A method and system for predicting critical number of dry-wet cycles of coated concrete in sulfate environment and evaluating performance thereof

Abstract

The application discloses a kind of coating concrete sulphate dry-wet cycle critical number of times prediction, performance evaluation method and system, comprising: the test damage degree data of coating concrete under different cycle numbers is obtained by sulphate dry-wet cycle test. According to the stage characteristics of coating concrete sulphate dry-wet cycle damage evolution, two-stage damage model including damage incubation stage model and damage development stage model is constructed. Based on test damage degree data, with model calculation error minimum as objective function, optimal model parameters of two-stage damage model are identified using optimization algorithm, and optimal model parameters are substituted into two-stage damage model to determine optimal two-stage damage model. According to the stage turning cycle number in optimal model parameters, calculate stage turning point damage degree, and compare critical damage degree with stage turning point damage degree, select the stage damage model of coating concrete adaptation to inverse coating concrete critical dry-wet cycle number.

Description

Technical Field

[0001] This invention relates to the field of computational materials science and technology, specifically to a method and system for predicting the critical number of sulfate wet-dry cycles and evaluating the performance of coated concrete. Background Technology

[0002] In environments characterized by sulfate attack, alternating wet and dry conditions, and their coupling, sulfate ion migration, salt crystallization, and corrosion product formation easily occur within concrete, leading to changes in pore structure, microcrack propagation, and degradation of mechanical properties. To improve the durability of concrete in saline soil areas, regions with high groundwater sulfate content, bridge piers, tunnel linings, and hydraulic structures, surface coatings, anti-corrosion paints, or composite protective layers are commonly used in engineering to prevent corrosive media from penetrating the concrete interior.

[0003] Current methods for evaluating sulfate resistance typically refer to the sulfate wet-dry cycle test, which assesses concrete's resistance to sulfate attack by measuring the morphology, compressive strength, and corrosion resistance coefficient of specimens after different cycles. While this method reflects performance changes after a specified number of cycles, it is primarily suitable for evaluating the erosion resistance of ordinary concrete. For coated concrete, it remains difficult to accurately characterize the differences in how different coating systems block corrosive media, delay damage initiation, and inhibit subsequent damage propagation. Furthermore, it is challenging to predict the number of wet-dry cycles required for coated concrete to reach a critical damage state.

[0004] Furthermore, the damage evolution of coated concrete under sulfate wet-dry cycles typically exhibits phased characteristics. In the initial stages of the cycle, the barrier effect of the coating and the pore-filling effect of a small amount of corrosion products may keep the specimen strength stable or even slightly improved. In the middle and later stages of the cycle, with the localized deterioration of the coating, the development of weak interfacial zones, the expansion of corrosion products, and the increase in salt crystallization pressure, microcracks inside the concrete gradually expand, and the compressive strength and corrosion resistance coefficient decrease significantly. Existing single empirical models or ordinary fitting methods cannot describe the damage development process of coated concrete, and therefore cannot accurately predict the critical number of cycles for coated concrete. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a method and system for predicting the critical number of sulfate wet-dry cycles and evaluating the performance of coated concrete, which can accurately predict the critical number of wet-dry cycles for coated concrete. The specific technical solution is as follows: In a first aspect, a method for predicting the critical number of sulfate wet-dry cycles in coated concrete is provided. In a first implementable mode of the first aspect, the method includes: The experimental damage data of the coated concrete under different cycles were obtained by sulfate wet-dry cycle test; A two-stage damage model was established based on the staged characteristics of damage evolution of coated concrete. Based on all experimental damage data, the optimal model parameters of the two-stage damage model were searched using an optimization algorithm with the objective function of minimizing the error between the experimental damage and the damage calculated by the model. The damage degree at the stage transition point of the coated concrete is determined by the number of stage transition cycles in the optimal model parameters. The critical damage degree of the coated concrete is then compared with the damage degree at the stage transition point. Based on the comparison result, the appropriate stage damage model is selected to invert the critical number of wet-dry cycles of the coated concrete. The two-stage damage model includes a damage incubation stage model and a damage development stage model. The specific expression for the damage incubation stage model is as follows: ; The specific expression for the damage development stage model is as follows: ; in, This represents the cumulative damage coefficient during the damage incubation stage. The number of loops. This is the strength compensation coefficient during the damage incubation stage. This refers to the number of cycles in a phase transition. The theoretical limit of damage, These are the initial state parameters for the damage development stage. This refers to the damage development rate parameter during the damage development stage. The compressive strength damage degree during the damage incubation stage. This represents the compressive strength damage degree during the damage development stage.

