Intelligent monitoring method for crack repair performance of cement-based materials based on resistance

Abstract

This invention discloses an intelligent monitoring method for the crack repair performance of cement-based materials based on resistance, comprising the following steps: (1) during the molding process of cement materials, a conductive medium is added, electrodes are pre-embedded, and cement-based material specimens are obtained after curing; (2) the resistance data of the above specimens and the cracked specimens are measured respectively; (3) the cracked specimens are repaired by grouting with cement-based materials containing conductive medium during molding, and then cured; (4) the resistance data of the cement-based material specimens after grouting are measured, and the repair rate of the cement-based material cracks is characterized by the degree of resistance recovery. The intelligent monitoring method of this invention can accurately determine the degree of crack repair by the degree of resistance recovery, and this method can achieve non-destructive and rapid detection of cement-based material cracks without damaging the specimens; in addition, the testing tools used in this invention are simple and easy to apply in engineering sites, and have the characteristics of convenient operation and high accuracy.

Description

Technical Field

[0001] This invention relates to a method for monitoring the crack repair performance of cement-based materials, and more particularly to an intelligent monitoring method for the crack repair performance of cement-based materials based on resistance. Background Technology

[0002] Cement concrete possesses excellent properties such as abundant raw materials, good plasticity, high compressive strength, good durability, easily adjustable performance, and the ability to be reinforced with steel bars. It is a major civil engineering material and currently the most widely used man-made material, extensively applied in building construction, bridge and road engineering, water conservancy projects, and underground engineering. However, concrete undergoes volume changes during the hardening process. Besides deformation caused by loads, it also deforms due to various physical and chemical factors. When this deformation is constrained, tensile stress often occurs. When this tensile stress exceeds the tensile strength of the concrete, cracks will form. How to repair cement-based concrete cracks in a timely and effective manner is one of the urgent problems that needs to be solved to ensure the long-term safe operation of engineering projects.

[0003] Currently, there are two main methods for repairing cracks in cement concrete: passive grouting and active self-deposition of minerals, both of which have achieved good crack repair results. Existing methods for characterizing the degree of crack repair include image recognition area repair rate, water penetration resistance, chloride ion penetration resistance, and non-destructive X-ray tomography (NDT). However, image recognition area repair rate can only assess the surface and cannot present the overall repair status; water penetration resistance and chloride ion penetration resistance methods cannot be applied to practical engineering projects; and NDT, while an excellent indoor detection method, is difficult to use in engineering applications. Therefore, there is an urgent need to develop a simple, efficient crack characterization method applicable to both indoor and field use. Summary of the Invention

[0004] Purpose of the invention: The present invention aims to provide an intelligent monitoring method for the crack repair performance of cement-based materials based on resistance, which can be used for non-destructive, simple and rapid determination of cracks in cement-based materials.

[0005] Technical solution: The intelligent monitoring method for crack repair performance of cement-based materials based on resistance, as described in this invention, includes the following steps:

[0006] (1) During the molding process of cement materials, a conductive medium is added, electrodes are pre-embedded, and cement-based material specimens are obtained after curing.

[0007] (2) Measure the resistance data of the above-mentioned specimens and the specimens after cracking respectively;

[0008] (3) For cracked specimens, the cracks were repaired by grouting with cement-based materials containing conductive media during molding, and then cured.

[0009] (4) Measure the resistance data of the cement-based material specimens after grouting, and characterize the repair rate of the cracks in the cement-based material by the degree of resistance recovery.

[0010] Furthermore, the conductive medium is one or more of carbon fiber, steel fiber, steel slag powder, carbon black, and multi-walled carbon nanotubes.

[0011] Furthermore, the amount of carbon fiber or carbon black added accounts for 0.1-2.0% of the volume fraction of the cement material.

[0012] Furthermore, the amount of steel fiber, steel slag powder or multi-walled carbon nanotubes added accounts for 1%-5% of the mass fraction of the cement material.

[0013] Furthermore, the pre-embedded electrode is a nickel sheet electrode, a copper sheet electrode, or a metal mesh electrode.

[0014] Furthermore, the pre-embedded electrodes have dimensions of 20mm × 60mm and a spacing of 10-200mm.

[0015] Furthermore, the system used for testing the resistance data is a resistance monitoring system, which includes a voltage regulator for adjusting the input voltage, a conductive medium for transmitting electrical signals, electrical signal receiving electrodes, and a multimeter for measuring electrical signals.

[0016] Furthermore, the crack width is 100-1000 μm.

