CN113919115B - A method for establishing a prediction model for the chloride ion corrosion life of existing concrete - Google Patents
A method for establishing a prediction model for the chloride ion corrosion life of existing concrete Download PDFInfo
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Abstract
本发明涉及核电厂混凝土结构评估领域，特别是一种建立既有混凝土氯离子侵蚀寿命预测模型的方法。现有的混凝土室内耐久性试验参数大都采用业内通用的试验参数，该类试验适用于在工程设计阶段选取混凝土材料时衡量不同混凝土材料的耐久性能好坏，而对于核电厂既有混凝土结构，其材料参数已经确定，目前尚无基于混凝土结构现状来预测既有混凝土结构的预期寿命的方法。本发明包括步骤一：条件调研；步骤二：设计实验环境；步骤三：进行实验；步骤四：进行验证。本发明提出一种基于相似性理论，对混凝土试样进行氯离子加速侵蚀试验，并根据试验结果预测既有结构预期寿命的方法。
The present invention relates to the field of nuclear power plant concrete structure assessment, and in particular to a method for establishing a chloride ion corrosion life prediction model for existing concrete. Most of the existing concrete indoor durability test parameters adopt the test parameters commonly used in the industry. This type of test is suitable for measuring the durability of different concrete materials when selecting concrete materials in the engineering design stage. For the existing concrete structures of nuclear power plants, their material parameters have been determined. Currently, there is no method for predicting the expected life of existing concrete structures based on the current status of the concrete structures. The present invention includes step one: condition investigation; step two: designing the experimental environment; step three: conducting experiments; and step four: conducting verification. The present invention proposes a method for conducting a chloride ion accelerated corrosion test on concrete samples based on similarity theory, and predicting the expected life of existing structures based on the test results.
Description
Technical Field
The invention relates to the field of concrete structure evaluation of nuclear power plants, in particular to a method for establishing an existing concrete chloride ion erosion life prediction model.
Background
The reinforced concrete structure is the most widely used structure of the nuclear power plant, the nuclear power plant in China is located along the sea area, the marine aggressive environment in the coastal area can cause the reinforced concrete of the nuclear power plant structure to generate chloride corrosion, sulfate corrosion and atmospheric carbonization prematurely, and further cause the aging problems of concrete cracking and peeling, steel bar corrosion and rust expansion, empty coating falling off and the like, so that serious threat is brought to the durability (supporting capacity and containing capacity) of the structure, and even the safe operation of the nuclear power plant is threatened. In recent years, with increasing importance of domestic nuclear power plants on safety important structures monitoring and detecting work and increasing of service life of the structures, similar experience feedback reports of structural failure of reinforced concrete in aggressive marine environments are also continuously presented to safety important structures such as safety shells, marine structures and the like, and with increasing number of nuclear power new units in China and longer running time of the nuclear power units, durability problems of the safety important structures of the nuclear power plants in the aggressive marine environments are also increasingly outstanding. Therefore, the method has very important value and significance in deeply researching the diffusion rule and the protective measures of chloride ions in the specific environment of the power plant.
In the concrete structure in the marine environment, chloride ions mainly invade the concrete by virtue of diffusion under the action of seawater, however, in the dry-wet alternating area of the seawater, such as a tidal range area and a splash area in the marine environment, the erosion mechanism of the chloride ions on the surface layer of the concrete is more complex, and the chloride ions mainly comprise capillary adsorption action, permeation action, diffusion action and the like on the surface layer of the concrete, and the diffusion action is still mainly in the deep layer. Indoor acceleration tests and field tests have been used for researching the durability of a concrete structure for a long time, but how to relate the indoor acceleration test results with the field detection results to establish a set of concrete durability life prediction models suitable for specific environments still remains a key problem in the durability research of the current concrete structure. The existing concrete indoor durability test parameters are generally test parameters which are common in the industry, the test is suitable for measuring the durability of different concrete materials when the concrete materials are selected in the engineering design stage, and for the existing concrete structure of a nuclear power plant, the material parameters are already determined, and how to apply the test parameters which are more 'severe' than the real environment to the existing concrete material in a laboratory, so that the service life of the existing structure in the real environment is the core of the technology. The similarity theory is proposed to build a connection between the simulation experiment and the real environment, and restrict the selection of the test parameters through the internal relation of the similarity ratio, so as to achieve the purpose of simulating the behavior rule of the research object in the real environment.