[0006] In conjunction with the first possible implementation of the first aspect, in the second possible implementation of the first aspect, obtaining the test damage data of the coated concrete includes: The initial compressive strength of the coated concrete and its compressive strength after undergoing multiple sulfate wet-dry cycles were obtained. The test damage data of the coated concrete were calculated based on the initial compressive strength and the compressive strength after multiple sulfate wet-dry cycles.

[0007] Combining the first feasible approach of the first aspect, in the third feasible approach of the first aspect, a two-stage damage model is constructed by introducing a continuity constraint at the stage inflection point. The constructed two-stage damage model is as follows: ; in, The compressive strength damage degree corresponds to the number of transition cycles in the phase transition.

[0008] In conjunction with the third feasible method of the first aspect, in the fourth feasible method of the first aspect, The initial state parameters of the damage development stage are calculated based on the theoretical limit damage degree and the compressive strength damage degree corresponding to the number of stage transition cycles.

[0009] In conjunction with the first possible implementation of the first aspect, in the fifth possible implementation of the first aspect, the strength compensation coefficient is calculated based on the number of stage transition cycles, the damage accumulation coefficient, the damage development rate parameter, and the theoretical limit damage degree.

[0010] In conjunction with the first feasible method of the first aspect, the sixth feasible method of the first aspect employs an optimization algorithm to search for the optimal model parameters of the two-stage damage model, including: The optimal model parameters are searched using genetic algorithm, nonlinear least squares method, particle swarm optimization algorithm, and simulated annealing algorithm.

[0011] Secondly, a method for evaluating the performance of coated concrete is provided, including: The critical number of sulfate wet-dry cycles for coated concrete is predicted by any of the first to sixth possible methods of the first aspect. The critical number of wet-dry cycles corresponding to the critical damage state of coated concrete with different coating systems is predicted. The protective performance of coated concrete with different coating systems is evaluated based on the critical number of wet-dry cycles and the optimal model parameters of the two-stage damage model corresponding to different coating systems.

[0012] Thirdly, a system for predicting the critical number of sulfate wet-dry cycles in coated concrete is provided, including: The data acquisition module is configured to acquire test damage data of the coated concrete under different cycles through sulfate wet-dry cycle tests; The model building module is configured to establish a two-stage damage model based on the stage characteristics of damage evolution of coated concrete, and to use an optimization algorithm to search for the optimal model parameters of the two-stage damage model based on all experimental damage data, with the objective function being to minimize the error between the experimental damage and the damage calculated by the model. The inversion calculation module is configured to determine the damage degree at the stage transition point of the coated concrete by using the number of stage transition cycles in the optimal model parameters, compare the critical damage degree of the coated concrete with the damage degree at the stage transition point, and select the appropriate stage damage model to invert the critical number of wet-dry cycles of the coated concrete based on the comparison result. The two-stage damage model includes a damage incubation stage model and a damage development stage model. The specific expression for the damage incubation stage model is as follows: ; The specific expression for the damage development stage model is as follows: ; in, This represents the cumulative damage coefficient during the damage incubation stage. The number of loops. This is the strength compensation coefficient during the damage incubation stage. This refers to the number of cycles in a phase transition. For the theoretical limit of damage, These are the initial state parameters for the damage development stage. This refers to the damage development rate parameter during the damage development stage. This refers to the compressive strength damage degree during the damage incubation stage. This represents the compressive strength damage degree during the damage development stage.

[0013] Fourthly, a performance evaluation system for coated concrete is provided, comprising: The prediction module is configured to use the critical number of sulfate wet-dry cycles prediction method for coated concrete as described in any of the first to sixth implementable methods of the first aspect, to predict the critical number of wet-dry cycles corresponding to the critical damage state of coated concrete with different coating systems. The evaluation module assesses the protective performance of coated concrete with different coating systems based on the critical number of wet-dry cycles and the optimal model parameters of the two-stage damage model corresponding to different coating systems.

[0014] Beneficial Effects: The method and system for predicting the critical number of cycles and evaluating the performance of coated concrete according to this invention can establish a quantitative relationship between compressive strength damage and the number of cycles, and perform inverse calculations based on the critical damage level to obtain the critical dry-wet cycle number of coated concrete for different coating systems, providing a clear quantitative indicator for evaluating the sulfate resistance of coated concrete. Furthermore, by using compressive strength or corrosion resistance coefficient data at finite cycle points, an optimization algorithm can accurately search for the optimal model parameters, thereby determining the optimal two-stage damage model. Thus, the durability evaluation results of coated concrete can be obtained within a shorter experimental cycle, which helps reduce experimental time costs and material selection costs. Moreover, compared to using a single empirical model or a common fitting model, the constructed two-stage damage model better conforms to the evolution law of cyclic damage in coated concrete, and the prediction results are more accurate. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to scale.

