Corrosion current and corrosion prediction method, device and equipment for steel bars in concrete in low-pressure environment

Abstract

The invention provides a method, a device and equipment for predicting corrosion current and corrosion of steel bars in concrete in a low-pressure environment, and belongs to the technical field of engineering simulation modeling. The method comprises the following steps: establishing a coupling transmission model in concrete considering oxygen concentration, sulfate ion diffusion behavior and chloride ion diffusion behavior; building a reinforcement corrosion current density and corrosion depth prediction model for predicting the number of charges at different positions of the reinforcement in the concrete, and calculating the corrosion depth and the corrosion product content based on the corrosion current density; and establishing a linear elastic damage model for simulating concrete damage evolution caused by steel bar corrosion according to the corrosion product content output by the steel bar corrosion current density prediction model so as to realize accurate prediction of corrosion and damage. According to the method, oxygen concentration changes under low air pressure are considered, oxygen diffusion is described, output of a transmission model serves as a dynamic variable to be introduced into the corrosion current calculation process, and the accuracy of corrosion current and steel bar corrosion prediction is improved.

Description

Technical Field

[0001] The present application relates to the field of computer-aided design technology in engineering simulation modeling, and in particular to a method, device and equipment for predicting corrosion current and rust of steel bars in concrete in a low-pressure environment. Background Art

[0002] Rebar corrosion is a key factor contributing to the degradation of reinforced concrete structures. After corrosion occurs, the volume of the corrosion products increases. In the early stages of corrosion, the corrosion products fill the pores surrounding the rebar. As corrosion progresses, when the rust expansion force exceeds the tensile strength of the concrete, it causes concrete cracking, further accelerating the intrusion of corrosive ions. Furthermore, rebar corrosion reduces the effective cross-sectional area of ​​the rebar, thereby reducing the bearing capacity of the rebar and, consequently, the bearing capacity of the reinforced concrete structure, thus affecting the service life of the reinforced concrete structure.

[0003] Traditional steel corrosion simulation and damage prediction are primarily conducted in plain environments. In plain environments, reinforced concrete structures experience normal oxygen partial pressure, resulting in a sufficient cathodic reaction and high corrosion rates. Oxygen diffusion is primarily influenced by the density of the concrete. However, in plateau environments, steel corrosion in reinforced concrete structures differs significantly from that in plain environments. Simply applying the same treatment methods used in plain environments is likely to result in significant deviations. This is due to the following reasons: The low atmospheric pressure in plateau environments (only 50% to 70% of that in plains) directly affects the oxygen supply, leading to insufficient cathode reactants and, in turn, suppressing the steel corrosion rate. Furthermore, low oxygen concentrations reduce the net diffusion of oxygen into concrete, also affecting steel corrosion. Finally, oxygen concentration cells (surface oxygen enrichment / internal oxygen deficiency) are prone to forming in plateau reinforced concrete structures, causing localized pitting corrosion.

[0004] Currently, there is a relative lack of research that considers the changes in corrosion current density around steel bars caused by oxygen concentration and ion corrosion in plateau environments. Alternatively, the corrosion of steel bars in reinforced concrete structures in plateau environments is simply treated the same as in plain environments. However, due to the influence of these factors, the existing simulation methods for internal steel bar corrosion in concrete in plateau environments are not very accurate and differ greatly from actual results. Summary of the Invention

[0005] The purpose of this application is to provide a method, device and equipment for predicting steel corrosion current and rust in concrete in a low-pressure environment, so as to improve the accuracy of steel corrosion current and rust prediction in a low-pressure environment.

[0006] In order to achieve the above objectives, this application provides the following technical solutions: In a first aspect, the present application provides a method for predicting corrosion current and rust of steel bars in concrete in a low-pressure environment, comprising: A coupled transport model for concrete is established under low plateau pressure, taking into account oxygen concentration, sulfate ion diffusion behavior, and chloride ion diffusion behavior; the coupled transport model includes a chloride ion transport model, a sulfate ion transport model, and an oxygen diffusion model; Establish a prediction model for steel bar corrosion current density and corrosion depth; The steel bar corrosion current density and corrosion depth prediction model is used to predict the charge number at different positions of the steel bars inside the concrete under the participation of different oxygen concentrations based on the coupled transmission model, thereby obtaining the corrosion current density of the steel bars inside the concrete; and based on the corrosion current density, calculate the corrosion depth and rust product content; Establish a linear elastic damage model; The linear elastic damage model is used to simulate the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

[0007] This approach constructs a three-level progressive structure consisting of a coupled transmission model, a steel bar corrosion current density and corrosion depth prediction model, and a linear elastic damage model. Starting from ion transport, through electrochemical reactions, and ultimately linking to structural damage, this completes the computational chain from environmental erosion to concrete cracking. Furthermore, the modeling system incorporates the plateau's low-pressure environment, and uses an oxygen diffusion model to reflect the impact of low oxygen partial pressure on the corrosion process. This supports the prediction of the spatial distribution of corrosion current density at different steel bar locations, accurately reflecting the characteristics of localized corrosion in low-pressure environments and improving the accuracy of steel bar corrosion and damage prediction.

[0008] In conjunction with the first aspect, in some optional implementations, in the coupled transmission model, Fick's second law is used to describe the diffusion of chloride ions and sulfate ions in concrete, thereby obtaining the chloride ion transmission model and the sulfate ion transmission model. Based on Fick's second law, a plateau low-pressure correction factor is introduced to correct oxygen diffusion and obtain an oxygen diffusion model, which is used to reflect the impact of low-pressure environment. The plateau low pressure correction factor is expressed as: , where 、 They represent plain pressure and plateau pressure respectively.

