Method for detecting bonding quality of post-cast and precast concrete of single-sided laminated wall

Abstract

The invention relates to the technical field of nondestructive testing of concrete structures, and discloses a method for detecting the bonding quality of post-poured and prefabricated concrete of a single-sided laminated wall. According to the method, detection points are delimited on the surface of a single-sided superimposed wall, an electrode system is arranged, an alternating current excitation signal covering a dielectric relaxation characteristic frequency band is applied, and current and voltage response data are synchronously collected to calculate a joint surface impedance spectrum. The impedance spectrum is analyzed by using a numerical fitting algorithm, an equivalent circuit model is constructed, and key element parameters such as interface capacitance and charge transfer resistance are extracted. By comparing the parameters with a preset qualified threshold range, the bonding quality of the bonding surface is accurately evaluated, and the method has the advantages of non-invasiveness, high efficiency, high precision and the like.

Claims

1. A method for testing the bond quality between cast-in-place and precast concrete in a single-sided composite wall, characterized in that, The method includes: Multiple detection points are marked on the surface of a single-sided composite wall. An electrode system is arranged at each detection point. The electrode system includes a pair of conductive electrodes that contact the post-cast concrete and the precast concrete surface respectively. The pair of conductive electrodes spans the interface between the post-cast and precast concrete. An alternating current excitation signal is applied through the electrode system, and the signal frequency range covers the dielectric relaxation characteristic band. Synchronously acquire current and voltage response data, and calculate the impedance spectrum of the junction surface; The impedance spectrum is analyzed using a numerical fitting algorithm to construct an equivalent circuit model and extract component parameters, including interface capacitance and charge transfer resistance. The component parameters are compared with a preset acceptable threshold range. If the parameter values ​​meet the threshold requirements, the bonding quality of the joint surface is deemed acceptable; otherwise, it is deemed unacceptable.

2. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 1, characterized in that, The AC excitation signal is generated by a function generator. The signal waveform is a sine wave, and the frequency range is linearly scanned from low frequency to high frequency, covering the dielectric relaxation characteristic frequency band of the concrete interface. The voltage amplitude of the excitation signal remains constant; During signal application, opto-isolators are used for electrical isolation, and digital signal processors control the step interval and dwell time of frequency scanning.

3. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 1, characterized in that, The calculation of the impedance spectrum includes: Windowed Fast Fourier Transform is performed on the current and voltage response data to obtain the voltage spectrum in the frequency domain. and current spectrum ,in Angular frequency; Then calculate the complex impedance. Its expression is .

4. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 3, characterized in that, The impedance spectrum is further processed by wavelet transform for noise reduction, and the real part is extracted. and the virtual part ,in , The imaginary unit; A preliminary fit was performed using the Cole-Cole model, and its impedance expression is as follows: in, It is a DC resistance. For high-frequency limiting resistance, Let be the relaxation time constant. The distribution coefficient characterizes the interfacial dispersion effect.

5. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 4, characterized in that, The numerical fitting algorithm employs nonlinear least squares optimization based on the Levenberg-Marquardt algorithm, with the objective function... Defined as: in, For frequency points, and For the first Experiments were conducted at various frequency points to measure the real and imaginary parts of the complex impedance. and For the first Calculate the real and imaginary parts of the complex impedance using an equivalent circuit model at each frequency point. and This represents the variance of the experimental measurements.

6. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 5, characterized in that, The numerical fitting algorithm uses the differential evolution algorithm to search for initial values ​​of parameters; Goodness of fit was evaluated using the Akaike Information Criterion (AIC), and its calculation formula is as follows: in, The number of parameters in the equivalent circuit model. It is the sum of squared residuals; The posterior probability distribution of the algorithm's output parameters is used to quantify uncertainty.

7. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 6, characterized in that, The equivalent circuit model adopts a distributed component structure, and its total impedance Represented as: in, For the resistance of the solution, Interface capacitance, For charge transfer resistor, For geometric inductance, The impedance of a constant-phase element.

8. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 7, characterized in that, The impedance of the constant phase element Defined as: in, For constant phase element coefficients, The diffusion index; The equivalent circuit model further considers the interface roughness effect and introduces the fractal dimension. The diffusion index is corrected, and the relationship is as follows: .

9. The method for detecting the bond quality between cast-in-place and precast concrete in a single-sided composite wall as described in claim 8, characterized in that, The comparison of component parameters with a preset acceptable threshold range includes: For interface capacitance Determine whether its value is within the threshold range. Inside; For charge transfer resistance Determine if its value is less than the threshold. ; If all parameters simultaneously meet the threshold requirements, the bonding quality is deemed acceptable; otherwise, it is deemed unacceptable.

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