Method, product and equipment for revealing chloride ion distribution in concrete diffusion area

Abstract

The invention discloses a method, a product and equipment for revealing chloride ion distribution in a concrete diffusion area, and belongs to the technical field of buildings. The method comprises the following steps: determining a nonlinear diffusion equation capable of expressing the diffusion of chloride ions in concrete; determining a to-be-introduced single-parameter transformation group, and substituting the to-be-introduced single-parameter transformation group into the nonlinear diffusion equation to obtain a first transformation formula; aiming at the first transformation formula, performing equation solving according to a conformal invariance condition when the chloride ion diffusion coefficient is a constant, a given initial condition and a boundary condition to obtain a corresponding chloride ion concentration distribution analytical expression; and / or, aiming at the first transformation formula, according to a conformal invariance condition when the chloride ion diffusion coefficient changes along with time, a given initial condition and a boundary condition, performing equation solution to obtain a corresponding chloride ion concentration distribution analytical expression. According to the method, the intrinsic curve of the chloride ion concentration distribution in the concrete diffusion area can be deduced, the applicability is high, and the limitation that a traditional chloride ion transmission model cannot be universal is solved.

Description

Technical Field

[0001] The invention belongs to the field of building technology, and in particular relates to a method, a product and a device for revealing the distribution of chloride ions in a diffusion zone of concrete. Background Art

[0002] In coastal environments, chloride ion corrosion is one of the main causes of the deterioration of reinforced concrete structures. Over time, chloride ions gradually enter the interior through the diffusion process on the concrete surface and accumulate near the surface of the steel bars. When the concentration of chloride ions reaches or exceeds the threshold of the steel bar surface, the steel bars begin to rust, which in turn causes the concrete structure to expand and crack, causing irreversible damage to the durability of buildings and infrastructure.

[0003] In order to predict and evaluate the durability of concrete structures during long-term use, the diffusion behavior and concentration distribution of chloride ions in the diffusion zone of concrete are usually focused on. However, since chloride ion diffusion is affected by many factors, such as concrete composition, environmental conditions, and the service life of the structure, it is extremely challenging to establish a universal prediction model.

[0004] At present, there are many predictive models used to describe the diffusion process of chloride ions in concrete, which can be divided into two categories: mechanism models and engineering models. Mechanism models integrate key processes such as diffusion, penetration, water absorption and chloride ion binding, and can accurately predict the migration of chloride ions. However, these models require complex experiments to obtain the necessary data, and their reliability decreases as the input parameters increase. This increases the difficulty of testing and modeling. In contrast, engineering models simplify these processes into a unified formula, assuming that only diffusion is the transport mechanism, and only need to understand the apparent chloride ion diffusion coefficient (D app ) and chloride ion boundary concentration can be used to draw the chloride ion distribution, so it has become the most widely used model in the engineering field. However, the engineering model only fits the chloride ion distribution for a specific project, and is not universal due to different working conditions. Therefore, it is necessary to develop a high-precision and universal calculation model for chloride ion distribution in the diffusion zone of concrete.

[0005] Group transformation theory provides a new approach to solving the above problems. Transformation group theory is used to describe the symmetry of the system and the resulting conservation laws. Since diffusion equations such as Fick's law often show symmetry in various situations, transformation group theory can be used to describe chloride ion diffusion. The similar solutions of these equations can be determined using transformation groups, thereby exploring invariant solutions under the action of a specific group. Therefore, based on diffusion group theory, it is expected that a universal chloride ion concentration distribution prediction method can be developed to obtain the chloride ion concentration distribution eigenline suitable for various working conditions. Summary of the invention

[0006] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0007] To this end, the purpose of the present invention is to provide a method, product and equipment for revealing the distribution of chloride ions in the diffusion zone of concrete, which can derive the intrinsic curve of the chloride ion concentration distribution in the diffusion zone of concrete, has strong applicability, and solves the limitation that the traditional chloride ion transmission model cannot be universally used.

