JP2004239682A - Concrete durability evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete durability evaluation method capable of evaluating concrete durability even when the number of passed years is small or when both concrete composition or the like and the elapsed time from concrete placing are unknown or the like. <P>SOLUTION: In the preliminary process, ph gradients a<SB>1</SB>-a<SB>6</SB>are detected on each concrete (X<SB>1</SB>-X<SB>6</SB>) having each known elapsed time (t<SB>1</SB>-t<SB>6</SB>) from concrete placing and each different composition, and the correlation between the ph gradients a<SB>1</SB>-a<SB>6</SB>and neutralization speed coefficients (A<SB>1</SB>-A<SB>6</SB>) in a neutralization speed equation is detected beforehand. In the main process, the ph gradient a<SB>10</SB>is detected relative to concrete (X<SB>10</SB>) whose durability is to be evaluated, and the neutralization speed coefficient (A<SB>10</SB>) of the concrete (X<SB>10</SB>) is detected by utilizing the correlation detected in the preliminary process. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for evaluating the durability of concrete.
[0002]
[Prior art]
In reinforced concrete, concrete loses alkalinity by the action of carbon dioxide gas in the air and gradually neutralizes from the surface. When concrete is neutralized, it loses its rust-preventing effect on reinforcing steel. Corrosion then progresses on the rebars, which causes them to lose the required strength and expand and destroy concrete. Therefore, in a reinforced concrete structure, it is extremely important to evaluate the difficulty of neutralizing concrete, that is, the durability of concrete.
[0003]
As a conventional general method for measuring the neutralization depth of concrete, for example, as described in Patent Document 1, etc., a method of measuring the neutralization depth inside concrete using a phenolphthalein solution There is. Here, in the coloration range of the phenolphthalein solution, since the pH value is about 8.3 to 10.0, the colored portion is defined as an unneutralized region, and the non-colored portion is defined as a neutralized region. The width of the carbonized region is measured to determine the carbonation depth.
[0004]
On the other hand, as a method for evaluating the durability of concrete, a method based on a neutralization rate equation shown below is widely and generally used.
C = At^0.5
C: Neutralization depth (distance from the concrete surface at a position where the pH value becomes a predetermined value)
A: Neutralization rate coefficient determined by concrete mix
t: Elapsed time since casting
[0005]
The neutralization rate coefficient A in the above-described neutralization rate equation is determined by the concrete ratio of the water-cement ratio, the material used, and the like. Since the neutralization speed can be grasped, it represents the durability of the concrete. It can be grasped as an indicator.
[0006]
The above-mentioned neutralization rate equation is preferably used when both the concrete mixing and the like for determining the neutralization rate coefficient A and the elapsed time t from the casting, that is, the number of years, are known. it can.
[0007]
Even if one of the concrete composition and the like and the age is unknown, the other can be used if the other is known. Since the neutralization depth C can be relatively easily determined by, for example, the method described in Patent Document 1, the one from the determined neutralization depth C and the other is known. This is because it can be determined by the following neutralization rate equation.
[0008]
[Patent Document 1]
JP-A-2002-040013, paragraphs [0016] to [0026]
[0009]
[Problems to be solved by the invention]
By the way, the method of measuring the neutralization depth inside concrete using a phenolphthalein solution described in Patent Literature 1 or the like requires that concrete has been aged for about 5 to 10 years since its casting. The reason is that the pH value in the coloration range of the phenolphthalein solution is about 8.3, and therefore, in order to measure the neutralization depth of concrete with a predetermined accuracy, the pH value of the part of about 8.3 is required. Must reach about 5 to 10 mm from the concrete surface. Therefore, in the method described in Patent Document 1 or the like, it is difficult to measure the neutralization depth of concrete that has been cast for less than about 5 years, and this neutralization depth is difficult. It is also difficult to evaluate the durability of concrete by obtaining a neutralization rate coefficient from the above-mentioned neutralization rate equation using the above.
