Application Of Ti-extracted Residues In Magnesium Oxychloride/Oxysulfate Cement

Magnesium oxychloride magnesium oxysulfide cement is an aerosetting cementitious material formed by active magnesium oxide and a certain concentration of magnesium chloride/magnesium sulfate aqueous solution,which has the advantages of light weight,wear resistance,low thermal conductivity and so on.However,the poor water resistance of mgo/mgo cement restricts its application in construction,roads and other industries,so it is particularly important to improve the performance of mgo/mgo cement.In addition,panzhihua and other regions in sichuan province are rich in vanadium-titanium magnetite.However,after the treatment of vanadium-titanium magnetite,the tailings contain a very high concentration of chloride ions,which will corrode steel bars and pollute the environment.Therefore,the comprehensive utilization of titanium tailings is very important.In order to improve the performance of mgo/mgo cement,this paper USES various admixtures to modify mgo/mgo cement respectively,and analyzes the influence of various admixtures on the strength,water resistance,chloride ion dissolution rate and setting time of mgo/mgo cement.The changes of phase composition,microstructure,pore structure and thermal stability of tartaric acid-modified magnesium oxychloride cement were systematically analyzed by means of XRD,FTIR,SEM,MIP,tg-dsc and other detection equipment.In addition,according to L9(34) orthogonal test and comprehensive balance method,the optimal ratio of modified agents to improve the performance of mgo/mgo cement was selected.The results show that the water resistance of pure mgo/mgo cement is extremely poor.Tartaric acid,citric acid,phosphoric acid and alum can improve the performance of magnesium oxychloride cement.According to the orthogonal test,the optimal proportions of the four modifiers are: 1% tartaric acid,0.5% citric acid,1%phosphoric acid and 1% alum.After adding the composite modifier,the strength of magnesium oxychloride cement decreased to 82.4 mpa on 28 days,the chloride ion dissolution rate decreased to 1.32% on 28 days,and the strength retention coefficient increased to 0.94 after 28 days of immersion.In addition,tartaric acid,citric acid and phosphoric acid can also improve the strength and water resistance of magnesium sulfide cement.But styrene-acrylic emulsion did not improve its strength and water resistance.According to the orthogonal test,the optimal ratio of compound modifier is: 0.5% tartaric acid,0.5% citric acid,0.5% phosphoric acid and 1% styrene-propylene emulsion.After adding the composite modifier,the strength of magnesium sulfide cement increased to 85.3 MPa in 28 days,and the strength retention coefficient increased to 0.93 in 28 days after soaking.In order to obtain the alkali magnesium cement products with better performance,the compound modifier was added into the alkali magnesium cement with titanium tailings,the influence of the compound modifier on the performance of the alkali magnesium cement with titanium tailings was analyzed,and the optimal formula ofthe alkali magnesium cement with titanium tailings was obtained.In addition,according to the standard of basic magnesium cement product industry,the feasibility of titanium residue extraction in magnesite industry was analyzed.The test results show that the alkali magnesium cement products mixed with titanium tailings are not suitable for practical production and application.After adding the corresponding composite modifier into magnesium oxychloride/magnesium oxysulfide cement with 50% content of titanium extraction tailings,the compressive strength was reduced to 69.6mpa and 68.4mpa on 28 days,respectively.The dissolution rate of chloride ions in 28 days decreased to 1.64% and 0.44%,respectively.The strength retention coefficient was increased to 0.86 after 28 days of immersion.In addition,the light partition slabs of magnesium oxychloride cement and the decorative slabs of magnesium oxysulfide cement respectively prepared by the above experimental formulas meet the requirements of the standards,which proves that titanium tailings can be applied in magnesite industry.