load is applied by the pre-crack introducing means. The tensile force loading means includes a housing containing a group of boosting gears, a rod case containing a pulling rod that moves forward and backward in the tensile direction, and a handle for creating tensile force. Those equipped with a tensile force generating means are used.

JP-A-2007-155665

As mentioned above, in the past, since the actual structure of heavy concrete columns was exposed and dismantled as it was, large-scale construction such as using heavy machinery was required, and moreover, Performing the work can be extremely time consuming and labor intensive.

For this reason, it has become indispensable to establish a simple test method for clarifying the relationship between the progress of the crack width of the concrete column and the corrosion state of the internal reinforcing bars.

Further, in the case of Patent Document 1 described above, the pre-crack introduction device includes a housing containing a booster gear group, a rod case containing a tension rod that moves forward and backward in the tensile direction, and a handle for creating tensile force. Since it depends on the tensile force loading means having the above, the configuration becomes very complicated and expensive.

Moreover, in the pre-cracking introduction device of Patent Document 1, a small test piece is surrounded by a compressive force receiving member, a handle, a rod case, etc. and becomes an obstacle. It's difficult to do.

Further, in the case of Patent Document 1 described above, it is an object or purpose of the invention to control the length and depth of the pre-crack, but there is no disclosure regarding controlling the crack width.

That is, the mode of occurrence of the crack width varies depending on how the load is applied (acting area, acting position, etc.). Therefore, in order to improve the efficiency of the evaluation test, it is indispensable to be able to control the crack width in micron units with high accuracy.

Therefore, the present invention was created in view of the above-mentioned conventional circumstances, and a test method using a small simple test piece that enables an inexpensive and simple evaluation test has been established, and a crack due to a load load has been established. It is an object of the present invention to provide an evaluation test method for reinforcing bar corrosion associated with a crack in a concrete column, which can dramatically improve the efficiency of the evaluation test by enabling the width to be controlled accurately in micron units.

The evaluation test method for reinforcing bar corrosion associated with cracks in a concrete column according to the present invention includes a cutting step of cutting out a concrete piece containing at least one reinforcing bar from a concrete column as a specimen (test piece).
In the cut-out specimen (test piece), a sealing step of sealing a portion other than the planned surface on which a predetermined crack (crack) is to be generated with a sealing material, and a sealing step.
A crack introduction process in which the specimen (test piece) is installed on a pedestal and cracks are generated on the surface other than the part sealed with the sealing material.
An exposure process in which the specimen (test piece) is exposed for a predetermined period while observing the crack width of the specimen (test piece).
The above-mentioned problems were solved by disassembling the specimen (test piece) after exposure and confirming the progress of neutralization of the concrete material and the corrosion status of the reinforcing bars.

The evaluation test method for reinforcing bar corrosion associated with cracks in concrete columns according to the present invention establishes a test method using a small simple test piece that enables an inexpensive and simple evaluation test, and dramatically improves the efficiency of the evaluation test. Can be done.

It is a perspective view which shows the outline of the state which the concrete piece (specimen) was attached to the pedestal for evaluation test. Similarly, the outline of the state in which the concrete piece (specimen) is attached to the gantry for the evaluation test is shown, (a) is a plan view, (b) is a front view, and (c) is a side view. It is an exploded perspective view of the frame for evaluation test. It is a perspective view which shows the assembled state of the gantry for evaluation test. It is a perspective view which shows the process from cutting out a concrete piece (specimen) of a reinforced concrete column to sealing with a sealing material other than the surface where a predetermined crack is generated. It is a perspective view which shows the outline of the state which the concrete piece (specimen) is attached to the pedestal for evaluation test. It is a side view which shows the outline of the state which the concrete piece (specimen) was attached to the pedestal for evaluation test. It is a side view which shows the outline of the introduction state of the crack by the three-point bending load through a bolt in the concrete piece (specimen) attached to the frame for evaluation test. It is a block diagram explaining the work procedure of an evaluation test. An image of three-point bending is shown, where (a) is an explanatory view before applying a load, and (b) is an explanatory view after applying a load. The outline of the crack generation range of the concrete piece (specimen) is shown. FIG. A specific example of the pressing jig is shown. FIG. Is. Similarly, a specific example of the pressing jig is shown, and is a front view and a side view when the pressing jig is in contact with each other in a planar or linear manner. A comparative example of the shapes of the pressing jigs is shown. FIG. It is a side view.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<Embodiment>
In the evaluation test device for reinforcing bar corrosion associated with cracks in concrete columns (hereinafter referred to as this device) used in the present invention, a specimen (test piece) P containing at least one reinforcing bar of a concrete piece cut out from a concrete column is installed. It is composed of a stand 1 for fixing the positions of both ends thereof. The gantry 1 is provided with a pressing jig 3 that applies an overload to the intermediate portion of the specimen (test piece) P.

