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In order to reveal the dielectric properties of the nonaqueous reactive polyurethane grouting material, combined with the electron microscope test analysis, it can be seen that the nonaqueous reactive polyurethane material is a porous two-phase body composed of a polyurethane matrix and closed cells. At the microscopic scale, the porous two-phase physical model is established, and the dielectric model of the material is constructed on this basis. In order to verify the dielectric model, 40 groups of nonaqueous reactive polyurethane specimens with different densities were designed and prepared in this paper. The dielectric permittivity was measured by a vector network analyzer (VNA) with an open coaxial probe within the frequency range of 1050 MHz~5010 MHz for the first time, and the dielectric properties and influencing factors were revealed according to the test data. The result shows that the dielectric permittivity of nonaqueous reactive polyurethane materials increases with the increase of density, and decreases slightly with the increase of frequency. Compared with the three models of the Rule of Mixture, Clausius-Mossotti Model and Lichtenecker Model, the calculation accuracy of the Maxwell-Garnett Model is higher, and the calculation results are more consistent with the experimental results of nonaqueous reactive polyurethane grouting materials. The experimental results can be applied to the nondestructive testing of polyurethane grouting materials and provide reference and basis for the quality evaluation of polymer structures.

The dielectric properties of cement concrete are not only related to the dielectric properties and volume ratio of each component, but also related to frequency and temperature. In order to analyze these influencing factors, a dielectric constant test was done in the laboratory. Experimental results show that the dielectric constants decrease linearly with temperature increasing and decreases exponentially with the increase of frequency. Based on the experimental rules, a new dielectric model including frequency and temperature is established and verified by experiments. The verification results show that the calculation accuracy of the comprehensive dielectric model after considering the influence of frequency and temperature is improved by 25.5%, which meets the requirements of engineering detection accuracy. The model is applied to engineering practice, and the calculation methods of pavement structural layer thickness and moisture content are developed. The results show that the comprehensive dielectric model established in this paper has smaller error and higher accuracy. Using this dielectric model, the data conversion between different frequency and temperature can be achieved. The research results of this paper can provide reference and basis for the quality evaluation of concrete structures.

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