Study On Performance And Microstructure Of Shield Muck Solidified By Alkali-activated Blast Furnace Slag

With the development of subway construction in China,shield muck has become the main source of urban solid waste,with small particles,high water content and certain mobility.The discharge of shield muck will not only occupy land resources,but also lead to a series of environmental and safety problems.Therefore,it is of great ecological significance and economic value to study the solidification and recycling of shield residue Compared with the traditional cement materials,alkali activated slag is an alternative cementitious material with high strength,low energy consumption and low pollution,which has a better application prospect.It is an effective way to activate industrial solid waste such as slag by using alkali activator so as to realize its resource functionBased on cscec-2018-z-1,the key technology and industrialization research of Metro residue treatment,combined with the shield construction project of Changfeng station and Xinyuan station section of Changsha Metro Line 6,this paper studies the performance and microstructure of the shield residue produced by the project solidified by alkali activated slag cementitious material,in order to realize the resource utilization of shield residue and slag use for reference.The main research work and results are as follows:Geotechnical tests were carried out to measure the physical properties such as moisture content and particle grading of fully weathered slate shield muck.The chemical composition and mineral composition of fully weathered slate shield muck and blast furnace slag were tested by XRF and XRD,respectivelyThrough laboratory tests,the effects of slag/slag ratio,liquid/solid ratio,water glass/sodium hydroxide solution ratio,molding pressure,and curing temperature on the mechanical properties of solidified muck were studied.The results show that when the compressive strength of the solidified muck and the utilization rate of the shield muck are used as the evaluation indicators,the better ratio is:slag/slag ratio=30%,liquid/solid ratio=20%,water glass/sodium hydroxide solution ratio=1.5,molding pressure=10MPa,curing temperature=60?,28d compressive strength can reach 31.76MPaXRD results show that the main products of alkali-activated blast furnace slag solidified muck are C-S-H and C-S-A-H.SEM results show that with the increase of slag content,the structure of solidified muck is denser and fewer defects;EDS results confirm that the products C-S-H and C-S-A-H are evenly distributed.The microstructure analysis conclusion is basically consistent with the change trend of compressive strength and bulk density.In order to study the durability of solidified muck,freeze-thaw tests,chemical erosion tests and thermal stability studies were carried out.The results show that the frost resistance level of the solidified muck is at least D25;the solidified muck has excellent resistance to sodium sulfate corrosion and poor resistance to sulfuric acid and hydrochloric acid;the strength of the solidified muck did not decrease significantly when the temperature was below 600?.