[0010]
In addition, even if the concrete is approximately 5 to 10 years or more after casting, if both the concrete composition and the age are not known, the concrete neutralization rate formula is used to determine the durability of the concrete. Sex evaluation cannot be performed.
[0011]
It is an object of the present invention to provide a concrete capable of evaluating the durability of concrete even when the age is small, or when both the mixing time of concrete and the like and the elapsed time from casting are unknown. It is to provide a durability evaluation method.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the invention described in claim 1 is, for example, as shown in FIGS.
A method for evaluating the durability of concrete,
Concrete with different composition (X₁~ X₆), The rate of change of the pH value inside the concrete with respect to the distance from the concrete surface (pH gradient a₁~ A₆) And the rate of change (a₁~ A₆) And the following formula:
C = At^z
C: Neutralization depth (distance from the concrete surface at a position where the pH value becomes a predetermined value)
A: Neutralization rate coefficient
t: Elapsed time since casting
z: constant
Neutralization rate coefficient (A₁~ A₆) Is detected in advance ([preliminary step]),
Concrete to be evaluated for durability (X₁₀), The rate of change of the pH value inside the concrete with respect to the distance from the concrete surface (pH gradient a₁₀), And utilizing the correlation detected in the preliminary step ([preliminary step]), the concrete (X₁₀) Neutralization rate coefficient (A₁₀) Is detected ([this step]).
[0013]
According to the invention as set forth in claim 1, in the preliminary step, a change rate of a pH value inside the concrete with respect to a distance from the concrete surface is detected across concretes having different compositions, and the change rate and the change rate are determined. The correlation with the neutralization rate coefficient in the above equation is grasped in advance. In this step, the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface is detected for the concrete to be evaluated for durability, and the concrete is used for the concrete based on the correlation. A characterization rate coefficient is detected.
[0014]
That is, according to this method, for concrete for which durability is to be evaluated, by detecting the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface, neutralization as an index for evaluating the durability is detected. The speed coefficient can be detected. Therefore, it is possible to detect the neutralization rate coefficient of concrete in which both the concrete composition and the like and the elapsed time from casting are unknown, and thereby to evaluate the durability.
[0015]
The constant z is, for example, 0.5, but is not particularly limited.
[0016]
Note that the preliminary step may be specifically performed as follows.
That is, first, in a plurality of types of concrete different in composition, each of which has a known elapsed time from the casting, the pH value is measured at a plurality of points in the depth direction inside the concrete, and the plurality of types are determined from the results. For each of the concretes, the rate of change is detected. Specifically, the relationship between the distance from the concrete surface and the pH value, for example,
y = ax + b
x: distance from concrete surface
y: pH value at distance x from concrete surface
a: pH gradient
b: pH value of concrete surface
If expressed as, the pH gradient corresponds to the rate of change. The relationship between the distance from the concrete surface and the pH value is not limited to the above-described linear expression, but is expressed by a secondary expression, a tertiary expression, or any other expression. Of course, it is good. At this time, the method for measuring the pH value inside the concrete is not particularly limited. That is, any method may be used, such as a method of measuring concrete by cutting it, a method of measuring with a core removed, a method of measuring by drilling with a drill, or a method of measuring and photographing a concrete cross section with a digital camera, which will be described later.
[0017]
Next, for each of the plurality of types of concrete, the neutralization rate coefficient is detected from the above equation using the pH value measured as described above and the elapsed time since casting. Finally, a correlation between the rate of change and the neutralization rate coefficient is detected. This correlation may be formulated as needed.
[0018]
It should be noted that the preliminary step needs to be carefully performed, for example, only once before evaluating the durability of the concrete, and need not be performed each time this step, that is, every time the durability of the concrete is evaluated.
[0019]
According to a second aspect of the present invention, in the method for evaluating the durability of concrete according to the first aspect, for example, as shown in FIGS.