[0017] Furthermore, the humidity of the maintenance environment is 90-95%, and the temperature is 20-23℃.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) It realizes non-destructive testing. The intelligent monitoring method described in the present invention embeds conductive medium and electrodes when the cement-based material is formed. It can quickly detect the cracks in the cement-based material without damaging the specimen. It is a simple and convenient non-destructive testing method; (2) It realizes the accurate judgment of the repair rate of cement-based material. After the crack is generated, the resistance of the cement-based material increases. After grouting repair, the resistance decreases. After the crack is completely repaired, the resistance returns to the initial value. The degree of crack repair is judged by the degree of resistance recovery, so the crack repair rate can be accurately judged; (3) The testing tools relied upon by the method of the present invention are simple and easy to apply in the engineering site. It has the characteristics of convenient operation and high accuracy. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of resistance detection;

[0020] Figure 2 A graph showing the relationship between different grouting levels and electrical resistance;

[0021] Figure 3This is a graph showing the relationship between grouting depth and the degree of resistance repair. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1

[0024] A smart monitoring method for the crack repair performance of cement-based materials based on electrical resistance, comprising the following steps:

[0025] (1) Cement-based material specimens of 40mm×40mm×160mm were formed according to the mass ratio of cement, sand and water of 1:3:0.5. During the forming process, conductive carbon fiber was added with a volume content of 1.0%. Nickel sheet electrodes were pre-embedded with an electrode size of 20mm×60mm and a spacing of 120mm. The specimens were cured under standard conditions of 90%-95% humidity and 20-23℃ temperature.

[0026] (2) After the cement-based material specimens were cured to 28 days, the basic resistance data of the uncracked cement-based material specimens were measured by a resistance monitoring system consisting of a voltage regulator for adjusting the input voltage, a conductive medium for transmitting electrical signals, an electrode for receiving electrical signals, and a multimeter for measuring electrical signals. Cracks were artificially created by a pressure testing machine with a crack width of 600 μm, and the resistance after cracking was measured.

[0027] (3) Cracks are repaired by grouting with cement-based materials containing conductive media during molding. The grouting degree is 25% of the crack depth. The cracks are cured under standard conditions of 90%-95% humidity and 20-23℃.

[0028] (4) After the cement-based material specimens have been cured for 7 days, the resistance of the cement-based material specimens with a grouting degree of 25% of the crack depth is measured.

[0029] Example 2

[0030] A smart monitoring method for the crack repair performance of cement-based materials based on electrical resistance, comprising the following steps:

[0031] (1) Cement-based material specimens of 40mm×40mm×160mm were formed according to the mass ratio of cement, sand and water of 1:3:0.5. During the forming process, conductive carbon fiber was added with a volume content of 1.0%. Nickel sheet electrodes were pre-embedded with an electrode size of 20mm×60mm and a spacing of 120mm. The specimens were cured under standard conditions of 90%-95% humidity and 20-23℃ temperature.

[0032] (2) After the cement-based material specimens were cured to 28 days, the basic resistance data of the uncracked cement-based material specimens were measured by a resistance monitoring system consisting of a voltage regulator for adjusting the input voltage, a conductive medium for transmitting electrical signals, an electrode for receiving electrical signals, and a multimeter for measuring electrical signals. Cracks were artificially created by a pressure testing machine with a crack width of 600 μm, and the resistance after cracking was measured.

[0033] (3) Cracks are repaired by grouting with cement-based materials containing conductive media during molding. The grouting degree is 25% of the crack depth. The cracks are cured under standard conditions of 90%-95% humidity and 20-23℃.

[0034] (4) After the cement-based material specimens have been cured for 7 days, the resistance of the cement-based material specimens with a grouting degree of 50% of the crack depth is measured.

[0035] Example 3

[0036] A smart monitoring method for the crack repair performance of cement-based materials based on electrical resistance, comprising the following steps:

[0037] (1) Cement-based material specimens of 40mm×40mm×160mm were formed according to the mass ratio of cement, sand and water of 1:3:0.5. During the forming process, conductive carbon fiber was added with a volume content of 1.0%. Nickel sheet electrodes were pre-embedded with an electrode size of 20mm×60mm and a spacing of 120mm. The specimens were cured under standard conditions of 90%-95% humidity and 20-23℃ temperature.

[0038] (2) After the cement-based material specimens were cured to 28 days, the basic resistance data of the uncracked cement-based material specimens were measured by a resistance monitoring system consisting of a voltage regulator for adjusting the input voltage, a conductive medium for transmitting electrical signals, an electrode for receiving electrical signals, and a multimeter for measuring electrical signals. Cracks were artificially created by a pressure testing machine with a crack width of 600 μm, and the resistance after cracking was measured.

