Non-Destructive Characterization And Quantitative Analysis Of Hydration Process Of Cement-Based Materials

The hydration process of cement-based materials is vitally important because it has direct effects on the macroscopic properties and microstructure of the cement-based materials.However,due to the complexity of the hydration process of cement-based materials,the whole hydration process of cement-based materials still do not fully understood.In addition,most of the testing methods currently used to study the hydration process of cement-based materials are destructive,which will cause the damage of the sample during the test,so these methods cannot be used to track the hydration process of cement-based materials continuously and it is also impossible to visualize the changes of the microstructure of cement-based materials during hydration.Therefore,to further study the hydration process of cement-based materials,electrochemical impedance spectroscopy and X-ray computed tomography are used to track and analyze the entire hydration process of cement-based materials.The main findings are as follows:?1?The hydration process of cement-based materials was studied by electrochemical impedance spectroscopy,and the electrochemical impedance spectroscopy curves was fitted and analyzed by a novel equivalent circuit model.The results show that the novel equivalent circuit is more suitable for studying the hydration process of cement-based materials.?2?The hydration process of cement-based materials was studied by electrochemical impedance spectroscopy with the novel equivalent circuit model.The experimental results show that the electrochemical impedance behaviour of cement-based materials is closely related to the curing ages,water-cement ratio and the amount of mineral admixtures such as fly ash and slag.With the increase of the curing ages,the R_ct1t1 value?the transfer resistance of ions in cement-based materials?increases,leading to the increase of the radius of the semicircle;the R_ct1t1 value and the radius of the semicircle decrease with the increase of the water-cement ratio;the R_ct1t1 value and the radius of the semicircle decrease with the increase of the amount of fly ash and slag.?3?The relationship between R_ct1t1 and microstructure and macroscopic mechanical properties of cement-based materials was analyzed.The evolution of the R_ct1t1 value and the compressive strength of cement-based materials is similar and they have a good linear relationship.?4?The hydration process of cement paste was studied by X-ray computed tomography.The experimental results show that the three-dimensional distribution and morphological changes of pores,hydration products and unhydrated cement particles within the cement paste can be visualized clearly.?5?Based on the gray value histogram of the image,a novel quantitative analysis method,deconvolution method,is used to analyze the hydration characteristics of the cement paste quantitatively.Compared the degree of hydration of the cement paste obtained by the chemical combination water with the results obtained by the deconvolution method,it can found that the results obtained by the deconvolution method is close to the results of the chemically bound water,which demonstrate that the deconvolution method is a feasible and effective method.