Concrete crack real-time monitoring method based on conductive coating

Abstract

The invention is applicable to the technical field of concrete monitoring, and provides a concrete crack real-time monitoring method based on a conductive coating, which comprises the following steps: coating the surface of a concrete member with the prepared conductive coating; an electrode is arranged at a to-be-tested part of a concrete member, and data is processed through an existing ERT test system to obtain a crack distribution image of the concrete surface. The ERT test system comprises a current source, a data acquisition system and a computer, current excitation is carried out on any two adjacent electrodes by using the current source, a data acquisition unit records a voltage value between the adjacent electrodes irrelevant to excitation, the data acquisition unit transmits data to the computer for data processing, and the analyzed data is utilized to determine whether the electrode is an electrode or not. And a crack image is inverted based on the electrical resistance tomography technology. The invention provides an efficient, economical and reliable new method for real-time and accurate detection of concrete cracks by using the conductive coating and arranging the electrodes, and has important engineering application value and wide market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete monitoring, and in particular relates to a real-time monitoring method for concrete cracks based on conductive coatings. Background Art

[0002] Concrete is a versatile, safe, reliable, durable building material with advantages such as high compressive strength and durability. It is widely used in various building structures. However, cracks in concrete can greatly aggravate the degradation of structural performance and shorten its service life. Therefore, how to efficiently and accurately detect and monitor cracks in concrete has become an important research topic in the field of civil engineering.

[0003] At present, concrete crack detection is mainly divided into two categories: destructive testing and non-destructive testing. Although destructive testing can provide detailed internal damage information, its damage to the structure and high cost limit its application. In contrast, non-destructive testing technology has received widespread attention and application due to its characteristics of not causing secondary damage to the structure. Commonly used non-destructive testing methods include ultrasonic testing, infrared thermal imaging and ground penetrating radar. Although these methods can detect defects inside concrete to a certain extent, they still have shortcomings in terms of accuracy, real-time performance and cost.

[0004] In recent years, electrical resistivity tomography (ERT), as an emerging detection method, has gradually been applied in the field of civil engineering due to its advantages such as rapidity, no radiation, low cost, and visualization. ERT technology was first applied in the medical field for imaging detection of internal human tissues, and later expanded to fields such as geophysical exploration, and achieved remarkable results. In the field of civil engineering, the application of ERT technology is mainly focused on the detection of internal defects in concrete. By laying electrodes on the surface of concrete, applying excitation current, and collecting voltage change data between electrodes, the resistivity distribution image inside the concrete can be reconstructed, thereby detecting cracks and other defects on the concrete surface. However, the internal conductivity of concrete is low, and traditional ERT hardware equipment and software algorithms have problems such as large image artifacts and inaccurate positioning when detecting concrete cracks. For this reason, a real-time monitoring method for concrete cracks based on conductive coatings is proposed. Summary of the invention

[0005] The purpose of the present invention is to provide a real-time monitoring method for concrete cracks based on conductive coatings, aiming to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: A real-time monitoring method for concrete cracks based on conductive coatings comprises the following steps: Prepare a conductive coating and apply it on the surface of the concrete component to form a conductive network on the concrete surface; arrange electrodes at the tested part of the concrete component, collect data through the ERT test system, and analyze and invert the data to obtain a crack distribution image on the concrete surface; The ERT test system includes a current source, a data acquisition system and a computer, wherein the current source is used to provide an excitation current, the data acquisition unit is used to collect voltage change data between electrodes, and the computer is used to perform data processing and image reconstruction; The specific process of collecting data through the ERT test system and analyzing and inverting the data is as follows: A current source is used to excite any two adjacent electrodes. The data acquisition unit records the voltage value between the adjacent electrodes that is unrelated to the excitation. The data acquisition unit transmits the data to a computer, which processes the data and then uses the analyzed data to invert the crack image based on the electrical resistance tomography technology.

[0007] Furthermore, the conductive coating comprises the following raw materials: 42.5 type cement, water, fine sand with a particle size of less than 1 mm, calcined kaolin, carbon fiber and admixture; the ratio of cement, water and fine sand is 2:1:2; the amount of calcined kaolin added is 1.6% of the cement mass; the amount of carbon fiber added is 1% of the concrete volume; the admixture includes vinyl acrylic copolymer and polycarboxylic acid water reducer, the amount of vinyl acrylic copolymer added is 0.8% of the cement mass, and the amount of polycarboxylic acid water reducer is 0.4% of the cement mass; The preparation steps of the conductive coating are as follows: Add cement, fine sand, carbon fiber, admixture, and calcined kaolin into a cement mortar mixer in proportion, and mix for 5 minutes; then add water in proportion and mix for 15 minutes; put the mixed conductive coating into a bucket for later use.

