Research On The Dielectric Constant Model Of Cement Concrete Considering Chloride Effect

Cement concrete is a common construction material and is widely used in various engineering fields.It is a composite material composed of several different materials.Its dielectric constant is mainly related to the dielectric constant of the constituents,the volume fraction of the constituents,the chloride content,the frequency,and the external temperature,reflecting the dielectric constant of the composites and the above effects.The formula for the relatio nship between factors is the composite dielectric model.If the dielectric constant model of cement concrete is established,the dielectric constant can be measured based on the non-destructive testing technology to realize the detection of the pavement quality parameters such as structural layer porosity,moisture content and chloride.Therefore,based on the theory of electromagnetic wave propagation,establishing the dielectric model of cement concrete is the basis and key to the inspection of cement concrete pavement.In view of the different dielectric properties of various composite materials,scholars at home and abroad have conducted extensive research and established dielectric constant models suitable for their respective research fields.However,there are few dielectric models for cement concrete.At the same time,various dielectric models have been established under certain assumptions,without considering the effects of chloride content,temperature and frequency,which will inevitably cause errors and affect the accuracy of measurement.Based on the electromagnetic wave propagation theory,this article has established a dielectric model considering chlorides based on the theory of electromagnetic wave propagation and studied the effects of chloride,temperature,and frequency.Based on the measured experimental data,the above-mentioned newly established dielectric model was verified.At the same time,the detection accuracy of the existing classical dielectric constant models(linear model,rms model,Rayleigh model)in concrete is also verified.The main research contents and conclusions are as follows:(1)Based on theoretical analysis and experimental research,the influencing factors of the dielectric constant of cement concrete are analyzed.The results show that the dielectric constant is not only related to the volume fraction and dielectric constant of its constituents,but also related to the chloride,temperature and frequency of cement concrete.Among them,the dielectric constant and the chloride content are approximately linearly increasing,that is,as the chloride content gradually increases,the dielectric constant also gradually increases;the dielectric constant decreases linearly with increasing temperature;the dielectric constant increases with frequency It decreases exponentially.(2)Based on the influence laws of various factors,an integrated dielectric model for cement concrete considering chloride,temperature,and frequency was established.(3)Based on the measured test data,the established model of integrated dielectric constant was verified.The results show that compared with the existing common models,linear models and Rayleigh models,the integrated dielectric model established in this paper has high precision and is suitable for describing the dielectric properties of cement concrete.