Disclosure of Invention
Purpose(s)
In order to solve the problem that a method for predicting the life expectancy of the existing concrete structure based on the current situation of the concrete structure is not available at present, the invention provides a method for predicting the life expectancy of the existing structure based on a similarity theory by performing a chloride ion accelerated erosion test on a concrete sample and according to a test result.
Technical proposal
The technical scheme adopted for solving the technical problems is as follows:
A method for establishing an existing concrete chloride ion erosion life prediction model comprises the following steps of firstly, condition investigation, secondly, designing an experimental environment, thirdly, performing experiments and fourthly, performing verification.
The first step of condition investigation comprises two parts of natural environment investigation and concrete design parameter investigation. The natural environment investigation comprises the average temperature and average humidity of the month of history of concrete structure construction, the sea water tide period and sea water chloride ion content parameters. The investigation of the concrete design parameters comprises investigation of the mixing ratio, design strength and reinforcement protection layer thickness h of the collected concrete.
The method comprises the steps of designing experimental environments, and specifically comprises the steps of (1) dividing the environments into three types of concrete in an atmospheric area, concrete in a dry-wet alternate area and concrete in an underwater area, and (2) respectively designing three indoor chloride ion accelerated erosion tests in the underwater area, the dry-wet alternate area and the atmospheric area.
The underwater region selects the chloride ion concentration of the soaking solution and the temperature of the soaking solution as control parameters, the dry-wet alternating region selects the chloride ion concentration of the soaking solution and the temperature of the soaking solution, the dry-wet circulation time proportion is used as control parameters, and the atmospheric region selects the chloride ion concentration in salt mist and the salt mist test temperature as control parameters.
The environment where the existing concrete structure is located is divided into three types, namely, concrete in an atmosphere area, concrete in a dry-wet alternating area and concrete in an underwater area, wherein the concrete in the atmosphere area mainly contacts salt in air and is not in direct contact with seawater, the concrete in the dry-wet alternating area only contacts the seawater for a part of time, and the underwater area is positioned below a horizontal plane and is immersed in the seawater throughout the year.
And step three, performing experiments, wherein the step three comprises the following steps:
(1) Filling an underwater area simulation test box with a soaking solution with the chloride ion concentration of C, the range of 8220-35000 mg/L, the liquid temperature of T and the temperature of T of 20-60 ℃, and then placing 24 concrete samples with the height of H and H of more than 2H for soaking experiments;
(2) Putting 24 concrete samples with the height H being more than 2 hours into a dry-wet alternating area simulation test box, wherein the chloride ion concentration of a solution set by the dry-wet alternating area simulation test is c, the temperature of the solution is T, and the time ratio of a test drying stage to a soaking stage is 2:1;
(3) And placing 24 concrete samples with the height H of more than 2H in an atmospheric region test box, wherein the salt fog chloride ion concentration in the atmospheric region is c, and the salt fog test temperature is T.
In the test process, 3 samples are taken out from three test boxes respectively every month for testing, the test method is to cut and grind every 5mm layer by layer along the depth direction of the concrete, the chloride ion content of the powder is measured to be c0, c1, c2, c3 and c4, and the powder is tested by the second law of FickFitting to obtain the chloride ion diffusion coefficient Dm of the current time.
And step four, verification is carried out, namely judging whether the chloride ion concentration at the position, which is away from the upper surface h of the sample, reaches 1.4% of a chloride ion concentration limit value, and if the chloride ion concentration at the position, which is away from the upper surface h of the sample, reaches 1.4%, recording the test time at the moment as time t m, wherein the steel bars start to be corroded, and the concrete structure is damaged.