In at least one of the preliminary step ([preliminary step]) and the main step ([main step]), the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface (pH gradient a)₁~ A₆, A₁₀) Is detected ([pH value change rate detection step])
a coloring color grasping step (<coloring color grasping step>) in which the coloration of the pH value detection indicator corresponding to the pH value is grasped in advance;
a photographing step (<photographing step>) of photographing a concrete section colored by the pH value detection indicator with a digital camera;
For each pixel of the photographed image obtained in the photographing step, a photographed image analysis processing step (<photographed image analysis processing step>) of grasping the color and assigning a position in the concrete section;
For each position of the concrete cross section, by comparing the colored colors grasped in the colored color grasping step (<colored color grasping step>) and the photographed image analysis processing step (<captured image analysis processing step>), respectively. Of the change rate (pH gradient a₁~ A₆, A₁₀) For detecting a color-based color contrast analysis step (<color-colored contrast analysis step>).
[0020]
According to the invention described in claim 2, in at least one of the preliminary step and the main step, the detection of the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface is performed as follows. Is
First, in the coloring color grasping step, the coloring color corresponding to the pH value of the pH value detection indicator is grasped in advance. Then, in the photographed image analysis processing step, for each pixel in the photographed image of the concrete cross section obtained from the photographing step, the color development color is grasped and the position in the concrete cross section is assigned. Further, in the coloring color comparison analysis step, by comparing the coloring colors grasped in the coloring color grasping step and the photographed image analysis processing step, a pH value for each position of the concrete cross section is obtained. Thus, the change rate is detected. Here, the coloring color grasping step, the photographed image analysis processing step, and the coloring color comparison analysis step can be performed using a computer, so that these operations can be performed quickly and accurately. That is, it is possible to quickly and accurately obtain the pH value of the concrete section colored by the pH value detection indicator, while reducing the burden on the operator, such as the trouble of visually determining.
[0021]
According to a third aspect of the present invention, there is provided a concrete durability evaluation method according to the second aspect, as shown in FIG.
In the coloring color grasping step (<coloring color grasping step>) and the photographed image analyzing / working step (<photographed image analyzing / working step>), grasping of the color is performed by digitization.
[0022]
According to the third aspect of the present invention, in the coloring color grasping step and the photographed image analysis processing step, the grasping of the coloring color is performed by digitizing, so that the comparison of the coloring colors in the coloring color comparison analysis step is performed. It can be performed quickly and accurately using a computer or the like, and the pH value inside the concrete can be more quickly and accurately determined. Therefore, the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface can be more quickly and accurately determined.
[0023]
According to a fourth aspect of the present invention, as shown in FIGS. 2 and 3, for example, in the concrete durability evaluation method according to the second or third aspect,
The pH value detection indicator is methyl green, pentamethoxy red, tropeolin ooh, hexamethoxy red, methyl orange, methyl red, bromthymol blue, neutral red, α-naphtholphthalein, thymol blue, phenol phthalate Rain, Nile Blue, Xylenolphthalein, Thymolphthalein, Alizanin Yellow, Polier Blue, Tropeolin O, or at least two of them in a prescribed proportion It is characterized by being mixed with.
[0024]
According to the invention as set forth in claim 4, the pH value detection indicator is one of the plurality of pH value detection indicators, or at least two of them at a predetermined ratio. It is a mixture. In particular, when a plurality of the pH value detection indicators described above are mixed at a predetermined ratio and used as a new pH value detection indicator, the coloring color increases as compared with the case where the pH value detection indicator is used alone. The difference clearly appears as a difference in the color of the pH detection indicator. This makes it possible to accurately calculate the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface even for concrete with a small age. Therefore, it is possible to reliably evaluate the durability of concrete with a small age.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
The present embodiment relates to a method for evaluating the durability of concrete by measuring the rate of change of carbonation of concrete and the like. The present invention, as shown in FIG. 1, for example, is largely composed of a [preliminary step] and a [main step]. The [preliminary step] comprises a [pH value change rate detecting step] and a [correlation detecting step], and the [main step] comprises a [pH value change rate detecting step] and a [neutralization rate coefficient detecting step]. Is done. Further, the [pH value change rate detection step] includes a <colored color grasping step>, a <photographing step>, a <photographed image analysis processing step>, and a <colored color contrast analysis step>. The details will be described below.
