Nondestructive evaluation method for corrosion degree of reinforced concrete structure

Abstract

The invention discloses a nondestructive evaluation method for the corrosion degree of a reinforced concrete structure. An ultrasonic sensor is installed on the surface of a test piece; electrifying the test piece for electrochemical accelerated rusting, starting ultrasonic signal acquisition equipment, and recording ultrasonic signals at different moments; according to the relation between the power-on time and the steel bar corrosion rate, the steel bar corrosion rate corresponding to different moments is calculated; calculating to obtain relative wave velocity changes and decorrelation coefficients corresponding to different steel bar corrosion rates; establishing a function relationship between the steel bar corrosion rate and the relative wave velocity change and the decorrelation coefficient; and acquiring ultrasonic signals of an initial state and a certain unknown state of the reinforced concrete structure, calculating the relative wave velocity change and the decorrelation coefficient in the state, and substituting the relative wave velocity change and the decorrelation coefficient into the function relation to obtain the steel bar corrosion rate of the current state of the reinforced concrete structure. According to the method, sampling on the existing structure is not needed, the existing structure cannot be damaged, in-situ evaluation of the corrosion degree of the reinforced concrete structure can be achieved, the evaluation time is short, and the operation and maintenance cost can be greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of reinforced concrete structure monitoring, and particularly relates to a non-destructive assessment method for the corrosion degree of reinforced concrete structures. Background Art

[0002] In the prior art, two methods are generally used to evaluate the corrosion of reinforced concrete structures: the probe method and the AC impedance method.

[0003] The probe method detects steel corrosion by placing probes in corrosion-risk areas. The corrosion products (non-conductive) produced during the corrosion process reduce the cross-sectional area of the steel that is electrically conductive, increasing its resistance. By measuring this change in resistance, the corrosion rate can be inferred. This method allows for real-time data collection, is simple to operate, and allows for easy data analysis. It is widely applicable, but is insensitive to early-stage corrosion.

[0004] The AC impedance method uses the impedance spectrum to analyze the changes in the electrical properties of steel bars after corrosion, which can be used to determine the corrosion status of the steel bars. This method is accurate and repeatable, but in practice it is time-consuming and requires repeated data analysis, making it inefficient. Furthermore, the instrumentation used in the AC impedance method is expensive. Summary of the Invention

[0005] The purpose of the present invention is to provide a non-destructive assessment method for the degree of corrosion of reinforced concrete structures. It does not require sampling on existing structures and will not damage existing structures. It can realize in-situ assessment of the degree of corrosion of reinforced concrete structures, and the assessment time is short, which can greatly reduce operation and maintenance costs.

[0006] To achieve the above object, the present invention provides a method for nondestructive assessment of the corrosion degree of reinforced concrete structures, comprising the following steps:

[0007] S1. Construct reinforced concrete structures and make a batch of test pieces made of the same material at the same time;

[0008] S2. Soak the specimen in a chloride solution;

[0009] S3. Install ultrasonic sensors on the reinforced concrete structure and the surface of the specimen;

[0010] S4, energizing the test piece to perform electrochemical accelerated corrosion;

[0011] S5, connect and start the ultrasonic signal acquisition device, start synchronously with S4, and record the ultrasonic signal U at that moment every 12 hours. i , the ultrasonic signal at the initial moment is recorded as U0;

[0012] S6. Calculating the steel corrosion rate corresponding to different times based on the relationship between the power-on time and the steel corrosion rate;

[0013] S7, carry out signal analysis, U i The relative wave velocity changes and decorrelation coefficients corresponding to different steel bar corrosion rates were obtained by cross-correlation calculation with U0;

[0014] S8. Establish the functional relationship between the steel bar corrosion rate, relative wave velocity change and decorrelation coefficient during the corrosion process of the specimen;

[0015] S9, collecting ultrasonic signals of the reinforced concrete structure in an initial state and an unknown state, and calculating the relative wave velocity change and decorrelation coefficient in the state;

[0016] S10. Substitute the relative wave velocity change and decorrelation coefficient obtained in S9 into the functional relationship in S8 to calculate the steel corrosion rate of the reinforced concrete structure in the current state.

[0017] As a further solution of the present invention: in S2, the test piece is immersed in a chloride salt solution with a mass fraction of 5% for 7 days.

[0018] As a further solution of the present invention: the calculation formula of the steel bar corrosion rate at different times in S6 is as follows:

[0019]

[0020] Where, t i is the i-th moment, η i is the steel corrosion rate at the i-th moment; M is the atomic mass of the corroded material; i is the corrosion current density; Z is the valence of the anode after the reaction (iron is +2); F is the Faraday constant; R is the steel diameter; ρ s The steel density is 3.

