SVIBOR - Project code: 2-15-124

MINISTRY OF SCIENCE AND TECHNOLOGY

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tel.: +385 1 459 44 44, fax: +385 1 459 44 69
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Project code: 2-15-124


Process research in the field of silicate, oxide and similar systems


Main researcher: KRSTULOVIĆ, RUŽA (24032)


Assistants
Type of research: developmental
Duration from: 01/01/93. to 12/31/95.
Papers on project (total): 49
Papers on project quoted in Current Contents: 3
Institution name: Tehnološki fakultet, Split (11)
Department/Institute: LABORATORY OF INORGANIC TECHNOLOGY AND METALLURGY INSTITUTE OF CHEMICAL ENGINEERING
Address: TEHNOLOŠKI FAKULTET,TESLINA 10/V
City: 21000 - Split, Croatia
Communication
Phone: 385 (0)21 341-633
Fax: 385 (0)21 341-624
E-mail: krstul@mateh.tehst.hr
Summary: The project proposed examined some silicate, oxide and carbonate materials such as cement, asbestos-cement, alumina and calcium carbonate. Their reaction kinetics and mechanisms have been examined as they play an important role in individual phases of technological processing such as hydration, dehydration, adsorption, precipitation and phase transformations. The microcalorimetrical method was used to monitor cement hydration. Measurements of results - for heat of hydration - were used to calculate kinetic parameters affecting the process. UV-spectrophotometry and conductometry were used to examine the mechanism of adsorption of organic polymeric admixtures in cement and in synthetic solutions of pure ionic species and admixtures, and their mixtures similar to those contained in cement. The effect of asbestos on cement hydration intensity was examined calorimetrically (the thermos flask method), as well as adsorption of calcium hydroxide on asbestos fibers. A computer used a mathematical model to provide a calculation for obtaining the optimum asbestos mixture out of different asbestos mixture types as compared to the asbestos mixture taken to be the standard. Processes of dehydroxylation of aluminium hydroxide and oxyhydroxide as same as the phase transformations of calcium carbonate polymorphs (vaterite, aragonite/calcite) have been examined. Basic kinetic parameters of the aforesaid processes (k, n, Ea) were determined. The precipitated calcium carbonate was prepared by different methods. The kinetic and the mechanism of the process of carbonation of milk of the lime and of calcium-nitrate solution of monoethanolamine (MEA) were examined by variation of starting materials as same as the process parameters (T, reactant concentration, additives, system hydrodinamic...). The optimal conditions of the process related to the rate of the carbonation process and the properties of CaCO3 obtained (size and crystal size distribution, morphology, specific surface, phase composition, chemical purity...) were determined.

Keywords: cement, azbestos cement, boehmite, gibbsite, calcium carbonate, admixtures, hydrata-tion, dehydratation, adsorption, precipitation, crystallization, additives, image analysis, kinetic, mechanism, calorimetry, morphology, thermal analysis, spectrophotometry, conductivity

Research goals: The objective was to contribute to theoretical understanding of heterogenious reacti-ons in solid-liquid systems and to apply that knowledge to real systems such as hydration in cement (in the presence of admixtures) and asbestos-cement, dehydration and dehydroxylation of aluminium hydroxide and oxyhydroxide, and precipitation of calcium carbonate with specific physical, chemical and structural properties. THE RESULTS: Admixtures introduced into cement hydration only modify some kinetic parameters. In the accelerated hydration period the hypothetic process mechanism, described by Avrami equation with one dominant process taking place, was confirmed. The pre-exponential factor (A) in the Arrhenius equation changes its value relative to the type of admixture used. The conductograms obtained show that there exist an interaction of some ionic species and superplastificator-type admixtures in synthetic solutions and in cement, and that it depends on ion type and the relation analyte: admixture. Hydration is more intensive in the accelerated hydration period in the presence of asbestos. The highest reaction rate occurs at the time of formation of the largest quality of the CH-phase. The number of molecules adsorbed per asbestos surface unit in calcium hydroxyde solutions (order of magnitude 10 e 18) proves high affinity of asbestos to cement particles. This explains the effect of different particle size and asbestos origin on asbestos-cement hydration. A redefined linear programming model (in TurboPascal 5.5) provided a mathematical model for choosing the optimum asbestos mixture for asbestos-cement materials. The processes of dehydroxylation of aluminium hydroxide and oxyhydroxide and the phase transformation of the calcium carbonate polymorphs (vaterite, aragonite/calcite) have been examined by thermal methods (TG, DSC) under non-isothermal conditions. The kinetic parameters were determined by mathematical analysis of the experimental TG and DSC curves using the stationary point theory. Conditions for precipitation of calcium carbonate with different crystal morphology, crystal size distribution and different chemical purity by carbonation of different solutions (milk of lime, calcium nitrate solution of monoethanolamine) were determined. The chemical and physical properties of the PCC were determined by different methods and techniques (chemical analysis, Meigen assay, XRD, FTIR, SEM, BET, microsieves, laser diffraction...). The possibility of application of image analysis for morphological characterization of PCC samples was examined.

COOPERATION - PROJECTS


  1. Name of project: Quantification of Crystal Shape Using Image Analysis
    Name of institution: Laboratoire des Sciences du G‚nie Chimique-CNRS-ENSIC-INPL
    City: 54001 - Nancy, Francuska

COOPERATION - INSTITUTIONS


  1. Name of institution: Government Industrial Research Institute, Kyushu
    Type of institution: State institute
    Type of cooperation: Occasional exchange of information
    City: Tosu, Japan

  2. Name of institution: Institut "Ruđer Bošković"
    Type of institution: State institute
    Type of cooperation: Joint publishing of scientific papers
    City: 10000 - Zagreb, Croatia

  3. Name of institution: Fakultet kemijskog inženjerstva i tehnologije Sveučilišta u Zagrebu
    Type of institution: University/Faculty
    Type of cooperation: Systematic exchange of information
    City: 10000 - Zagreb, Croatia

  4. Name of institution: RH DRŽAVNI ZAVOD ZA NORMIZACIJU I MJERITELJSTVO
    Type of institution: Institution whose primary activities ar
    Type of cooperation: Systematic exchange of experts
    City: 10000 - Zagreb, Croatia

  5. Name of institution: Hochschule fr Architektur und Bauwesen
    Type of institution: University/Faculty
    Type of cooperation: Occasional exchange of information
    City: Weimar, Njemačka

  6. Name of institution: pit‹anyagok Tansz‚k, Budapesti Mszaki Egytem pit‹m‚rn‹ki Kar
    Type of institution: State institute
    Type of cooperation: Systematic exchange of information
    City: Budapest, Hungary

  7. Name of institution: Silik tk‚mi i ‚s Technol˘giai, Tansz‚k Veszpr‚mi Egyetem
    Type of institution: University/Faculty
    Type of cooperation: Occasional exchange of information
    City: Veszpr‚m, Hungary

  8. Name of institution: Laboratoire des Sciences du G‚nie Chimique
    Type of institution: State institute
    Type of cooperation: Joint project
    City: 54001 - Nancy, Francuska

  9. Name of institution: Schaefer Kalk
    Type of institution: Economical/Production
    Type of cooperation: Other
    City: Diez/Lahn, Njemačka

OTHER ACHIEVEMENTS


  1. Name: Tehničko-tehnološko rješenje obrade otpadne vode iz pogona pocinčavanja d.d. "Poliscom"-Split
    Type of achievement: Studies of conduct
    Authors: J. Perić, P. Krolo, J. Zelić, M. Vučak, P. Dabić, A. Beroš
Other information about the project.
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