Mechanochemical treatment of Serbian kaolin clay to obtain high reactive pozzolana

Abstract

Mechanochemical treatment of Serbian kaolin clay was carried out in a planetary ball mill using two different milling media, hardened steel or zirconia vials and balls. The samples obtained with various milling times were characterized by the particle size laser diffraction (PSLD), X-ray diffraction (XRD), differential scanning calorimetry/thermogravimetry (DTA/TGA) and Fourier-transform infrared (FTIR) analyses. Mechanochemical treatment induced amorphization of the kaolinite phase accompanied by dehydroxylation. It was found that for the given milling parameters, amorphization mainly took place in the milling period up to 15 min, and was completed after about 30 min of milling for both milling media used. The pozzolanic activities were determined by the Chapelle method. Milling in the hardened steel milling medium had no significant influence on pozzolanic activity, even though there was accumulated iron contamination. For both milling media, pozzolanic activity of 0.79 was obtained for the samples milled for 15 min and it remained almost unchanged with prolonged milling. The determined pozzolanic activity values are close to these of commercial metakaolinite or metakaolinite obtained by the calcination of the same clay, therefore, indicating possibility for obtaining high reactive pozzolana by mechanochemical treatment of Serbian kaoline clay. [Projekat Ministarstva nauke Republike Srbije, br. TR 36017 and 45001

Reactividad puzolánica de arcillas caoliníticasuna revisión

“…The pozzolanic activity index evaluated in after 28 days with a grinding time of 60 minutes was 0.79, and 0.85 after 120 minutes. It was shown that longer grinding times produce finer materials with higher SAI, which seems to contradict the results of Mitrovic et al (2013). It would also be convenient to evaluate if the energy and economic costs of longer grinding times are justified with regard to the benefit obtained in the Pozzolanic Activity Index.…”

Pozzolanic activity of mechanochemically and thermally activated kaolins in cement

“…It should be noted that the long grinding times were specific to the low mechanical load grinding device used in this study. As shown by various other researchers [16,17,25,26], the use of more energy intensive grinding equipment such as disc mills or high speed planetary ball mills enables grinding times of less than 1 h.…”

“…In contrast, little work on the pozzolanic activity of mechanochemically activated kaolinite has been published. The scarce data available seem to indicate that the reactivity of mechanochemically activated kaolinite is similar to or slightly inferior to that of thermally activated kaolinite [25,26]. However, a general description of the effect of mechanochemically activated kaolinite on the hydration reactions and properties of blended cements is lacking.…”

Adsorption of Industrial Pollutants by Natural and Modified Aluminosilicates

“…In the first grinding stages, a decrease of particle sizes and an increase in clay surface area are observed, including variations of their porosity. Further grinding causes adhesion of the particles, followed by a decline of the specific surface area, amorphization of the structure, and change in plastic and dispersion properties of clays [19,20]. Mechanical exposure is accompanied by the new active sites appearing at the boundaries of the particles faults and an increase in cation-exchange capacity of the mineral, as often observed for kaolinite and other clay minerals.…”