[0016] Figure 1 A flowchart of a method for predicting the critical number of sulfate wet-dry cycles in coated concrete according to an embodiment of the present invention; Figure 2 This is a system block diagram of a sulfate wet-dry cycle critical number prediction system for coated concrete provided in an embodiment of the present invention; Figure 3 The fitting results of the two-stage damage evolution model for the CG group are shown in the figure. The first-stage model is the damage incubation stage model, and the second-stage model is the damage development stage model. Figure 4 The figure shows the fitting results of the two-stage damage evolution model for Group A. The first-stage model is the damage incubation stage model, and the second-stage model is the damage development stage model. Figure 5 The figure shows the fitting results of the two-stage damage evolution model for Group B. The first-stage model is the damage incubation stage model, and the second-stage model is the damage development stage model. Figure 6 The figure shows the fitting results of the two-stage damage evolution model for Group C. The first-stage model is the damage incubation stage model, and the second-stage model is the damage development stage model. Detailed Implementation

[0017] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0018] like Figure 1 The flowchart shown illustrates a method for predicting the critical number of sulfate wet-dry cycles in coated concrete. This prediction method includes: Step 1: Obtain test damage data of coated concrete under different cycles of sulfate wet-dry cycling test; Step 2: Establish a two-stage damage model based on the stage characteristics of damage evolution of coated concrete, and use an optimization algorithm to search for the optimal model parameters of the two-stage damage model based on all experimental damage data, with the objective function being to minimize the error between the experimental damage and the damage calculated by the model. Step 3: Determine the damage degree of the stage transition point corresponding to the coated concrete by using the number of stage transition cycles in the optimal model parameters, and compare the critical damage degree of the coated concrete with the damage degree of the stage transition point. Based on the comparison result, select the corresponding stage damage model to invert the critical number of wet-dry cycles of the coated concrete.

[0019] Specifically, firstly, the experimental damage data of the coated concrete under different cycles of sulfate wet-dry cycling can be obtained through sulfate wet-dry cycling tests. Then, based on the staged characteristics of the damage evolution of the coated concrete under sulfate wet-dry cycling, a two-stage damage model including a damage incubation stage model and a damage development stage model can be constructed. Next, using all the obtained experimental damage data as a sample set, and based on a set objective function, existing optimization algorithms are used to search for the optimal model parameters corresponding to the two-stage damage model. Based on the searched optimal model parameters, an optimal two-stage damage model characterizing the damage development effect of the coated concrete at different stages is constructed. Finally, the stage transition point damage degree of the coated concrete can be calculated based on the stage transition cycle number in the optimal model parameters. By comparing the critical damage degree specified in existing standards with the stage transition point damage degree, the appropriate stage damage model for the coated concrete can be determined. The critical wet-dry cycle number of the coated concrete can then be calculated using the stage damage model.

[0020] In this embodiment, the experimental damage data of the coated concrete under different cycles of sulfate wet-dry cycling were obtained through sulfate wet-dry cycling tests, specifically including: First, concrete specimens are molded based on the predicted concrete mix proportions. After standard curing, different coating systems, anti-corrosion coating systems, or composite protection systems are applied to the surface of the concrete specimens according to the prescribed process, forming multiple groups of coated concrete samples. Each group of samples corresponds to one coating protection system, and the concrete specimens without protective coating serve as the control group.

[0021] In this embodiment, the coating system can be a single-layer organic coating, an inorganic coating, a polymer coating, a resin coating, a geopolymer coating, or a multi-layer composite protective system. For different coating systems, parameters such as coating type, coating process, coating thickness, curing conditions, or design dosage can be recorded for subsequent protective performance evaluation and comparative analysis between different coating systems.

[0022] Different coating systems have different effects on the evolution of sulfate wet-dry cycle damage in coated concrete. Therefore, the protective effect of different coating systems can be characterized and evaluated by the variation of damage degree with the number of sulfate wet-dry cycles, the parameters of the two-stage damage model, and the critical number of wet-dry cycles.