[0008] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0009] An embodiment of the present invention provides a method for revealing chloride ion distribution in a diffusion zone of concrete, the method comprising:

[0010] Determine the nonlinear diffusion equation that can express the diffusion of chloride ions in concrete;

[0011] Determine a single parameter transformation group to be introduced, and substitute it into the nonlinear diffusion equation to obtain a first transformation formula;

[0012] For the first transformation formula, the equation is solved according to the conformal invariance condition when the chloride ion diffusion coefficient is a constant, the given initial conditions and the boundary conditions, and an analytical expression for the chloride ion concentration distribution when the chloride ion diffusion coefficient is a constant is obtained; and / or,

[0013] For the first transformation formula, the equation is solved according to the conformal invariance condition when the chloride ion diffusion coefficient changes with time, the given initial conditions and boundary conditions, and the first chloride ion concentration distribution analytical expression when the chloride ion diffusion coefficient changes with time is obtained.

[0014] In addition, the method for revealing chloride ion distribution in the diffusion zone of concrete according to the present invention may also have the following additional technical features:

[0015] In some embodiments, the conformal invariance condition when the chloride ion diffusion coefficient is constant includes:

[0016] β1=2β2, β3 is an arbitrary constant; β1, β2 and β3 are the exponents to be determined in the single parameter transformation group for time t, space x and concentration C respectively;

[0017] Invariant transformation conditions:

[0018] In some embodiments, the initial conditions when the chloride ion diffusion coefficient is constant and when the chloride ion diffusion coefficient changes with time are:

[0019] C(0,x)=C i

[0020] The boundary conditions are:

[0021]

[0022] C0 is the concentration corresponding to the chloride ion penetration depth x = 0, C i It is the concentration corresponding to the chloride ion penetration depth x=i.

[0023] In some embodiments, the expression of the chloride ion diffusion coefficient D changing with time is:

[0024]

[0025] Among them, t test It's testing time, D test is the test time t test is the corresponding diffusion coefficient, and m is the age coefficient.

[0026] In some embodiments, the conformal invariance condition for the chloride ion diffusion coefficient as it changes with time is:

[0027] (1+m)β1=2β2, β3 is an arbitrary constant;

[0028] Among them, β1, β2 and β3 are the exponents to be determined in the single parameter transformation group for time t, space x and concentration C, respectively, and m is the age coefficient.

[0029] In some embodiments, the method further comprises:

[0030] Determine an approximately invariant transformation, and substitute it into the nonlinear diffusion equation to obtain a second transformation equation;

[0031] For the second transformation formula, the equation is solved according to the initial boundary conditions to obtain the second chloride ion concentration distribution analytical expression when the chloride ion diffusion coefficient changes with time.

[0032] In some of the embodiments, the approximately invariant transformation is:

[0033]

[0034] Among them, n is the time index to be determined, t is time, x is space, and C is the chloride ion concentration.

[0035] In some embodiments, the relationship between chloride ion diffusion coefficient, concentration and time is calibrated as follows:

[0036] The chloride concentration is related to the single variable λ = x / t n The distribution law of chloride ion concentration is calibrated by determining the value of the time index n, thereby determining the relationship between the chloride ion diffusion coefficient, concentration and time;

[0037] The process of determining the value of n includes: the maximum depth of chloride ion penetration is xf The time required is t f ; According to λ=x / t n get Given a data point (t i ,x fi ), where x f Yes i The penetration depth of chloride ions in concrete at the moment; for n∈[0,1], search n with a certain step length i , and let x f =λT, T = t n ; Based on the data point (t i ,x fi ), for each n i Fitting a line x using linear regression f =λT; select n that makes the data points fit the straight line best i as the time index n.

[0038] An embodiment of the present invention further provides a computer program product, including a computer program, characterized in that when the computer program is executed by a processor, the steps of the method for revealing the distribution of chloride ions in the diffusion zone of concrete as described in any of the above items are implemented.

[0039] An embodiment of the present invention also provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for revealing chloride ion distribution in a diffusion zone of concrete as described in any one of the above items.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] In an embodiment of the present invention, a method for revealing chloride ion distribution in a diffusion zone of concrete is provided: an intrinsic curve of chloride ion concentration distribution in a diffusion zone of concrete can be derived, which is not yet achieved in the prior art. Through this curve, the chloride ion concentration distribution under long-term service conditions can be predicted, thereby helping to evaluate the long-term durability of concrete structures;

