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Joaquin Bastida, Universidad de Valencia (UVEG) (Spain)
Alberto Lazaro, Universidad de Valencia (UVEG) (Spain)
M. Mar Urquiola, Universidad de Valencia (UVEG) (Spain)
Rafael Ibaņez, Universidad de Valencia (Spain)
Pablo Pardo, Universidad de Valencia (UVEG) (Spain)
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Products made of fine ground or micronised carbonates of high purity (impurities <3%, and particle size <45 μ) are known as calcium carbonates in the industrial minerals market. GCC (ground calcium carbonate) and PCC ( precipitated calcium carbonate) are distinguished according to their production processes. In the European market the products obtained from dolostones are not included in that definition.
Papers, plastics and coats are their traditional markets, and PCC and GCC are rivals in paper and plastic manufacture. Marble wastes are also used in Italy as well as in Spain to produce GCC. World consumption in 2004 for that markets were 39, 18 and 7% respectively of 57.4 MTm.
The mining and processing of marbles in quarries and factories produce wastes of marble rocks and stones, and sludges. Fragmentary rocks and stones can be used for agregate production but also to obtain ground calcium carbonate (GCC) that can be marketed as different products (dry micronised,surface-treated or not , slurry).
This communication shows results of simplified X Ray diffraction microstructural analysis (to characterize "crystallinity" of carbonate minerals) and colorimetric measurements in the monitoring and technological evaluation for ground grades from mechanical sizing of marble waste aggregates as well as for sludges from processing, in marble productive areas of Spain (Alicante and Almeria) and for comparative samples of GCC from Spanish chalks.
Laboratory tests of high energy grinding were performed on a vibrating cup mill (Fritsch Pulverisette 9) at different grinding times. Materials were analysed by powder X Ray Diffraction (Bruker D5000 equipment). Particle size distributions in the range 0.06 - 2000 μ, were obained by laser diffraction (Mastersizer 2000, Malvern Instruments). Colorimetric measurements in a Minolta CR-400 colorimeter (xenon lamp, Si detector, standard observation CIE 1931, and L*, a*, b* , values, referenced to UNE 80117 standard).
FWHM values for 104 reflection (that of greater intensity ) of calcite show clear differences for the used raw materials. The evolution of calcite crystallinity in ground carbonates of laboratory tests is studied. Similar FWHM values to that of some commercial GCC from Spanish chalks had been measured for sludges and ground marbles. That is relevant because the obtained microstructural parameters has been found in previous papers as indicative for the monitoring of milling as well as in the evaluation of the opacification performances of the obtained fillers.
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