[0009] In the above scheme, chloride ions, sulfate ions and oxygen are all modeled based on Fick's second law, ensuring the consistency of the model system; by introducing the plateau low-pressure correction factor, the macro-environmental parameters (air pressure) are integrated into the micro-diffusion process, making the oxygen diffusion model environmentally adaptable and improving the authenticity of the oxygen diffusion simulation. The correction factor is given in the form of a ratio with a clear numerical range, which is convenient for direct assignment and application in numerical simulation without the need for additional calibration of complex parameters.

[0010] In combination with the first aspect, in some optional implementations, the coupled transmission model is also used to describe: the time difference between chloride ions and sulfate ions reaching the surface of the steel bars. In a low-pressure environment, the time difference has a phased effect on the corrosion process with the participation of oxygen.

[0011] In conjunction with the first aspect, in some optional embodiments, the time difference between chloride ions and sulfate ions reaching the steel bar surface, in a low-pressure environment, has a phased effect on the corrosion process in the presence of oxygen, specifically: Chloride ions first diffuse to the steel bar surface, where charge exchange occurs and the corrosion current density begins to be calculated; Sulfate ions diffuse to the steel bar surface later than chloride ions, and destroy the passive film of the steel bar by expansion. Chloride ions further penetrate the passive film and directly cause local corrosion of the steel bar, and oxygen participates in the low-pressure environment to further accelerate the corrosion.

[0012] In conjunction with the first aspect, in some optional implementations, based on the coupled transmission model, the charge number at different positions of the steel bars inside the concrete is predicted to obtain the corrosion current density of the steel bars inside the concrete, specifically: Based on the electrochemical kinetics theory, the Tafel equation was used to calculate the anodic current density and the cathodic current density, and then the corrosion current density of the steel bars inside the concrete was calculated.

[0013] In combination with the first aspect, in some optional embodiments, the Tafel equation is used to calculate the anode current density and the cathode current density respectively, and also includes: directly embedding the chloride ion concentration into the expression of the anode Tafel slope to dynamically adjust the corrosion rate by affecting the electrochemical polarization behavior.

[0014] In combination with the first aspect, in some optional embodiments, the chloride ion concentration is directly embedded in the expression of the anode Tafel slope. Specifically, the chloride ion concentration is embedded in the expression of the anode Tafel slope in the form of a power function to characterize the nonlinear characteristics of the chloride ion, which has a significant effect at low concentrations and tends to saturation at high concentrations.

[0015] In combination with the first aspect, in some optional implementations, the Tafel equation is used to calculate the anode current density and the cathode current density respectively, and also includes: when the electrode reaction is controlled by the oxygen content, the limiting current density is introduced during the electrode reaction process of the cathode to correct the cathode current density.

[0016] In a second aspect, this embodiment provides a device for predicting corrosion current and rust of steel bars in concrete in a low-pressure environment. The device is used to perform the method provided in any of the above embodiments, and the device includes: a diffusion modeling unit configured to establish a coupled transmission model within concrete that takes into account oxygen concentration, sulfate ion diffusion behavior, and chloride ion diffusion behavior under low plateau pressure; the coupled transmission model includes a chloride ion transmission model, a sulfate ion transmission model, and an oxygen diffusion model; a corrosion modeling unit configured to establish a steel bar corrosion current density and corrosion depth prediction model; The steel bar corrosion current density and corrosion depth prediction model is used to predict the charge number at different positions of the steel bars inside the concrete under the participation of different oxygen concentrations based on the coupled transmission model, thereby obtaining the corrosion current density of the steel bars inside the concrete; and based on the corrosion current density, calculate the corrosion depth and rust product content; The corrosion simulation unit is configured to establish a linear elastic damage model for simulating the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

[0017] In a third aspect, this embodiment provides a computer device comprising a memory and a processor, wherein the memory and the processor are connected; the memory is used to store computer execution instructions; and the processor is used to call the computer execution instructions to execute the steps of the method provided in any one of the above embodiments.

[0018] The technical effects of the second and third aspects of this application can refer to the description of the first aspect and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a method for predicting corrosion current and rust of steel bars in concrete in a low-pressure environment according to some embodiments of the present application.

[0020] Figure 2 The present invention provides an example of a process for predicting corrosion current and rust of steel bars in concrete in a low-pressure environment according to some embodiments of the present application.

[0021] Figure 3 Schematic diagram of the steel bar corrosion process caused by the intrusion of corrosive media in the low-pressure environment of the plateau.

[0022] Figure 4 Schematic diagram of the test and simulation under the low-pressure environment of the plateau, where (a) is a schematic diagram of the cross-sectional structure of the concrete specimen in the test, and (b) is a schematic diagram of the structure and key dimensions of the concrete specimen in the numerical simulation.

[0023] Figure 5 Schematic diagram of chloride ion concentration distribution inside concrete.

[0024] Figure 6 Schematic diagram of sulfate ion concentration distribution inside concrete.

[0025] Figure 7 Schematic diagram of oxygen concentration distribution and streamlines inside concrete.

[0026] Figure 8 Schematic diagram of the comparison between the numerical simulation results of the time-varying steel corrosion current density in the plateau low-pressure environment and the experimental data.

[0027] Figure 9 Schematic diagram of the concrete cover damage mode during the steel bar corrosion expansion process in the plateau low-pressure environment.

[0028] Figure 10 Schematic diagram comparing the numerical results and experimental results of concrete damage caused by steel bar corrosion, where (a) is the experimental result and (b) is the simulation result of this application.

