In-situ test and verification method for corrosion resistance of reinforcing steel bar under acidic condition

Abstract

The invention provides an in-situ test and verification method for the corrosion resistance of a reinforcing steel bar under an acidic condition, and belongs to the technical field of durability test of building engineering materials. The method comprises the steps of in-situ sensing and parameterization of an on-site corrosion environment, laboratory simulation acceleration and electrochemical monitoring based on on-site parameters, multi-dimensional performance degradation correlation analysis and standardization protocol formulation and in-situ verification and judgment of the anti-corrosion performance of a construction site. The invention aims to solve the technical problem of how to verify the anti-corrosion performance of the reinforcing steel bar used in engineering construction in an acidic corrosion environment, the laboratory and the site are bridged, the prospective and closed-loop verification of the anti-corrosion performance of the reinforcing steel bar in the construction stage is realized, the evaluation accuracy is high, and the engineering application value is good.

Description

Technical Field

[0001] This invention belongs to the field of durability testing technology for building materials, and more specifically, it relates to an in-situ testing and verification method for the corrosion resistance of steel bars under acidic conditions. Background Technology

[0002] In water conservancy and civil engineering, reinforced concrete structures are exposed to complex environments for extended periods. Acidic environments (such as acid rain zones, industrial pollution areas, and acidic soil geological conditions) can severely reduce the alkalinity of concrete, damage the passivation film on the reinforcing bars, accelerate bar depassivation, and threaten structural safety and durability. Therefore, during the construction phase, especially in acid-sensitive areas, it is of great engineering significance to conduct effective and reliable verification of the anti-corrosion performance of the proposed reinforcing bars and their protective measures (such as coatings and rust inhibitors).

[0003] Existing methods for evaluating the rust resistance of reinforcing steel mainly include accelerated laboratory testing and in-situ non-destructive testing. Laboratory methods (such as salt spray testing and accelerated electrochemical testing) are typically conducted in idealized solutions (such as dilute acids with a single component). While these methods allow for control of variables and rapid data acquisition, the experimental environment differs significantly from the complex microenvironment experienced by reinforcing steel within real concrete (multi-ion coupling, alternating wet and dry conditions, and the presence of stress). This results in a weak correlation between the evaluation results and actual engineering performance. In-situ non-destructive testing methods (such as half-cell potential method, resistivity method, and electrochemical impedance spectroscopy) are mostly used for diagnosing the rust condition of in-service structures. These methods are considered "post-construction testing" and are insufficient for proactively and confirmatoryly evaluating the inherent material and process property of "rust resistance" before or during construction.

[0004] Therefore, there is an urgent need in engineering practice for a method that can bridge the gap between the laboratory and the field. This method should be able to conduct laboratory simulations based on real environmental characteristics and transfer the evaluation indicators established in the laboratory to the construction site for in-situ comparative verification, thereby achieving a closed-loop and reliable evaluation of the performance of the anti-corrosion solution. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ testing and verification method for the corrosion resistance of reinforcing bars under acidic conditions, aiming to solve the technical problem of how to verify the corrosion resistance of reinforcing bars used in engineering construction under acidic corrosive environment.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: to provide an in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions, comprising the following steps: S100: In-situ sensing and parameterization of the corrosion environment: At the target engineering site, environmental media samples are collected in situ to obtain basic chemical parameters, and sensors are deployed to continuously monitor dynamic environmental parameters. Based on the basic chemical parameters and dynamic environmental parameters, the multiphysics coupling boundary conditions for laboratory accelerated simulation are jointly determined. S200: Laboratory simulation acceleration and electrochemical monitoring based on field parameters: Based on the coupling boundary conditions determined by S100, a simulated corrosion solution is prepared and a dynamic simulation environment is constructed; the steel bar sample to be tested is placed in this simulation environment, and the load conditions of simulated construction stress are applied simultaneously; during the accelerated corrosion test, the electrochemical impedance spectroscopy evolution data of the steel bar sample is collected in real time. S300: Multi-dimensional performance degradation correlation analysis and standardization protocol development: Mechanical property tests are performed on steel bar samples after accelerated corrosion to obtain mechanical property degradation data; the mechanical property degradation data is correlated with the electrochemical impedance spectroscopy evolution data collected in real time in S200 to extract electrochemical characteristic frequencies or characteristic spectra that have a mapping relationship with specific mechanical property degradation indicators, which are used as alternative evaluation indicators for corrosion resistance, and a standardized rapid testing protocol suitable for field operation is developed based on the alternative evaluation indicators. S400: In-situ verification and judgment of corrosion prevention performance at construction site: At the construction site, in accordance with the standardized rapid testing protocol established in S300, rapid and non-destructive in-situ electrochemical impedance spectroscopy tests are performed on the structural steel bars or steel bars in the accompanying specimens to obtain the field data of the electrochemical characteristic frequency or characteristic spectrum; the field data is compared with the benchmark characteristic spectrum or preset threshold established in S300. If the field data meets the benchmark requirements, the corrosion prevention performance is judged to be qualified.

[0007] In one possible implementation, in step S100 above, the in-situ collection of environmental media samples is achieved by using a micro-destructive sampling device to obtain soil pore fluid or simulated concrete pore fluid from the site in order to determine the types and initial concentrations of corrosive ions. The continuous monitoring of dynamic environmental parameters includes at least time-series data on pH, temperature, humidity, and chloride ion concentration, and the monitoring duration covers at least one complete climate change cycle. The basic chemical parameters and the dynamic environmental parameters are used together to determine the multiphysics coupling boundary conditions of the laboratory simulation in step S200.

