Study On The Substitution Tendency Of Heavy Metal Ions In Sulphoaluminate Cement Clinker

As a kind of low-carbon environmentally friendly cement,sulphoaluminate cement has excellent characteristics such as:good corrosion resistance,high early strength,fast setting rate,low unit carbon emission,and wide application prospects.It has been received extensive attention from researchers in the cement industry.At present,natural raw materials are mainly used to prepare sulphoaluminate cement clinker,which consumes a lot of natural resources and is costly.Using industrial solid waste to replace some raw materials to prepare sulphoaluminate cement clinker can not only reduce the cost.,It can also treat solid waste,which is one of the current research hotspots.However,because industrial solid waste contains more heavy metal ions,it may affect the performance of sulphoaluminate cement clinker after being mixed,however,the current doping mechanism is not clear enough,and research is urgently needed.This paper studies the substitution tendency and doping mechanism of Ba and Pb in sulphoaluminate cement clinker.Mainly through backscattered electrons and X-ray diffraction detection methods combined with density functional theory simulation,the research results are as follows:（1）Ba ions tend to replace the Ca sites in C₄A₃S,this substitution tendency can be explained by changes in electronic properties such as partial density of states,electron density difference and local distortions.Since Ba and Ca belong to the same main group of elements,their electronic structure is less different,and Ba replaces Ca sites in C₄A₃S,the local distortion produced is small.（2）Pb ions tend to replace the Ca sites in C₄A₃S and cause distortion of the crystal lattice,making the（422）,（444）and（066）crystal plane spacing smaller,resulting in the shift of the peak position of XRD.The distribution of Pb in the element distribution is basically the same as that of S,indicating that Pb is well dissolved into C₄A₃S.The doping mechanism is confirmed by theoretical simulation analysis,and the Pb ion doping mechanism is obtained.Which follows the principle of electronic adaptation,Pb and Ca have similar electronic structures.This paper contains a total of 32 pictures,12 tables,and 64 references.