JP6214003B2 - Evaluation method of neutralization resistance - Google Patents

Description

  The present invention relates to a method for evaluating resistance to neutralization.

  Reinforced concrete usually has the effect of preventing corrosion of the reinforcing steel because the concrete is alkaline. However, it is known that the pH of concrete decreases with time due to the influence of carbon dioxide in the atmosphere (that is, becomes neutralized), and corrosion of the reinforcing bars proceeds.

  For example, when the concrete used for the reinforced concrete is concrete produced by centrifugal compaction, the water-cement ratio (W / C) of the concrete is as low as about 26%. Therefore, the outer side (outer peripheral side) of the reinforced concrete becomes solid and has high resistance to neutralization. On the other hand, the resistance to neutralization is not necessarily high because the reinforced concrete is in a rough state in which a void exists on the center side. That is, it is expected that the degree of neutralization resistance varies depending on the depth from the outside of the reinforced concrete.

  Here, for example, the following methods can be considered as a method of evaluating the resistance to neutralization for each depth of reinforced concrete. That is, first, a concrete member is cut out for each distance from the surface from the surface of the reinforced concrete column to be tested to the inside. Thereafter, each cut-out member is sealed with a resin or the like, and a neutralization promotion test or an exposure test is performed. And pH is measured by the phenolphthalein method with respect to each member of the reinforced concrete pillar after a test.

Sato, S. et al., “Fundamental study on detailed evaluation technology for carbonation of concrete by phenolphthalein method”, Annual report on concrete engineering, Vol.31, No.1, p2023-2028, 2009. Ueda Hiroshi et al., “Neutralization of concrete utility poles and chloride ion permeation characteristics and the effect of formwork joints”, 58th Annual Conference of Japan Society of Civil Engineers, p67-68, 2003.

  However, in the above method, it is not possible to evaluate continuous (fine) neutralization resistance characteristics from the surface of the reinforced concrete column to be tested to the vicinity of the reinforcing bar. Then, this invention makes it a subject to solve the above-mentioned problem and to evaluate the detailed neutralization resistance characteristic from the surface of the reinforced concrete column of a test object to the reinforcement vicinity.

  In order to solve the above-described problem, the present invention is a method for evaluating the neutralization characteristics of a reinforced concrete column including one or more reinforcing bars, and the reinforced concrete column to be evaluated is placed inside the reinforced concrete column. Parallel to the tangential line of the reinforced concrete column at the intersection of the reinforced concrete column and the outer periphery of the reinforced concrete column that extends from the center of the reinforced concrete column and the outer periphery of the reinforced concrete column. The concrete portion of the reinforced concrete column is cut in the direction to be, and the resistance to neutralization is evaluated using the cut surface.

  ADVANTAGE OF THE INVENTION According to this invention, the detailed neutralization resistance characteristic from the surface of the reinforced concrete pillar of a test object to the reinforcement vicinity can be evaluated.

Drawing 1 is a figure showing an example of a member cut out from a reinforced concrete pillar and a reinforced concrete pillar. FIG. 2 is a flowchart showing a procedure of the evaluation method of the neutralization resistance characteristic of the present embodiment. FIG. 3 is a view of the member cut out in FIG. 1 as viewed obliquely and upward. FIG. 4 is a diagram illustrating an example of a cut surface. FIG. 5 is a diagram showing a prediction example of the reaction of the phenolphthalein method on the cut surface.

  Hereinafter, embodiments (embodiments) for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment.

  Here, the case where the object of evaluation of the neutralization resistance is the reinforced concrete column 101 shown in FIG. 1 will be described as an example. Centrifugal compacted concrete is used for the concrete portion of the reinforced concrete column 101. Of course, the shape of the reinforced concrete column 101 may be, for example, a columnar type as well as a frustoconical type as shown in FIG. One or more reinforcing bars 103 are arranged inside the reinforced concrete column 101. Further, the reinforced concrete column 101 includes a hollow portion 105.

  Next, the procedure of the evaluation method of the neutralization resistance characteristic of the present embodiment will be described with reference to FIG. First, the evaluator cuts out the member 102 for which the neutralization resistance characteristic is to be evaluated from the reinforced concrete column 101 (S1). For example, the evaluator makes a cut vertically to the reinforcing bar 103 from the reinforced concrete column 101 of FIG.

  Next, the evaluator creates the specimen 106 by cutting the member 102 cut out in S1 along a predetermined cut surface (S2). For example, as shown in FIG. 3, the evaluator touches the member 102 with any one reinforcing bar 103 (for example, the reinforcing bar 103a) in the member 102, and extends a line connecting the center of the member 102 and the reinforcing bar 103a. The concrete part of the member 102 is cut at a cutting surface 104 in a direction parallel to the tangent to the member 102 at the intersection with the outer periphery of the member 102 and parallel to the length direction of the reinforcing bar 103a, and the specimen 106 is obtained. The cut surface 104a of the specimen 106 is in a state as shown in FIG. 4, for example. Note that the filled portion (for example, a portion indicated by reference numeral 401 or the like) in the cut surface 104a in FIG. 4 is an aggregate, and the aggregate is close to the outside due to centrifugal force during the production of concrete.

  After S2, the tester performs a neutralization promotion test or an exposure test on the specimen 106 (S3: test execution), and performs a neutralization evaluation (S4). For example, the evaluator seals the specimen 106 other than the cut surface 104a with an epoxy resin or the like, and performs a neutralization promotion test or an exposure test. After the test, the neutralized region of the cut surface 104a of the specimen 106 is evaluated by the phenolphthalein method.

