Study On Pozzolanic Activity Of Lithium Slag From Lithium Mica In Yichun And Its Effect On The Performance Of Cement And Concrete

The lithium mica accompanying with tantalum-niobium ore is the largest lithium resource in the world.After extracting lithium from lithium mica,an amount of solid waster residue was produced（short for lithium slag）.Therefore,the development of the application of lithium slag in cement and concrete has great significance for the utilization of the lithium slag as well as environment protection.In this paper,different methods have been applied to compare the pozzolanic activity of lithium slag and some common admixtures.Also,the influence on cement and concrete performance by adding lithium slag alone and adding lithium slag mixtures（lithium slag + slag powder,lithium slag + fly ash）are discussed.In addition,the mixing amount of lithium slag impact on shrinkage,chlorion penetration resistance,carbonation resistance and abrasion resistance of concrete have also been researched.The interface structure of lithium slag was observed by SEM and the orthogonal experiments was conducted,producing the C70 high-strength concrete as well as the optimization of the mixture ratio of lithium slag concrete.Accordingly,following conclusions can be reached:（1）The primary chemical composition of lithium slag are SiO₂ and Al₂O₃,XRD results show that the main phase of lithium slag is analcite.The pozzolanic activity of lithium slag was investigated by pozzolanicity test,pozzolanic activity index,hydration rate method,selective dissolution method and TG-DTA method.As a result,the lithium slag have a greater pozzolanic activity compared with calcined gangue,fly ash and granite powder.（2）The lithium slag can significantly increase water requirement of normal consistency and delay setting time.Also,it makes more contributions to strength than fly ash,but less than slag powder.However,adding the mixture of lithium slag and slag powder is better than adding lithium slag or slag powder alone.（3）A small amount of lithium slag has thickening effect,which can improve flowability,cohesiveness and water retentiveness of concrete.When the amount of lithium slag exceeds 20%,the flowability will reduce gradually as the amount of lithium slag increases.（4）The lithium slag is of high quality admixture of concrete.The concrete possesses the best mechanical behavior while the amount of lithium slag is 20% approximately.（5）As the amount of lithium slag is lower than 20%,Shrinkage,chlorion penetration resistance,and abrasion resistance of concrete will be increased along with the amount of lithium slag increasing,however,decreasing of carbonation resistance of concrete will be encountered.（6）The lithium slag can improve the interface structure of common concrete.Compared with concrete without lithium slag,a remarkable reduction of CH and a number of C-S-H gel could be observed at interface,which appeared even tighter,in the concrete with 20% lithium slag.