Experimental Study On High Silicon Iron Tailings Effect On Concrete Workability And Compressive Strength

This thesis takes high silicon iron tailings as the object of study (tailings are from QiDa Moutain, AnShan, Liaoning Province) and carries out performance testing and analysis, including analysis of tailings' chemical component analysis, mineral composition analysis, particle size analysis, and activation analysis. The results show that the main chemical component of the tailings is SiO2, major mineral composition quartz, grading above 100 micron accounts for 50%, and it has no volcanic ash activation.The composite gelatinized material which is composited from high silicon iron tailings after mechanical chemistry activation and cement has similar water requirement of normal consistency and initial and final setting time with cement, and the stability is qualified. Based on the chemistry basic principle of mechanical force, tailings studied in this thesis are carried out mechanical grind and particle size is 12.231 micron after grinding. XRD shows that after grinding crystallization degree of SiO2 decreases obviously, amorphous number increases, the volcanic ash activation is qualified.High silicon iron tailings after mechanochemical activation are used as supplementary cementing material of concrete and take place of cement in concrete batching at a certain ration. The influence of the tailings on workability and compressive strength of concrete mixture is explored through experiments. Test results of workability show that with the increase of tailings, the slump of concrete mixture reduces significantly, but the adhesiveness and water retention of concrete mixture increases significantly. Concrete mixture with 20% tailings instead of cement could meet the requirement of slump. Test results of compressive strength show that with the increase of tailings replacing cement, strength of concrete declines in different degrees. Tailings instead of cement less than 30% could meet the requirement of designed strength C30. The compressive strength of concrete could be improved significantly with water reducing agent, and by that time, tailings instead of cement amounts to 40% and could still meet the requirement of designed strength C30.Phase and microscopic test analysis of cement paste and tailings-cement hardened pastes are carried out through XRD and SEM. The results show that diffraction maximum of Ca(OH)2 always appears in net cement slurry when comparison carries out in the same age. Meanwhile, SEM shows that with the increase of age, the surface of unreacted tailings particles is gradually covered by hydration products that mainly are C-S-H comparing with cement slurry in the same age, and Ca(OH)2 is rarely observed in cement slurry. According to the basic theory of gelatinized material and mechanochemical activation tailings performace, secondary hydration reaction happens in tailings cement pastes.