[0023] Then, referring to the sulfate wet-dry cycle test method, sulfate wet-dry cycle tests were conducted on each group of coated concrete specimens, and performance data to characterize the degree of performance degradation of the specimens were obtained at preset cycle nodes. The performance data includes at least the initial compressive strength of the specimen and the compressive strength after different numbers of sulfate wet-dry cycles. Alternatively, it may include the corrosion resistance coefficient calculated based on the compressive strength. The cycle nodes can be set to 0, 15, 30, 45, 60, 90, 120, 150 cycles, or other cycle number nodes can be set according to the actual test cycle, service environment simulation requirements, and evaluation accuracy requirements. The obtained test damage data are shown in Table 1 below: Table 1. Damage degree of coated concrete samples tested

[0024] The concrete samples corresponding to the specimen numbers are shown in Table 2 below: Table 2 Explanation of Specimen Numbers

[0025] In this embodiment, the appearance damage, mass change, coating surface morphology, or coating-concrete interface damage of the specimen can also be obtained at each cycle node. The appearance damage includes one or more of the following: coating blistering, cracking, peeling, surface cracks, edge damage, and localized powdering. The mass change is used to help reflect the absorption of sulfate solution, deposition of corrosion products, and loss of surface material.

[0026] In this embodiment, optionally, obtaining the test damage data of the coated concrete includes: The initial compressive strength of the coated concrete and its compressive strength after undergoing multiple sulfate wet-dry cycles were obtained. The test damage data of the coated concrete were calculated based on the initial compressive strength and the compressive strength after multiple sulfate wet-dry cycles.

[0027] Specifically, the test damage data of the coated concrete samples can be calculated and obtained based on the initial compressive strength of the coated concrete samples and the compressive strength of the coated concrete samples after experiencing different numbers of sulfate wet-dry cycles. The specific calculation formula is as follows: ; in, For coated concrete experience The degree of damage after each cycle, i.e., the compressive strength damage. For coated concrete experience Compressive strength after 1 cycle This represents the initial compressive strength of the coated concrete.

[0028] Since the compressive strength of coated concrete may be higher than the initial strength in the early stage of sulfate wet-dry cycle, the compressive strength damage degree is a damage index relative to the initial compressive strength, and its value can be positive, zero or negative.

[0029] when When this occurs, it indicates that the compressive strength of the coated concrete has decreased. When this occurs, it indicates that the compressive strength of the coated concrete remains essentially unchanged. When The term "compressive strength damage" indicates that the coated concrete exhibits increased compressive strength in the early stages of a sulfate wet-dry cycle due to coating barrier, pore filling by corrosion products, or temporary densification of the internal structure. Therefore, the compressive strength damage can comprehensively describe the evolution of coated concrete at different stages.

[0030] In this embodiment, the corrosion resistance coefficient can also be used to calculate the test damage data of the coated concrete sample. The specific formula for calculating the corrosion resistance coefficient is as follows: ; .

[0031] After obtaining experimental damage data of coated concrete under different sulfate wet-dry cycles, a two-stage damage model, including a damage incubation stage model and a damage development stage model, can be constructed based on the stage characteristics of damage evolution in coated concrete. Then, using all experimental damage data as a sample set, an optimization algorithm is employed to search for the optimal model parameters of the two-stage damage model based on a pre-constructed objective function.

[0032] In this embodiment, optionally, the two-stage damage model includes a damage incubation stage model and a damage development stage model.

[0033] Specifically, the two-stage damage model includes damage models corresponding to two development stages of coated concrete: an initial damage incubation stage model and a mid-to-late stage damage development stage model.

[0034] The initial coating provides strong barrier properties, inhibiting the migration of sulfate solution into the concrete interior. Simultaneously, a small amount of corrosion products entering the pores may contribute to densification. Therefore, the increase in compressive strength damage is relatively slow during this stage. Using only a monotonically increasing linear damage model is insufficient to describe the potential increase in compressive strength and negative apparent damage that may occur in coated concrete during the initial stages of sulfate wet-dry cycles.

[0035] Therefore, a damage incubation stage model composed of a damage accumulation term and an early strength compensation term can be established to describe the evolution of coated concrete in its initial stage. The specific expression of the established damage incubation stage model is as follows: .

[0036] in, This represents the cumulative damage coefficient during the damage incubation stage. The number of loops. This is the strength compensation coefficient during the damage incubation stage. This represents the number of cycles in a phase transition.

[0037] in, This refers to the compressive strength damage degree during the damage incubation stage. This indicates the initial damage that gradually accumulates with increasing wet-dry cycles. This indicates the effect of early strength compensation during the damage incubation stage on the apparent damage level. or hour, All values ​​are 0, ensuring the model simultaneously satisfies the continuity requirements of the initial state and the transition points between stages. The damage incubation stage model can describe both the early increase in compressive strength and the accumulation of damage in the specimen from the initial stage of the cycle.

