JP7461199B2 - Method for evaluating the possibility of efflorescence on the surface of hardened cementitious materials - Google Patents

Description

The present invention relates to a method for evaluating the possibility of efflorescence occurring on the surface of a cementitious hardened body (e.g., the pavement surface of an interlocking block).

It is known that a phenomenon called efflorescence can occur on the surface of a cementitious hardened body (specifically, a hardened body made of concrete, mortar, or cement paste).
Efflorescence is a phenomenon in which moisture, including soluble components, in a cement-containing composition (such as concrete) containing cement, water, etc., moves from the inside of a molded body of the cement-containing composition to the surface, where the soluble components react with carbon dioxide in the air to form a white substance on the surface. Efflorescence is undesirable because it mars the appearance of a product made of a cementitious hardened body.

Conventionally, methods for predicting the occurrence of efflorescence on a concrete surface and methods for evaluating the level (degree) of efflorescence on a concrete surface are known.
As an example, Patent Document 1 describes a method for predicting the occurrence of efflorescence in a quick-removable concrete block, which includes the steps of measuring the amount of water evaporating from the quick-removable concrete block, measuring the amount of calcium ions eluting from the quick-removable concrete block and confirming whether or not the integrated value of eluted calcium ions exceeds a specific value, and measuring the block filling rate of the quick-removable concrete block and confirming whether or not the block filling rate exceeds a specific value.

As another example, Patent Document 2 describes a method for evaluating the degree of efflorescence in concrete, which involves taking images of a concrete specimen before and after the occurrence of efflorescence, calculating the average values of R (red), G (blue), and B (green), which are the three primary colors of light obtained from each image data, calculating the sum of the average values of R (red), G (blue), and B (green) as the RGB total value, calculating the RGB change value by subtracting the RGB total value before the occurrence of efflorescence from the RGB total value after the occurrence of efflorescence, and evaluating the degree of efflorescence in concrete based on the RGB change value.

JP 2009-13021 A Japanese Patent Application Publication No. 2014-41027

An object of the present invention is to provide a method that can evaluate the possibility of efflorescence occurring on the surface of a hardened cementitious body (for example, the paved surface of an interlocking block).

The inventors discovered that the above-mentioned object could be achieved by applying X-ray CT to a hardened cementitious body to obtain an image showing the density distribution inside the hardened cementitious body, then analyzing this image and evaluating areas in the image with relatively high density as areas likely to develop efflorescence, and thus completed the present invention.

The present invention provides the following [1] to [3].
[1] A method for evaluating the possibility of efflorescence occurring on the surface of a cementitious hardened body, comprising: an image acquiring step of applying an X-ray CT method to the cementitious hardened body to obtain an image showing a density distribution inside the cementitious hardened body, in which the higher the whiteness, the higher the density; and an image analyzing step of analyzing the image and evaluating a portion in the image in which the density is relatively high as a portion with a higher whiteness and a higher possibility of efflorescence occurring.
[2] The method for evaluating the possibility of efflorescence occurrence described in [1] above, wherein the cementitious hardened body is an interlocking block consisting of a surface layer having a pavement surface and a base layer laminated thereon.
[3] A method for evaluating the possibility of efflorescence occurrence described in [2] above, in which the acquisition of the image in the image acquisition process is carried out by one or more of the following (a) to (c).
(a) applying the X-ray CT method to an arbitrarily determined point in the thickness direction of the surface layer of the interlocking block, so as to obtain an image of a cross section parallel to the pavement surface; (b) applying the X-ray CT method to an arbitrarily determined point in the thickness direction of the base layer of the interlocking block, so as to obtain an image of a cross section parallel to the pavement surface; (c) applying the X-ray CT method to an arbitrarily determined point in the length or width direction of the pavement surface of the surface layer of the interlocking block, so as to obtain an image of a cross section perpendicular to the pavement surface.

According to the method of the present invention, it is possible to evaluate the possibility of occurrence of efflorescence on the surface of a hardened cementitious body.

It is a perspective view showing an example of an interlocking block. 1 is a photograph showing the occurrence of efflorescence on the pavement surface of the interlocking blocks used in Example 1. 2 is an X-ray CT image of a cross section extending in the horizontal direction of the surface layer portion of the interlocking block used in Example 1. 2 is an X-ray CT image of a cross section extending in the horizontal direction of the base layer portion of the interlocking block used in Example 1. 1 is an X-ray CT image of a cross section extending vertically at the center in the width direction of the interlocking block used in Example 1. This is an image in which the X-ray CT image shown in FIG. 5 is binarized to emphasize brightness and darkness.