[0029] Figure 11 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0030] This application provides a method, device, and equipment for predicting corrosion current and corrosion of steel bars in concrete under low-pressure conditions. This technical solution establishes a coupled transmission model for concrete under low-pressure conditions on the plateau that takes into account oxygen concentration, sulfate ion diffusion behavior, and chloride ion diffusion behavior. The model predicts the charge at different locations of steel bars in the concrete at different times under different oxygen concentrations, and then predicts the corrosion current value of the steel bars in the concrete. On this basis, the content of steel corrosion products is quantified, and the formation and expansion process of cracks in the concrete caused by steel corrosion is simulated. From the perspective of the coupled transmission model, the solution, on the one hand, reflects the effect of low oxygen partial pressure on corrosion by incorporating oxygen transmission into the coupled transmission model, avoiding the systematic deviation caused by treating plateau environments and plain environments the same. On the other hand, although the diffusion behaviors of oxygen, sulfate ions, and chloride ions are independent of each other, they are coupled in time series to form a complete corrosion path, laying the foundation for the subsequent dynamic prediction of corrosion current. In terms of corrosion current prediction, oxygen is introduced as a dynamic variable into the corrosion current calculation process to reflect its control effect on the cathodic reaction rate, and the environmental dependence of the dynamic change of corrosion current density under different oxygen concentrations is modeled, significantly improving the accuracy of corrosion current density prediction in plateau environments. Based on the corrosion current density, the corrosion depth is deduced, and the accumulation of corrosion products is further predicted. This is used as input for the mechanical effect analysis of the linear elastic damage model, achieving accurate prediction of corrosion and damage. This improves the accuracy of predicting corrosion current and corrosion of steel bars inside concrete in the low-pressure environment of the plateau. In addition, this solution connects the entire process from environmental conditions to multi-ion transport, electrochemical reactions, and finally concrete damage evolution, forming a closed-loop, dynamic, and visual degradation process simulation system. This provides a systematic tool for studying the performance degradation of reinforced concrete structures in complex corrosive environments, suitable for accurately simulating coupled degradation behavior in the complex environment of the western plateau.

[0031] The embodiments of the present application are described below with reference to the accompanying drawings.

[0032] The embodiments of the present application can be applied to Figure 11 Among the computer devices shown, the computer device can be, but is not limited to, mobile terminals such as mobile phones, tablet computers, handheld computers, personal digital assistants (PDAs), smart home devices such as smart TVs and smart cameras, wearable devices such as smart bracelets, smart watches, and smart glasses, or other computer devices such as desktops, laptops, notebook computers, ultra-mobile personal computers (UMPCs), netbooks, and smart screens.

[0033] like Figure 11As shown, the computer device 200 may include one or more of the following components: a processor 201, a memory 203, a communication interface 202, and a communication bus 204. The memory 203 may be connected to the processor 201 via the bus 204. The bus can transmit data between the processor 201 and the memory 203. The bus can be divided into an address bus, a data bus, a control bus, and the like.

[0034] The processor 201 may include one or more processing cores. The processor 201 may utilize various interfaces and lines to connect various components within the entire computer device 200. By running or executing instructions, programs, code sets, or instruction sets stored in the memory 203, and calling data stored in the memory 203, the processor 201 performs various functions and processes data of the computer device 200. For example, the processor 201 may include an application processor (AP), a modem processor, a CPU, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic array (PLA), and / or a neural network processing unit (NPU). Among them, the CPU mainly processes the operating system, user interface, and application programs; the GPU is responsible for rendering and drawing the content to be displayed; the NPU is used to implement artificial intelligence (AI) functions; and the modem is used to handle wireless communications. Different processing units can be independent devices or integrated into one or more processors. For example, the multiple processing units shown above are all integrated into a SoC, or the AP is a separate semiconductor chip and the other processing units are integrated into a SoC. This application is not limited to this.

[0035] The memory 203 may include random access memory (RAM), read-only memory (ROM), or non-transitory computer-readable storage medium. The memory 203 may be used to store instructions, programs, codes, code sets, or instruction sets. The memory 203 may include a program storage area and a data storage area. The program storage area may store instructions for implementing an operating system and instructions for at least one function, such as a method for predicting corrosion current and rust of steel bars in concrete in a low-pressure environment. The data storage area may store data created based on the use of the computer device 200, such as input data for numerical solutions.

[0036] In addition, those skilled in the art will appreciate that the structure of the computer device 200 shown in the above figures does not limit the computer device 200. The computer device may include more or fewer components than shown, or may combine certain components or arrange the components differently. For example, the computer device 200 may also include a microphone, a speaker, a radio frequency circuit, a sensor, an audio circuit, a power supply, a Bluetooth module, and other components, which will not be described in detail here.

[0037] This embodiment provides a method for predicting corrosion current and rust of steel bars in concrete under low pressure environment. The method can be executed by the above-mentioned computer equipment, such as Figure 1 As shown, the method includes the following steps: Step S1: Establish a coupled transport model (hereinafter referred to as the transport model) within concrete that takes into account oxygen concentration, sulfate ion diffusion, and chloride ion diffusion under low plateau pressure. The coupled transport model includes a chloride ion transport model, a sulfate ion transport model, and an oxygen diffusion model. By constructing a coupled transport model that considers the diffusion of oxygen, chloride ions, and sulfate ions, the transport behavior of chloride ions, sulfate ions, and oxygen in concrete is simulated.

[0038] Step S2: establishing a steel bar corrosion current density and corrosion depth prediction model (hereinafter referred to as corrosion model).

[0039] Among them, the steel bar corrosion current density and corrosion depth prediction model is used to predict the charge number at different positions of the steel bars inside the concrete under the participation of different oxygen concentrations based on the coupled transmission model, and obtain the corrosion current density of the steel bars inside the concrete; and based on the corrosion current density, calculate the corrosion depth and rust product content.

[0040] In the coupled transmission model, the ion diffusion behavior includes the plateau low-pressure transmission of oxygen, chloride ions, and sulfate ions. The three interact with each other: chloride ions, as the ions with the fastest diffusion rate, accumulate continuously on the surface of the steel bars, and begin to undergo electrochemical corrosion and generate corrosion current. As sulfate ions diffuse to the surface of the steel bars, the passivation film is destroyed, the corrosion current continues to increase, and under the action of oxygen, the steel bars are corroded. This process continuously obtains the corrosion current value; after the content of steel bar corrosion products reaches a certain amount, the concrete cracks. As time increases, the concrete rust expansion cracking continues to develop, and the degree of concrete damage at different times is obtained.