The apparatus is provided with a bolt B that is screwed from the gantry 1 side toward the back surface of the specimen (test piece) P and presses the pressing jig 3 against the back surface of the specimen (test piece) P. The crack width generated on the surface of the specimen (test piece) P is controlled by a rotation pitch of 1 mm to 2.5 mm (advance distance due to one rotation of the bolt), which is a general pitch of the above.

<Configuration of this device>
Next, the specific configuration of this device will be described in detail with reference to FIGS. 1, 2, 3, and 4.

The gantry 1 is made of H-shaped steel having flanges F at both ends of the central web W. Holding members 2 that sandwich and fix both ends of the specimen (test piece) P are arranged at both ends of the flange F surface on one side in the length direction.

The holding member 2 includes, for example, a support contact member 2A made of an L-shaped plate-shaped angle member or the like, and a bolt B and a nut N for fixing the support support member 2A to the flange F surface on one side.

In using the sandwiching member 2, first, the end portion of the specimen (test piece) P is sandwiched between the flange F surface on one side and the support contact member 2A, and a pair of holes provided on the flange F surface on one side and the support contact member 2A, respectively. The shaft portion of the bolt B is passed through H, and the nut N is applied to the shaft portion protruding from the flange F surface on one side and tightened.

A pressing jig 3 that presses the specimen (test piece) P to generate a crack C is arranged at a substantially central portion of the flange F surface on one side.

At the center of the gantry 1, a pair of substantially trapezoidal plate-shaped guide pieces 3A installed facing each other along the width direction of the flange F surface on one side and a vertical groove formed in the center of each of the pair of guide pieces 3A. It is provided with a pressing jig 3 that is laid horizontally so as to straddle the guide grooves 3B facing each other and is movable in a direction away from the flange F surface on one side along the guide grooves 3B.

The pressing jig 3 of the present embodiment includes, for example, a cylindrical pressing rod 3D for uniformly contacting the center of the back surface of the specimen (test piece) P along the width direction, and the rear of the pressing rod 3D. It is formed by a rectangular plate-shaped pressing member 3C in which the tip of a bolt B, which will be described later, is in contact with the rear surface, which is welded to the rear surface.

In the present embodiment, the pressing rod 3D is welded to one side of the pressing member 3C to be integrated, but the pressing rod 3D and the pressing member 3C may be separate bodies.

Then, the pressing jig 3 presses the pressing member 3C and moves the pressing member 3C in a direction away from the one-side flange F surface in the center of the one-side flange F in the opening 3E formed between the lower surface of the one-side flange F and the web W. A bolt B into which the shaft portion B1 is screwed is provided in the bolt hole 3F (see FIG. 3) formed in.

In this way, in the pressing jig 3, the shaft portion B1 of the bolt B is screwed into the bolt hole on the flange F surface on one side, the tip of the shaft portion B1 is brought into contact with the pressing member 3C, and the pressing rod 3D is pressed. It is moved in a direction away from the F surface of the flange on one side.

Further, as shown in FIG. 9, the evaluation test method for reinforcing bar corrosion associated with a crack in a concrete column according to the present invention is a cutting step of cutting out a concrete piece containing at least one reinforcing bar Q from a reinforced concrete column K as a specimen P. In S1) and the cut-out specimen (test piece) P, a sealing step (S2) in which a portion other than the surface where a predetermined crack (crack) C is generated is sealed with the sealing material V, and the specimen (test). Piece) The crack introduction step (S3) in which the P is installed on the gantry 1 and the crack C is generated on the surface other than the portion sealed by the sealing material V, and the width of the crack C in the specimen (test piece) P (FIG. While observing (see 8), the exposure step (S4) in which the specimen (test piece) P is exposed for a predetermined period and the specimen (test piece) P after exposure are disassembled to neutralize the concrete material. It consists of a disassembly confirmation step (S5) for confirming the degree of progress and the corrosion status of the reinforcing bar.

Here, the neutralization of concrete material is a phenomenon in which concrete, which is originally alkaline, loses its alkalinity due to the influence of the external environment, such as carbon dioxide gas in the atmosphere and acid rain. Neutralization destroys and activates the passivation film of the internal reinforcing bars, and the corrosion of the reinforcing bars progresses.

Next, the procedure of the evaluation test of the reinforcing bar corrosion using the above-mentioned gantry 1 will be described in detail.

<Cutout process>
In the cutting step S1, as shown in FIG. 5, a part of the cylindrical reinforced concrete column K is cut out in an annular shape having a predetermined length, and the cut out annular portion is substantially centered on one reinforcing bar Q. It is cut out along the direction of the cylindrical axis so as to come to the sample (test piece) P of a rod-shaped concrete piece having a substantially trapezoidal cross section.