[0008] In one possible implementation, step S200 specifically includes: S210: Preparation of simulation solution. Based on the chemical analysis results of the field samples determined in S100, an acidic simulation solution containing the main corrosive ions is prepared. Its pH value and ion concentration range reproduce the statistical characteristic values ​​of the field monitoring results. S220: Electrode block preparation, the steel bar sample to be tested is encapsulated in mortar or concrete block, and a reference electrode and an auxiliary electrode are pre-embedded to form a three-electrode electrochemical testing system; S230: Stress-coupled loading, using loading equipment to apply static or alternating loads to the steel bars in a partially encapsulated test block. The stress level is determined based on the design stress state of the steel bars during the construction stage, and the load application is synchronized with the exposure to the simulated corrosive environment. S240: Dynamic environment simulation. The prepared test block is placed in the acidic simulated solution prepared in S210. The dry-wet cycle or solution flow is realized through program control. The frequency and amplitude of the dry-wet cycle are set according to the on-site humidity change spectrum monitored in S100. S250: Multi-parameter electrochemical monitoring. Throughout the accelerated corrosion test cycle, an electrochemical measurement system is used to monitor the open circuit potential and linear polarization resistance of the steel reinforcement sample at regular intervals, and to periodically collect full-spectrum electrochemical impedance spectroscopy data.

[0009] In one possible implementation, in step S300 above, the electrochemical characteristic frequency or characteristic spectrum that has a mapping relationship with a specific mechanical property degradation index is: The rate of change of low-frequency impedance modulus within the preset early corrosion period.

[0010] In one possible implementation, the low frequency is one or more characteristic frequency points in the range of 0.01 Hz to 1 Hz.

[0011] In one possible implementation, the preset early corrosion period is the first 1 to 10 wet-dry cycles after the start of the laboratory accelerated test.

[0012] In one possible implementation, step S400 specifically includes: S410: Initial value measurement, before concrete pouring, the initial value of the electrochemical impedance spectrum is directly measured at the test points reserved for the steel reinforcement; S420: On-site measurement. After the concrete reaches the predetermined age, the internal steel reinforcement is measured in situ using non-destructive testing on the concrete surface to obtain the on-site measured values ​​of electrochemical characteristic frequencies or characteristic spectra. S430: Qualification judgment. The actual measured value on site is compared with the benchmark feature spectrum established in step S300 or the qualified threshold preset according to the benchmark feature spectrum. If the actual measured value on site falls within the qualified range, the anti-corrosion performance is judged to be qualified.

[0013] In one possible implementation, the non-destructive in-situ measurement in step S420 above includes: A porous ceramic probe is pre-embedded or drilled into the concrete surface, and the probe is filled with a conductive medium to form an ion conduction path with the internal steel reinforcement of the concrete. A portable electrochemical workstation was used, with an auxiliary electrode pre-embedded in the concrete surface as the counter electrode, a steel bar as the working electrode, and a reference electrode placed inside the probe as the reference electrode, forming a three-electrode testing system. Before testing, the reinforcing steel was subjected to short-term cathodic depolarization treatment to eliminate the interference of the initial passivation film formed during concrete pouring on the test results.

[0014] In one possible implementation, the in-situ verification object in step S400 above also includes the reinforcing steel in the concrete accompanying specimens that are fabricated and cured simultaneously on the construction site and contain the same reinforcing steel as the main structure.

[0015] In one possible implementation, step S500, which is performed after step S400, is also included: long-term performance monitoring and model iteration. During the engineering operation period, long-term durability performance data of the structure is continuously acquired, and the mapping relationship between the electrochemical characteristic frequency or characteristic spectrum established in step S300 and the mechanical performance degradation is corrected and iteratively optimized using the data.

[0016] The beneficial effects of the in-situ testing and verification method for the corrosion resistance of reinforcing bars under acidic conditions provided by this invention are as follows: 1) Achieving a bridge between the field and the laboratory: real environmental parameters are obtained through on-site sensing in step S100 and used as boundary conditions for laboratory simulation in step S200. This makes the results of accelerated laboratory tests highly correlated with the actual corrosion performance in engineering, solving the problem of unrealistic traditional laboratory tests.

[0017] 2) Establish the mapping relationship between mechanical properties and electrochemical characteristics. Through the multi-dimensional performance degradation correlation analysis in step S300, extract the electrochemical characteristic frequencies or characteristic spectra that have a clear mapping relationship with mechanical performance degradation, so that on-site non-destructive testing can indirectly reflect mechanical properties.

[0018] 3) Achieve forward-looking verification during the construction phase. Through the on-site verification in step S400, the evaluation indicators established in the laboratory are efficiently transferred to the construction site. The rust prevention performance can be quickly and non-destructively judged before and after concrete pouring, thus achieving pre-verification. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating an in-situ testing and verification method for the corrosion resistance of reinforcing bars under acidic conditions, provided in an embodiment of the present invention. Figure 2 A schematic diagram of the process for accelerating laboratory simulation and electrochemical monitoring based on field parameters for an in-situ testing and verification method of the corrosion resistance of steel bars under acidic conditions, provided in an embodiment of the present invention. Figure 3 This is a flowchart illustrating the in-situ verification and determination of the corrosion resistance performance of reinforcing bars under acidic conditions, as provided in this embodiment of the invention. Detailed Implementation

[0021] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0022] In acidic environments (such as acid rain zones and water conservancy projects with acidic soil geology), steel corrosion is the primary threat to structural durability. Currently, there is a lack of effective means to reliably verify the long-term effectiveness of anti-corrosion solutions (such as anti-corrosion coatings and rust inhibitors) during the engineering construction phase.