[0038] As coated concrete enters the mid-to-late stages of damage development, local defects in the coating, weak interfacial areas, and existing microcracks promote the continued migration of sulfate solution, thus influencing subsequent damage propagation based on the scale of currently activated damage. Simultaneously, as the damage level gradually approaches the theoretical limit, the remaining effective structure capable of further deterioration gradually decreases, and the damage growth potential gradually diminishes.

[0039] Based on the above mechanism, a damage rate equation for the damage development stage can be established, and the specific expression is as follows: ; Integrating the damage rate equation yields the damage development stage model corresponding to the damage development stage, specifically expressed as: ; For the theoretical limit of damage, These are the initial state parameters for the damage development stage. This refers to the damage development rate parameter during the damage development stage. This represents the compressive strength damage degree during the damage development stage.

[0040] In this embodiment, optionally, to avoid abrupt changes at the stage boundaries of the segmented model and to make the model more consistent with the actual damage evolution process of the coated concrete, a continuity constraint at the stage transition point can be introduced to construct a two-stage damage model. The constructed two-stage damage model is as follows: ; in, The compressive strength damage degree corresponding to the number of stage transition cycles can be calculated based on the damage accumulation coefficient of the damage incubation stage and the number of stage transition cycles. The specific calculation formula is as follows: .

[0041] At the stage transition cycle number, the compressive strength damage degree calculated by the damage development stage model and the damage incubation stage model is equal.

[0042] In the two-stage damage model described above, the damage accumulation term in the damage incubation stage model reflects the cumulative damage effect caused by early sulfate intrusion and initial micro-damage, while the strength compensation term reflects the early strength compensation effect caused by coating barrier, corrosion product pore filling, and structural densification. The damage development stage model reflects the nonlinear damage development process under the combined effects of corrosion product expansion, salt crystallization pressure, and microcrack propagation after the coating's protective ability has weakened. Therefore, the constructed two-stage damage model better conforms to the evolution law of sulfate wet-dry cycle damage in coated concrete compared to a single empirical model or fitting model, and the critical wet-dry cycle prediction results obtained through the two-stage damage model are more accurate.

[0043] In this embodiment, optionally, the strength compensation coefficient is calculated based on the number of stage transition cycles, the damage accumulation coefficient, the damage development rate parameter, and the theoretical limit damage degree.

[0044] In this embodiment, optionally, to make the transition between the damage incubation stage and the damage development stage smoother at the stage transition point, the damage model of the two stages can satisfy the following first derivative continuity condition at the stage transition cycle number: .

[0045] Therefore, the specific formula for calculating the strength compensation coefficient can be determined as follows: .

[0046] In this embodiment, optionally, the initial state parameters of the damage development stage are calculated based on the theoretical limit damage degree and the compressive strength damage degree corresponding to the number of stage transition cycles. The specific calculation formula is as follows: .

[0047] This not only allows the two-stage damage evolution model to have a smoother transition at the stage inflection point, but also reduces the number of independent parameters to be identified, thus improving prediction efficiency.

[0048] After constructing the two-stage damage model, the optimal model parameters can be searched using an optimization algorithm based on a pre-built sample set, with the objective function being minimizing the error between the experimental damage degree and the damage degree calculated by the model. The specific expression of the objective function is as follows: ; in, The number of circular nodes. Calculate the damage degree for the model. To test the degree of damage.

[0049] In this embodiment, the model parameters searched include the number of stage transition cycles, damage accumulation coefficient, strength compensation coefficient, damage development rate parameter, and theoretical limit damage degree. The number of stage transition cycles reflects the coating system's ability to delay damage initiation and postpone the arrival of the main damage stage. The damage accumulation coefficient reflects the damage accumulation rate caused by early sulfate intrusion and initial micro-damage. The strength compensation coefficient reflects the early strength compensation effect caused by coating barrier, corrosion product pore filling, and structural densification. The damage development rate parameter reflects the deterioration rate of the main damage stage after the coating's protective ability weakens. The theoretical limit damage degree reflects the ultimate damage level that the coated concrete may reach under current erosion conditions.

[0050] In this embodiment, optionally, to reduce the degree of parameter freedom and improve model stability, the theoretical limit damage degree can be set to 1. This allows searching only the parameters of stage transition cycle number, damage accumulation coefficient, and damage development rate.

