Research On White Composite Portland Cement Using Lithium Slag From Lithium Mica By Chlorine Salt Autoclaving Technology

The lithium mica mine accompanying with tantalum and niobium mine is China’slargest raw material base of tantalum,niobium and lithium. The chlorine saltautoclaving technology of extracting lithium from the lithium mica is currently thetechnique of the lowest cost in our country. But it generates a lot of pressure-leachingwaste(referred to as “lithium slag” below).Its disposal and comprehensive utilizationis of great importance in clean production and energy conservation.The lithium slag was produced in the process of extracting lithium slag from thelithium mica by "the chlorine salt autoclaving method" in Jiangxi Ganfeng lithiumcompany.This article focuses on lithium slag used as mixing material in whitePortland cement. The activity of the original lithium slag and lithium slag after heattreatment was tested in volcano ash experiment and comparative strength experiment.The activity level of lithium slag was estimated by comparing with the pozzolanicactivity of shale, fly ash and other materials. The strength of white portland cementmixed with lithium slag or slag,and re-mixed lithium slag and slag were tested inthis paper. The chemical means to stimulate the activity of lithium slag was studied,such as alkali-activated, sulfate-activated, AlCl3-activated and limestone-activatedand so on, and the activity of activated-lithium slag with different preparationprocess in white cement was compared. Using analyzing measurement such as XRDand SEM to describe the white Portland cement’s hydration products andmicrostructure of the hardened cement paste were researched in this paper.Then wediscussed the microscopic mechanism to stimulate the activity of lithium slag andcement reinforced and prepared the composite white portland cement of physical andmechanical properties which meet the requirements of national standard.From volcanic ash experiment and comparative strength experiment, we foundthat lithium slag had good pozzolanic activity; that thermal activation for the purposeof further enhancing the activity of lithium slag did not work.The strength of whitecement single-doped with lithium slag was significantly decreased with increasingcontent of the lithium slag, while the strength of the cement single mixed with the slag was increased.Co-doped with lithium slag and slag can significantly reduce thenegative impact of lithium slag on the white cement’s strength, which cansignificantly increase the admixture amount of lithium slag.Limestone can stimulatethe activity of lithium slag,by mixing lithium slag grinding process, making lithiumslag-slag cementitious composite system achieve the best activity. When the totaldosage of lithium slag and slag is70%, compressive strength after28days is up to35.2Mpa,compressive strength ratio is up to82%. Its initial and final setting timehas reduced significantly to improve the lithium slag less-clinker cement long-settingtime problem. The hydration hardened paste’s microstructure is more dense comparedwith non-doped white cement.Its tensile bond strength is0.87MPa. It has a greataffluence compared to white-finishes cement in market. The lithium slag-compositeportland cement prepared in the study can extensively use lithium slag, and all of thetechnical performances meet national standards, thus it has broad applicationprospect.