[0023] This invention aims to overcome the shortcomings of existing technologies and provide an in-situ testing and verification method for the corrosion resistance performance of reinforcing steel bars under acidic conditions. This method establishes a complete evaluation process from environmental simulation and accelerated performance degradation to rapid on-site comparison through four core steps: in-situ perception and parameterization of the on-site corrosive environment, accelerated laboratory simulation and electrochemical monitoring, multi-dimensional performance degradation correlation analysis and standardized protocol development, and in-situ verification and judgment of corrosion resistance performance at the construction site. This enhances the reliability, authenticity, and engineering guidance value of verifying the corrosion resistance performance of reinforcing steel bars during the construction phase.

[0024] Please see Figure 1-3 The present invention provides an in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions. The method comprises the following steps: S100: In-situ sensing and parameterization of the corrosion environment: At the target engineering site, environmental media samples are collected in situ to obtain basic chemical parameters, and sensors are deployed to continuously monitor dynamic environmental parameters. Based on the basic chemical parameters and dynamic environmental parameters, the multiphysics coupling boundary conditions for laboratory accelerated simulation are jointly determined. S200: Laboratory simulation acceleration and electrochemical monitoring based on field parameters: Based on the coupling boundary conditions determined by S100, a simulated corrosion solution is prepared and a dynamic simulation environment is constructed; the steel bar sample to be tested is placed in this simulation environment, and the load conditions of simulated construction stress are applied simultaneously; during the accelerated corrosion test, the electrochemical impedance spectroscopy evolution data of the steel bar sample is collected in real time. S300: Multi-dimensional performance degradation correlation analysis and standardization protocol development: Mechanical property tests are performed on steel bar samples after accelerated corrosion to obtain mechanical property degradation data; the mechanical property degradation data is correlated with the electrochemical impedance spectroscopy evolution data collected in real time in S200 to extract electrochemical characteristic frequencies or characteristic spectra that have a mapping relationship with specific mechanical property degradation indicators, which are used as alternative evaluation indicators for corrosion resistance, and a standardized rapid testing protocol suitable for field operation is developed based on the alternative evaluation indicators. S400: In-situ verification and judgment of corrosion prevention performance at construction site: At the construction site, in accordance with the standardized rapid testing protocol established in S300, rapid and non-destructive in-situ electrochemical impedance spectroscopy tests are performed on the structural steel bars or steel bars in the accompanying specimens to obtain the field data of the electrochemical characteristic frequency or characteristic spectrum; the field data is compared with the benchmark characteristic spectrum or preset threshold established in S300. If the field data meets the benchmark requirements, the corrosion prevention performance is judged to be qualified.

[0025] In the existing technology, electrochemical impedance spectroscopy is a testing technique used to study electrode interfaces and electrochemical reaction kinetics. Obtaining electrochemical impedance spectroscopy (EIS) data on steel bars usually needs to be carried out in a laboratory or field corrosion research environment. The core of the operation is to construct a standard three-electrode electrochemical measurement system and apply a weak AC signal to measure the impedance response of the system.

[0026] The present invention provides an in-situ testing and verification method for the corrosion resistance of steel bars under acidic conditions. Compared with the prior art, it 1) achieves a bridge between the field and the laboratory. By obtaining real environmental parameters through in-situ sensing in step S100, the actual environmental parameters are used as boundary conditions for laboratory simulation in step S200, so that the laboratory accelerated test results are highly correlated with the actual corrosion performance of the project, thus solving the problem of unrealistic traditional laboratory tests.

[0027] 2) Establish the mapping relationship between mechanical properties and electrochemical characteristics. Through the multi-dimensional performance degradation correlation analysis in step S300, extract the electrochemical characteristic frequencies or characteristic spectra that have a clear mapping relationship with mechanical performance degradation, so that on-site non-destructive testing can indirectly reflect mechanical properties.

[0028] 3) Achieve forward-looking verification during the construction phase. Through the on-site verification in step S400, the evaluation indicators established in the laboratory are efficiently transferred to the construction site. The rust prevention performance can be quickly and non-destructively judged before and after concrete pouring, thus achieving pre-verification.

[0029] 4) It enhances the "targeting" and engineering applicability of in-situ testing. On-site verification is not simply a repetitive and time-consuming complete test, but rather a rapid test based on extensive prior laboratory work, precisely selecting the most sensitive and relevant indicators. This makes performance verification during construction efficient and targeted, enabling rapid judgment at key construction nodes without delaying the construction period, and ensuring strong engineering practicality.

[0030] In some embodiments, in step S100 above, the in-situ collection of environmental media samples is achieved by using a micro-destructive sampling device to obtain soil pore fluid or simulated concrete pore fluid to determine the types and initial concentrations of corrosive ions; the continuous monitoring of dynamic environmental parameters includes at least time-series changes in pH, temperature, humidity, and chloride ion concentration, and the monitoring duration covers at least one complete climate change cycle; wherein, the basic chemical parameters and the dynamic environmental parameters are used together to determine the multiphysics coupling boundary conditions of the laboratory simulation in step S200.