[0041] Step S3: Establish a linear elastic damage model (referred to as damage model).

[0042] Among them, the linear elastic damage model is used to simulate the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

[0043] The technical solution of this embodiment constructs a coupled transmission model within concrete that considers oxygen, chloride ions, and sulfate ions in the low-pressure environment of the plateau. Based on this coupled transmission model, a steel bar corrosion current density and corrosion depth prediction model is established to predict the corrosion current density, thereby estimating the content of rust products. Subsequently, a linear elastic damage model is used to simulate damage evolution. This solution overcomes the limitation of existing models that ignore the influence of oxygen concentration. It can truly reflect the physical mechanism of the suppressed corrosion current density in the low-oxygen environment of the plateau, providing a prerequisite for subsequent corrosion prediction and damage evolution, improving the environmental adaptability and accuracy of steel bar corrosion prediction, and providing a scientific and systematic numerical analysis tool for the durability design, life prediction, and maintenance decision-making of reinforced concrete structures in plateau areas.

[0044] In a further improvement scheme, in the coupled transmission model of step S1, Fick's second law is used to describe the diffusion of chloride ions and sulfate ions in concrete, and corresponding chloride ion transmission models and sulfate ion transmission models are obtained; based on Fick's second law, a plateau low pressure correction factor is introduced to correct the oxygen diffusion, and an oxygen diffusion model is obtained. The oxygen diffusion model is used to reflect the impact of the low pressure environment; wherein, the plateau low pressure correction factor is the ratio between the plateau pressure and the plain pressure.

[0045] In this embodiment, the diffusion models for oxygen, chloride ions, and sulfate ions constructed are consistent and are all described using Fick's second law. The diffusion of chloride ions and sulfate ions within concrete is described using the classic Fick's second law. Specific diffusion equations can be constructed with reference to existing technologies and are not detailed here for brevity.

[0046] In this embodiment, the oxygen diffusion model is a diffusion model based on the correction of plateau low pressure. This model is used to reflect the dynamic impact of changes in oxygen concentration at different time points on steel corrosion in a plateau low pressure environment. Specifically, during the transmission of oxygen inside the concrete, it does not react with other ions or cement hydration products. The transmission process of oxygen inside the concrete is a non-steady-state diffusion process driven by concentration under a low pressure environment. Fick's second law is used to describe the transmission of oxygen inside the concrete. The oxygen diffusion is corrected by introducing a plateau low pressure correction factor to accurately describe the diffusion behavior of oxygen. The plateau low pressure correction factor is the ratio between the plateau pressure and the plain pressure. The oxygen diffusion model is obtained as follows: (1) Where, Indicates time, Indicates the oxygen concentration inside the concrete (mol / m 3 ); represents the oxygen diffusion coefficient in the concrete pore solution (m 2 / s), value ; 、 Represents plain pressure and plateau pressure respectively. It is the pressure ratio, which is used as the pressure correction factor to correct the oxygen diffusion behavior. The general value range is 1.4-2.0.

[0047] Unlike traditional models that generally assume that oxygen diffusion is only affected by concrete density and humidity, this embodiment explicitly models plateau low pressure as a key external parameter affecting oxygen diffusion. By incorporating ambient air pressure as an independent variable into the diffusion model, it is used to characterize how plateau low pressure causes a decrease in oxygen partial pressure, which in turn affects the cathode reaction rate and corrosion process, thereby simulating the differences in steel corrosion mechanisms under plateau environments.

[0048] Furthermore, the coupled transmission model in step S1 is also used to describe the time difference between chloride ions and sulfate ions reaching the steel bar surface. In a low-pressure environment, this time difference, combined with the presence of oxygen, has a phased impact on the corrosion process. Specifically, chloride ions diffuse to the steel bar surface first, where charge exchange occurs and the corrosion current density begins to be calculated. Sulfate ions diffuse to the steel bar surface later than chloride ions, expanding and destroying the steel bar's passive film. Chloride ions further penetrate the passive film, directly causing localized corrosion of the steel bar. In a low-pressure environment, oxygen further accelerates corrosion.

[0049] In the above technical steps, the coupled transport model is also used to describe the difference in the diffusion rate of chloride ions and sulfate ions in concrete, as well as the time series relationship between the two reaching the steel bar surface at different times. ) has a significantly greater diffusion coefficient than sulfate ions ( During the corrosion process, chloride ions preferentially diffuse to the steel bar surface and accumulate. When chloride ions diffuse to the steel bar surface, they compete with hydroxide ions in the passive film for adsorption, forming soluble iron ion complexes. This is when charge exchange occurs, and the corrosion current density begins to be calculated. Sulfate ions, however, lag behind chloride ions in reaching the steel bar surface due to their slower diffusion rate. This means that sulfate ions diffuse to the steel bar surface later than chloride ions. Subsequently, sulfate ions indirectly damage the integrity of the steel bar's passive film by inducing concrete expansion and cracking. Chloride ions further penetrate the passive film, directly leading to localized corrosion of the steel bar. This is further accelerated by oxygen, leading to the corrosion current density value obtained under the low-pressure environment of the plateau.