[0026]
[Preliminary process]
This step detects the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface for a plurality of types of concrete different in composition, each of which has a known elapsed time from the casting, and the rate of change, The following neutralization rate equation:
C = At^z
C: Neutralization depth (distance from the concrete surface at a position where the pH value becomes a predetermined value)
A: Neutralization rate coefficient
t: Elapsed time since casting
z: constant
In this step, the correlation with the neutralization rate coefficient is detected in advance. Hereinafter, for convenience, a plurality of types, for example, six types of concrete X₁~ X₆And the elapsed time from these castings is t₁~ T₆  And The [preliminary step] includes a [pH value change rate detecting step] and a [correlation detecting step]. Hereinafter, the [pH value change rate detecting step] will be described.
[0027]
[PH value change rate detection step]
In this process, the above-mentioned six types of concrete X₁~ X₆The pH gradient a, which is the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface.₁~ A₆Is a step of detecting Specifically, for example, as shown in FIG.₁~ X₆In each case, the concrete section is colored with the pH value detection indicator shown in FIGS. 2 and 3, and the colored concrete section is photographed with a digital camera. Then, by analyzing the captured images, six types of concrete X₁~ X₆In each case, pH values were measured at a plurality of points in the depth direction of the concrete cut surface, and from these results, six types of concrete X were measured.₁~ X₆For each, the pH gradient a₁~ A₆Is a step of detecting The [pH value change rate detecting step] includes a <colored color grasping step>, a <photographing step>, a <photographed image analysis processing step>, and a <colored color contrast analysis step>. Hereinafter, description will be made in order from <colored color grasping step>.
[0028]
<Color detection process>
This step is a step in which, for each of a plurality of types of pH value detection indicators as shown in FIGS. 2 and 3, for example, the coloring color corresponding to the pH value is grasped in advance.
In addition, as a pH detection indicator, methyl green, pentamethoxy red, tropeolin ooh, hexamethoxy red, methyl orange, methyl red, bromthymol blue, neutral red, α-naphtholphthalein, thymol blue, phenol One of phthalein, nile blue, xylenol phthalein, thymol phthalein, alizanin yellow, polier blue, tropeolin o, or at least two of these These are mixed in proportions.
[0029]
FIG. 2 shows the coloring color and the pH value at that time when the above-described pH detection indicator is used alone. FIG. 3 shows a mixture of a plurality of the above-described pH detection indicators at a predetermined ratio. This shows the color and the pH value at that time when used. In the present embodiment, as a method of grasping the color corresponding to the pH value, a method of digitizing and indicating the color corresponding to the pH value is used. Specifically, there are, for example, additive color mixing and subtractive color mixing described later. In addition to the digitizing method, a color sample corresponding to the pH value, that is, a color sample may be created in advance as a method of grasping the color corresponding to the pH value.
[0030]
<Photographing process>
In this step, for example, as shown in FIG.₁~ X₆In each case, the concrete section is colored by the pH value detection indicator shown in FIGS. 2 and 3, and the colored concrete section is photographed by a digital camera.
[0031]
When a plurality of the pH value detection indicators described above are mixed at a predetermined ratio and used as a new pH value detection indicator, the coloring color increases as compared with the case where the pH value detection indicator is used alone. The difference is clearly shown as a difference in the color of the pH detection indicator. This makes it possible to accurately calculate the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface even for concrete with a small age.