[0051] In this embodiment, optionally, an optimization algorithm is used to search for the optimal model parameters of the two-stage damage model, including: The optimal model parameters are searched using genetic algorithm, nonlinear least squares method, particle swarm optimization algorithm, and simulated annealing algorithm.

[0052] Specifically, existing genetic algorithms, nonlinear least squares methods, particle swarm optimization algorithms, and simulated annealing algorithms can be used to search for the number of stage transition cycles, damage accumulation coefficient, strength compensation coefficient, damage development rate parameter, and theoretical limit damage degree of the two-stage damage model.

[0053] Taking the genetic algorithm as an example, the parameters can be set as follows: population size of 40, maximum number of generations of evolution of 100, crossover probability of 0.8, mutation probability of 0.05, and number of elite individuals retained of 2. When the rate of change of the optimal objective function is less than 0.1% for 10 consecutive generations, the algorithm is considered to have converged and the iteration stops.

[0054] It should be understood that the above genetic algorithm parameters are only exemplary settings and can be adjusted according to the scale of experimental data, computational accuracy requirements, and parameter search space.

[0055] Based on the evolution law of sulfate dry-wet cycle damage and the setting of test nodes, the parameter search range of the number of stage transition cycles, damage accumulation coefficient and damage development rate can be set.

[0056] In this embodiment, the search range for the number of stage transition cycles is set to between 30 and 120 cycles. The search range for the damage accumulation coefficient is set to between 0 and 0.003. The search range for the damage development rate parameter is set to between 0.005 and 0.030.

[0057] It should be understood that the above search range is only an example range determined by this embodiment based on the test nodes and damage degree change characteristics. In other embodiments, it can be adjusted according to the test data distribution, candidate stage transition intervals and evaluation accuracy requirements.

[0058] The parameter search process should meet the following constraints: When searching for the optimal model parameters for the damage incubation stage model, the following should be satisfied: ; .

[0059] When searching for the optimal model parameters for the damage development stage model, the following should be satisfied: ; in, This represents the critical damage level.

[0060] The optimization algorithm is used to search for the parameter combination that minimizes the objective function, thereby obtaining the optimal two-stage damage model parameters for each group of specimens. The parameter search results are shown in Table 3 below.

[0061] Table 3 Search results for parameters of the two-stage damage model

[0062] As shown in Table 3, the model fit of each group of specimens is high, indicating that the two-stage damage model that satisfies the conditions of continuity and first derivative continuity can well describe the damage evolution process of coated concrete under sulfate wet-dry cycle.

[0063] Further analysis of the model parameters reveals that the number of stage transition cycles in group CG is 63.36, which is lower than that in groups A, B, and C. Furthermore, the damage development rate parameter in the second stage is relatively large, indicating that ordinary concrete without a protective coating enters the main damage development stage earlier and deteriorates faster in the middle and later stages.

[0064] The number of stage transition cycles in Group A was 102.13, significantly higher than that in Groups B and C, indicating that the coating system in Group A could more effectively delay the arrival of the main damage development stage. The number of stage transition cycles in Groups B and C were 79.13 and 68.82, respectively, indicating that they also had some ability to delay damage initiation, but were weaker than that in Group A.

[0065] Group A has a smaller damage accumulation coefficient and a greater strength compensation coefficient than the damage accumulation coefficient, indicating that it has a more significant strength compensation effect in the early stages of cycling, which can explain the negative damage degree that appears after 30 and 45 cycles. Although Groups B and C also have a certain protective effect of the coating, their damage initiation delay ability and critical dry-wet cycle count are lower than those of Group A.

[0066] After finding the optimal model parameters, these parameters can be substituted into the two-stage damage model to construct the optimal two-stage damage model. Based on the optimal two-stage damage model, the critical number of wet-dry cycles for the coated concrete can be calculated by inversion according to the critical damage degree set in existing specifications.

[0067] In this embodiment, the sulfate wet-dry cycle evaluation method in the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T50082-2024) can be referred to. The critical damage degree is calculated when the corrosion resistance coefficient drops to 0.75. The specific calculation formula for the critical damage degree is as follows: ; in, The corrosion resistance coefficient is 0.75 as specified in the standard.

[0068] When the critical damage level is in the damage incubation stage, that is .

[0069] If the strength compensation coefficient in the model is greater than 0, the critical number of wet-dry cycles can be calculated using the following formula: ; If the strength compensation coefficient in the model is equal to 0 .