[0042] In the embodiment of the present invention, the method for revealing the chloride ion distribution in the diffusion zone of concrete is provided: due to the different types of cement used, curing time, exposure areas (immersion area, tidal area, splash area, atmospheric area), and exposure chloride ion concentrations under different working conditions, the D value of concrete under different working conditions is different. Therefore, the traditional chloride ion distribution engineering model needs to solve a chloride ion diffusion coefficient D value for concrete under different working conditions, resulting in lack of universality; in comparison, the method of the present invention introduces the transformation group theory, and only needs to consider three variables: chloride ion penetration depth, time, and chloride ion concentration, without considering solving D app; Therefore, the method of the present invention is applicable to various types of concrete and various working conditions, overcoming the limitation that the traditional chloride ion concentration prediction model can only be used under specific working conditions;

[0043] In an embodiment of the present invention, a method for revealing chloride ion distribution in a diffusion zone of concrete is provided: in actual engineering, D has a large influence over time, and it is extremely difficult to accurately calibrate D; the uncertainty of D and the approximation of the numerical method have a large influence on the accuracy of the numerical solution, thereby resulting in inaccurate chloride ion concentration prediction values; the present invention innovatively applies group transformation theory, and only needs to consider three variables, namely, chloride ion penetration depth, time, and chloride ion concentration, thereby significantly improving the fitting accuracy of chloride ion distribution; it can effectively cope with the challenges brought about by the change of D over time in actual engineering, reduce errors caused by parameter uncertainty, and thus provide a more reliable chloride ion distribution.

[0044] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flow chart of a method for revealing chloride ion distribution in a diffusion zone of concrete disclosed in one embodiment of the present invention;

[0046] Figure 2 The chloride ion concentration distribution curve disclosed in Example 1 of the present invention;

[0047] Figure 3 This is the chloride ion concentration distribution curve disclosed in Example 2 of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0050] See also Figure 1 As shown, in some embodiments of the present invention, a method for revealing the distribution of chloride ions in the diffusion zone of concrete is provided. Given a complex partial differential nonlinear diffusion equation, the complex partial differential equation is reduced to an ordinary differential equation or an algebraic problem by mathematical transformation, and the parameters are calibrated in combination with experimental data, so as to finally realize the prediction of chloride ion diffusion behavior. The specific technical solutions for implementation include:

[0051] The diffusion of chloride ions in concrete is determined by the following nonlinear diffusion expression:

[0052]

[0053] Where D is the chloride ion diffusion coefficient, C is the chloride ion concentration [mol / L], t is time [T], and x is the position coordinate [L]. The left side of the equation represents the rate of change of chloride ion concentration over time, and the right side is the diffusion term, which reflects the diffusion behavior of chloride ions caused by the concentration gradient. This equation is the starting point for analyzing chloride ion diffusion problems. Its nonlinearity comes from the fact that the diffusion coefficient D may change with concentration or time. All subsequent analyses (such as conformal invariance and introduction of transformation groups) revolve around this equation.

[0054] In order to analyze the conformal invariance of equation (1), the following single-parameter transformation group is introduced:

[0055]

[0056] Among them, a is a non-zero real constant, which plays a scaling role in the transformation; β i (i=1,2,3) is the index to be determined, which is used to keep the form of the equation unchanged after the transformation. This formula introduces a single parameter transformation group to perform scaling transformations on time t, space x, and concentration C. Through scaling transformation, the conformal invariance of equation (1) is explored (that is, the equation remains unchanged after the transformation). This invariance means that there are self-similar solutions, which can simplify the analytical solution process.

[0057] Substituting the transformation into equation (1), we can obtain:

[0058]

[0059] By comparing the equations before and after the transformation, the relationship between the exponents to be determined can be derived, and then the conditions for conformal invariance (i.e., the following equation (5)) can be determined.

[0060] When D is a constant, formula (3) can be written as:

[0061]

[0062] Under the premise that D is a constant, the diffusion term on the right side of the equation only contains the second-order spatial derivative. To make equation (4) conformal to equation (1), the following conditions must be met:

[0063] β1-β3=2β2-β3 (5)

[0064] Right now:

[0065] β1=2β2,β3 is an arbitrary constant (6)

[0066] When considering the change over time, Equation (1) is conformally invariant, and the corresponding invariant transformation is:

[0067]

[0068] Since β3 is an arbitrary constant, β3=0 can be set to simplify the problem.

[0069] Therefore, transformation (7) is simplified to:

[0070]

[0071] According to formula (6), formula (8) can be written as:

[0072]

[0073] By combining equation (9) with the initial and boundary conditions, the analytical expression for the chloride ion concentration distribution of equation (1) can be obtained (equation (12)).