[0031] Specifically, the minimally invasive sampling device can employ an existing spiral drilling structure, with the drill bit diameter controlled within the range of 5-10 mm, to minimize disturbance to the structural substrate, ensure the representativeness of the sampling area, and reduce the risk of damage to the reinforcing steel cover. The sampling depth is determined based on the location of the reinforcing steel, typically needing to penetrate 20-30 mm into the steel surface to ensure that the obtained soil or pore fluid accurately reflects the direct environment in which the steel is located.

[0032] For continuously monitored parameters, pH monitoring utilizes a glass electrode sensor with an accuracy of ±0.01 pH; temperature monitoring covers a range from -20℃ to 60℃; humidity monitoring accuracy reaches ±2%RH; and chloride ion concentration is determined using an ion-selective electrode method with a detection limit as low as 0.01 mg / L. The monitoring frequency is set to record data every 2 hours, with a monitoring duration of no less than 12 months for a complete climate cycle, to comprehensively capture the dynamic impact of environmental factors such as seasonal temperature changes, alternating wet and dry periods, and chloride ion migration caused by rainfall on the risk of steel corrosion.

[0033] Typical locations were selected at the construction site of the target project for in-situ collection and monitoring of environmental corrosion factors. This specifically included: 1) Environmental media sample collection: Use a minimally invasive sampling device (such as a micro-core extractor) to collect soil, surface water, or pore liquid samples from existing structures. Seal and preserve these samples and send them to the laboratory for full-ion chromatography analysis to determine corrosive ions (such as SO42-). 2- Cl - NO3 - Basic chemical parameters such as type and concentration, pH value, etc.

[0034] 2) Dynamic environmental parameter monitoring: Deploy multi-parameter sensors at selected locations to continuously monitor the medium's pH value, temperature, humidity, redox potential, and chloride ion concentration for at least one complete climate cycle (such as a rainy season), obtain time-varying spectra of the above parameters, and clarify the fluctuation characteristics and extreme conditions of the corrosive environment.

[0035] In some embodiments, please refer to Figure 2 The above step S200 specifically includes the following steps: S210: Preparation of simulation solution. Based on the chemical analysis results of the field samples determined in S100, an acidic simulation solution containing the main corrosive ions is prepared. Its pH value and ion concentration range reproduce the statistical characteristic values ​​of the field monitoring results. S220: Electrode block preparation, the steel bar sample to be tested is encapsulated in mortar or concrete block, and a reference electrode and an auxiliary electrode are pre-embedded to form a three-electrode electrochemical testing system; S230: Stress-coupled loading, using loading equipment to apply static or alternating loads to the steel bars in a partially encapsulated test block. The stress level is determined based on the design stress state of the steel bars during the construction stage, and the load application is synchronized with the exposure to the simulated corrosive environment. S240: Dynamic environment simulation. The prepared test block is placed in the acidic simulated solution prepared in S210. The dry-wet cycle or solution flow is realized through program control. The frequency and amplitude of the dry-wet cycle are set according to the on-site humidity change spectrum monitored in S100. S250: Multi-parameter electrochemical monitoring. Throughout the accelerated corrosion test cycle, an electrochemical measurement system is used to monitor the open circuit potential and linear polarization resistance of the steel reinforcement sample at regular intervals, and to periodically collect full-spectrum electrochemical impedance spectroscopy data.

[0036] Among them, the electrochemical measurement system, also known as the electrochemical workstation, is a commonly used measurement device in electrochemical research and teaching. It is divided into single-channel workstations and multi-channel workstations.

[0037] In step S200 above, based on the coupling boundary conditions determined in step S100, a simulated corrosion solution is prepared and a dynamic simulation environment is constructed. Specifically, this includes: 1) Simulation Environment Construction: Based on the chemical analysis results of field samples, a composite acidic simulation solution containing the main corrosive ions is prepared, with its pH value and ion concentration range replicating the typical values ​​and fluctuation ranges of field monitoring. A programmable wet-dry cycle or solution flow device is established to simulate the alternating wet-dry and wet conditions or groundwater seepage in the field.

[0038] 2) Sample Preparation and Testing under Coupled Stress Loading: The reinforcing bars to be verified (e.g., ordinary reinforcing bars and control bars with anti-corrosion coating) are processed into standard samples. A portion of the samples are cast and encapsulated in mortar or concrete simulation blocks, with reference electrodes (e.g., Mn / MnO2 electrodes or Ag / AgCl electrodes) and auxiliary electrodes (e.g., graphite or stainless steel sheets) pre-embedded in the blocks, forming a three-electrode testing system suitable for concrete systems. Based on the stress state of the reinforcing bars during the construction stage as calculated by structural design or measured, dead or alternating loads are applied to the reinforcing bars in the encapsulated blocks using mechanical loading equipment to simulate the stress conditions during construction and the initial stages of service.

[0039] 3) Multi-parameter electrochemical monitoring: Immerse the prepared specimen system in the simulated environment and start the environmental simulation program. Throughout the accelerated testing cycle, use the electrochemical measurement system to periodically (e.g., daily) or continuously monitor the open circuit potential and linear polarization resistance of the steel reinforcement specimen, and periodically (e.g., weekly) measure its electrochemical impedance spectroscopy. Completely record the evolution of corrosion electrochemical parameters.

[0040] In step S300 above, the electrochemical characteristic frequency or characteristic spectrum that maps to a specific mechanical property degradation index is the rate of change of the low-frequency impedance modulus within a preset early corrosion period. In one possible implementation, the low-frequency frequency is one or more characteristic frequency points in the range of 0.01 Hz to 1 Hz. The preset early corrosion period is the first 1 to 10 dry-wet cycle cycles after the start of the laboratory accelerated test.