The method of the present invention is a method for evaluating the possibility of occurrence of efflorescence on the surface of a hardened cementitious body, and the method is a method for evaluating the possibility of occurrence of efflorescence on the surface of a hardened cementitious body. An image acquisition process that obtains an image showing the distribution of density inside the cell, and the resulting image is analyzed to evaluate areas with relatively high density in this image as areas where there is a high possibility of efflorescence occurring. The method includes an image analysis step.
Hereinafter, the case where the cementitious hardened body is an interlocking block will be explained in detail for each step.

In FIG. 1, an interlocking block 1 is formed by laminating a surface layer 2 having a paved surface 4 and a base layer 3 .
Here, the pavement surface refers to the top surface of a pavement structure (the road surface for pedestrians, etc.) when multiple interlocking blocks are laid at a construction site to form a pavement structure (usually consisting of interlocking blocks and joint sand interposed between the interlocking blocks).
Either water-impermeable or water-permeable interlocking blocks can be used as the interlocking block 1. Among them, water-impermeable ones are preferably used in the present invention, since they have no voids and therefore the density level in an image obtained by X-ray CT can be evaluated without being affected by voids.

An example of a non-permeable interlocking block 1 is one in which the surface layer 2 consists of cement, fine aggregate (e.g., silica sand), and water, and the base layer 3 consists of cement, fine aggregate (e.g., mountain sand), coarse aggregate (e.g., crushed stone with a particle size of 13 mm or less), and water.
In this case, the water-cement ratio (mass ratio of water/cement×100%) in the surface layer 2 is preferably 25 to 35%. The water-cement ratio in the base layer 3 is preferably 22 to 32%.
In the present invention, other examples of the cementitious hardened body include immediately removable concrete products other than interlocking blocks (e.g., concrete slabs) and concrete products produced by methods other than immediately removable concrete products (e.g., those produced by removing the form after a specified curing period).
The dimensions of the interlocking block 1 are not particularly limited, but may be, for example, a length of 150 to 300 mm, a width (a dimension equal to or smaller than the length) of 50 to 200 mm, and a thickness of 50 to 200 mm. In this case, the thickness of the surface layer portion 2 is 3 to 10 mm.

[Image acquisition process]
The image acquisition step is a step of applying the X-ray CT method to the interlocking block 1 to obtain an image showing the density distribution inside the interlocking block 1.
Image acquisition is performed by one or more of the following (a) to (c).
(a) Applying the X-ray CT method to an arbitrarily determined point in the thickness direction of the surface layer 2 of the interlocking block 1 so as to obtain an image of a cross section parallel to the pavement surface 4 (b) ) Applying the X-ray CT method to an arbitrarily determined point in the thickness direction of the base layer portion 3 of the interlocking block 1 so as to obtain an image of a cross section parallel to the pavement surface 4. (c) Interlocking block 1 Apply the X-ray CT method to an arbitrarily determined point in the length direction or width direction of the pavement surface 4 of the surface portion 2 of the rocking block 1 so as to obtain an image of a cross section perpendicular to the pavement surface 4. thing

In the present invention, the X-ray CT method refers to a computer that stores information regarding the absorption of X-rays that traverses the cross section of the cementitious hardened body (interlocking block 1) that is the target surface for image acquisition. A method of obtaining an image of the cross section based on the cross section.
Note that "CT" in the X-ray CT method means computed tomography.
Among the methods (a) to (c) above, the method (a) above images the internal cross-section of the surface layer 2, and unlike the method (c) above, it images the entire paved surface 4. This method is most preferable because information regarding the area can be obtained, and unlike (b) above, it is not affected by coarse aggregate.

[Image analysis process]
The image analysis step is a step in which the image obtained in the image acquisition step is analyzed and a portion of the image with relatively high density is evaluated as a portion with a high possibility of efflorescence occurring.
Image analysis may be performed visually or by applying artificial intelligence (AI) or the like.
In an image, a portion with relatively high density is represented as a portion with higher whiteness, for example.
Portions with relatively high density in the image are represented more clearly by binarizing the image and emphasizing the brightness and darkness so that the difference from the portions with relatively low density can be easily recognized with the naked eye. I can do it.