[0074] The initial conditions are:

[0075] C(0,x)=C i (10)

[0076] The boundary conditions are:

[0077]

[0078] The analytical expression for the chloride ion concentration distribution is:

[0079]

[0080] In actual engineering, the diffusion coefficient D changes with time, as shown in formula (13):

[0081]

[0082] Among them, D test is the test time t test The corresponding diffusion coefficient at time , m is the age coefficient.

[0083] To simplify the calculation, formula (13) is simplified to:

[0084] D=D0t m (14)

[0085] Formula (1) can now be written as:

[0086]

[0087] Combining equations (1)-(3), we can know that:

[0088]

[0089] To make equation (15) and equation (16) conformal, the following conditions must be met:

[0090] β1-β3=2β2-β3-mβ1 (17)

[0091] Right now:

[0092] (1+m)β1=2β2, β3 is an arbitrary constant, and m is the age coefficient, whose value depends on the composition of the concrete.

[0093] When considering the change over time, Equation (15) is conformally invariant, and the corresponding invariant transformation is:

[0094]

[0095] Since β3 is an arbitrary constant, in order to simplify the problem, let β3=0.

[0096] Therefore, transformation (18) simplifies to:

[0097]

[0098] λ is a function related to time t and chloride ion penetration depth x; f represents a function related to time t and chloride ion concentration, which is C in equation (19). Because β3 = 0 is assumed here, f is not related to time t, but only to concentration. Therefore, C = C (λ) is written in equation (19). C (λ) represents that the chloride ion concentration is a function related to λ, in other words, C is related to time t and chloride ion penetration depth x.

[0099] When D0 is a constant, the chloride ion distribution can be obtained by using transformation (19) and initial boundary conditions (10) and (11):

[0100]

[0101] It should be noted that the invariant transformations (8) and (19) are obtained under the special case of D. In practical engineering, the variation of D over time is extremely complex. Therefore, the following approximate invariant transformation is considered:

[0102]

[0103] Wherein, n is the time index to be determined.

[0104] By transforming equation (21), equation (1) can be transformed into equation (22):

[0105]

[0106] Combined with the initial boundary conditions, the distribution law of chloride ion concentration can be obtained by numerical method formula (22), but the functional relationship of D(C, t) must be given. D(C, t) is a function of the relationship between the chloride ion diffusion coefficient and the concentration and time. Because the accurate calibration of D is extremely difficult in the actual process, the uncertainty of D and the inherent approximation of the numerical solution method will inevitably lead to inaccurate determination of chloride ion concentration. Therefore, the present invention does not seek to give a specific functional relationship of D(C, t), but adopts the following calibration method.

[0107] The calibration method of D(C,t) is as follows: By observing the transformation (21), it can be seen that the chloride ion concentration is related to the single variable λ = x / t n Here, we only need to determine the value of the time index n to calibrate the distribution law of chloride ion concentration C.

[0108] The calibration strategy of n value is as follows: The maximum depth of chloride ion penetration is x f The time required is t f According to λ=x / t n You can know Given a data point (t i ,x fi ), where x f Yes i The penetration depth of chloride ions in concrete at the moment. For n∈[0,1], search n with a certain step size. i , and let x f =λT, T = t n Based on the data point (t i ,x fi ), for each n i , use linear regression to fit the straight line x f =λT. Select n that best fits the data points to the straight line. i as the time index n.

[0109] The functional relationship between concentration and similar variables is shown in (23):

[0110]

[0111] Where λ = x / t n , c i (i=1,2,3,4) are coefficients to be determined, which are obtained by regression using the lsqcurvefit function.

[0112] The present invention analyzes conformal invariance, introduces the transformation group formula (2), derives the exponential constraint formula (5), and determines the existence of self-similar solutions (12). The time-dependent diffusion coefficient is also determined. When D changes with time (13), the transformation group formula (19) is adjusted, and a new invariant condition formula (17) is derived to expand the scope of application of the analytical solution. For complex D relationships that cannot be calibrated, an approximate transformation formula (21) is used, and the parameter n is calibrated in combination with experimental data, and the concentration distribution (22) is solved by a numerical method.

[0113] Example 1: Taking the data in the paper (Magazine of Concrete Research Volume 67 Issue 18980-987) as an example, the distribution diagram of chloride ion concentration in concrete of different saturation states is fitted.

