Abstract
The newly developed compositions of raw mixtures for clinker production contain minimized amounts of coloring oxides and are controlled by a specially designed computer program CLINKER. The study used various types of enriched carbonate, aluminum- and silica-containing raw materials from different parts of Ukraine to reveal the peculiarities of coagulated structures and phase transformations of dispersions. It has proved that control of the parameters of coagulated structures of slurry dispersions (such as viscosity, fluidity, and kinetic stability) is essential for optimizing raw mixture compositions for wet and combined production of white Portland cement. We have assessed the effect of mineralizing additives necessary to intensify clinker sintering on the characteristics of the slurry coagulated structure and identified the peculiarities of clinker minerals С 3 S, C 2 S, C 3 A, C 4 AF, and C 12 A 7 that are formed in burning the novel raw mixtures. In addition, we have proved that optical and physical properties of crystalline phases are related to clinker whiteness and traced how burning raw mixtures based on the oxide system CaO–Al 2 O 3 –SiO 2 results in crystalline phases with a relatively lower refractive index of the optically isotropic and transparent mayenyte C 12 A 7 (Ng=2.85–2.90) as a factor of increasing clinker whiteness. The supplied example shows how to obtain clinker with increased whiteness (80–83 %) by intensifying the synthesis of C 12 A 7 , C 2 AS, and C 3 A.
Highlights
The new compositions of mixtures are based on enriched raw materials that ensure obtaining white Portland cement whose main characteristics meet DSTU B V.2.7-257:2011, whereas whiteness meets the standards of leading manufacturers (EN 197-1:2011 and ASTM C 150)
The study has proved the effectiveness of the developed computer program CLINKER in a rapid specifying of the composition of a raw mixture for white Portland cement clinker and analyzing how the projected whiteness depends on the set characteristics of the material, provided the kinds and concentration of raw materials are varied
By implementing the designed program we have determined the versions of raw mixtures with minimized contents of coloring oxides in clinker – from 0.74–0.77 to 0.11–0.13 wt. %
Summary
Owing to its high decorative properties, performance characteristics and numerous areas of practical application, white Portland cement is an advanced material of the 21st century. The development of non-metallic ore industry in Ukraine has ensured the production of new varieties of mineral raw materials with various enrichment rates The efficiency of these varieties for the production of white Portland cement can be estimated after close study and analysis of differences in their chemical and mineralogical compositions. The world experience in producing white Portland cement is based on the technological requirements to minimize contamination of raw materials and clinker, increase the temperature of clinker burning up to over 1450 °C, use special operations for clinker bleaching at the final stage of its burning and cooling, and improve the final product’s fineness [4]. Since the reviewed studies lack attention to the effect of optical and physical properties of clinker minerals on the degree of clinker and cement whiteness, it becomes a relevant aspect of this research
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