[0041] In some embodiments, the specific monitoring process in step S250 above is as follows: Before the test begins, the electrochemical measurement system needs to be calibrated to ensure test accuracy. The monitoring frequency is dynamically adjusted according to the corrosion process. In the early stage of corrosion, monitoring can be performed once every 24 hours. When a negative shift in open circuit potential exceeding 50mV or a decrease in linear polarization resistance exceeding 20% ​​of the initial value is detected, the monitoring frequency is increased to once every 12 hours or even once every 6 hours. For electrochemical impedance spectroscopy testing, the frequency range is set to 100kHz to 10mHz, and the amplitude of the AC excitation signal is 10mV to avoid disturbing the corrosion state of the steel reinforcement surface. After each monitoring, the changes in ambient temperature, pH value of the simulated solution, and concentration of major ions need to be recorded simultaneously for subsequent analysis of the impact of environmental factors on the monitoring results.

[0042] For example, three representative low-frequency points—0.01Hz, 0.1Hz, and 1Hz—can be selected to calculate the rate of change of their impedance modulus values ​​from the first to the tenth wet-dry cycle after the start of the test. Specifically, the impedance modulus value at the end of the first wet-dry cycle at each frequency point is used as the initial reference value. Then, the impedance modulus value at the end of each subsequent wet-dry cycle (e.g., the second to the tenth cycle) is compared with the initial reference value. The rate of change at each time point is calculated using the formula (impedance modulus of the next cycle - initial reference value) / initial reference value * 100%. The sum of the absolute values ​​of the rates of change within that time period or the maximum rate of change is taken as the specific index value for measuring the early corrosion sensitivity of the steel reinforcement at that frequency point. By comprehensively analyzing the electrochemical impedance spectra at multiple low-frequency points, the electrochemical behavior characteristics of the steel reinforcement in the initial corrosion stage under acidic conditions can be captured more comprehensively and accurately, thus providing a more reliable early warning basis for evaluating its corrosion resistance performance.

[0043] In step S300 above, after the test, destructive testing and data analysis are performed on the sample to establish the correlation between corrosion indicators and performance degradation. Specifically, this includes: 1) Mechanical property test: After the accelerated test, the steel bar sample was removed, the corrosion products were cleaned, and a tensile test was performed on a universal testing machine to determine its yield strength, tensile strength and elongation. The performance degradation rate compared with the uncorroded sample was calculated.

[0044] 2) Data Correlation Analysis and Index Extraction: Statistical analysis is performed on corrosion electrochemical monitoring data (such as the integrated charge of corrosion current density time-history curves, characteristic frequency parameters of electrochemical impedance spectroscopy, etc.) and mechanical property degradation data. One or more electrochemical parameters that are sensitive to acidic environments and stress coupling effects and show a significant correlation with the mechanical property degradation rate are extracted and presented as electrochemical impedance spectroscopy data. For example, the rate of decrease in the impedance modulus value in the low-frequency region (e.g., 0.1 Hz) of the electrochemical impedance spectroscopy during the first significant wet-dry cycle can be determined as a sensitive index for evaluating the performance of a specific coating.

[0045] 3) Develop a rapid testing protocol: Based on the extracted "sensitivity indicators," design a simplified, standardized operating procedure suitable for rapid on-site testing. This procedure should clearly define the test instrument settings, excitation signal parameters (such as the applied AC potential amplitude, frequency range, or DC step value), data acquisition duration, and indicator calculation methods.

[0046] In some embodiments, please refer to Figure 3 The above step S400 specifically includes the following steps: S410: Initial value measurement, before concrete pouring, the initial value of the electrochemical impedance spectrum is directly measured at the test points reserved for the steel reinforcement; S420: On-site measurement. After the concrete reaches the predetermined age, the internal steel reinforcement is measured in situ using non-destructive testing on the concrete surface to obtain the on-site measured values ​​of electrochemical characteristic frequencies or characteristic spectra. S430: Qualification judgment. The actual measured value on site is compared with the benchmark feature spectrum established in step S300 or the qualified threshold preset according to the benchmark feature spectrum. If the actual measured value on site falls within the qualified range, the anti-corrosion performance is judged to be qualified.

[0047] During concrete pouring, accompanying test specimens were prepared using the same mix proportions, vibration methods, and curing conditions as the structural concrete, ensuring that their environment was as similar as possible to that of the reinforcing steel in the actual structure. During in-situ measurements, in addition to measuring the pre-reserved test points on the reinforcing steel inside the structure, electrochemical impedance spectroscopy was also performed on the reinforcing steel in these accompanying specimens. By comparing and analyzing the in-situ measurement data of the structure with the measurement data of the accompanying specimens, the impact of on-site environmental factors on the corrosion resistance of the reinforcing steel can be more comprehensively assessed. This further verifies the correlation and applicability between laboratory data and actual on-site conditions, thereby improving the accuracy and reliability of the entire in-situ testing and verification method.

[0048] The non-destructive in-situ measurement in step S420 above includes: A porous ceramic probe is pre-embedded or drilled into the concrete surface, and the probe is filled with a conductive medium to form an ion conduction path with the internal steel reinforcement of the concrete. A portable electrochemical workstation was used, with an auxiliary electrode pre-embedded in the concrete surface as the counter electrode, a steel bar as the working electrode, and a reference electrode placed inside the probe as the reference electrode, forming a three-electrode testing system. Before testing, the reinforcing steel was subjected to short-term cathodic depolarization treatment to eliminate the interference of the initial passivation film formed during concrete pouring on the test results.