[0114] Table 1 Working condition 1 (saturated concrete)

[0115]

[0116] Table 2 Working condition 2 (saturated concrete)

[0117]

[0118] Table 3 Working condition 3 (unsaturated concrete)

[0119]

[0120]

[0121] Using the method developed by the present invention, the data of the first, second, third, fifth, tenth, twentieth and thirtieth years under the above three working conditions are used for fitting. Figure 2 As shown in the figure, the chloride ion concentration data in all working conditions can be fitted into a chloride ion concentration distribution curve. It should be noted that working condition 3 is unsaturated concrete, and its chloride ion concentration varies greatly at the starting point (x=0), so it needs to be normalized (that is, the chloride ion concentration at the starting point is unified to 1), and the results can still be fitted into a curve. All curve expressions are as follows:

[0122]

[0123] The piecewise cubic Hermite interpolation method was used to predict the chloride ion distribution data for the 30th year under three operating conditions and compared with the measured results. The root mean square error (RMSE) and determination coefficient (R 2 ) as the prediction quality evaluation index, the results are as follows:

[0124] Table 4 Condition 1 (predicted values)

[0125]

[0126] Table 5 Condition 2 (predicted values)

[0127]

[0128] Table 6 Condition 3 (predicted values)

[0129]

[0130] Table 7 Prediction quality evaluation indicators

[0131] Working conditions Root mean square error (RMSE) <![CDATA[Coefficient of determination (R 2 )]]> Condition 1 0.01247 0.9941 Condition 2 0.007084 0.9969 Condition 3 0.095729 0.9285

[0132] It can be seen from Table 7 that under different working conditions, the RMSE values ​​of the predicted values ​​of chloride ion distribution in concrete are all less than 0.1, indicating that the difference between the predicted value and the true value is very small. In addition, under different curing ages, the R 2 The values ​​are all greater than 0.92, indicating that the chloride ion distribution curves under the above three working conditions have high fitting accuracy.

[0133] Example 2: Taking the data in the paper (Construction and Building Materials 368 (2023) 130411) as an example, the distribution diagram of chloride ion concentration in concrete at different curing ages is fitted.

[0134] Table 8 Curing for 3 days

[0135]

[0136] Table 9 Curing for 7 days

[0137]

[0138] Table 10 Curing for 14 days

[0139]

[0140] Table 11 Curing for 28 days

[0141]

[0142] Using the method developed by the present invention, the data of the 40th day, 80th day, 120th day, 160th day, 200th day, 240th day, 280th day and 320th day under the above different curing ages are used for fitting. Since the concrete under this working condition is all unsaturated concrete, normalization processing is required. The fitting results are as follows: Figure 3 As shown in the figure, the chloride ion concentration data at all curing ages can be fitted into a chloride ion concentration distribution curve, and its expressions are as follows:

[0143]

[0144] The piecewise cubic Hermite interpolation method was used to predict the chloride ion distribution data of 320 days of immersion under four curing ages, and compared with the measured results. The mean square error and determination coefficient R 2 As a prediction quality evaluation indicator, the results are as follows:

[0145] Table 12 Curing for 3 days (predicted value)

[0146]

[0147] Table 13 Curing for 7 days (predicted value)

[0148]

[0149]

[0150] Table 14 Curing for 14 days (predicted value)

[0151]

[0152] Table 15 Curing for 28 days (predicted value)

[0153]

[0154]

[0155] Table 16 Prediction quality evaluation indicators

[0156] Maintenance age Root mean square error (RMSE) <![CDATA[Coefficient of determination (R 2 )]]> 3 days maintenance 0.026042 0.994055 7 days maintenance 0.058387 0.976347 14 days maintenance 0.020619 0.996598 Maintenance for 28 days 0.024473 0.995028

[0157] It can be seen from Table 16 that at different curing ages, the RMSE values ​​of the predicted values ​​of chloride ion distribution in concrete after 320 days of chloride ion immersion are all less than 0.1, indicating that the difference between the predicted value and the true value is very small. 2 The values ​​are all greater than 0.97, indicating that the chloride ion distribution curves under the above four groups of curing ages have high fitting accuracy.

[0158] To further verify the accuracy of the method developed by the present invention, two chloride ion concentration time-varying models, exponential function model and logarithmic function model, were used to fit the four groups of data in Example 2. The R 2 The values ​​are shown in Table 17.