The calculation formula of the life expectancy (t) of the existing concrete structure is as follows:
The unit is unified as month
Wherein D m(m2/s) is the diffusion coefficient of chloride ions under an indoor simulation test;
D (m 2/s) is the diffusion coefficient of chloride ions in the field real environment, and is obtained by an electric quantity method or a field sampling method;
And t m is the time for the chloride ion concentration at the position, which is away from the upper surface h of the sample, to reach 1.4% under the indoor simulation test, and the expected service life t of the concrete structure under the real environment can be obtained after the parameters are brought into the time.
Effects of
The method has the remarkable effect that the method establishes the quantitative relation between the chloride ion erosion process in the indoor simulated acceleration environment and the chloride ion real erosion process of the field structure by adopting the similarity principle. And by utilizing the number relation and combining the diffusion coefficient Dm obtained by the chloride ion simulation test under three conditions, the service life of the concrete structure in the real environment can be predicted.
1. Establish a quantitative relationship
2. Life prediction suitable for existing concrete structures
Drawings
FIG. 1 is a schematic diagram of a lifetime prediction method according to the present invention;
FIG. 2 is a flow chart of life expectancy calculation.
Detailed Description
According to the invention, real environment data are converted into simulation acceleration test parameters according to a similarity principle, so that the quantitative relation between the service life of a sample of a simulation acceleration test and the real life of a concrete structure in the real environment is obtained, and the service life prediction of the existing concrete structure is realized. The specific embodiments of the present invention are as follows:
And researching the environment where the existing concrete structure is located and structural material parameters to obtain real service environment data and concrete material information of the structure. The investigation of natural environment data comprises the average temperature and average humidity of the month of history of concrete structure construction, the sea water tide period and sea water chloride ion content parameters. The concrete material information comprises the mix proportion, the design strength and the thickness (50 mm) of the reinforcement protection layer of the concrete.
The environment where the existing concrete structure is located is divided into three types, namely, the concrete in the atmosphere area, the concrete in the dry-wet alternating area and the concrete in the underwater area. The concrete in the air area is mainly contacted with salt in the air and is not directly contacted with the seawater, the concrete in the dry-wet alternating area is only partially contacted with the seawater, and the underwater area is positioned below the water level and is immersed in the seawater throughout the year.
And respectively designing three indoor chloride ion accelerated corrosion tests of an underwater region, a dry-wet alternating region and an atmospheric region, wherein the underwater region selects the chloride ion concentration of a soaking solution and the temperature of the soaking solution as control parameters, the dry-wet alternating region selects the chloride ion concentration of the soaking solution and the temperature of the soaking solution, the dry-wet cycle time ratio is used as control parameters, and the atmospheric region selects the chloride ion concentration in salt mist and the salt mist test temperature is used as control parameters.
The underwater area simulation test box is filled with a soaking solution with the chloride ion concentration of 14436mg/L and the liquid temperature of 52.2 ℃, and then 24 concrete samples with the height of 150mm are put into the test box for soaking experiments.
Putting 24 concrete samples with the height of 150mm into a dry-wet alternating area simulation test box, wherein the chloride ion concentration of a solution set in the dry-wet alternating area simulation test is 14436mg/L, the solution temperature is 52.2 ℃, and the time ratio of a test drying stage to a soaking stage is 2:1;
24 concrete samples with the height of 150mm are placed in an atmospheric area test box, the concentration of salt fog chloride ions in the atmospheric area is 14436mg/L, and the salt fog test temperature is 52.2 ℃.
In the test process, 3 samples are taken from three test boxes respectively every month for testing, wherein the test method comprises the steps of slicing and grinding every 5mm layer by layer along the depth direction of the concrete, measuring the chloride ion content (c 0, c1, c2, c3 and c 4) of the powder, and determining the second law of FickFitting to obtain the chloride ion diffusion coefficient D m＝4.74×10-11m2/s at the current time.
Meanwhile, judging whether the chloride ion concentration at the position h away from the upper surface of the sample reaches 1.4 percent of the chloride ion concentration limit value specified in the durability design Specification,
If the concentration of chloride ions at a position 50mm away from the upper surface of the sample reaches 1.4%, the test time at this time is recorded as 8 months, the steel bars start to rust, and the concrete structure is destroyed.
