Collaborative Preparation Of Unburned Building Materials From Red Mud,Gold Tailings And Shale

The storage of red mud,tailings and other industrial solid wastes not only occupies valuable land resources,but also pollutes urban groundwater and brin gs troubles to residents' living environment.In addition,there are huge reserves of shale in mines and mountains,which often lead to landslides and debris fl ows and affect people's driving safety.Therefore,it is urgent to solve such en vironmental and safety problems.3D printing building materials and non-burnin g brick materials provide convenience for the preparation of green and energysaving materials from solid waste.Common solid waste in cities and surroundi ng areas can be comprehensively utilized,thus reducing the cost of raw materi als and transportation,and saving energy and environmental protection.This dis sertation mainly uses red mud,tailings and shale as the main raw materials to prepare 3D printing building materials and non-burning bricks,including:(1)us ing red mud,fly ash and iron tailings to produce 3D printable building materi als;(2)coordinated preparation of unburned bricks by gold tailings and surroun ding rocks in the tailings mountain;(3)using large amount of shale in the mo untain to prepare building materials of unburned bricks.The three materials are produced by adding a large amount of industrial solid wastes,which has certa in social and economic benefits.The physical properties,mechanical properties,microstructure and heavy m etal leaching properties of red mud/fly ash/tailings based 3D printable building materials were studied.The results show that the mortar material consisting of 15% red mud,45% tailings,9% fly ash,30% cement and 1% FDN water red ucer has good physical and mechanical properties.The initial setting time and final setting time were 80 min and 130 min,respectively,the fluidity was 205 mm,and the 28-day flexural and compressive strength were 11.91 MPa and 39.1 MPa,respectively,satisfying the basic requirements of 3D printable buildin g materials.Through SEM observation,the hydration products of this material are mainly calcium hydroxide,ettringite and C-S-H gel.The tailings are used as fine aggregate to be wrapped by C-S-H gel in the hardened matrix,and the cementing matrix is closely bonded with the aggregate.The results of leaching toxicity test show that the developed 3D printable building materials are enviro nmentally acceptable.The mechanical properties of gold tailings/surrounding rock unburned brick s were systematically studied.The effects of curing method,raw material additi on and ratio of aggregate to cementitious material on mechanical properties of unburned brick were discussed.It is found that dry curing is more suitable for gold tailings/surrounding rock unburned brick than wet curing.It is beneficial t o the steady growth of its mechanical properties.When the dosage of gold tail ings was 45% with surrounding rock of 30% and aggregate to cementitious ma terial ratio of 1.2,the mechanical properties of unburned bricks of gold tailings were the best,reaching 25.63 MPa.In addition,the effects of curing method,molding pressure and aggregate to cementitious material ratio on mechanical pr operties of shale bricks without burning were studied.The results show that w et curing is more suitable for the shale unburned brick.When the molding pre ssure is 45 KN and the aggregate to cementitious material ratio is 0.16(shale 65% and tailings 5%),the 28-day strength of the shale unburned brick is the highest,which can reach 37.32 MPa.