[0049] The in-situ verification object in step S400 above also includes the reinforcing steel in the concrete accompanying specimens that are fabricated and cured simultaneously on the construction site and contain the same reinforcing steel as the main structure.

[0050] In step S400 above, the results of laboratory research are applied to the engineering site to rapidly verify the corrosion resistance of steel bars in the solid structure in situ. Specifically, this includes: 1) On-site testing preparation: After the steel reinforcement of the engineering structure is tied and before the concrete is poured, test points are reserved at key locations. At the same time, a batch of "accompanying specimens" with the same steel reinforcement are poured on the construction site to ensure that their curing and exposure conditions are consistent with those of the engineering structure.

[0051] 2) In-situ rapid testing: Using portable electrochemical testing equipment, the initial value of the "electrochemical impedance spectrum" of the steel bars is measured directly at the reserved point before concrete pouring, in accordance with the "rapid testing protocol" established in step three. After the concrete reaches a certain age (e.g., 7 days, 28 days), non-destructive or minimal-destructive in-situ testing is performed on the steel bars inside the structure and in the "accompanying specimens" through the concrete surface to obtain the field value of the electrochemical characteristic frequency or characteristic spectrum or its short-term change trend.

[0052] 3) Performance Comparison and Judgment: The electrochemical impedance spectroscopy data (values ​​or trends) obtained from the on-site in-situ test are compared with the data of the same type of protective steel reinforcement in the accelerated laboratory test in Step 2 within the same period or similar environmental action cycle, or with the pre-established "performance qualification threshold range". If the on-site data falls within the qualification range or is consistent with the trend of the effective protective samples in the laboratory, the anti-corrosion measure is deemed to have passed the performance verification under the current on-site conditions; otherwise, an early warning is issued, and the "accompanying specimen" can be dissected for direct observation and auxiliary judgment.

[0053] In some embodiments, the method further includes step S500, which is performed after step S400: long-term performance monitoring and model iteration. During the engineering operation period, long-term durability performance data of the structure is continuously acquired, and the mapping relationship between the electrochemical characteristic frequency or characteristic spectrum and mechanical performance degradation established in step S300 is corrected and iteratively optimized using the data.

[0054] Specifically, continuous in-situ electrochemical impedance spectroscopy (EIS) tests can be conducted on the reinforcing steel in the structure periodically (e.g., every six months, annually, or according to the structural importance and the degree of environmental erosion). Simultaneously, long-term environmental data, such as humidity, temperature, acidic medium concentration, and chloride ion content, should be recorded. This long-term monitoring data should be combined with the actual service condition of the structure (e.g., whether cracks or spalling appear on the concrete surface, and whether visible corrosion or other macroscopic defects occur in the reinforcing steel) and input into the parameters established in step S200. Through statistical analysis and machine learning, the original parameters in the model (e.g., acceleration factors, corrosion rate constants, environmental impact coefficients, etc.) should be optimized and iteratively updated. This allows the parameters to more accurately reflect the long-term corrosion behavior of the reinforcing steel and the deterioration patterns of structural performance in actual complex acidic environments. This provides a more scientific and reliable theoretical basis and technical support for the full life-cycle safety assessment of the structure, maintenance and reinforcement decisions, and corrosion prevention design for similar subsequent projects.

[0055] In this embodiment, during engineering operation, the structure is periodically inspected using non-contact or minimally destructive methods such as electromagnetic and ultrasonic methods. This is combined with destructive testing of the "accompanying specimens" subjected to long-term exposure to obtain actual long-term performance data. This data is then fed back to correct the "time-damage" accelerated model coefficients of the laboratory accelerated testing in step two, continuously optimizing the predictive ability of the method.

[0056] Existing electrochemical on-site testing technologies, such as half-cell potential method and linear polarization method, are mainly used for diagnosing the corrosion status of service structures, primarily in chloride ion or carbonization environments. Although they are also on-site testing methods as described in this application, they are "post-event testing" and are not specifically designed for acidic environments.

[0057] Existing non-destructive testing technologies include electromagnetic field methods, ultrasonic methods, and piezoelectric sensing methods. Their main purpose is to monitor the degree or location of rust, and the environment they target is mostly general or chloride-salt environments. They focus on monitoring the "rust results" rather than conducting forward-looking verification of "rust prevention performance".

[0058] Existing laboratory electrochemical tests include polarization curve methods and electrochemical impedance spectroscopy (EIS). The main purpose of these tests is to study the corrosion mechanism and rate of materials. The environment is a controlled laboratory solution environment. Although similar to the technical methods in this application, the environmental simulation is disconnected from actual engineering.

[0059] This invention proposes a closed-loop process from on-site environmental perception to laboratory simulation and then to on-site verification. Existing technologies either involve laboratory testing detached from the actual on-site environment or post-hoc testing that cannot verify performance. This invention is the first to systematically combine these two approaches, resolving the contradiction between laboratory testing being detached from the real environment and on-site testing being unable to verify performance.

[0060] In this invention, environmental data collection and solution complexation verification are conducted for acidic environments (such as pH value and specific corrosive ions). However, most existing field detection methods (such as the half-cell potential method) are primarily focused on chloride ion environments, while the corrosion mechanisms and evaluation standards for acidic environments differ.

[0061] In this invention, "construction period stress" and "acidic environment" are actively coupled and tested in a laboratory simulation. Existing research, however, often focuses on a single corrosion factor or service load.