[0008] Furthermore, the specific operation of the step of coating the conductive coating on the surface of the concrete component is as follows: When there are no cracks in the concrete component and it is working normally, use a scraper to dip the conductive coating and apply it to the tested part of the concrete component. The thickness of the conductive coating is 4mm.

[0009] Furthermore, after the step of coating the conductive coating on the surface of the concrete component, a PE engineering ground film is covered on the surface of the conductive coating, and the edges are fixed with tape, and the film is removed after waiting for 24 hours and the coating is cured.

[0010] Furthermore, the specific operation of the step of arranging electrodes at the to-be-tested position of the concrete component is as follows: A rectangular conductive coating area with several electrodes arranged in the horizontal and vertical directions is called a measurement unit; one electrode is arranged every 3 cm in the narrow side direction of the measurement unit; and one electrode is arranged every 3 cm in the long side direction of the measurement unit.

[0011] Furthermore, after the step of arranging electrodes at the part to be tested of the concrete component, at each electrode arrangement point and at the edge of the conductive coating, a copper foil with a length not exceeding 5 cm is bonded using a conductive silver paste, the diameter of the conductive silver paste is less than 1 cm, the thickness is not less than 3 mm, and the copper foil is welded to the wire; after the connection is completed, wait for 24 hours, and connect the wire to the ERT test system after the conductive silver paste is cured.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. Improve detection accuracy: The present invention uses a conductive coating made of cement mortar mixed with carbon fiber to treat the surface of concrete components to form a stable conductive network, which significantly improves the accuracy of concrete crack detection. The ERT test system can reconstruct a high-resolution resistivity distribution image and accurately display the location and shape of the cracks.

[0013] 2. Realize real-time monitoring: The system of the present invention can collect and process data in real time, provide immediate structural health status information, and help to timely discover and deal with potential problems in concrete structures. The application of real-time monitoring technology improves the efficiency and safety of engineering structure maintenance and management.

[0014] 3. Nondestructive testing: The present invention uses ERT technology for monitoring without destroying the concrete structure, thus avoiding secondary damage to the structure caused by traditional destructive testing methods. This nondestructive testing method is suitable for long-term online monitoring and helps to extend the service life of the concrete structure.

[0015] 4. Reduce detection costs: The present invention reduces detection costs by simplifying detection equipment and operation procedures. The system is easy to operate and does not require high professional and technical personnel training costs. The use of conductive coatings is lower in cost than traditional detection methods and is suitable for health monitoring of large-scale engineering structures.

[0016] 5. Improve detection efficiency: The system of the present invention has high integration and fast detection speed, and can complete the detection of large-area concrete structures in a short time, which greatly improves the detection efficiency. The data processing and image reconstruction process has a high degree of automation, which reduces human operation errors and improves the reliability of the detection results.

[0017] 6. Broad application prospects: The present invention is applicable to the health monitoring of various concrete structures, including important infrastructure such as bridges, tunnels, dams, etc. Continuous monitoring and evaluation of concrete structures can help prevent structural failure and ensure engineering safety.

[0018] In summary, the present invention provides a new efficient, economical and reliable method for real-time and accurate detection of concrete cracks by combining conductive coatings and electrode layout, which has important engineering application value and broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram of the conductive coating process of the present invention.

[0020] Figure 2 This is a physical picture of the electrode array in the present invention.

[0021] Figure 3 This is a diagram of the electrode layout in the present invention.

[0022] Figure 4 This is a detailed diagram of the electrode connection in the present invention.

[0023] Figure 5 This is a schematic diagram of current excitation and data acquisition in the present invention.

