Study On Corrosion Testing Of HOC Grouting Material In Sulfate Environment

In recent years,with the rapid development of Chinese economy and the expansion of large-scale infrastructure projects,adverse effects on the environment are inevitable.To meet the needs of the nation and society to meet the needs of the nation and society,we must increase the capacity of the society,strengthen the awareness of green environment protection and promote the healthy development of civil engineering.As far as grouting materials are concerned,the new type of cement-based grouting materials with low energy consumption and low pollution is one of the development trends of grouting materials in the future.In this paper,a new type of green cement-based grouting material（HOC）is formed on the basis of optimizing the optimal ratio of high belite sulphoaluminate cement（HBSC）,ordinary portland cement（OPC）and metakaolin（CMK）.According to the environment of HOC grouting material,the corrosion law of the material immersed in single sulfate solution and the influence of chloride salt on sulfate corrosion law are studied The appearance,quality change,compressive strength,electrochemical impedance spectroscopy,XRD,SEM and other indicators of the specimens before and after corrosion were analyzed,and the corrosion degree and corrosion mechanism of the specimens were evaluated and studied:（1）By analyzing the results of soaking test of single sulfate solution and sulfate chloride solution are analyzed,the erosion process of the test block after soaking changes from the inside to the outside,namely,the cement ash-light blue-the dark blue,the boundary between the cement gray and the blue is obvious,and the blue area is the corrosion part.The corrosion depth of the test block was positively correlated with the age.Under the single sulfate corrosion,the mass of the test block increases the most when the sulfate concentration is 55g/L;the case of sulfate chloride mixed corrosion,with the increase of chlorine concentration,the weight of sample block increases.（2）By analyzing the test results of mechanical properties after soaking in single sulfate solution and sulfate chloride combined solution,it is concluded that the compressive strength of the test block increases continuously during the test period;under single sulfate corrosion,with the increase in chloride concentration,the range of pressure resistance increases first,then decreases,and the peak strain decreases first and then rises;und er sulphate chloride,corrosion combines with the increase in chloride concentration,the increased range of pressure resistance increases first and then decreases,and the peak strain decreases first and then increases the increase in pressure strength decreases,the voltage strain curve shifts to the right,and the peak load decreases gradually.（3）By analyzing the Nyquist diagram of EIS,it is concluded that the diameter of high frequency semicircle in the Nyquist diagram increases first and then decreases with the increasing concentration of sodium sulfate in the solution under single sulfate corrosion in the same age.Under the combined corrosion of sulfate and chloride,the high frequency semicircle diameter of the test block immersed in the control group is larger than that of the test block immersed in the test group.For the test block immersed in the combined solution,the high frequency semicircle diameter decreases with the increase of sodium chloride concentration.（4）By analyzing the electrochemical impedance parameters,it is concluded that the impedance parameters Rs and Rct are increasing with age;under single sulfate corrosion,with the increase of sodium sulfate concentration,the impedance parameters Rs and Rct show a trend of first increasing and then decreasing;under sulfate chloride combined corrosion,the parameters Rs and Rct of the test block immersed in single corrosion solution are higher than those immersed in combined corrosion solution The parameters of the material are large,and Rs and Rct increase with the increase of Na Cl content in the solution.（5）By analyzing the results of XRD and SEM tests,it is concluded that the main products of single sulfate corrosion are AFt and C-S-H gels.Because of the presence of SO₄^2-,there is no AFm.Under the combined corrosion of sulfate and chloride,the formation of AFt is promoted due to the presence of chloride salt,which promotes the formation of Friede’s salt,that is,the main products are AFt,C-S-H gel and Friede’s salt.（6）By analyzing the relationship between impedance parameters,fractal dimension and compressive strength,it is concluded that there is a significant linear correlation between compressive strength and impedance parameters Rs and Rct1;there is also a good corresponding relationship between compressive strength and pore integral dimension D,both of which also show a positive linear correlation.Based on the new equivalent circuit model,it is feasible to test the compressive strength of cement mixture according to the fitting parameters Rs and Rct1 of EIS.