JP2004198119A - Crack monitoring material for concrete structure, and monitoring method using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monitoring material with superior economy and conductivity and a simple structure capable of monitoring generation and progress of a crack of a concrete structure on a real time basis, and a monitoring method using it. <P>SOLUTION: In the crack monitoring material 4 for the concrete structure, conductive powder 2 is filled in a flexible tube 1, and a terminal 3 is attached for measuring a value of resistance of the powder 2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crack monitoring material for a concrete structure and a monitoring method using the same, which are capable of monitoring in real time the generation of cracks due to deterioration of the concrete structure and the progress of the cracks in real time.
[0002]
[Prior art]
Concrete such as tunnels and viaducts deteriorates after a certain period of time from casting, causing cracks in the concrete, which may lead to serious accidents. Therefore, monitoring for concrete cracking is being conducted. Therefore, as a concrete crack monitoring device, cracks have been monitored by embedding an optical fiber in the surface or inside of concrete.
[0003]
An example of the use of optical fiber is the use of the micro-bending principle, in which the light passing through the optical fiber has a bent path, the light leaks out at that location, and the intensity of the light passing through the fiber decreases. Etc. are known. However, the method of monitoring the position of a crack by cutting an optical fiber has a problem that if the fiber is cut, it is impossible to perform subsequent monitoring, and there is also a problem that the cost of the optical fiber is high.
[0004]
Attempts have also been made to monitor cracks in concrete with strain gauges embedded in the concrete, but the method of measuring this strain has too high a measurement accuracy, making it difficult to become a criterion for maintenance. There is.
[0005]
Therefore, the conventional method for monitoring cracks in concrete is to install one or more electrically conductive materials having different elongation properties on the surface or inside of the concrete via an insulating material, and to conduct the electrical conductivity of the material. To measure the occurrence of cracks due to the loss of conductivity and the outline of the width of the cracks, or on the concrete surface or inside, crossing the cracks already occurring Two or more different materials with electrical conductivity are installed via an insulating material, the electrical conductivity of the material is measured, and the change in cracking is monitored after the conductivity is lost. (For example, see Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-257768
However, in the above-described known invention, two or more types of electrically conductive materials having different elongation properties are installed on the surface or inside of the concrete via an insulating material, and there is a problem that the construction is not easy.
[0008]
Further, as the electrically conductive material used in the above-mentioned known invention, a one-part silicone resin, a two-part silicone resin or an epoxy resin mixed with carbon black (carbon powder) is used. Use a putty filler having a conductivity of 5 kΩ · cm or less and exhibiting a putty shape, or use a one-part silicone resin, a two-part silicone resin or an epoxy resin as a material having electrical conductivity with carbon black (carbon powder). ) And a material that reduces the fluidity without impairing the conductivity, and has a conductivity of 5 kΩ · cm or less and a putty-like filler. The material has a problem that the electric resistance value is large.
[0009]
[Problems to be solved by the invention]
The present invention provides a monitoring material having a simple structure, which is excellent in economy and conductivity and capable of monitoring the occurrence and progress of cracks in a concrete structure in real time, and a monitoring method using the same.
[0010]
[Means for Solving the Problems]
The present invention relates to a method for monitoring cracks in a concrete structure in which a flexible tube is filled with a conductive powder or an electrolyte solution, and terminals for measuring the resistance of the conductive powder or the electrolyte solution are attached to both ends. The conductive powder is made of carbon powder or metal oxide powder, and the electrolyte solution is made of a crack monitoring material for concrete structures using NaOH solution or Nacl solution. .
[0011]
Furthermore, the above-mentioned crack monitoring material is disposed on the surface or inside of the concrete structure, and the concrete structure for monitoring the occurrence and progress of cracking of the concrete structure by detecting an increase in the electric resistance value of the crack monitoring material. Crack monitoring method.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a material for monitoring cracks of a concrete structure and a monitoring method using the same according to the present invention will be described with reference to the drawings.
[0013]
First, the concept of the present invention will be described. That is, as shown in the perspective view of FIG. 1, the crack monitoring material 4 of the concrete structure is provided in a flexible tube 1 such as rubber or the like, in a flexible tube 1 such as carbon powder or metal oxide powder such as titanium oxide or zinc oxide. And the like, and a terminal 3 for measuring the resistance value of the powder 2 is attached thereto, and its structure is simple.
[0014]
Next, in the concrete structure monitoring method using the crack monitoring material 4, the crack monitoring material 4 is disposed on the surface of the concrete structure 5 to be monitored as shown in FIG. In the state before the occurrence of the crack, the cross section of the crack monitoring material 4 is constant as shown in FIG. 3, so that the electric resistance value of the crack monitoring material 4 is constant.
[0015]
Further, as shown in FIG. 4, when a crack occurs in the concrete structure 5, the cross-sectional area of the tube 1 and the powder 2 of the monitoring material 4 is reduced and deformed as shown in FIG.
[0016]