[0032]
<Shooting image analysis process>
This step is, for example, as shown in FIG. 4 (a), a step of grasping the coloring color and assigning the actual position in the concrete section to each pixel p of the captured image obtained in the [photographing step]. Each pixel p is also called a pixel, and an image captured by a digital camera is formed as an aggregate of these pixels. In order to grasp the color of each pixel p, for example, it is preferable to use a method of digitizing a color corresponding to the pH value and expressing the color in advance. As this method, for example, a method using RGB values by additive color mixing or subtractive color mixing using CMY values can be used.
[0033]
FIG. 4B is a diagram showing the color of the pixel ascertained using the RGB values. The RGB values represent the emission luminance of each of Red, Green, and Blue in hexadecimal notation from 00 to ff, and are expressed in six digits in the order of RGB.
[0034]
<Color comparison process>
In this step, the pH value at each position of the concrete section is determined by comparing the color colors obtained in the <colored color grasping step> and the <photographed image analysis / processing step>, respectively, to obtain a pH gradient a.₁~ A₆Is a step of detecting In addition, since the grasp of the coloring colors in the <coloring color grasping step> and the <photographed image analysis processing step> is digitized, the pH value inside the concrete can be quickly and quickly determined by comparing the coloring colors using a computer. Can be determined accurately, which results in a pH gradient a₁~ A₆Can be determined more quickly and accurately.
[0035]
The method of measuring the pH value by photographing with a digital camera as described above has the following advantages. That is, since the <colored color grasping step>, the <photographed image analysis processing step>, and the <colored color contrast analysis step> can be performed using a computer, the pH value of the concrete section colored by the pH value detection indicator is used. Can be obtained quickly and accurately while saving the burden on the operator, such as the trouble of visually determining.
[0036]
From the pH values obtained as described above, six types of concrete X₁~ X₆For the pH gradient a₁~ A₆Are respectively detected. Specifically, the relationship between the distance from the concrete surface and the pH value obtained as described above is, for example, as shown in FIG.
y_i= A_i・ X_i+ B_i  (I = 1-6)
x_i： Distance from concrete surface
y_i： Distance x from concrete surface_iPH value at
a_i: PH gradient
b_i: PH value of concrete surface
If expressed as_i  Is the pH gradient. The pH gradient a₁~ A₆Can also be appropriately performed using a computer.
[0037]
As described above, the [pH value change rate detecting step] is completed. Hereinafter, the [correlation detection step] subsequent to this will be described.
[0038]
(Correlation detection step)
This step is based on the results obtained in the [pH value change rate detecting step] and the elapsed time t since the casting.₁~ T₆And the following neutralization rate equation:
C = At^z
C: Distance from the concrete surface at the position where the pH value becomes a predetermined value
A: Neutralization rate coefficient
t: Elapsed time since casting
z: constant
From several types of concrete X₁~ X₆For the neutralization rate coefficient A₁~ A₆Each is calculated, and the calculated neutralization rate coefficient A₁~ A₆And the pH gradient a obtained in the [pH value change rate detecting step].₁~ A₆This is a step of detecting a correlation with Here, the constant z in the above equation is, for example, 0.5.
[0039]
That is, as shown in FIG. 5B, the distance x from the concrete surface at which the pH value measured in the [pH value change rate detecting step] becomes a predetermined value, for example, about 8.3.₁~ X₆And the elapsed time t since the casting₁~ T₆Are respectively substituted into the above-described neutralization rate equation, whereby the neutralization rate coefficient A₁~ A₆Can be calculated. Then, the pH gradient a obtained in the aforementioned [pH value change rate detecting step]₁~ A₆Find the correlation with Specifically, the neutralization rate coefficient A₁~ A₆  And pH gradient a₁~ A₆May be plotted on a graph and formulated (for convenience, A = f (a)). Thus, the [preliminary process] is completed.