As a result, the back surface R3 of the specimen (test piece) P corresponds to the inner peripheral surface of the cylindrical reinforced concrete column K, and the surface R0 of the specimen (test piece) P is the outer peripheral surface of the cylindrical reinforced concrete column K. Corresponds to.

<Sealing process>
In the sealing step S2, as shown in FIG. 5, a substantially trapezoidal upper and lower end surfaces R1 and a rectangle other than the surface that causes cracks C (cracks) in the specimen (test piece) P cut out in the cutting step S1. Epoxy resin is applied as a weather-resistant sealing material V to each of the left and right side surfaces R2 and the back surface R3 corresponding to the inner peripheral surface of the cylindrical reinforced concrete column K.

<Rhagades introduction process>
In the crack introduction step S3, as shown in FIGS. 1, 2, and 6, the back surface R3 of the specimen (test piece) P corresponding to the inner peripheral surface of the cylindrical reinforced concrete column K is a flange on one side of the gantry 1. The specimen (test piece) P is installed along the gantry 1 so as to be located on the F surface, and both ends of the specimen (test piece) P are placed on the support contact member 2A of the holding member 2 and the flange F on one side. It is sandwiched between the surfaces and fixed.

Then, as shown in FIGS. 7 and 8, the pressing rod 3D of the pressing jig 3 is attached to the substantially central portion of the back surface R3 of the specimen (test piece) P, and one side from the opening 3E side in the web W. The shaft portion B1 of the bolt B is screwed into the bolt hole 3F of the flange F, and the pressing member 3C is moved away from the flange F surface on one side at the tip of the shaft portion B1 of the bolt B to use the pressing rod 3D as a specimen. A load is applied so as to be pressed against the back surface R3 of the (test piece) P to generate a crack C in a substantially central portion of the surface R0 of the specimen (test piece) P corresponding to the outer peripheral surface of the cylindrical reinforced concrete column K.

The method of applying the bending load here will be described with reference to FIG.

In the crack introduction step S3, both ends of the specimen (test piece) P obtained in the cutting step S1 and the sealing step S2 fixed to the gantry 1 and the specimen (test) in which a load is applied perpendicularly to the front direction. One piece) Due to the three-point bending load with the back surface R3 part in the center of P, the front surface R0 of the specimen (test piece) P expands (pulls along the front surface) and the back surface R3 is compressed. , Crack C (crack) is introduced in the surface R0 portion.

<Exposure process>
In the exposure step S4, the degree of development of the width of the crack C is observed under the same conditions as the external environment in which the reinforced concrete column K is installed at the site. In this case, since the influence of rain is large when the gantry is placed horizontally, the gantry 1 is placed vertically in the same manner as the actual structure.

<Disassembly confirmation process>
In the disassembly confirmation step S5, the degree of corrosion of the reinforcing bar Q inside the specimen (test piece) P with time after the crack C is generated on the surface of the specimen (test piece) P by the crack introduction step S3 is determined. taking measurement. In this way, by evaluating the corrosion of the reinforcing bars due to the dismantling after the exposure step S4, the estimated values of the deterioration state and deterioration rate of the reinforcing bars Q and the concrete material after the cracks C are generated in the reinforced concrete columns K of the actual structure can be obtained. Obtainable.

<Verification of crack width>
Here, in order to keep the test conditions constant, it is necessary to align the crack generation positions in the height direction for each specimen (test piece) P. As shown in FIG. 11A, the three-point bending caused cracks within the thickness range of the test piece on the opposite surface of the load-bearing position.

Further, as shown in FIG. 11B, the four-point bending caused cracks in a wide range further deviated from the load load width at two locations on the opposite surface of the load load position by the thickness of the test piece.

Further, as shown in FIG. 11C, in the case of cantilever three-point bending in which the end is the load-bearing position in the three-point bending, a wide range from the central fixed position serving as the fulcrum to the load-load position at the end. Cracked.

From this, it was found that the three-point bending method is effective in making it possible to accurately control the crack width due to the load generated on the surface of the specimen (test piece) in micron units.

<Load-loading method>
As described above, the method of loading the load in the present embodiment is a method using the displacement (pitch) due to the rotation of the bolt B. That is, in order to control the crack width in units of 0.01 mm, it was found that it was necessary to control the stroke in units of 0.1 mm, and the bolt method was adopted.

The material of the bolt B and the pressing jig 3 is stainless steel having a chromium (Cr) content of 17% or more. Although it is in contact with alkaline concrete, as a result of the test, steel materials with a chromium (Cr) content of less than 17% are significantly rusted after long-term use in an outdoor environment, and bolt B sticks to the crack width during the test. Cannot be adjusted.