[0050] Specifically, in the low-pressure environment of the plateau, oxygen, as a key participant in the cathode reaction, has a concentration that decreases with decreasing air pressure, resulting in a weakening of the cathode depolarization capacity and an overall suppression of the corrosion reaction. When chloride ions arrive first and trigger the formation of a local anode area, although the oxygen concentration is low at this time, a weak cathode reaction can still be maintained, generating an initial corrosion current and initiating the early corrosion process. However, under low-oxygen conditions, early corrosion is limited by the cathode reaction, and even depassivation is difficult to form significant rust expansion. Subsequently, sulfate ions gradually diffuse to the surface of the steel bars, and sulfate corrosion reactions occur inside the concrete, generating expansive products such as calcium aluminate, causing microcracks in the concrete to expand, further destroying the integrity of the interface between the steel bars and concrete, and indirectly weakening the protective effect of the passivation film. At the same time, the cracking of the concrete caused by sulfate improves the oxygen transmission path, accelerating corrosion. Therefore, this process promotes the stable establishment of the corrosion cell in the presence of oxygen, significantly increasing the corrosion current density and entering the accelerated corrosion stage.

[0051] In summary, by considering the differences in arrival times of chloride ions and sulfate ions, the coupled transmission model can transmit these differences in real time to the steel bar corrosion current density and corrosion depth prediction model. Combined with the influence of changes in oxygen concentration under low pressure on the plateau, the steel bar corrosion current density and corrosion depth prediction model can dynamically simulate the staged evolution characteristics of the corrosion process, thereby improving the dynamics and accuracy of the corrosion current density prediction.

[0052] For example, the staged evolution can be divided into two stages: the first stage is the chloride ion induced depassivation + low oxygen current limiting corrosion stage, and the second stage is the sulfate ion induced interface degradation + corrosion channel penetration + corrosion intensification stage. In another example, the staged evolution can also be divided into: start-up period and acceleration period. By introducing the time difference of ion arrival and the time-varying influence of oxygen participation to describe the staged influence of different ions on the corrosion current, the nonlinear characteristics of the slow start and rapid development of the corrosion process in a low-pressure environment are revealed, which is closer to the measured degradation behavior in plateau areas.

[0053] After the coupled transmission model is constructed, in step S2, a prediction model for the steel bar corrosion current density and corrosion depth is established, and the charge number at different positions of the steel bars inside the concrete is predicted to obtain the corrosion current density of the steel bars inside the concrete. Specifically, based on the electrochemical kinetics theory, the Tafel equation is used to calculate the anode current density and the cathode current density, respectively, and then the corrosion current density of the steel bars inside the concrete is calculated.

[0054] Refer to the following Figure 3 Describe the calculation process of corrosion current density.

[0055] Figure 3 The upper middle part shows the chemical reaction equations of rust products, which include two key chemical reaction equations: and The lower part shows the electrochemical corrosion process at the interface between steel and concrete. According to electrochemical kinetics theory, when chloride ions reach the steel surface, they compete with hydroxide ions in the passivation film for adsorption, forming soluble iron ion complexes, which trigger the anodic dissolution reaction ( ), generates a charge ( ) transfer, and a reduction reaction occurs in the cathode area (the contact surface between concrete and steel bars, i.e., the corrosion interface). The reaction formula is: , providing an electronic circuit for anodic oxidation. This electrochemical process initiates the corrosion current. By monitoring or calculating the change of this current density over time, dynamic prediction of the steel bar corrosion process can be achieved. The relevant simplified chemical reaction formula is as follows: Fe(passivation film)+2Cl - →FeCl2+2 e - (2) In this embodiment, the electrochemical corrosion reaction at the steel / concrete interface is described by the basic electrode kinetic equation, and the local corrosion current density is It is determined by the anodic oxidation reaction and the cathode reduction reaction, and its expression is shown in formula (3): (3) Where: is the local current density of the electrode reaction (A / m 2 ); is the charge number; is the exchange current density of the electrode reaction (A / m 2 ); is the Faraday constant (96485 C / mol); is the ideal gas constant; is the absolute temperature; and is the charge transfer coefficient between the anode and cathode, and satisfies ; is the overpotential at the electrode-electrolyte interface, The calculation formula is as follows: (4) Where, is the external electric potential of the steel bar; is the electrolyte potential; is the equilibrium potential of the electrode reaction (V).

[0056] When the overpotential at the electrode-electrolyte interface When it is higher, formula (3) can be simplified to formula (5), which is as follows: (5) Where, is the exchange current density of the anodic reaction (A / m 2 ), let the Tafel slope of the anode be ,in, Representing the charge number of the anode, the anode corrosion current density can be obtained as shown in Formula 6: (6) Where, the Tafel slope of the anode is The unit is V / decade.

[0057] Similarly, the cathode corrosion current density can be obtained as shown in formula (7): (7) Where: is the Tafel slope of the cathode (V / decade); is the exchange current density of the cathode reaction (A / m 2 ).

[0058] The above formulas (6) and (7) respectively use the Tafel equation to calculate the anode current density and cathode current density.

[0059] Furthermore, after the steel bar is depassivated, the chloride ion concentration around it will directly affect the Tafel slope of the anodic reaction. , considering the influence of chloride ion concentration, therefore, the chloride ion concentration influence factor is introduced to correct the corrosion current density of the anode, that is, the chloride ion concentration is directly embedded in the expression of the anode Tafel slope to dynamically adjust the corrosion rate by affecting the electrochemical polarization behavior. The expression is as follows: (8) Where: is the influence factor of chloride ion concentration around the steel bar on the anode Tafel slope, that is, the chloride ion concentration influence factor.

[0060] In traditional corrosion current prediction, chloride ion concentration is usually used to determine whether depassivation occurs or as an empirical input parameter for corrosion current. The correction of the anode Tafel slope is introduced in the form of a power function. That is, based on the traditional electrochemical model, the quantitative influence mechanism of the environmental ion concentration on the kinetic parameters is introduced, thereby affecting the anode corrosion current density and realizing the dynamic prediction of the corrosion current density. Furthermore, the chloride ion concentration is embedded in the expression of the anode Tafel slope in the form of a power function, so that Including constant terms and negative power law terms ( ), which can characterize the nonlinear characteristics of significant effects at low chloride ion concentrations and saturation at high concentrations.