[0040]
[This step]
This step is performed, for example, as shown in FIG.₁₀The pH value of the cross section of₁₀And the detected pH gradient a₁₀Is substituted for A = f (a) detected in the [preliminary step], whereby the neutralization rate coefficient A₁₀Is a step of detecting [This step] includes a [pH value change rate detection step] and a neutralization rate coefficient detection step. Hereinafter, the [pH value change rate detecting step] will be described.
[0041]
[PH value change rate detection step]
In this process, concrete X whose elapsed time since casting is unknown.₁₀The pH gradient a, which is the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface.₁₀Is a step of detecting Concrete X₁₀The pH value was measured at a plurality of points in the depth direction of the cut section of the concrete, and from the results, the concrete X₁₀PH gradient a₁₀May be detected. The [pH value change rate detecting step] includes a <colored color grasping step>, a <photographing step>, a <photographed image analysis processing step>, and a <colored color contrast analysis step> performed in the [preliminary step].
[0042]
That is, since the pH value is measured by a method using a digital camera, the pH value of the concrete section colored by the pH value detection indicator can be quickly and accurately reduced without the burden of the operator, such as the trouble of visually judging the pH value. Can be sought. In addition, since a plurality of the above-mentioned pH value detection indicators are mixed at a predetermined ratio and used as a new pH value detection indicator, the concrete X whose durability is to be evaluated is used.₁₀PH gradient a₁₀Can be accurately detected. In addition, since the grasping of the coloring colors in the <coloring color grasping step> and the <photographed image analyzing / processing step> is performed by digitizing, in the <coloring color comparison analysis step>, the comparison of the coloring colors is performed quickly using a computer. And can be performed accurately. Thereby, the concrete X whose durability should be evaluated₁₀PH value inside the concrete of the concrete can be determined more quickly and accurately.₁₀Can be determined more quickly and accurately.
[0043]
(Neutralization rate coefficient detection step)
In this step, the concrete X detected in [pH value change rate detecting step] of [this step] is used.₁₀PH gradient a for₁₀Is determined by A = f (a) (neutralization rate coefficient A₁~ A₆  And pH gradient a₁~ A₆The correlation with concrete)₁₀Neutralization rate coefficient A for₁₀Is a step of detecting Thus, [this step] is completed.
[0044]
Neutralization rate coefficient A detected as described above₁₀Is determined by the concrete composition and the like as described above.₁₀It is one index for evaluating the durability of the steel. That is, when the number of years since the casting is small, or when the concrete X in which both the concrete mixing and the elapsed time since the casting are unknown,₁₀, The durability can be evaluated.
[0045]
In addition, from A = f (a) detected in the [preliminary step], the above-described neutralization rate equation can be calculated, for example, as shown in FIG.
C = f (a) · t^z
C: Distance from the concrete surface at the position where the pH value becomes a predetermined value
a: pH gradient
t: Elapsed time since casting
z: constant
Can be expressed as Here, the constant z is, for example, 0.5.
[0046]
As described above, according to the present embodiment, the following effects can be obtained.
[0047]
(1) In the [preliminary process], six types of concrete X having different compositions₁~ X₆Over time, the pH gradient a, which is the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface₁~ A₆Are detected, and these pH gradients a₁~ A₆And the neutralization rate coefficient A in the neutralization rate equation₁~ A₆(A = f (a)) is grasped in advance. In this process, the concrete X to be evaluated for durability₁₀Against the pH gradient a₁₀Is detected, and the concrete X is detected using the correlation (A = f (a)).₁₀Neutralization rate coefficient A₁₀Is detected.
[0048]
That is, according to this method, the concrete X whose durability is to be evaluated₁₀The rate of change a of the pH value inside the concrete relative to the distance from the concrete surface a₁₀, A neutralization rate coefficient A as an index for evaluating durability₁₀Can be detected. Therefore, the concrete X in which both the concrete mix and the like and the elapsed time from the casting are unknown.₁₀The neutralization rate coefficient A₁₀Is detected, whereby the durability can be evaluated.