[0070] When the critical damage degree is in the damage development stage, that is The critical number of wet-dry cycles can be calculated using the following formula: .

[0071] The critical number of wet-dry cycles required for different coating systems to reach the critical damage threshold, obtained from inversion calculations, is shown in Table 4 below: Table 4 Critical wet-dry cycle count for different coating systems

[0072] A method for evaluating the performance of coated concrete, comprising: Using the above-mentioned method for predicting the critical number of sulfate wet-dry cycles in coated concrete, the critical number of wet-dry cycles corresponding to the critical damage state of coated concrete with different coating systems is predicted. The protective performance of coated concrete with different coating systems is evaluated based on the critical number of wet-dry cycles and the optimal model parameters of the two-stage damage model corresponding to different coating systems.

[0073] Specifically, firstly, the aforementioned method for predicting the critical number of sulfate wet-dry cycles in coated concrete can be used to predict the critical number of wet-dry cycles for different coating systems when they reach the critical damage state. Since the stage transition cycle number, damage accumulation coefficient, strength compensation coefficient, and damage development rate parameters can all reflect the coating system's ability to delay damage initiation, inhibit early damage accumulation, and control later damage propagation, then, based on the critical number of wet-dry cycles for the coated concrete and the model parameters of the two-stage damage models for different coating systems, the sulfate wet-dry cycle resistance of different coating systems can be ranked and evaluated, providing a technical basis for the selection of coated concrete materials, durability design, and optimization of engineering protection schemes.

[0074] like Figure 2 The system block diagram shown is for a system that predicts the critical number of sulfate wet-dry cycles in coated concrete. The system includes: The data acquisition module is configured to acquire test damage data of the coated concrete under different cycles through sulfate wet-dry cycle tests; The model building module is configured to establish a two-stage damage model based on the stage characteristics of damage evolution of coated concrete, and to use an optimization algorithm to search for the optimal model parameters of the two-stage damage model based on all experimental damage data, with the objective function being to minimize the error between the experimental damage and the damage calculated by the model. The inversion calculation module is configured to determine the damage degree of the stage transition point corresponding to the coated concrete by using the number of stage transition cycles in the optimal model parameters, and compare the critical damage degree of the coated concrete with the damage degree of the stage transition point. Based on the comparison result, the corresponding stage damage model is selected to invert the critical number of wet-dry cycles of the coated concrete.

[0075] Specifically, the prediction system includes a data acquisition module, a model building module, and an inversion calculation module. The data acquisition module obtains experimental damage data of the coated concrete at different cycle numbers through sulfate wet-dry cycle tests. The model building module constructs a two-stage damage model, including a damage incubation stage model and a damage development stage model, based on the staged characteristics of sulfate wet-dry cycle damage evolution in the coated concrete. Then, using all acquired experimental damage data as a sample set, and based on a set objective function, existing optimization algorithms are used to search for the optimal model parameters corresponding to the two-stage damage model. Based on the searched optimal model parameters, an optimal two-stage damage model characterizing the damage development effect of the coated concrete at different stages is constructed. The inversion calculation module calculates the stage inflection point damage degree of the coated concrete based on the stage inflection cycle number in the optimal model parameters. By comparing the critical damage degree specified in existing standards with the stage inflection point damage degree, the appropriate stage damage model for the coated concrete can be determined. The critical wet-dry cycle number of the coated concrete can then be calculated using the stage damage model.

[0076] A coating concrete performance evaluation system, comprising: The prediction module is configured to use the above-mentioned method for predicting the critical number of sulfate wet-dry cycles of coated concrete to predict the critical number of wet-dry cycles when coated concrete of different coating systems reaches the critical damage state. The evaluation module assesses the protective performance of coated concrete with different coating systems based on the critical number of wet-dry cycles and the optimal model parameters of the two-stage damage model corresponding to different coating systems.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for predicting the critical number of sulfate wet-dry cycles in coated concrete, characterized in that, include: The experimental damage data of the coated concrete under different cycles were obtained by sulfate wet-dry cycle test; A two-stage damage model was established based on the staged characteristics of damage evolution of coated concrete. Based on all experimental damage data, the optimal model parameters of the two-stage damage model were searched using an optimization algorithm with the objective function of minimizing the error between the experimental damage and the damage calculated by the model. The damage degree at the stage transition point of the coated concrete is determined by the number of stage transition cycles in the optimal model parameters. The critical damage degree of the coated concrete is compared with the damage degree at the stage transition point. Based on the comparison result, the corresponding stage damage model is selected to invert the critical number of wet-dry cycles of the coated concrete. The two-stage damage model includes a damage incubation stage model and a damage development stage model. The specific expression for the damage incubation stage model is as follows: ； The specific expression for the damage development stage model is as follows: ； in, This represents the cumulative damage coefficient during the damage incubation stage. The number of loops. This is the strength compensation coefficient during the damage incubation stage. This refers to the number of cycles in a phase transition. For the theoretical limit of damage, These are the initial state parameters for the damage development stage. This refers to the damage development rate parameter during the damage development stage. This refers to the compressive strength damage degree during the damage incubation stage. This represents the compressive strength damage degree during the damage development stage.