[0062] The method of this invention makes a forward-looking prediction and verification of the long-term effectiveness of the rust prevention scheme from the source of construction, rather than just monitoring the rust that has already occurred.

[0063] Example 1: Verification of the anti-corrosion performance of epoxy-coated steel bars in an irrigation canal project in an acidic soil area Project Background: A newly constructed irrigation canal traverses an acidic soil zone with a pH value of 4.0-5.5. The design uses epoxy resin coated steel bars (HRB400) to improve durability, and the effectiveness of the coating needs to be verified during the construction phase.

[0064] Implementation process: Step 1 At station K5+200, soil samples were taken from a depth of 1 meter using a core sampler, and pore fluid was extracted by centrifugation. Laboratory analysis showed a pH of 4.5, with SO42- as the main corrosive ion. 2- (1200 mg / L) and Cl - (300 mg / L). A pH / temperature and humidity / chloride ion sensor array was deployed for two months to obtain dynamic data on pH between 4.3 and 4.9 and humidity saturation during the rainy season.

[0065] Step Two Preparation of the simulated solution: Adjust the pH to 4.6 using deionized water, Na₂SO₄, NaCl, and dilute H₂SO₄. 2- and Cl - Simulated liquid for matching analysis.

[0066] Sample preparation: Take 6 bare steel bars A and 6 epoxy-coated steel bars B (with the ends ground to make electrical connection points), and cast 3 bars in each group into C40 mortar blocks (40mm*40mm*160mm), and pre-embed electrodes.

[0067] Loading and Testing: Mortar test blocks were installed on a loading frame, and a constant pressure of 30 MPa (simulating the initial compressive stress at the bottom of the channel) was applied to half of the test blocks (groups A1 and B1) via a hydraulic system. All test blocks were placed in an environmental chamber and immersed in simulated liquid, with a daily cycle of "immersion for 8 hours - air drying for 16 hours" controlled by a program. The linear polarization resistance of all reinforcing bars was measured daily, and the electrochemical impedance spectroscopy (frequency range 100 kHz - 10 mHz) was measured every 3 days.

[0068] Step 3 The experiment was stopped after 60 days. The reinforcing bars were removed for tensile testing. The results showed that the yield strength of bare reinforcing bars A1 (under stress) decreased by 22%, and that of A2 (under no stress) decreased by 15%; the mechanical properties of coated reinforcing bars B1 and B2 groups showed no significant changes.

[0069] Analysis of electrochemical data revealed that for coated steel bar B, the impedance modulus |Z| at 0.1 Hz was... 0.1h The rate of change of z (Δ|Z|%) in the initial stage of the experiment (the first 10 wet-dry cycles) is strongly correlated with the occurrence of local damage to the coating in the later stages, and corresponds well with the stability of mechanical properties. Therefore, the determination of Δ|Z| 0.1h z (10 cycles) represents the electrochemical impedance spectroscopy used in this verification.

[0070] Establish a rapid protocol: Using portable equipment, apply a sinusoidal perturbation of 10 Mv / ms to the rebar, perform narrow-band measurements around 0.1 Hz, and record |Z| before and after wet-dry cycles. 0.1h The z-value is calculated, and the rate of change is determined. A single test takes approximately 15 minutes.

[0071] Step Four After the reinforcement of the canal bottom slab is tied, select 10 points on the coated reinforcement and use a portable impedance meter to measure the initial |Z| according to the above protocol. 0.1h z-value. Ten accompanying test blocks were prepared during concrete pouring.

[0072] On the 28th day after pouring, the same instrument was used to measure the bottom slab reinforcement (non-destructive) and accompanying test blocks through the concrete surface. The measured Δ|Z| was obtained on-site. 0.1h The average z-value (simulated over 10 cycles) is 4.5%.

[0073] Comparison and judgment: Laboratory data shows that the coated steel bars in group B with good performance have Δ|Z| 0.1h The z-value (simulated over 10 cycles) is typically less than 8%. Field measurements showed 4.5% falling within this range. Additionally, an accompanying test block was chiseled open, revealing an intact coating.

[0074] Conclusion: The rust prevention performance of the epoxy-coated steel bars under the acidic conditions of the current project has been verified.

[0075] The method of this invention can be directly applied to the construction stage of reinforced concrete structures facing the threat of acid corrosion, such as water conservancy projects (canals, reservoirs), transportation projects (bridges, tunnels), municipal engineering projects (pipe galleries), and building foundations. It provides project owners, construction and supervision units with a scientific, systematic, and efficient tool for verifying the performance of anti-corrosion materials and processes, helping to control project quality from the source, predict durability, and avoid later losses. It has broad engineering application prospects and significant economic and social benefits.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions, characterized in that, Includes the following steps: S100: In-situ sensing and parameterization of the corrosion environment: At the target engineering site, environmental media samples are collected in situ to obtain basic chemical parameters, and sensors are deployed to continuously monitor dynamic environmental parameters. Based on the basic chemical parameters and dynamic environmental parameters, the multiphysics coupling boundary conditions for laboratory accelerated simulation are jointly determined. S2 00: Accelerated laboratory simulation and electrochemical monitoring based on field parameters: Based on the coupled boundary conditions determined by S100, a simulated corrosion solution is prepared and a dynamic simulation environment is constructed; the steel bar sample to be tested is placed in this simulation environment, and the load conditions of simulated construction stress are applied simultaneously; during the accelerated corrosion test, the electrochemical impedance spectroscopy evolution data of the steel bar sample are collected in real time. S300: Multi-dimensional performance degradation correlation analysis and standardization protocol development: Mechanical property tests are performed on steel bar samples after accelerated corrosion to obtain mechanical property degradation data; the mechanical property degradation data is correlated with the electrochemical impedance spectroscopy evolution data collected in real time in S200 to extract electrochemical characteristic frequencies or characteristic spectra that have a mapping relationship with specific mechanical property degradation indicators, which are used as alternative evaluation indicators for corrosion resistance, and a standardized rapid testing protocol suitable for field operation is developed based on the alternative evaluation indicators. S400: In-situ verification and judgment of corrosion prevention performance at construction site: At the construction site, in accordance with the standardized rapid testing protocol established in S300, rapid and non-destructive in-situ electrochemical impedance spectroscopy tests are performed on the structural steel bars or steel bars in the accompanying specimens to obtain the field data of the electrochemical characteristic frequency or characteristic spectrum; the field data is compared with the benchmark characteristic spectrum or preset threshold established in S300. If the field data meets the benchmark requirements, the corrosion prevention performance is judged to be qualified.

2. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 1, characterized in that, In step S100 above, the in-situ collection of environmental media samples is achieved by using a micro-destructive sampling device to obtain soil pore fluid or simulated concrete pore fluid from the site in order to determine the types and initial concentrations of corrosive ions. The continuous monitoring of dynamic environmental parameters includes at least time-series data on pH, temperature, humidity, and chloride ion concentration, and the monitoring duration covers at least one complete climate change cycle. The basic chemical parameters and the dynamic environmental parameters are used together to determine the multiphysics coupling boundary conditions of the laboratory simulation in step S200.

3. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 1, characterized in that, The above step S200 specifically includes: S210: Preparation of simulation solution. Based on the chemical analysis results of the field samples determined in S100, an acidic simulation solution containing the main corrosive ions is prepared. Its pH value and ion concentration range reproduce the statistical characteristic values ​​of the field monitoring results. S220: Electrode block preparation, the steel bar sample to be tested is encapsulated in mortar or concrete block, and a reference electrode and an auxiliary electrode are pre-embedded to form a three-electrode electrochemical testing system; S230: Stress-coupled loading, using loading equipment to apply static or alternating loads to the steel bars in a partially encapsulated test block. The stress level is determined based on the design stress state of the steel bars during the construction stage, and the load application is synchronized with the exposure to the simulated corrosive environment. S240: Dynamic environment simulation. The prepared test block is placed in the acidic simulated solution prepared in S210. The dry-wet cycle or solution flow is realized through program control. The frequency and amplitude of the dry-wet cycle are set according to the on-site humidity change spectrum monitored in S100. S250: Multi-parameter electrochemical monitoring. Throughout the accelerated corrosion test cycle, an electrochemical measurement system is used to monitor the open circuit potential and linear polarization resistance of the steel reinforcement sample at regular intervals, and to periodically collect full-spectrum electrochemical impedance spectroscopy data.

4. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 1, characterized in that, In step S300 above, the electrochemical characteristic frequencies or characteristic spectra that have a mapping relationship with specific mechanical property degradation indicators are: The rate of change of low-frequency impedance modulus within the preset early corrosion period.

5. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 4, characterized in that, The low frequency is one or more characteristic frequency points in the range of 0.01Hz to 1Hz.

6. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 4, characterized in that, The preset early corrosion period is the first 1 to 10 dry-wet cycles after the start of the laboratory accelerated test.

7. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 1, characterized in that, The above step S400 specifically includes: S410: Initial value measurement, before concrete pouring, the initial value of the electrochemical impedance spectrum is directly measured at the test points reserved for the steel reinforcement; S420: On-site measurement. After the concrete reaches the predetermined age, the internal steel reinforcement is measured in situ using non-destructive testing on the concrete surface to obtain the on-site measured values ​​of electrochemical characteristic frequencies or characteristic spectra. S430: Qualification judgment. The actual measured value on site is compared with the benchmark feature spectrum established in step S300 or the qualified threshold preset according to the benchmark feature spectrum. If the actual measured value on site falls within the qualified range, the anti-corrosion performance is judged to be qualified.

8. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 7, characterized in that, The non-destructive in-situ measurement in step S420 above includes: A porous ceramic probe is pre-embedded or drilled into the concrete surface, and the probe is filled with a conductive medium to form an ion conduction path with the internal steel reinforcement of the concrete. A portable electrochemical workstation was used, with an auxiliary electrode pre-embedded in the concrete surface as the counter electrode, a steel bar as the working electrode, and a reference electrode placed inside the probe as the reference electrode, forming a three-electrode testing system. Before testing, the reinforcing steel was subjected to short-term cathodic depolarization treatment to eliminate the interference of the initial passivation film formed during concrete pouring on the test results.

9. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 7, characterized in that, The in-situ verification object in step S400 above also includes the reinforcing steel in the concrete accompanying specimens that are fabricated and cured simultaneously on the construction site and contain the same reinforcing steel as the main structure.

10. The in-situ testing and verification method for the corrosion resistance of reinforcing steel bars under acidic conditions as described in claim 1, characterized in that, It also includes step S500, which is performed after step S400: long-term performance monitoring and model iteration. During the engineering operation period, long-term durability performance data of the structure is continuously acquired, and the mapping relationship between the electrochemical characteristic frequency or characteristic spectrum and mechanical performance degradation established in step S300 is corrected and iteratively optimized using the data.

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