[0061] In some embodiments, the Tafel equation is used to calculate the anode current density and the cathode current density respectively, and further includes: when the electrode reaction is controlled by the oxygen content, introducing a limiting current density during the cathode electrode reaction process to correct the cathode current density.

[0062] Specifically, when the electrode reaction is controlled by the oxygen content, a limiting current density needs to be introduced during the cathode electrode reaction. Formula (3) is modified to obtain the corrected cathode current density, which is expressed as follows: (9) (10) Where: is the corrosion current density of the cathode reaction (A / m 2 ); is the limiting current density; is the diffusion layer thickness.

[0063] According to the above description, the corrosion current density prediction process in the steel bar corrosion current density and corrosion depth prediction model can be summarized as follows: the anode and cathode corrosion current densities are calculated according to formulas (6) and (7). When calculating the anode corrosion current density, the dynamic effect of chloride ion concentration on the corrosion current density is considered by formula (8). When calculating the cathode corrosion current density, the corrosion current density of the cathode reaction is corrected by formulas (9) and (10).

[0064] Based on the dynamic prediction of the steel bar corrosion current density, step S2 also calculates the corrosion depth and the content of rust products based on the corrosion current density. Specifically, when chloride ions penetrate the passivation film and directly cause local corrosion of the steel bar, according to Faraday's law, the mass change of the rust products on the steel bar surface is proportional to the charge around the electrode. Therefore, the corrosion depth of the steel bar in the concrete is closely related to the corrosion current density. The corrosion current density is used to quantify the corrosion products. The greater the corrosion current density, the faster the steel bar corrosion rate. The relevant calculation formula is as follows: (11) Where: is the steel bar corrosion depth ( ); is the chemical equivalence coefficient (value = 2); is the molar mass of iron (=0.056 kg / mol); is the density of iron (7860kg / m 3 ); is the number of valence electrons of iron participating in the reaction (value = 2, corresponding to ), is the corrosion current density, where .

[0065] Substituting the calculated corrosion current density into formula (11), the steel bar corrosion depth can be calculated to quantify the steel bar corrosion products.

[0066] In step S3, the linear elastic damage model is used to simulate the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

[0067] In other words, this embodiment describes the process of concrete crack development based on the quantified content of steel bar corrosion products through the concrete linear elastic damage model, characterizing the formation and expansion of cracks; and simulates the entire process of concrete cracking caused by harmful ion erosion, steel bar corrosion, and then steel bar corrosion expansion in a low-pressure plateau environment.

[0068] Specifically, the process of concrete cracks developing due to the increase in the content of steel corrosion products is studied. Based on the continuum mechanics, a linear elastic damage model is established, and the concrete internal variable damage parameter is introduced. To characterize the crack formation and propagation process of the cement matrix, a scalar damage model is used to describe the cracking of the concrete area. The expressions of the scalar damage model are shown in formulas (12) and (13): (12) (13) Furthermore, the damage evolution is driven by the non-local equivalent strain, and the implicit gradient method is used to describe the non-local equivalent strain. and equivalent strain The relationship between them is shown in formula (14): (14) Where: is lossy stiffness; is the lossless linear elastic stiffness; is a state variable; is the internal length dimension under implicit gradient. It should be pointed out here that the equivalent strain obeys the Rankine stress criterion.

[0069] The damage evolution during crack propagation can be expressed in the form of exponential strain softening, as shown in formulas (15) and (16): (15) (16) Where: is the critical strain value for the onset of damage; is the fracture energy per unit area of ​​concrete; is the characteristic unit size; is the tensile strength of concrete; is the initial elastic modulus of concrete.

[0070] Numerical simulation was carried out using computer numerical simulation software. The material parameters (such as water-cement ratio, initial elastic modulus of concrete, etc.), multi-ion transport parameters (such as chloride ion, sulfate ion, oxygen concentration, etc.) obtained by dynamic calculation of the coupled transmission model, and electrochemical parameters (such as anode and cathode corrosion current density, etc.) calculated by the corrosion model were substituted into the above damage model to simulate the concrete damage distribution.

[0071] As an example, the embodiment of the present application can also be Figure 2 The steps shown are performed, including: A transport model (i.e., a coupled transport model) was constructed that takes into account the diffusion of oxygen, chloride ions, and sulfate ions in the low-pressure environment of the plateau to simulate the transport behavior of chloride ions, sulfate ions, and oxygen in concrete. The charge transfer of steel bars inside concrete is calculated using an ion transport model (i.e., coupled transport model), which can then be used to predict the corrosion current of steel bars inside concrete. Quantify the content of steel bar corrosion products through steel bar corrosion current density and corrosion depth model; The linear elastic damage model of concrete in the low-pressure environment of the plateau is simulated to describe the development process of concrete cracks and characterize the formation and expansion of cracks.

[0072] In summary, in this embodiment, by constructing a coupled transmission model considering oxygen, chloride ions, and sulfate ions, the corrosion current density at different times and locations is dynamically calculated using a corrosion model under the staged influence of multi-ion transmission, filling the research gap in the change of corrosion current density under the combined action of oxygen concentration and chloride ion and sulfate ion corrosion in plateau environments.

[0073] In a specific embodiment, the coupled transmission model clearly distinguishes between modeling plateau and plain environments, eliminating the traditional plain model and proposing a correction mechanism for plateau low pressure to accurately describe oxygen diffusion behavior. Furthermore, the solution of this embodiment not only simultaneously considers the three key media—oxygen, chloride ions, and sulfate ions—but also distinguishes their diffusion rates, mechanisms of action, and temporal relationships. This reveals the synergistic degradation mechanism of chloride ion depassivation, sulfate ion damage, and oxygen rate control in low-pressure environments, enabling in-depth research on multi-factor coupling mechanisms.

