Preparation And Performance Of Iron Tailing Ceramsites And Baking-free Bricks

Mining industry is the basis of the economy providing the enriched resources of the human survival.However,the utilization efficiency of the mining is low producing a large amount of tailing.The generated tailing takes great pollution to atmosphere,water and soil.Therefore,it is of importatant research significance to comprehensively utilize the tailing.The composition and structure of the iron tailing was systemly analyzed.The iron tailing ceramsites and baking-free bricks were prepared.The influences of the iron tailing content and preparation parameters on the performance of the iron tailing ceramsites and baking-free bricks were investigated.The optimal iron tailing content and preparation parameters were determined.The iron tailing ceramsites and baking-free bricks with high performance using iron tailing as the main resource can solve the problem of the difficult treatement and environmental pollution of the iron tailing which is of important economical and social significance for the comprehensively utilization of the solid waste.The main composition of the iron tailing（mass percentage）is listed as follows:Si O₂ 41.98%,Mg O 18.09%,Fe₂O₃ 11.92%,Ca O 10.03%,Al₂O₃ 9.59%,P₂O₅ 3.33%,K₂O 2.82%,Ti O₂ 0.519%,Na₂O 0.485%.The particle size distribution range is 39 nm-101μm.The detailed particle distribution is listed as follws:101-50μm 5.68%,50-25μm 15.51%,25-10μm 30.97%,10-5μm 22.29%,5-1μm 22.31%,1-0.039μm 3.22%.The iron tailing is composed of hexagonal Si O₂,cubic Fe₂O₃,orthorhombic Al₂O₃,triclinic Ca₃（PO₄）₂,orthorhombic Ca CO₃ and cubic Mg O phases.The main composition of the iron tailing distributes in the iron tailing particles with different sizes.The structure and micro-morphology of the iron tailing with different particle sizes are similar.Particle size has no effect in the composition,structure and micro-morphology of the iron tailing.The optimal sintering parameter for the tailing ceramsites,iron tailing/sludge ceramsites and iron tailing/sludge/fly ash ceramsites is 1100℃for 30 min.The stacking density,cylinder compressive strength and softening factor of iron tailing ceramsites are 1245.56 kg·m^-3,14.3 MPa and 0.94.The optimal composition of the iron tailing/sludge ceramsites is listed as follows:Iron tailing 90wt.%,sludge 10wt.%.The stacking density of the iron tailing ceramsites is 1036.57 kg·m^-3.And the cylinder compressive strength and softening factor are 10.1 MPa and 0.87.The optimal composition of the iron tailing/sludge/fly ash ceramsites is listed as follows:Iron tailing70wt.%,sludge 10wt.%,fly ash 20wt.%.The stacking density of the iron tailing ceramsites is 1036.57 kg·m^-3.And the cylinder compressive strength and softening factor are 9.5 MPa and 0.87.XRD patterns of the iron tailing ceramsites show that the Ca Si O3,Al2Si O5,Mg Si O₃,Ca₂Fe₂O₅,Ca₇Si₂P₂O₁₆ and Ca Al₂Si₂O₈ phases are formed when the sintering temperature is 700℃.The obtained iron tailing ceramsites are mainly composed of Ca Si O₃,Al₂Si O₅,Mg Si O₃,Ca₇Si₂P₂O₁₆,Ca Al₂Si₂O₈ and Ca₂Fe₂O₅phases when the sintering temperature and duration time increase to 1100℃and 30min,respectively.SEM observation shows that the ceramsites are composed of loose particles and pores with microscale and sub-microscale size when the sintering temperature is lower than 900℃and duration time is 10 min.Dense and irregular large size particles with several dozens of micrometers exist in the ceramsites besides irregular particles with the size of lower than 10μm when the sintering temperature and duration time increase to 1000℃and 30 min.The ceramsites are composed of dense structure and pores with the size of lwer than 50μm and the cylinder compressive strength increases obviously when the sintering temperature increases to1100℃.The optimal component is listed as follows:65wt.%iron tailing,5wt.%titanium gypsum,17wt.%slag,5wt.%acetylene sludge,8wt.%waste brick powder.The optimal forming pressure is 10MPa.The density of the iron tailing solid brickds is 1529.08kg·m^-3 and 28 d compressive strength is 17.9 MPa.The density of the iron tailing hollow bricks is 895.35 kg·m^-3 and 28 d compressive strength is 9.4 MPa.The iron tailing baking-free bricks are mainly composed of hexagonal Ca₆Al₂（SO₄）₃（OH）₁₂·26H₂O（Aft）and orthorhombic Ca₅Si₆O₁₆（OH）₄·4H₂O phases after the baking-free bricks were curved for 28 d.Residue hexagonal Si O₂,cubic Fe₂O₃,orthorhombic Al₂O₃,triclinic Ca₃（PO₄）₂,orthorhombic Ca CO₃,cubic Mg O and monoclinic Ca SO₄·2H₂O phases.The hydration products including Aft and orthorhombic Ca₅Si₆O₁₆（OH）₄·4H₂O promote the strength enhancement of the iron tailing baking-free bricks.Micro-morphology analysis shows that the iron tailing baking-free bricks are composed of irregular particles and Aft nanorods with the diameter of 200 nm,length of 2μm.The content of the Aft nanorods increases with increasing the curving time and forming pressure.The Aft nanorods and microscale particles connect with each other forming dense structure and promoting the enhancement of the strength of the iron tailing baking-free bricks.