[0159] Table 17 Determination coefficients (R 2 )

[0160]

[0161] Obviously, the R after the model developed by the present invention fits the four groups of data in Example 2 2 The values ​​are higher than the R after fitting the exponential function model and the logarithmic function model. 2 This proves the high accuracy of the model developed by the present invention.

[0162] The parts of the present invention that are not described in detail may refer to the prior art or are known to those skilled in the art, and this embodiment does not limit this and will not be described in detail here.

[0163] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for revealing the distribution of chloride ions in the diffusion zone of concrete, characterized in that: The method comprises: Determine the nonlinear diffusion equation that can express the diffusion of chloride ions in concrete; Determine a single parameter transformation group to be introduced, and substitute it into the nonlinear diffusion equation to obtain a first transformation formula; For the first transformation formula, the equation is solved according to the conformal invariance condition when the chloride ion diffusion coefficient is a constant, the given initial conditions and the boundary conditions, and an analytical expression for the chloride ion concentration distribution when the chloride ion diffusion coefficient is a constant is obtained; and / or, For the first transformation formula, the equation is solved according to the conformal invariance condition when the chloride ion diffusion coefficient changes with time, the given initial conditions and boundary conditions, and the first chloride ion concentration distribution analytical expression when the chloride ion diffusion coefficient changes with time is obtained.

2. A method for revealing chloride ion distribution in a diffusion zone of concrete according to claim 1, characterized in that: The conformal invariance conditions when the chloride ion diffusion coefficient is constant include: β1=2β2, β3 is an arbitrary constant; β1, β2 and β3 are the exponents to be determined in the single parameter transformation group for time t, space x and concentration C respectively; Invariant transformation conditions:

3. The method for revealing chloride ion distribution in the diffusion zone of concrete according to claim 1, characterized in that: The initial conditions when the chloride ion diffusion coefficient is constant and when the chloride ion diffusion coefficient changes with time are: C(0,x)=C i The boundary conditions are: C0 is the concentration corresponding to the chloride ion penetration depth x = 0, C i It is the concentration corresponding to the chloride ion penetration depth x=i.

4. The method for revealing chloride ion distribution in the diffusion zone of concrete according to claim 1, characterized in that: The expression of the chloride ion diffusion coefficient D changing with time is: Among them, t test It's testing time, D test is the test time t test is the corresponding diffusion coefficient, and m is the age coefficient.

5. The method for revealing chloride ion distribution in the diffusion zone of concrete according to claim 1, characterized in that: The conformal invariance condition for the chloride ion diffusion coefficient as it changes with time is: (1+m)β1=2β2, β3 is an arbitrary constant; Among them, β1, β2 and β3 are the exponents to be determined in the single parameter transformation group for time t, space x and concentration C, respectively, and m is the age coefficient.

6. The method for revealing chloride ion distribution in the diffusion zone of concrete according to claim 1, characterized in that: The method further comprises: Determine an approximately invariant transformation, and substitute it into the nonlinear diffusion equation to obtain a second transformation equation; For the second transformation formula, the equation is solved according to the initial boundary conditions to obtain the second chloride ion concentration distribution analytical expression when the chloride ion diffusion coefficient changes with time.

7. A method for revealing chloride ion distribution in a diffusion zone of concrete according to claim 6, characterized in that: The approximately invariant transformation is: Among them, n is the time index to be determined, t is time, x is space, and C is the chloride ion concentration.

8. The method for revealing chloride ion distribution in the diffusion zone of concrete according to claim 6, characterized in that: The relationship between chloride ion diffusion coefficient, concentration and time is calibrated as follows: The chloride concentration is related to the single variable λ = x / t n The distribution law of chloride ion concentration is calibrated by determining the value of the time index n, thereby determining the relationship between the chloride ion diffusion coefficient, concentration and time; The process of determining the value of n includes: denoting the maximum depth of chloride ion penetration as x f The time required is t f ; According to λ=x / t n get Given a data point (t i ,x fi ), where x f Yes i The penetration depth of chloride ions in concrete at the moment; for n∈[0,1], search n with a certain step length i , and let x f =λT, T = t n ; Based on the data point (t i ,x fi ), for each n i Fitting a line x using linear regression f =λT; select n that makes the data points fit the straight line best i as the time index n.

9. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for revealing chloride ion distribution in the diffusion zone of concrete as claimed in any one of claims 1 to 8 are implemented.

10. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for revealing chloride ion distribution in the diffusion zone of concrete as claimed in any one of claims 1 to 8.

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