[0021] As a further solution of the present invention: the calculation formulas for the relative wave velocity change and decorrelation coefficient corresponding to different steel bar corrosion rates in S7 are as follows:

[0022]

[0023] Where U0(t) is the ultrasonic wave field when signal U0 is collected, U i (t) is the signal U i The ultrasonic wave field during acquisition, ε is the signal U i The expansion factor is the center point of the coda wave time window, ΔT is the time window length, DC is the decorrelation coefficient, and R is the cross-correlation coefficient. According to the above formula, the expansion factor ε corresponding to the maximum cross-correlation of the two signals, that is, the maximum R value, is obtained, and corresponds to the relative wave velocity change dvi / v.

[0024] As a further solution of the present invention: the functional relationship in S8 is expressed as: η=g(f1(dv / v), f2(DC)), wherein η is the steel corrosion rate, dv / v is the relative wave velocity change, DC is the decorrelation coefficient, and f and g are the fitting relationship formulas of the corrosion rate and dv / v and DC, respectively.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention uses ultrasound to monitor the corrosion process of the specimen, obtains the ultrasonic response of the specimen under different corrosion rates, and then analyzes and extracts the relative wave velocity changes and decorrelation coefficients corresponding to different steel bar corrosion rates, and the functional relationship between the steel bar corrosion rate, the relative wave velocity changes and the decorrelation coefficient. The established functional relationship is then used to infer the steel bar corrosion rate of the specimen with unknown corrosion rate.

[0027] The present invention does not require sampling from existing structures, does not damage existing structures, and can achieve in-situ assessment of the degree of corrosion of reinforced concrete structures;

[0028] The present invention utilizes ultrasonic sensors for detection, does not require complex detection equipment, and is very convenient to implement;

[0029] The present invention does not require the installation of an online monitoring system on the structure, and the assessment of the degree of structural corrosion can be completed in a relatively short time only when it is needed, thereby greatly reducing its operation and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a functional relationship diagram of the steel bar corrosion rate, relative wave velocity change and decorrelation coefficient of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below by way of examples.

[0032] A non-destructive assessment method for the corrosion degree of reinforced concrete structures comprises the following steps:

[0033] S1. While constructing reinforced concrete structures, a batch of test pieces made of the same material are produced.

[0034] S2. Soak the specimen in a chloride solution;

[0035] Furthermore, the specimens were immersed in a chloride solution with a mass fraction of 5% for 7 days.

[0036] S3. Install ultrasonic sensors on the reinforced concrete structure and the surface of the specimen.

[0037] S4. Power the test piece to perform electrochemical accelerated corrosion.

[0038] S5, connect and start the ultrasonic signal acquisition device, start synchronously with S4, and record the ultrasonic signal U at that moment every 12 hours. i , the ultrasonic signal at the initial moment is recorded as U0.

[0039] S6. Calculate the steel corrosion rate at different times based on the relationship between the power-on time and the steel corrosion rate. The calculation formula is as follows:

[0040]

[0041] Where, t i is the i-th moment, η i is the steel corrosion rate at the i-th moment; M is the atomic mass of the corroded material; i is the corrosion current density; Z is the valence of the anode after the reaction (iron is +2); F is the Faraday constant, which is F = 9.65 × 104 C / mol, also known as the Faraday constant; R is the steel diameter; ρ s is the steel density, take 7.85g / cm 3 .

[0042] S7, carry out signal analysis, U i The relative wave velocity change and decorrelation coefficient corresponding to different steel bar corrosion rates are obtained by cross-correlation calculation with U0; the calculation formula is as follows:

[0043]

[0044]

[0045] Where U0(t) is the ultrasonic wave field when signal U0 is collected, U i (t) is the signal U i The ultrasonic wave field during acquisition, ε is the signal U i The expansion factor is the center point of the coda wave time window, ΔT is the time window length, DC is the decorrelation coefficient, and R is the cross-correlation coefficient. According to the above formula, the expansion factor ε corresponding to the maximum cross-correlation of the two signals, that is, the maximum R value, is obtained, and corresponds to the relative wave velocity change dvi / v.

[0046] In this embodiment, a total of 110 sets of ultrasonic data are monitored, and signal analysis is performed on the 110 sets of ultrasonic data through S7 to obtain power-on time, relative wave velocity change and decorrelation coefficient data and draw a relationship diagram between the two.