<Aspect of pressing jig>
As shown in FIG. 12A, when the pressing jig 3 is in contact with the surface, the width LA of the pressing jig 3 in the longitudinal direction of the specimen needs to be 10% or more and 60% or less of the thickness of the specimen. Is. If it is 10% or less, cracks occur on the concrete surface of the pressed portion, and if it exceeds 60%, the variation of the crack generation position exceeds the thickness of the test piece.

As shown in FIG. 12B, when the pressing jig 3 is linearly contacted by a cylinder, the diameter of the cylinder needs to be 5 mm or more. If it is less than 5 mm, cracks will occur on the concrete surface of the pressing part.

As shown in FIG. 13, when the pressing jig 3 is in contact with each other in a planar or linear shape, the width WA of the pressing jig 3 in the width direction of the test body is 40% or more narrower than the width WB of the test body. It doesn't become. That is, when the width WA in the width direction of the test body is narrower than the width WB of the test body by 40% or more of the thickness of the test body, cracks occur on the concrete surface at the end of the pressing jig 3.

<Comparison of jig shapes>
As shown in FIG. 14A, when the pressing jig 3 is in contact with the bolt B surface or in a planar shape, the width WA of the pressing jig 3 in the width direction of the test body has a thickness of the test body as compared with the width WB of the test body. It does not become narrower than 40%%.

As shown in FIG. 14 (b), when the width WA in the width direction of the test body becomes 40% or more narrower than the thickness of the test body as compared with the width WB of the test body, the end portion of the pressing jig 3 and the concrete surface of the pressing surface crack. Occurs.

In addition, although not illustrated one by one, the present invention is carried out with various modifications within a range not deviating from the gist thereof.

The present invention is widely used in various work sites as a method capable of clarifying the correlation between the width of the crack C (crack) of the reinforced concrete column K and the degree of corrosion of the reinforcing bar Q.

S1 ... Cutting process S2 ... Sealing process S3 ... Crack introduction process S4 ... Exposure process S5 ... Disassembly confirmation process K ... Reinforced concrete column W ... Web F ... Flange P ... Specimen (concrete piece)
R0 ... Front surface R1 ... Upper and lower end surfaces R2 ... Left and right side surfaces R3 ... Back surface Q ... Reinforcing bars C ... Cracks
V ... Encapsulant B ... Bolt B1 ... Shaft N ... Nut H ... Hole 1 ... Stand 2 ... Holding member 2A ... Supporting member 3 ... Pushing jig 3A ... Guide piece 3B ... Guide groove 3C ... Pushing member 3D ... Pushing rod 3E ... Opening 3F ... Bolt hole

Claims (5)

A cutting process in which a concrete piece containing at least one reinforcing bar is cut out as a specimen (test piece) from a concrete column, and
In the cut-out specimen (test piece), a sealing step of sealing a portion other than the planned surface on which a predetermined crack (crack) is to be generated with a sealing material, and a sealing step.
A crack introduction process in which the specimen (test piece) is installed on a pedestal and cracks are generated on the surface other than the part sealed with the sealing material.
An exposure process in which the specimen (test piece) is exposed for a predetermined period while observing the crack width of the specimen (test piece).
A dismantling confirmation process that dismantles the specimen (test piece) after exposure and confirms the progress of neutralization of the concrete material and the corrosion status of the reinforcing bars.
An evaluation test method for reinforcing bar corrosion associated with cracks in concrete columns, which is characterized by consisting of. The exposure step is the evaluation test method for reinforcing bar corrosion associated with cracks in the concrete column according to claim 1, which is carried out under the same conditions as the external environment in which the concrete column is installed on site. The concrete according to claim 1, wherein the disassembly confirmation step measures the degree of corrosion of the reinforcing bars inside the specimen (test piece) over time after the specimen (test piece) is cracked by the crack introduction step. Evaluation test method for reinforcing bar corrosion associated with column cracks. The crack introduction process is carried out using a concrete piece cut out from a concrete pillar and containing at least one reinforcing bar as a specimen (test piece) and installed with the positions of both ends fixed. The concrete column according to claim 1, further comprising a pressing jig for pressing a central point on the back surface of the specimen (test piece), and controlling the width of cracks generated on the surface of the specimen (test piece). Evaluation test method for reinforcing bar corrosion associated with cracks in concrete. The gantry pressing jig includes a pair of guide pieces provided in the width direction of one side flange surface and a pressing member that can move along the pair of guide pieces in a direction away from one side flange surface, and has one side flange surface. A screw hole is provided in the bolt, and the shaft portion of the bolt is screwed into the screw hole to bring the tip of the shaft portion into contact with the pressing member, and the pressing member is moved in a direction away from the flange surface on one side.
In the crack introduction process, the crack width generated on the surface of the specimen (test piece) is controlled by the pressing jig by the rotation pitch of the bolt screwed from the gantry side toward the back surface of the specimen (test piece). The evaluation test method for reinforcing bar corrosion associated with cracks in a concrete column according to claim 4, which is carried out by holding.

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