[0049]
(2) In the [preliminary step] and the [main step], the pH gradient a₁~ A₆, A₁₀Is detected as follows. First, in the <colored color grasping step>, the color of the pH value detection indicator corresponding to the pH value is grasped in advance. Then, in the <photographed image analysis processing step>, for each pixel p in the photographed image of the concrete cross section obtained from the <photographing step>, the color is grasped and the position in the concrete cross section is assigned. Further, in the <colored color contrast analysis step>, the color values grasped in the <colored color grasping step> and the <photographed image analysis / processing step> are compared, so that the pH value at each position of the concrete cross section is obtained. Sought, the pH gradient a₁~ A₆, A₁₀Is detected. Here, the <colored color grasping step>, the <photographed image analysis processing step>, and the <colored color contrast analysis step> can be performed using a computer, so that these operations can be performed quickly and accurately. That is, it is possible to quickly and accurately obtain the pH value of the concrete section colored by the pH value detection indicator, while reducing the burden on the operator, such as the trouble of visually determining.
[0050]
(3) In the <colored color grasping step> and the <photographed image analyzing / processing step>, the grasping of the colored color is performed in a digitized manner. It can be performed quickly and accurately, and the pH value inside the concrete can be determined more quickly and accurately. Therefore, the pH gradient a₁~ A₆, A₁₀Can be determined more quickly and accurately.
[0051]
{Circle around (4)} The pH value detection indicator is a mixture of any one of the aforementioned plurality of pH value detection indicators or at least two of them at a predetermined ratio. In particular, when a plurality of the pH value detection indicators described above are mixed at a predetermined ratio and used as a new pH value detection indicator, the coloring color increases as compared with the case where the pH value detection indicator is used alone. The difference clearly appears as a difference in the color of the pH detection indicator. Thereby, concrete X₁₀PH gradient a even when the age of₁₀Can be accurately detected. Therefore, concrete X₁₀, The durability can be reliably evaluated.
[0052]
The method for evaluating the durability of concrete according to the present invention is not limited to the present embodiment, and various improvements and design changes may be made without departing from the gist of the present invention.
[0053]
For example, in the present embodiment, in the [main process] and the [preliminary process], the [pH value change rate detecting process], the pH gradient a₁~ A₆, A₁₀Is photographed by a digital camera, but the present invention is not particularly limited to this configuration. That is, the pH gradient a₁~ A₆, A₁₀May be detected without using a digital camera or the like, for example, by an operator visually confirming the color developed by the pH detection indicator.
[0054]
【The invention's effect】
According to the first aspect of the present invention, as for an index for evaluating the durability, the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface is detected for the concrete whose durability is to be evaluated. Neutralization rate coefficient can be detected. Therefore, it is possible to detect the neutralization rate coefficient of concrete in which both the concrete composition and the like and the elapsed time from casting are unknown, and thereby to evaluate the durability.
[0055]
According to the second aspect of the present invention, the same effects as those of the first aspect can be obtained, of course, the colored color grasping step, the photographed image analyzing / processing step, and the colored color contrast analyzing step. Can be performed using a computer, so that these operations can be performed quickly and accurately. That is, it is possible to quickly and accurately obtain the pH value of the concrete section colored by the pH value detection indicator, while reducing the burden on the operator, such as the trouble of visually determining.
[0056]
According to the third aspect of the present invention, the same effects as those of the second aspect can be obtained, and of course, the comparison of the colored colors in the colored color contrast analysis step can be performed quickly and using a computer or the like. It can be performed accurately and the pH value inside the concrete can be determined more quickly and accurately. Therefore, the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface can be more quickly and accurately determined.
