Investigation On The Phase Transformation Of Iron Ores In Concrete Under Aggressive Environment

At present,the research on the application of iron tailings in concrete was mainly aimed at its influence on concrete performance,and few studies had been done on the stability of iron ore.This paper mainly studied the chemical stability of iron ore in tailings when iron tailings were applied in concrete,revealed the phase transformation and its regularity of iron ore in concrete under eroded environment.This paper mainly studied the changes of pyrite,magnetite,hematite,ilmenite and limonite in concrete,and carried out two parts of experiments:The first part,five kinds of iron ores were immersed in 5%NaCl solution,simulated pore solution containing NaCl and 5%Na₂SO₄ solution respectively,at 20°C and 80°C,and then air was introduced.The second part,hardened paste specimens containing five kinds of iron ores were corroded in 5%NaCl solution and 5%Na₂SO₄ solution at 20°C and 80°C respectively.By means of XRD,SEM and EDS the mineral and micro-morphology changes of iron ore were studied.The following results were obtained:1)In 5%NaCl solution,pyrite did not react.Fe₃O₄ in magnetite,hematite and ilmenite was oxidized to hematite;ilmenite in ilmenite ore was oxidized to hematite and titanium dioxide.The oxidation of iron ore containing ferrous ions was the main reaction.2)In NaCl-containing simulated concrete pore solution,pyrite reacted to produce clinopyrite and fibrinite,magnetite reacted to produce pyroxene and perovskite,hematite reacted to produce striped pyroxene and peridotite,ilmenite reacted to produce titanium dioxide,perovskite olivine,perovskite and potassium titanium oxide,and limonite reacted to produce pyroxene.Increasing temperature accelerated the reaction rate.3)In 5%Na₂SO₄ solution,pyrite reacted to form jarosite.The oxidation of iron ore in magnetite ore,hematite ore and ilmenite ore mainly takes place.4)The surface of hematite ore,ilmenite ore and limonite ore in hardened paste eroded by chloride and sulfate showed no signs of corrosion,and there was no iron-rich product in the interface transition zone,which could exist stably in the age.Figure 71;Table 7;Reference 51.