Study On Mineral Admixture Of Concrete Prepared With Kaolinite-pyrite Cinder

This paper reviewed the characteristics, production and har m ofthe kaolinite-pyrite cinders. The present utilization of kaolinite-pyritecinders research status was introduced in detail.Chemical composition, phase, particle size distribution andstructure of kaolinite-pyrite cinders were studied. The results show thatmain components in kaolinite-pyrite cinders were Fe₂O₃, SiO₂andAl₂O₃, accounting about90%of the total kaolinite-pyrite cinders. Themain phases were composed by metakaolinite, hematite and anatase.Natural grain size greater than0.18mm accounted for87.6%.Metakaolinite and he matite exist in the form of intergrowth particles.Liberation degree of he matite is99%in grain size0.109mm⁰.096mm.Magnetic separation effe ct and pozzolanic activity ofkaolinite-pyrite cinders calcined under different te mperatures and atdifferent times were studied. The results show that hema tite can beeffectively reduce to magnetite, but also metakaolinite can be activatedmagnetic roasting for30min at800℃. Total iron content ofconcentrate of magnetic separation can reach the requirements for thethree-grade standard in national standards （GB/T25953-2010）. Tailingsof magnetic separation that were mainly consists by metakaolinite havehigh pozzolanic activity, which strength activity index was more than84%. It is obtained that tailings with s maller particles have highpozzolanic activity.Tailings were used as a concrete admixture results show that thefluidity and collapsed slump of concrete containing tailings werereduced. The setting time of concrete containing tailings was increased.Early strength of concrete included tailings was lower than thereference concrete, but28days the strength of concrete that content oftailings is less than15%can be more than the reference concrete. Thehydration mechanism analysis showed that the tailings can reduce heat hydration of concrete, react with Ca（OH）2in the late of hydration.This method using kaolinite-pyrite cinders has advantages of lowcost, high efficiency, no secondary pollution, high utilization, reducingthe environmental pollution, which conforming to the national policy ofenergy-saving, reducing emission and recycling resources. Moreover, itprovides a new road for high efficiency and environment friendlycomprehensive utilization of low-grade kaolinite-pyrite.