By applying the method of the present invention to a large number of interlocking blocks manufactured as products, it is possible to separate, for example, those that can be shipped as products (high-quality products) from those that have areas where efflorescence is likely to occur (defective products).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
[Example 1]
(A) Materials used: (1) Cement: Ordinary Portland cement (density: 3.16 g/cm ³ )
(2) Fine aggregate for base layer: mountain sand (FM: 2.68, surface dry density: 2.58 g/cm ³ )
(3) Coarse aggregate for base layer: No. 6 crushed stone (hard sandstone, FM: 6.05)
(4) Fine aggregate for surface layer: No. 5 silica sand (FM: 2.21, surface dry density: 2.60 g/cm ³ )
(5) Water: Tap water

(B) Manufacture of interlocking block With the materials and blending amounts shown in Table 1, an interlocking block having dimensions of 200 mm (length) x 100 mm (width) x 100 mm (thickness) is made as a two-layer block shown in Figure 1. Block 1 was produced. The thickness of the surface layer portion 2 was 5 mm, and the thickness of the base layer portion 3 was 95 mm.
Fourteen days after production, efflorescence was observed on interlocking block 1.
FIG. 2 shows a photograph taken from above of the interlocking block 1 having this efflorescence. In FIG. 2, the white part surrounded by the solid elliptical line indicates efflorescence appearing on the pavement surface 4.

(C) Application of X-ray CT Next, X-ray CT was applied to the interlocking block 1 to obtain the following images.
The X-ray CT method was performed using an X-ray CT device "Microfocus X-ray CT System" (manufactured by Shimadzu Corporation; product name "inspexio SMX-225CT").
The image shown in Fig. 3 is an image of a cross section (a cross section extending horizontally parallel to the pavement surface 4) of the surface layer 2 located 1 mm away from the pavement surface 4. In Fig. 3, the part surrounded by an ellipse with a dotted line indicates an area with a higher whiteness than the other parts. Higher whiteness indicates higher density.
The image shown in Fig. 4 is an image of a cross section (a cross section extending in a horizontal direction parallel to the pavement surface 4) of the base layer portion 3 located 30 mm away from the pavement surface 4. In Fig. 4, the part surrounded by an ellipse with a dotted line indicates an area with a higher whiteness than the part located to the left of the part surrounded by the dotted line.

The image shown in FIG. 5 is an image of a cross section (a cross section perpendicular to the paved surface 4) extending in the vertical direction at the center of the paved surface 4 in the width direction. In FIG. 5, the portion located above the black dotted line indicates a region with higher whiteness than other portions.
The image shown in FIG. 6 is an image obtained by binarizing the image shown in FIG. 5 and emphasizing the brightness (difference between the white part and the black part).
It can be seen from FIGS. 3 to 6 that the areas with high whiteness (areas with high density) in the images obtained by the X-ray CT method correspond to the areas where efflorescence has occurred as shown in FIG.
Therefore, even before efflorescence occurs, if you apply the X-ray CT method to the image of the manufactured interlocking block and look at the image, you will see areas with high whiteness (areas with high density). can be evaluated as areas where there is a high possibility of efflorescence occurring.

1 Interlocking block 2 Surface layer portion 3 Base layer portion 4 Paved surface

Claims (3)

A method for evaluating a possibility of efflorescence occurrence on a surface of a cementitious hardened body, comprising:
an image acquiring step of acquiring an image showing a density distribution inside the cementitious hardened body by applying an X-ray CT method to the cementitious hardened body , the image being such that the higher the whiteness, the higher the density ;
an image analysis step of analyzing the image and evaluating a portion of the image in which the density is relatively high as a portion having a higher whiteness and a higher possibility of efflorescence;
A method for evaluating the possibility of efflorescence occurring on the surface of a cementitious hardened body, comprising: 2. The method for evaluating the possibility of efflorescence generation according to claim 1, wherein the cementitious hardened body is an interlocking block formed by laminating a surface layer portion having a paved surface and a base layer portion. A method for evaluating the possibility of efflorescence occurrence as described in claim 2 , wherein the image acquisition process is performed by one or more of the following (a) to (c).
(a) applying the X-ray CT method to an arbitrarily determined point in the thickness direction of the surface layer of the interlocking block, so as to obtain an image of a cross section parallel to the pavement surface; (b) applying the X-ray CT method to an arbitrarily determined point in the thickness direction of the base layer of the interlocking block, so as to obtain an image of a cross section parallel to the pavement surface; (c) applying the X-ray CT method to an arbitrarily determined point in the length or width direction of the pavement surface of the surface layer of the interlocking block, so as to obtain an image of a cross section perpendicular to the pavement surface.

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