[0057]
According to the invention set forth in claim 4, it is needless to say that the same effects as those of the invention set forth in claim 2 or 3 can be obtained. When mixed as a proportion and used as a new pH value detection indicator, since the color of the color increases more than when used alone, a slight difference in the pH value in the concrete cross section clearly becomes a difference in the color of the pH detection indicator. Appears. This makes it possible to accurately calculate the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface even for concrete with a small age. Therefore, it is possible to reliably evaluate the durability of concrete with a small age.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall flow of a concrete durability evaluation method according to the present invention.
FIG. 2 is a view showing a coloring color corresponding to a pH value when the pH detection indicator according to the present invention is used alone.
FIG. 3 is a view showing a coloring color corresponding to a pH value when a plurality of kinds of pH detection indicators according to the present invention are mixed and used.
FIG. 4A is a diagram illustrating pixels of a digital camera, and FIG. 4B is a diagram illustrating a color of a pixel ascertained using RGB values.
FIG. 5 (a) is a diagram showing the relationship between the distance from the concrete surface and the pH value of a plurality of types of concrete, and FIG. Distance x from surface₁~ X₆And the elapsed time t since the casting₁~ T₆And the neutralization rate coefficient A₁~ A₆Is a diagram showing a situation in which is calculated, and (c) is a diagram showing a situation in which the correlation between the pH gradient a and the neutralization rate coefficient A is grasped.
FIG. 6 is a diagram showing a neutralization rate equation expressed using a pH gradient.
[Explanation of symbols]
X₁~ X₆          Concrete of different mixes with known time since casting
t₁  ~ T₆        Concrete X₁~ X₆Elapsed time since casting
a₁~ A₆          Concrete X₁~ X₆PH gradient of
A₁~ A₆          Concrete X₁~ X₆Neutralization rate coefficient
X₁₀                Concrete for which both the concrete mix and the elapsed time since casting are unknown
a₁₀                Concrete X₁₀PH gradient of
A₁₀                Concrete X₁₀Neutralization rate coefficient
p pixels

Claims (4)

A method for evaluating the durability of concrete,
Along with detecting the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface across concretes having different compositions, the rate of change and the following equation are calculated.
C = A · ^tz
C: Neutralization depth (distance from the concrete surface at a position where the pH value becomes a predetermined value)
A: neutralization rate coefficient t: elapsed time from casting z: preliminary step of previously detecting a correlation with the neutralization rate coefficient in a constant;
For the concrete to be evaluated for durability, the rate of change of the pH value inside the concrete with respect to the distance from the concrete surface is detected, and the correlation detected in the preliminary process is used to detect the pH value inside the concrete. And a main step of detecting a concreting rate coefficient. In at least one of the preliminary step and the main step, a step of detecting a rate of change of a pH value inside the concrete with respect to a distance from the concrete surface,
a coloring color grasping step of grasping in advance the coloring color corresponding to the pH value of the pH value detection indicator,
a photographing step of photographing a concrete section colored by the pH value detection indicator with a digital camera,
For each pixel of the photographed image obtained in the photographing step, a photographed image analysis processing step of allocating a position in the concrete cross section while grasping the coloring color,
By comparing the coloring colors grasped in the coloring color grasping step and the photographed image analysis processing step, a pH value for each position of the concrete section is determined, and a coloring color contrast analysis for detecting the change rate is performed. The method for evaluating durability of concrete according to claim 1, comprising a step. The method for evaluating the durability of concrete according to claim 2, wherein in the colored color grasping step and the photographed image analyzing / processing step, the colored color is grasped and digitized. The pH value detection indicator is methyl green, pentamethoxy red, tropeolin ooh, hexamethoxy red, methyl orange, methyl red, bromthymol blue, neutral red, α-naphtholphthalein, thymol blue, phenol phthalate Rain, Nile Blue, Xylenolphthalein, Thymolphthalein, Alizanin Yellow, Poarier Blue, Tropeolin O, or at least two of them in a prescribed proportion The method for evaluating the durability of concrete according to claim 2 or 3, wherein the concrete is mixed.

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