[0074] In the corrosion model, oxygen concentration is used as a variable during the cathode electrode reaction, and the limiting current density is introduced to correct the cathode current density, reflecting the control effect of oxygen concentration changes on the cathode reaction rate at different times and locations. Based on this, numerical simulations are used to obtain the corrosion current density at different locations on the steel bar surface to reflect the local pitting corrosion caused by the oxygen concentration cell.

[0075] In summary, in this embodiment, a transmission model, a corrosion model, and a damage model are established to describe the physical and chemical processes of the corrosion current prediction and rusting process of steel bars inside concrete under a low-pressure plateau environment, so as to express its degradation mechanism.

[0076] In order to verify the method proposed in this embodiment, the experimental process and numerical simulation process are described below.

[0077] First, prepare the concrete specimens. During the test, the concrete with a water-cement ratio of 0.45 and a cement dosage of 350 kg / m 3 , using 12mm diameter steel bars. The bars were fixed in the center of a cylindrical mold with an inner diameter of 75mm. Concrete was then poured into the mold. After demolding, the specimens were placed in a concrete curing chamber and cured for 28 days. After curing, the cylindrical reinforced concrete specimens were immersed in a 5% NaCl and 4% Na2SO4 solution. After the concrete specimens were prepared, tests were conducted in a low-pressure environment (approximately 70kPa) simulating a plateau, and the corrosion rate of the steel bars was measured regularly. To maintain the stability of the corrosion solution concentration in the container, the solution was replaced every two weeks during the test.

[0078] Secondly, numerical simulation was carried out using computer software. Figure 4 This is a schematic diagram of the test and simulation under the low pressure environment of the plateau. Figure 4In part (a), the cross section of the concrete specimen is a cylindrical section. The center of the specimen is the steel bar, and the concrete surrounds the steel bar. The contact area between the two is the corrosion interface, which is the main location for corrosion reaction. Figure 4 Part (b) shows the structure and key dimensions of the concrete specimen in the numerical simulation. Indicates the diameter of the steel bar ( ), Indicates the thickness of the protective film ( ), φ represents the diameter of the concrete specimen (i.e., specimen size, φ=75mm). The numerical simulation parameters are detailed in Table 1, which is as follows: Table 1 Main parameters of the numerical simulation process

[0079] In the table, represents the external (concrete exposed surface) sulfate ion concentration; represents the external chloride ion concentration; represents the initial sulfate ion concentration; represents the initial chloride ion concentration; Indicates the initial calcium aluminate content; represents the initial porosity, determined by experimental data; represents the diffusion coefficient of sulfate ions; represents the diffusion coefficient of chloride ions; represents the anode equilibrium potential; represents the cathode equilibrium potential; represents the threshold strain (4.0×10 -5 ); , represents the reaction rate of sulfate ion; It represents the chemical reaction rate of chloride ion; represents the fitting parameters based on the Ikumi method.

[0080] Using the model parameters shown in Table 1 and the transport model, corrosion model, and damage model described in this application, the electrochemical module and partial differential equation module of COMSOL software were used to numerically simulate the concentration distribution of different ions during the immersion of reinforced concrete specimens in 5% NaCl and 4% Na2SO4 solutions under a low-pressure plateau environment. The numerical simulation results of the chloride ion concentration distribution are shown in Figure 1. Figure 5 The numerical simulation results of sulfate ion concentration distribution are shown in Figure 6 The numerical simulation results of oxygen concentration are shown in Figure 7On this basis, the electrode surface corrosion current density is calculated and used to reflect the corrosion rate of steel bars in concrete, and compared with the test results. The results are shown in the figure below. Figure 8 As shown. Figure 8 It can be seen that the numerical simulation results are highly consistent with the experimental results. Taking into account the errors in the experimental process and the discrete nature of the data, the predicted values ​​of the numerical models established in this example (including the transmission model, corrosion model, and damage model) are in good agreement with the measured data, thus verifying the feasibility of these models in quantitatively predicting steel corrosion inside concrete in the low-pressure environment of the plateau.

[0081] The concrete cover damage mode caused by steel bar rust expansion in the plateau low pressure environment is as follows Figure 9 As shown. Figure 9 It can be seen that the front end of the steel bar corrodes due to the invasion of corrosive media (including chloride ions, sulfate ions, etc.), resulting in expansive corrosion products. When the expansion stress of the steel bar is greater than or equal to the tensile strength of the concrete, the concrete will crack. Concrete damage first occurs at the front end of the steel bar, and then gradually expands to the surrounding area of ​​the steel bar. As the erosion time increases, the concrete damage around the steel bar becomes more and more serious, the crack width becomes larger and larger, and continues to expand to the concrete surface. When t=120d, macro cracks have appeared on the exposed surface of the concrete. When t=130d, a slight crack damage zone has formed between the two steel bars. When t=140d, the crack damage zone has evolved into an obvious crack, and the concrete protective layer is in danger of overall peeling, such as Figure 10 As shown. Figure 10 It can be seen that the numerical simulation results of concrete cracking caused by steel bar corrosion in a low-pressure environment are in good agreement with the experimental results, which proves the accuracy of the prediction results of this application.

[0082] Based on experimental verification, it can be seen that the method provided in this embodiment can realistically simulate the impact of oxygen concentration and diffusion problems on steel corrosion in concrete under a low-pressure plateau environment; considering that charge exchange and corrosion current generation begin when chloride ions reach the steel bar surface, the corrosion current density is predicted, and then the steel bar corrosion product content is obtained. The corrosion current generation process is more consistent with the actual situation and the results are more accurate; the ion transport and concrete cracking research based on chloride ion diffusion, sulfate ion diffusion, and oxygen diffusion is more consistent with the actual situation of the plateau environment and the prediction results are more accurate.

