Caracterização de pastas minerais

Abstract

Important participation in the world mining usines have winninig the tailings disposition system in form of paste. In the particular case of Brazil, this tendence is more comum everyday, remplacing the convencional system of disposition of tailings in large dam embankments in form of minerals slurries. The paste disposition form presents various advantages: lower capital and operations costs, lower enviromental impacts, higher water recuperations for recicly in the process, higher mine recuperations. A mineral paste can be defined as well colloidal system equivalent to homogeneus liquidus, without solid particulate segregation, no presents significatives water losses when softly disposit on stable surface. The minerals pastes can be disposited superficially (pastefill) or filled underground cavities (backfill). Higher mine recuperations can be reached to use backfill te be usefull mineral processing wastes. Other alternative can be used is rockfill process, wichmisture waste rock and tailings pastes. Normally, these minerals pastes are cemented with binder, the clasic portland cement, or successly more economical alternatives: fly ash, metakaolim, lime, etc. As minerals pastes characterics can be mencionated are viscosity, shear stress, yield stress, slump, repose angle, compression and shear resistances, permeability, etc. This work objective was rheological, physical and chemical characterization of mineral pastes prepared with different tailings of iron mineral processing origined of Minas Gerais ferriferous quadrilate. As principals conclusions of this work can be destacated:- The minerals pastes viscosity incresed in direct relationship to solidsconcentration, with equivalents operation conditions, resulting pastes more viscous in contrast with those preparared with a sample II (slimes of cyclosizing). - In reference to rheological behavior of pastes preparared with original and blended samples, a sample III (flotation tailings) showed reotropic pastes if compared with others studied pastes. Blended pastes present more tixotropic, whereas sample II (slimes) pastes present both reotropic and tixotropic behavior. - Slump test showed fine distribution size samples requered highest waterproportions to form mineral paste (slump batween 0 and 100%).- In the flume test was determinated for higher slopes of plane produz lower studied pastes repose angles, for lower solids concentrations more gradual drop have in repose angles. Angles rised up to 15° in laboratory tested pastes. - For cemented pastes with 4 and 8% of Portland cement observed characteric behavior with ups and downs in the curves of instantaneous stress with time. - A use of blended with metakaolin and lime how mineral paste binder permited solids particle aglomeration, while a Portland cement adition higher yield stress can be reached because formed concrete structures.