That is, after the occurrence of the crack 6, the tube 1 is pulled by following the crack 6, and if the cross-sectional area of the conductive powder 2 is reduced as shown in FIG. 4, the electric resistance increases.
[0017]
Therefore, the relationship between the electric resistance value and the width of the crack 6 becomes as shown in the diagram of FIG. 5, and if this is grasped, by continuously measuring the electric resistance value, the concrete structure 5 can be obtained. Deformation, that is, the occurrence of cracks and the progress thereof can be monitored in real time.
[0018]
Next, experimental results of two series performed as confirmation experiments in the above embodiment will be described below.
[0019]
First, in the series 1, the crack monitoring material 4 shown in FIG. 6 was produced, and the monitoring material 4 was pulled, and the resistance value between the stainless steel terminals 3 was measured. Note that a soft black rubber tube was used as the tube 1 of the crack monitoring material, and carbon powder was used as the powder 2. The length L was 20 cm, the outer diameter D was 5.8 mm, and the inner diameter d was 4.0 mm. And
[0020]
The above-described experiment was performed three times, that is, the first time X, the second time Y, and the third time Z, as shown in FIG. 7, and the results are shown in a relationship diagram between the resistance value and the elongation amount of the tube 1. As can be seen from the diagram of FIG. 7, there is a tendency that the resistance value increases with respect to the amount of elongation of the tube 1, and there is no significant difference in the tendency of the resistance value increase in the results of three experiments. It was confirmed that the crack monitoring material 4 of the invention was a stable monitoring material.
[0021]
Next, in the series 2, as shown in FIG. 8, a rubber tube 1 made of the same material as that of the series 1 is used for a concrete specimen 7 having a size of 100 mm × 100 mm × 400 mm. A crack monitoring material (length: 400 mm) 4 having a rubber diameter of 8 mm X of 4.0 mm inner diameter and Y of 8.4 mm outer diameter and 6.0 mm inner diameter was arranged, and a bending test with a constant load 8 was performed. In this case, carbon powder was used as the conductive powder 2.
[0022]
FIG. 9 shows the relationship between the resistance change amount and the crack width of the concrete specimen 7 in the above experimental results.
[0023]
This resistance change is the difference between the resistance value at a certain crack width and the resistance value before conducting the bending load test. According to this result, the resistance value of the monitoring material increases as the crack width increases. It was confirmed that the material was a material capable of accurately estimating the crack width.
[0024]
In the present embodiment, the monitoring material 4 is arranged on the surface of the concrete structure 5, but may be arranged inside the concrete structure 5. The monitoring material 4 is a flexible tube 1 made of rubber or the like and filled with a conductive powder 2. However, as another embodiment, an electrolyte such as a NaOH solution or an NaCl solution is used. One filled with a solution can also be used.
[0025]
【The invention's effect】
In the above-described crack monitoring material for concrete structures of the present invention and the monitoring method using the same, the cracks and the progress thereof are arranged in real time by arranging a material having a simple structure on the surface or inside of the concrete structure. Monitoring can be easily performed, and the maintenance of the concrete structure can be reliably performed.
[0026]
In addition, the cost is lower than that of the conventional method for monitoring cracks using an optical fiber, and the economic efficiency is extremely high.
[Brief description of the drawings]
FIG. 1 is a perspective view of one embodiment of a crack monitoring material of the present invention.
FIG. 2 is a side cross-sectional view showing a state before the occurrence of cracks in which the monitoring material of FIG. 1 is disposed on a surface of a concrete structure.
FIG. 3 is a front sectional view of the monitoring material of FIG. 2;
FIG. 4 is a side sectional view of the concrete structure of FIG. 2 in a state after occurrence of cracks.
FIG. 5 is a graph showing the relationship between the electric resistance and the crack width during crack monitoring using the monitoring material in the state shown in FIGS. 2 to 4;
FIG. 6 is a perspective view of a monitoring material in a confirmation experiment of a method using the monitoring material of the present invention.
7 is a diagram showing the relationship between the resistance of the monitoring material and the amount of elongation of the tube, showing the experimental results of FIG. 6;
FIG. 8 is a schematic perspective view for explanation in which the monitoring material of the present invention is placed on a concrete specimen and a one-point loading bending test is performed.
9 is a graph showing the experimental results of FIG. 8, showing the relationship between the resistance change of the monitoring material and the crack width of the concrete specimen.
[Explanation of symbols]
1 Tube 2 Powder 3 Terminal 4 Crack monitoring material 5 Concrete structure 6 Crack

Claims (4)

A material for monitoring cracks in a concrete structure in which a flexible tube is filled with a conductive powder or an electrolyte solution and terminals for measuring the resistance value of the conductive powder or the electrolyte solution are attached to both ends. The material for monitoring cracks in concrete structures according to claim 1, wherein carbon powder or metal oxide powder is used as the conductive powder. The crack monitoring material for a concrete structure according to claim 1, wherein a NaOH solution or a Nacl solution is used as the electrolyte solution. A concrete structure in which the crack monitoring material according to claim 1 is disposed on the surface or inside of a concrete structure, and an increase in the electrical resistance value of the crack monitoring material is detected to monitor the occurrence and progress of cracking in the concrete structure. How to monitor cracks in objects.

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