Research of possibilities for use domestic kaolin clays for production of metakaolin

U oblasti građevinarstva, u svetu se intenzivno istražuju mogućnosti primene novih materijala kojima se može supstituisati deo klinkera u Portland cementu ili deo cementa u betonskim mešavinama. Novi materijali treba da zadovolje zahteve u pogledu održivog razvoja, a njihova primena ne sme negativno da utiče na karakteristike materijala. U ovom radu se govoriti o jednom takvom materijalu metakolinu (MK). Osnovna i najčešće korišćena sirovina za proizvodnju MK je kaolinska glina iz koje se MK proizvodi kalcinacijom ili 'termičkom aktivacijom'. Od karakteristika polazne gline zavise mogućnosti njene primene za dobijanje MK. U radu su dati rezultati ispitivanja hemijskog i mineraloškog sastava, kao i termičkih karakteristika uzoraka gline uzetih iz fabrika Kaolin a.d, Valjevo i Keramika, Mladenovac.Environmental concerns coming from the high energy consumption and CO2 emission associated with cement production have brought about pressures to reduce cement consumption through the use of new materials which can be applied for substitution of a part of clinker in Portland cement or a part of cement in concrete. One of the materials that satisfy requirements of sustainable development and, when added in appropriate shares, improves the properties of cement, mortars and concrete, is metakaolin (MK), a processed pozzolana. The main and widely used raw material for production of metakaolin is kaolin clay. MK is produced by calcination or 'thermal activation' of kaolin clay. The possibilities for metakaolin production are strongly related to the characteristics of the used kaolin clay. The samples of domestic kaolin clay used in this study were provided by factories Kaolin, Valjevo, and Keramika, Mladenovac. Chemical composition, mineralogical composition and thermal properties of these samples were determined. Thermal analysis (simultaneous recording of TG, DTG and DTA signals) was carried out at the temperature range from 20 to 1200 °C. For both clays the results show that the loss of mass occurred in two stages. The dehydroxillation of kaolinite and formation of metakaolin occurred in the second stage. Minerals quartz and kaolinite are dominant in the clay Kaolin, Valjevo. Dehydroxillation of kaolinite and formation of metakaolin took place in the temperature range 350-800 °C. This clay does not have clearly distinct exothermic and endothermic peaks. Clay from Keramika, Mladenovac, has a higher content of the kaolinite mineral, i.e. 81.51%. The dehydroxillation of kaolinite and formation of metakaolin occurred in the temperature range 400-700 °C. This clay has two distinct endothermic peaks at 60 and 490 °C. All these results show that both clays can be used for production of metakaolin