The calculation formula of the life expectancy (t) of the existing concrete structure is as follows:
(the units are unified as a month)
Wherein D m(m2/s) is the diffusion coefficient of chloride ions under an indoor simulation test;
D (m 2/s) is a chloride ion diffusion coefficient in a field real environment, and d=1.31×10 -13m2/s is measured according to the standard of the test method for long-term performance and durability of ordinary concrete in GB/T50082-2009;
life expectancy t= 2894.6 (months) was calculated.
Claims (1)
1. A method for establishing an existing concrete chloride ion erosion life prediction model is characterized by comprising the following steps of firstly, condition investigation, secondly, designing an experimental environment, thirdly, performing an experiment, and fourthly, performing verification;
the condition investigation comprises two parts of natural environment investigation and concrete design parameter investigation;
The natural environment investigation comprises the average temperature and the average humidity of the month of history of concrete structure construction, the sea water tide period and the sea water chloride ion content parameter, wherein the concrete design parameter investigation comprises the investigation of the mix proportion, the design strength and the reinforcement protection layer thickness h of collected concrete;
the method comprises the steps of designing experimental environments, namely (1) dividing the environments into three types of concrete in an atmospheric area, concrete in a dry-wet alternate area and concrete in an underwater area;
the underwater region selects the chloride ion concentration of the soaking solution and the temperature of the soaking solution as control parameters, the dry-wet alternating region selects the chloride ion concentration of the soaking solution and the temperature of the soaking solution, and the dry-wet cycle time proportion is used as control parameters;
The experiment comprises the steps of (1) filling a simulation test box in an underwater area with a soaking solution with chloride ion concentration of C and a range of 8220-35000 mg/L, wherein the solution temperature is T, and the temperature of T is 20-60 ℃, then placing 24 concrete samples with the height of H being more than 2H for soaking experiments, (2) placing 24 concrete samples with the height of H being more than 2H in a simulation test box in a dry-wet alternating area, wherein the chloride ion concentration of the solution set in the simulation test box in the dry-wet alternating area is C, the solution temperature is T, the time ratio of a test drying stage to a soaking stage is 2:1, and (3) placing 24 concrete samples with the height of H being more than 2H in an air area, wherein the salt mist chloride ion concentration of C and the salt mist test temperature of T in the air area;
In the test process, 3 samples are taken out from three test boxes respectively every month for testing, the test method is to cut and grind every 5mm layer by layer along the depth direction of the concrete, the chloride ion content of the powder is measured to be c0, c1, c2, c3 and c4, and the powder is tested by the second law of Fick Fitting to obtain a chloride ion diffusion coefficient Dm of the current time;
Judging whether the chloride ion concentration at the position which is away from the upper surface h of the sample reaches 1.4% of the chloride ion concentration limit value, and if so, recording the test time as time t m when the chloride ion concentration at the position which is away from the upper surface h of the sample reaches 1.4%, wherein the steel bars start to be corroded, and the concrete structure is damaged;
the calculation formula of the life expectancy t of the existing concrete structure is as follows:
The unit is unified as month
Wherein Dm is the diffusion coefficient of chloride ions under an indoor simulation test, and the unit is m2/s;
d is a chloride ion diffusion coefficient under a field real environment, the unit is m2/s, and the chloride ion diffusion coefficient is obtained by an electric quantity method or a field sampling method;
t m is the time for the chloride ion concentration at the position, which is away from the upper surface h of the sample, of the indoor simulation test to reach 1.4%, and the expected service life t of the concrete structure in the real environment can be obtained after the parameters are introduced;
The environment where the existing concrete structure is located is divided into three types, namely, concrete in an atmosphere area, concrete in a dry-wet alternating area and concrete in an underwater area, wherein the concrete in the atmosphere area is contacted with salt in air and is not directly contacted with seawater, the concrete in the dry-wet alternating area is only partially contacted with seawater, and the underwater area is positioned below a horizontal plane and is immersed in the seawater throughout the year.
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