Study On Activation Process And Technical Index Classification Of Iron Tailings

Iron tailings are solid wastes left after iron ore separation,but the problems of low utilization rate and environmental pollution are more prominent in highway engineering.As a kind of special stone material,iron tailings are unstable and usually active.There are certain differences between iron tailings and general engineering aggregates,which limit the scope of use.Based on the reconstruction and expansion project of Shanxi National Highway 108,this paper studies the iron tailings as cement active mixture,and selects appropriate technical indicators to study the performance classification of domestic iron tailings in highway engineering.In this paper,the basic properties of the five iron tailings collected were studied,mainly including the chemical composition,phase composition,crushing value and acid-base resistance of iron tailings.Due to the high activity of industrial waste residue ore itself,the importance of acid-base resistance cannot be ignored,but there is no requirement in the existing specifications.Therefore,the common limestone and granite in the construction are used as the control to evaluate the acid-base resistance of iron tailings.Then,from the macro and micro perspectives,the mortar strength method and lime adsorption method are used to study the activity values of the five iron tailings,and the activity level is comprehensively evaluated.It is considered that the iron tailings with low activity can be used as aggregates,and the iron tailings with high activity can be used as cement active mixture.Based on the project,using Shanxi red iron tailings and Shanxi blue iron tailings as raw materials,the cement-iron tailings cementitious system and large amount of iron tailings cementitious system were studied.The results show that the key time of grinding iron tailings is 30 min by mechanical grinding test,and the key sieve hole affecting the activity of iron tailings is 20 μm.The best cement-iron tailings cementitious material ratio is determined by orthogonal test : 20 % dosage of iron tailings + 0.4 water cement ratio + 1:1 red and blue iron tailings ratio.The optimum water-binder ratio and curing temperature were determined to be0.44 and 50 ℃,respectively.For the gelling system with large amount of iron tailings,the optimal chemical active activator is 4 % sodium silicate or 15 % fly ash.In view of the lack of technical evaluation index of iron tailings in existing norms,this paper selects chemical composition,crushing value,acid and alkali resistance,radioactivity,burning loss,boundary moisture content,free expansion rate,particle size distribution and other technical evaluation indexes through research results and combined with existing norms,and puts forward the classification standard of several iron tailings in the field of highway engineering based on multi-level classification method.