[0024] Figure 6 Schematic diagram of the actual crack and ERT simulated crack morphology in the present invention; (a) is the coating state of the front side of specimen 1, (b) is the coating state of specimen 2, (c) is the coating reconstruction result of specimen 1, and (d) is the coating reconstruction result of specimen 2. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0027] An embodiment of the present invention provides a method for real-time monitoring of concrete cracks based on conductive coatings, comprising the following steps: 1. Prepare a conductive coating with good conductivity and mechanical properties; the conductive coating comprises the following raw materials: 42.5 type cement, water, fine sand with a particle size of less than 1 mm, calcined kaolin, carbon fiber and admixture; the ratio of cement, water and fine sand is 2:1:2; the amount of calcined kaolin added is 1.6% of the cement mass; the amount of carbon fiber added is 1% of the total volume; the admixture comprises vinyl acrylic copolymer and polycarboxylic acid water reducer, the amount of vinyl acrylic copolymer added is 0.8% of the cement mass, and the amount of polycarboxylic acid water reducer is 0.4% of the cement mass; The preparation steps of the conductive coating are as follows: Add cement, fine sand, carbon fiber, admixture, and calcined kaolin into a cement mortar mixer in proportion, and mix for 5 minutes; then add water in proportion and mix for 15 minutes; put the mixed conductive coating into a bucket for later use.

[0028] 2. Apply the conductive coating to the surface of the concrete component to form a conductive network on the concrete surface: When the concrete component has no cracks and is working normally, use a scraper to dip the conductive coating and apply the conductive coating to the part of the concrete component to be tested. To ensure that the coating thickness is about 4mm, it must be applied twice. After the conductive coating is applied, cover the surface of the conductive coating with PE engineering film, fix the edges with tape, wait for 24 hours, remove the film after the coating is cured, and proceed to the next step. The process is shown in Figure 1 .

[0029] 3. Electrode array: Electrodes are arranged at the locations to be tested on concrete components. The electrodes are made of stainless steel. A rectangular conductive coating area with several electrodes arranged in the horizontal and vertical directions (see the actual picture) is formed. Figure 2 ) is called a measurement unit; in the narrow side direction of the measurement unit, one electrode is arranged every 3 cm; in the long side direction of the measurement unit, one electrode is arranged every 3 cm. Take the measurement unit with 4 electrodes arranged on the narrow side and 8 electrodes arranged on the long side as an example, Figure 3 shown.

[0030] 4. At each electrode arrangement point, at the edge of the conductive coating, use conductive silver paste to bond copper foil with a length not exceeding 5 cm, and the copper foil welding wire, such as Figure 4 As shown. The electrode contacts the conductive coating surface through the conductive silver paste to ensure good electrical contact. To minimize contact resistance, the diameter of the conductive silver paste at the connection should be kept below 1 cm, and to ensure a strong bond, its thickness should be no less than 3 mm. After the connection is completed, wait for 24 hours for the conductive silver paste to solidify before connecting the wire to the ERT test system.

[0031] 5. Collect data through the ERT test system, analyze and invert the data to obtain a crack distribution image on the concrete surface; the ERT test system includes a current source, a data acquisition system and a computer, the current source is used to provide an excitation current, the data acquisition unit is used to collect voltage change data between electrodes, and the computer is used to perform data processing and image reconstruction; The specific process of collecting data through the ERT test system and analyzing and inverting the data is as follows: Use a current source to stimulate any two adjacent electrodes, and the data acquisition unit records the voltage value between the adjacent electrodes that is not related to the stimulation. Figure 5As shown, the excitation current is 100 mA. Taking a 4*8 electrode array as an example, each measurement unit can obtain 504 (24×21) adjacent boundary voltage values. The data acquisition unit transmits the data to a computer, which processes the data. The analyzed data is then used to invert the crack image based on the electrical resistance tomography technology.

[0032] In the embodiment of the present invention, in actual operation, the electrical parameters of the coating on the surface of the concrete component need to be measured regularly and periodically using the above method as needed.

[0033] When cracks appear in concrete components due to load and other reasons, the conductive coating on its surface will also produce cracks or large deformations, and its resistivity distribution will change significantly. The ERT test system of the present invention will upload the data to the computer control device. The collected data will be analyzed using the self-developed software "Cement-based material health detection and analysis software based on carbon ink skin and four-electrode method". Using the analyzed data, based on the TV-SB regularization algorithm and electrical resistance tomography technology, the crack image can be inverted, thereby realizing real-time monitoring of concrete cracks.

[0034] Example 1: To verify the effectiveness of the present invention, we conducted a three-point bending experiment to demonstrate the application effect of conductive coatings in concrete crack detection and the application of electrical resistivity tomography (ERT) technology in actual engineering.

[0035] 1) Composition: Carbon ink slurry doped with nano-graphene is used as a conductive coating, sprayed on the surface of concrete aggregate and made into a concrete beam to form a conductive network. Stainless steel electrodes are arranged at both ends and the middle of the concrete beam to apply current and collect voltage data. The ERT test system is used to collect voltage data in real time, and perform data processing and image reconstruction.