2. The method for predicting the critical number of sulfate wet-dry cycles in coated concrete according to claim 1, characterized in that, Obtaining test damage data for the coated concrete includes: The initial compressive strength of the coated concrete and its compressive strength after undergoing multiple sulfate wet-dry cycles were obtained. The test damage data of the coated concrete were calculated based on the initial compressive strength and the compressive strength after multiple sulfate wet-dry cycles.

3. The method for predicting the critical number of sulfate wet-dry cycles in coated concrete according to claim 1, characterized in that, A two-stage damage model is constructed by introducing continuity constraints at stage inflection points. The constructed two-stage damage model is as follows: ； in, The compressive strength damage degree corresponds to the number of transition cycles in the phase transition.

4. The method for predicting the critical number of sulfate wet-dry cycles in coated concrete according to claim 3, characterized in that: The initial state parameters of the damage development stage are calculated based on the theoretical limit damage degree and the compressive strength damage degree corresponding to the number of stage transition cycles.

5. The method for predicting the critical number of sulfate wet-dry cycles in coated concrete according to claim 1, characterized in that: The strength compensation coefficient is calculated based on the number of stage transition cycles, the damage accumulation coefficient, the damage development rate parameter, and the theoretical limit damage degree.

6. The method for predicting the critical number of sulfate wet-dry cycles in coated concrete according to claim 1, characterized in that, An optimization algorithm is used to search for the optimal model parameters of the two-stage damage model, including: The optimal model parameters are searched using genetic algorithm, nonlinear least squares method, particle swarm optimization algorithm, and simulated annealing algorithm.

7. A method for evaluating the performance of coated concrete, comprising: Using the method for predicting the critical number of sulfate wet-dry cycles of coated concrete as described in any one of claims 1-6, the critical number of wet-dry cycles corresponding to the critical damage state of coated concrete with different coating systems is predicted. The protective performance of coated concrete with different coating systems is evaluated based on the critical number of wet-dry cycles and the optimal model parameters of the two-stage damage model corresponding to different coating systems.

8. A system for predicting the critical number of sulfate wet-dry cycles in coated concrete, characterized in that, include: The data acquisition module is configured to acquire test damage data of the coated concrete under different cycles through sulfate wet-dry cycle tests; The model building module is configured to establish a two-stage damage model based on the stage characteristics of damage evolution of coated concrete, and to use an optimization algorithm to search for the optimal model parameters of the two-stage damage model based on all experimental damage data, with the objective function being to minimize the error between the experimental damage and the damage calculated by the model. The inversion calculation module is configured to determine the damage degree of the stage transition point corresponding to the coated concrete by using the number of stage transition cycles in the optimal model parameters, and compare the critical damage degree of the coated concrete with the damage degree of the stage transition point. Based on the comparison result, the corresponding stage damage model is selected to invert the critical number of wet-dry cycles of the coated concrete. The two-stage damage model includes a damage incubation stage model and a damage development stage model. The specific expression for the damage incubation stage model is as follows: ； The specific expression for the damage development stage model is as follows: ； in, This represents the cumulative damage coefficient during the damage incubation stage. The number of loops. This is the strength compensation coefficient during the damage incubation stage. This refers to the number of cycles in a phase transition. For the theoretical limit of damage, These are the initial state parameters for the damage development stage. This refers to the damage development rate parameter during the damage development stage. This refers to the compressive strength damage degree during the damage incubation stage. This represents the compressive strength damage degree during the damage development stage.

9. A performance evaluation system for coated concrete, comprising: The prediction module is configured to use the critical number of sulfate wet-dry cycles prediction method for coated concrete as described in any one of claims 1-6 to predict the critical number of wet-dry cycles corresponding to the critical damage state of coated concrete with different coating systems. The evaluation module assesses the protective performance of coated concrete with different coating systems based on the critical number of wet-dry cycles and the optimal model parameters of the two-stage damage model corresponding to different coating systems.

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