[0083] Based on the same inventive concept, this embodiment provides a device for predicting corrosion current and corrosion of steel bars in concrete in a low-pressure environment. The device is used to execute the method for predicting corrosion current and corrosion of steel bars in concrete in a low-pressure environment provided in any of the above embodiments. The device includes: a diffusion modeling unit configured to establish a coupled transmission model inside concrete that considers oxygen concentration, sulfate ion diffusion behavior, and chloride ion diffusion behavior under plateau low pressure; the coupled transmission model includes: a chloride ion transmission model, a sulfate ion transmission model, and an oxygen diffusion model; a corrosion modeling unit configured to establish a steel bar corrosion current density and corrosion depth prediction model; The steel bar corrosion current density and corrosion depth prediction model is used to predict the number of charges at different positions of the steel bars inside the concrete based on the coupled transmission model to obtain the corrosion current density of the steel bars inside the concrete; and calculate the corrosion depth and rust product content based on the corrosion current density; The corrosion simulation unit is configured to establish a linear elastic damage model for simulating the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

[0084] The device for predicting corrosion current and rust of steel bars in concrete under low-pressure environment provided in this embodiment can implement the steps and processes of the method for predicting corrosion current and rust of steel bars in concrete under low-pressure environment provided in any of the above embodiments, and achieve the same technical effects, which will not be described in detail here.

[0085] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for predicting corrosion current and rust of steel bars in concrete under low pressure environment, characterized in that: include: A coupled transport model for concrete is established under low plateau pressure, taking into account oxygen concentration, sulfate ion diffusion behavior, and chloride ion diffusion behavior; the coupled transport model includes a chloride ion transport model, a sulfate ion transport model, and an oxygen diffusion model; Establish a prediction model for steel bar corrosion current density and corrosion depth; The steel bar corrosion current density and corrosion depth prediction model is used to predict the charge number at different positions of the steel bars inside the concrete under the participation of different oxygen concentrations based on the coupled transmission model, thereby obtaining the corrosion current density of the steel bars inside the concrete; and based on the corrosion current density, calculate the corrosion depth and rust product content; Establish a linear elastic damage model; The linear elastic damage model is used to simulate the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

2. The method according to claim 1, characterized in that In the coupled transmission model, Fick's second law is used to describe the diffusion of chloride ions and sulfate ions in concrete, and the chloride ion transmission model and the sulfate ion transmission model are obtained accordingly; Based on Fick's second law, a plateau low-pressure correction factor is introduced to correct oxygen diffusion and obtain an oxygen diffusion model, which is used to reflect the impact of low-pressure environment. The plateau low pressure correction factor is expressed as: , where 、 They represent plain pressure and plateau pressure respectively.

3. The method according to claim 2, characterized in that The coupled transmission model is also used to describe the time difference between chloride ions and sulfate ions reaching the steel bar surface. In a low-pressure environment, the time difference has a phased effect on the corrosion process with the participation of oxygen.

4. The method according to claim 3, characterized in that The time difference between chloride ions and sulfate ions reaching the steel bar surface, in a low-pressure environment, has a phased effect on the corrosion process with the participation of oxygen, specifically: Chloride ions first diffuse to the steel bar surface, where charge exchange occurs and the corrosion current density begins to be calculated; Sulfate ions diffuse to the steel bar surface later than chloride ions, and destroy the passive film of the steel bar by expansion. Chloride ions further penetrate the passive film and directly cause local corrosion of the steel bar, and oxygen participates in the low-pressure environment to further accelerate the corrosion.

5. The method according to claim 1, characterized in that Based on the coupled transmission model, the charge number at different positions of the steel bars inside the concrete is predicted under the participation of different oxygen concentrations, and the corrosion current density of the steel bars inside the concrete is obtained, specifically: Based on the electrochemical kinetics theory, the Tafel equation was used to calculate the anodic current density and the cathodic current density, and then the corrosion current density of the steel bars inside the concrete was calculated.

6. The method according to claim 5, characterized in that The Tafel equation is used to calculate the anode current density and cathode current density, including: The chloride ion concentration is directly embedded into the expression of the anodic Tafel slope to dynamically regulate the corrosion rate by affecting the electrochemical polarization behavior.

7. The method according to claim 6, characterized in that The chloride ion concentration is directly embedded into the expression of the anode Tafel slope. Specifically, the chloride ion concentration is embedded into the expression of the anode Tafel slope in the form of a power function to characterize the nonlinear characteristics of the chloride ion, which has a significant effect at low concentrations and tends to saturation at high concentrations.

8. The method according to claim 5, characterized in that The Tafel equation is used to calculate the anode current density and cathode current density respectively, including: When the electrode reaction is controlled by the oxygen content, a limiting current density is introduced during the cathode electrode reaction process to correct the cathode current density.

9. A device for predicting corrosion current and rust of steel bars in concrete under low pressure environment, characterized in that: The device is used to perform the method according to any one of claims 1 to 8, and the device includes: a diffusion modeling unit configured to establish a coupled transmission model inside concrete that considers oxygen concentration, sulfate ion diffusion behavior, and chloride ion diffusion behavior under plateau low pressure; the coupled transmission model includes: a chloride ion transmission model, a sulfate ion transmission model, and an oxygen diffusion model; a corrosion modeling unit configured to establish a steel bar corrosion current density and corrosion depth prediction model; The steel bar corrosion current density and corrosion depth prediction model is used to predict the charge number at different positions of the steel bars inside the concrete under the participation of different oxygen concentrations based on the coupled transmission model, thereby obtaining the corrosion current density of the steel bars inside the concrete; and based on the corrosion current density, calculate the corrosion depth and rust product content; The corrosion simulation unit is configured to establish a linear elastic damage model for simulating the damage evolution of concrete cracking caused by steel bar corrosion based on the corrosion product content output by the steel bar corrosion current density prediction model, so as to achieve accurate prediction of corrosion and damage.

10. A computer device comprising a memory and a processor, wherein the memory and the processor are connected; the memory is used to store computer-executable instructions; and the processor is used to call the computer-executable instructions to execute the method according to any one of claims 1 to 8.

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