[0047] S8. Establish a functional relationship between the steel corrosion rate, the relative wave velocity change, and the decorrelation coefficient during the specimen corrosion process; the functional relationship is expressed as: η = g(f1(dv / v), f2(DC)), where η is the steel corrosion rate, dv / v is the relative wave velocity change, DC is the decorrelation coefficient, and f and g are the fitting relationships between the corrosion rate and dv / v and DC, respectively.

[0048] The functional relationship diagram of steel bar corrosion rate, relative wave velocity change and decorrelation coefficient is obtained by fitting the functional relationship in S8, as shown in Figure 1 As shown; the fitting straight line is:

[0049]

[0050] S9. Collect ultrasonic signals of the reinforced concrete structure in an initial state and an unknown state, and calculate the relative wave velocity change and decorrelation coefficient in the state.

[0051] S10. Substitute the relative wave velocity change and decorrelation coefficient obtained in S9 into the functional relationship in S8 to calculate the steel corrosion rate of the reinforced concrete structure in the current state.

[0052] In this embodiment, dv / v = -0.0840 and DC = 0.2049 were measured for a certain state of the specimen. The steel corrosion rates of the specimen in the current state were calculated to be 8.06% and 8.22% respectively through the functional relationship in S8, and the average of the two was 8.14%. The specimen was destroyed to measure the true steel corrosion rate, and the calculated and evaluated steel corrosion rate was basically consistent with the true corrosion rate of the specimen, 7.98%.

Claims

1. A non-destructive assessment method for the corrosion degree of reinforced concrete structures, characterized in that: The following steps are involved: S1. Construct reinforced concrete structures and make a batch of test pieces made of the same material at the same time; S2. Soak the specimen in a chloride solution; S3. Install ultrasonic sensors on the reinforced concrete structure and the surface of the specimen; S4, energizing the test piece to perform electrochemical accelerated corrosion; S5, connect and start the ultrasonic signal acquisition device, start synchronously with S4, and record the ultrasonic signal U at that moment every 12 hours. i , the ultrasonic signal at the initial moment is recorded as U0; S6. Calculating the steel corrosion rate corresponding to different times based on the relationship between the power-on time and the steel corrosion rate; S7, carry out signal analysis, U i The relative wave velocity changes and decorrelation coefficients corresponding to different steel bar corrosion rates were obtained by cross-correlation calculation with U0; S8. Establish the functional relationship between the steel bar corrosion rate, relative wave velocity change and decorrelation coefficient during the corrosion process of the specimen; S9, collecting ultrasonic signals of the reinforced concrete structure in an initial state and an unknown state, and calculating the relative wave velocity change and decorrelation coefficient in the state; S10. Substitute the relative wave velocity change and decorrelation coefficient obtained in S9 into the functional relationship in S8 to calculate the steel corrosion rate of the reinforced concrete structure in the current state.

2. The non-destructive assessment method for the corrosion degree of reinforced concrete structure according to claim 1, characterized in that: In S2, the specimens were immersed in a chloride solution with a mass fraction of 5% for 7 days.

3. A non-destructive assessment method for the corrosion degree of reinforced concrete structure according to claim 1 or 2, characterized in that: The calculation formula for the steel bar corrosion rate at different times in S6 is as follows: Where, t i is the i-th moment, η i is the steel corrosion rate at the i-th moment; M is the atomic mass of the corroded material; i is the corrosion current density; Z is the valence of the anode after the reaction (iron is +2); F is the Faraday constant; R is the steel diameter; ρ s is the steel bar density.

4. The non-destructive assessment method for the corrosion degree of reinforced concrete structure according to claim 3, characterized in that: The calculation formulas for the relative wave velocity change and decorrelation coefficient corresponding to different steel bar corrosion rates in S7 are as follows: Where U0(t) is the ultrasonic wave field when signal U0 is collected, U i (t) is the signal U i The ultrasonic wave field during acquisition, ε is the signal U i The expansion factor is the center point of the coda wave time window, ΔT is the time window length, DC is the decorrelation coefficient, and R is the cross-correlation coefficient. According to the above formula, the expansion factor ε corresponding to the maximum cross-correlation of the two signals, that is, the maximum R value, is obtained, and corresponds to the relative wave velocity change dvi / v.

5. The non-destructive assessment method for the corrosion degree of reinforced concrete structure according to claim 4, characterized in that: The functional relationship in S8 is expressed as: η = g(f1(dv / v), f2(DC)), where η is the steel corrosion rate, dv / v is the relative wave velocity change, DC is the decorrelation coefficient, and f and g are the fitting relationships between the corrosion rate and dv / v and DC, respectively.

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