Influence Of Adjusting Admixture To The Hydration And AC Impedance Behavior Of Ordinary Portland Cement

Among the several techniques of investigation at present,those based on monitoring the electrical properties during the initial setting and in the subsequent hardening period appear to be very promising.The electrical methods have advantages over other methods in terms of sensitivity and speed.Moreover,D.C.or single-frequency a.c.measurements test may not be reliable techniques for studying changes in bulk conductance with time,complex impedance spectra can separate out bulk and electrode and obtain much useful informations.The purpose of this study is to explore the mechanism of EDTA and anhydrous sodium caubonate to ordinary Portland cement in the process of hydration.Then AC impedance method was used to study the hydration of ordinary Portland cement,which aims to establish the relationship between electrochemical parameters and the tradional hydration parameters,and to lay a foundation for the application of AC impedance technology in the cement hydration research.This study primarily researches the influence of two kinds of chemical admixtures-EDTA and andyrous sodium carbonate on the hydtation process of ordinary Portland cement,then compressive strength,setting time,hydration degree,chemical shrinkage,hydration heat of Portland cement were determined.Then,the ion concetration of pore solution which was obtained by squeezing method was determined,Meanwhile,By using DTA-TG and XRD techniques,the anthor studies the effect of EDTA and natrium carbonicum calcinatum on the characteristics of hydration products at the micro level.At last,the action mechanism of EDTA and natrium carbonicum calcinatum on hydration process of Portland cement is analyzed according to the test result.Subsequently,the hydtation process of ordinary Portland cement was studied by AC impedance method.Firstly,the author made a periodic measurement of ac impedance of Portland cement in the progress of hydration.,then the equivalent circuit of GU was choosed to sumulate the ac impedances which were obtained by electrochemical workstation,preliminary analysis was performed on the fitting data;on this basis,an effective method to get the bulk resistance was put forward from the ac impedance spectrum.According to the resistivity curves of cement,the hydration was divided into five stages,and further studies was performed on the resistivity of cement accompying EDTA and anhydrous sodium cement.Finally,by comparing and discussing the results obtained by the AC impedance and traditional hydration research method,the relationship between bulk resistivity and other parameters such as compressive strength,setting time,hydration degree,chemical shrinkage and hydration heat has been studied;on this basis,the broader application of AC impedance technology in cement hydration is prospected.