  In the evaluation by the phenolphthalein method, for example, 1 g of phenolphthalein powder dissolved in 90 ml of 95% ethanol and 100 ml added with water is used as a reagent. Then, the evaluator sprays the dried cut surface 104a with a sprayer or the like to such an extent that the reagent does not drip, and evaluates the progress of neutralization of each part by the red color development amount of the sprayed reagent.

  For example, as shown in FIG. 5, by performing the phenolphthalein method on the cut surface 104 a of the specimen 106, the neutralization evaluation from the portion close to the surface of the reinforced concrete column 101 to the portion close to the reinforcing bar 103 can be performed. Can be done finely. For example, by looking at the reaction state of phenolphthalein at the left and right end portions (corresponding to the portions indicated by reference numerals 301 and 302 in FIG. 5) of the cut surface 104 shown in FIG. The progress of neutralization can be evaluated. Further, by looking at the reaction state of phenolphthalein at the central portion (the portion indicated by reference numeral 303) of the cut surface 104a, it is possible to evaluate the progress of neutralization of the portion of the reinforced concrete column 101 close to the reinforcing bar 103a.

  When centrifugally compacted concrete is used for the concrete portion of the reinforced concrete column 101, the portion close to the surface of the reinforced concrete column 101 is in a state where the concrete is dense, so the progress of neutralization is slow, whereas the portion close to the hollow portion 105 It is predicted that the neutralization progresses rapidly because the concrete is rough. Therefore, when neutralization is evaluated by the method as described above, phenolphthalein turns red (pH 10 or more) in the region indicated by reference numerals 301 and 302 in the cut surface 104a in FIG. Then, it is considered that phenolphthalein does not change color (pH of about 8 to 9).

  And after obtaining the pH of each evaluation location from the color information obtained by the above phenolphthalein method, by dividing this by the time required for the neutralization promotion test or the exposure test, Find the neutralization rate. Thereby, the neutralization resistance characteristic of each evaluation location can be evaluated.

  In addition, it can be calculated | required as follows how much the evaluation location of the phenolphthalein method in the cut surface 104a is located from the surface of the reinforced concrete pillar 101. FIG. For example, the depth d of the point 304 located at a distance y from the right end of the cut surface 104a in FIG. 5 from the surface (outer periphery) of the member 102 can be obtained as follows.

  First, if the cover depth of the reinforcing bar 103a in the member 102 (reinforced concrete column 101) is t and the diameter of the member 102 is D (see FIG. 3), the length x of the cut surface 104 is obtained by the following equation (1). It is done.

  For example, when t = 20 mm and D = 300 mm, the length x of the cut surface 104 is 74.8 mm as shown in the following formula (2).

  Therefore, the depth d from the surface of the member 102 of the point 304 located at the distance y from the left end of the cut surface 104a can be obtained by the following equation (3).

  Therefore, for example, when t = 20 mm and D = 300 mm, the depth d from the surface of the member 102 of the point 304 located at the distance y from the left end of the cut surface 104a is obtained by the following equation (4). it can.

  As in the present embodiment, the member 102 of the reinforced concrete column 101 is in contact with any one reinforcing bar 103 in the member 102, and the outer periphery of the member 102 in which a line connecting the center of the member 102 and the reinforcing bar 103a is extended. A specimen 106 is prepared by cutting the concrete portion of the member 102 at a cutting surface 104 in a direction parallel to the tangent to the member 102 at the intersection with the member 102 and parallel to the length direction of the reinforcing bar 103a. A test surface greatly enlarged in the depth direction can be obtained. For example, rather than the case where the member 102 shown in FIG. 3 is cut at the cut surface 107 or the cut surface 108 to create a specimen, the specimen cut out by the above method is greatly enlarged in the depth direction. Test surface can be obtained. This makes it possible to meticulously evaluate the resistance to neutralization in the depth direction of the reinforced concrete column 101.

  The concrete used for the reinforced concrete column 101 may be concrete other than centrifugal compacted concrete (for example, vibration compacted concrete). However, the evaluation method of the neutralization resistance characteristic of the present embodiment is centrifugal force. It is considered that the application effect is particularly high for concrete, such as compacted concrete, which is expected to have different middle resistance characteristics between the outer peripheral portion and the central portion.

DESCRIPTION OF SYMBOLS 101 Reinforced concrete pillar 102 Member 103 Reinforcement 104 Cut surface 105 Hollow part 106 Specimen

Claims (3)

A method for evaluating the neutralization characteristics of a reinforced concrete column comprising one or more reinforcing bars,
The reinforced concrete column to be evaluated is in contact with any one reinforcing bar inside the reinforced concrete column, and at the intersection of the outer periphery of the reinforced concrete column that extends a line connecting the center of the reinforced concrete column and the reinforcing bar. The concrete portion of the reinforced concrete column is cut in a direction parallel to a tangent to the reinforced concrete column and parallel to the length direction of the reinforcing bar, and the neutralization characteristic is evaluated using the cut surface. A method for evaluating the resistance to neutralization. The evaluation of the neutralizing property is as follows:
After carrying out the neutralization promotion test or the exposure test by sealing other than the cut surface of the reinforced concrete column,
The method for evaluating neutralization resistance according to claim 1, wherein the cut surface is performed by using a phenolphthalein method. The concrete part of the reinforced concrete column is
3. The method for evaluating resistance to neutralization according to claim 1 or 2, wherein the concrete is made by centrifugal compaction.