[0039] (3) Cracks are repaired by grouting with cement-based materials containing conductive media during molding. The grouting degree is 25% of the crack depth. The cracks are cured under standard conditions of 90%-95% humidity and 20-23℃.

[0040] (4) After the cement-based material specimens have been cured for 7 days, the resistance of the cement-based material specimens with a grouting degree of 75% of the crack depth is measured.

[0041] Example 4

[0042] A smart monitoring method for the crack repair performance of cement-based materials based on electrical resistance, comprising the following steps:

[0043] (1) Cement-based material specimens of 40mm×40mm×160mm were formed according to the mass ratio of cement, sand and water of 1:3:0.5. During the forming process, conductive carbon fiber was added with a volume content of 1.0%. Nickel sheet electrodes were pre-embedded with an electrode size of 20mm×60mm and a spacing of 120mm. The specimens were cured under standard conditions of 90%-95% humidity and 20-23℃ temperature.

[0044] (2) After the cement-based material specimens were cured to 28 days, the basic resistance data of the uncracked cement-based material specimens were measured by a resistance monitoring system consisting of a voltage regulator for adjusting the input voltage, a conductive medium for transmitting electrical signals, an electrode for receiving electrical signals, and a multimeter for measuring electrical signals. Cracks were artificially created by a pressure testing machine with a crack width of 600 μm, and the resistance after cracking was measured.

[0045] (3) Cracks are repaired by grouting with cement-based materials containing conductive media during molding. The grouting degree is 25% of the crack depth. The cracks are cured under standard conditions of 90%-95% humidity and 20-23℃.

[0046] (4) After the cement-based material specimens have been cured for 7 days, the resistance of the cement-based material specimens with a grouting degree of 100% of the crack depth is measured.

[0047] Figure 1 This is a schematic diagram of the resistance detection of the present invention, including a voltage regulator for adjusting the input voltage, a conductive medium for conducting electrical signals, an electrical signal receiving electrode, and a multimeter for measuring electrical signals.

[0048] Figure 2 This is a graph showing the relationship between different grouting levels and electrical resistance. Figure 3 The graph shows the relationship between grouting depth and the degree of resistance repair. The degree of grouting refers to the grouting depth of the crack, which can also represent the crack repair rate. Grouting depths of 25%, 50%, 75%, and 100% indicate crack repair rates of 25%, 50%, 75%, and 100%, respectively. After grouting repair, the resistance of the specimen gradually recovers to its initial value. The degree of resistance recovery is used to characterize the crack repair rate. At grouting depths of 25%, 50%, 75%, and 100%, the crack repair rates characterized by resistance are 23.6%, 48.8%, 75.0%, and 99.2%, respectively. The crack repair rates characterized by grouting depth and those characterized by resistance recovery are highly consistent. Therefore, using resistance to characterize the crack repair rate is feasible.

Claims

1. A smart monitoring method for the crack repair performance of cement-based materials based on electrical resistance, characterized in that, Includes the following steps: (1) During the molding process of cement materials, a conductive medium is added, electrodes are pre-embedded, and cement-based material specimens are obtained after curing. (2) Measure the resistance data of the above-mentioned specimens and the specimens after cracking, respectively; (3) For cracked specimens, the cracks were repaired by grouting with cement-based materials containing conductive medium during molding, and then cured. (4) Measure the resistance data of the cement-based material specimens after grouting, and characterize the repair rate of the cracks in the cement-based material by the degree of resistance recovery.

2. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 1, characterized in that, The conductive medium is one or more of carbon fiber, steel fiber, steel slag powder, carbon black, and multi-walled carbon nanotubes.

3. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 2, characterized in that, The amount of carbon fiber or carbon black added accounts for 0.1-2.0% of the volume fraction of the cement material.

4. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 2, characterized in that, The amount of steel fiber, steel slag powder or multi-walled carbon nanotubes added accounts for 1-5% of the mass fraction of the cement material.

5. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 1, characterized in that, The embedded electrode is a nickel sheet electrode, a copper sheet electrode, or a metal mesh electrode.

6. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 1, characterized in that, The spacing between the pre-embedded electrodes is 10-200 mm.

7. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 1, characterized in that, The system used to test resistance data is a resistance monitoring system, which includes a voltage regulator to adjust the input voltage, a conductive medium for transmitting electrical signals, electrical signal receiving electrodes, and a multimeter for measuring electrical signals.

8. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 1, characterized in that, The width of the crack is 100-1000 μm.

9. The intelligent monitoring method for crack repair performance of cement-based materials based on resistance according to claim 1, characterized in that, The humidity of the maintenance environment should be 90-95%, and the temperature should be 20-23℃.

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