[0036] 2) Experimental steps: Before applying load, the background resistivity distribution of the concrete beam is trained to obtain benchmark data.

[0037] The three-point bending load was applied step by step, and the voltage change data after each loading was recorded.

[0038] The differential ERT algorithm is used to reconstruct resistivity distribution images under different loading conditions and monitor the generation and extension of cracks.

[0039] 3) Effect: Figure 6The actual cracks of specimens 1 and 2 and the schematic diagram of the ERT simulated crack morphology. The experimental results show that the conductive coating forms a stable conductive network on the surface of the concrete beam, ensuring the effective propagation of current. The ERT test system successfully monitors the resistivity changes of the concrete beam under different loading conditions, and the reconstructed image clearly shows the location and morphology of the cracks. Through real-time monitoring, the occurrence of cracks can be discovered in time and their expansion can be evaluated, providing an effective means for monitoring the health of concrete structures.

[0040] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A real-time monitoring method for concrete cracks based on conductive coating, characterized in that: The following steps are involved: Prepare a conductive coating, apply the conductive coating on the surface of the concrete component, so that a conductive network is formed on the concrete surface; Electrodes are placed at the test site of the concrete component, data is collected through the ERT test system, and the data is analyzed and inverted to obtain the crack distribution image of the concrete surface; The ERT test system includes a current source, a data acquisition system and a computer, wherein the current source is used to provide an excitation current, the data acquisition unit is used to collect voltage change data between electrodes, and the computer is used to perform data processing and image reconstruction; The specific process of collecting data through the ERT test system and analyzing and inverting the data is as follows: A current source is used to excite any two adjacent electrodes. The data acquisition unit records the voltage value between the adjacent electrodes that is unrelated to the excitation. The data acquisition unit transmits the data to a computer, which processes the data and then uses the analyzed data to invert the crack image based on the electrical resistance tomography technology.

2. The method for real-time monitoring of concrete cracks based on conductive coating according to claim 1 is characterized in that: The conductive coating comprises the following raw materials: 42.5 type cement, water, fine sand with a particle size of less than 1mm, calcined kaolin, carbon fiber and admixtures; the ratio of cement, water and fine sand is 2:1:2; the amount of calcined kaolin added is 1.6% of the cement mass; the amount of carbon fiber added is 1% of the concrete volume; admixtures include vinyl acrylic copolymer and polycarboxylic acid water reducer, the amount of vinyl acrylic copolymer added is 0.8% of the cement mass, and the amount of polycarboxylic acid water reducer is 0.4% of the cement mass; The preparation steps of the conductive coating are as follows: Add cement, fine sand, carbon fiber, admixture, and calcined kaolin into a cement mortar mixer in proportion, and mix for 5 minutes; then add water in proportion and mix for 15 minutes; put the mixed conductive coating into a bucket for later use.

3. The method for real-time monitoring of concrete cracks based on conductive coating according to claim 1, characterized in that: The specific operation of the step of coating the conductive coating on the surface of the concrete component is as follows: When there are no cracks in the concrete component and it is working normally, use a scraper to dip the conductive coating and apply it to the tested part of the concrete component. The thickness of the conductive coating is 4mm.

4. The method for real-time monitoring of concrete cracks based on conductive coating according to claim 1, characterized in that: After the step of coating the conductive coating on the surface of the concrete component, the surface of the conductive coating is covered with a PE engineering ground film, which is fixed at the edge with tape, and the film is removed after waiting for 24 hours and the coating is cured.

5. The method for real-time monitoring of concrete cracks based on conductive coating according to claim 1, characterized in that: The specific operation of the step of laying electrodes at the to-be-tested position of the concrete component is as follows: A rectangular conductive coating area with several electrodes arranged in the horizontal and vertical directions is called a measurement unit; one electrode is arranged every 3 cm in the narrow side direction of the measurement unit; and one electrode is arranged every 3 cm in the long side direction of the measurement unit.

6. The method for real-time monitoring of concrete cracks based on conductive coating according to claim 1, characterized in that: After the step of arranging electrodes at the part to be tested of the concrete component, at each electrode arrangement point and at the edge of the conductive coating, a copper foil with a length not exceeding 5 cm is bonded using a conductive silver paste, the diameter of the conductive silver paste is less than 1 cm, the thickness is not less than 3 mm, and the copper foil is welded to the wire; after the connection is completed, wait for 24 hours, and connect the wire to the ERT test system after the conductive silver paste is cured.

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