IMPACT OF VARIOUS ADDITIVES ONTO MORPHOLOGY OF GYPSUM CRYSTALS

Vestnik MGSU 4/2012
  • Ustinova Yuliya Valer'evna - Moscow State University of Civil Engineering (MSUCE) +7 (499) 183-32-92, Moscow State University of Civil Engineering (MSUCE), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
  • Sivkov Sergey Pavlovich - D. Mendeleyev University of Chemical Technology of Russia (MUCTR) 8 (495) 496-92-38, D. Mendeleyev University of Chemical Technology of Russia (MUCTR), 20 Geroev Panfilovtsev str., Moscow, 125047, Russian Federation; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
  • Barinova Ol'ga Pavlovna - D. Mendeleyev University of Chemical Technology of Russia (MUCTR) +7 (495) 496-93-40, D. Mendeleyev University of Chemical Technology of Russia (MUCTR), 20 Geroev Panfilovtsev str., Moscow, 125047, Russian Federation; opbar@rambler.ru; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
  • Sanzharovskiy Aleksandr Yur'evich - D. Mendeleyev University of Chemical Technology of Russia (MUCTR) +7 (495) 496-93-40, D. Mendeleyev University of Chemical Technology of Russia (MUCTR), 20 Geroev Panfilovtsev str., Moscow, 125047, Russian Federation.

Pages 140 - 144

Nowadays, functional additives represented by multiple classes of substances and compounds, including polymers of different origin, are available for introduction into dry mixtures based on gypsum binders. However, their impact onto the growth and formation of calcium sulfate dihydrate (CaSO∙2HO) crystals generated in the course of hardening of gypsum binders is not quite clear. Therefore, the objective of the research was to analyze the processes of growth and formation of calcium sulfate dihydrate crystals caused by functional additives based on polymers of different origin. The analysis was composed of three stages.
At the first stage, both pure and modified calcium sulfate dihydrate crystals were synthesized. Super plasticizers based on sulfonated melamine-formaldehyde resin, methylcellulose (MC) and redispersible polymer powder based on copolymer of vinyl acetate, ethylene and vinyl chloride (VAEVC) were applied as additives. At the second stage, the objective was to identify the influence of polymer additives on the shape and size of calcium sulfate dihydrate crystals; therefore, an X-ray analysis of synthesized crystals was performed. Following the X-ray analysis data and with the help of a special software programme, possible combinations of simple forms of CaSO∙2HO were simulated, and the habitus of generated crystals was also studied. At the third stage, the objective was to validate the models of calcium sulfate dihydrate crystals by means of an electron-microscopic analysis.
The following conclusions were made upon completion of the research:
A. It has been identified that additives based on polymers of different origin affect the processes of crystallization, the size and shape of gypsum crystals. The presence of the super plasticizer based on sulfonated melamine-formaldehyde resin, methylcellulose and redispersible polymer powder based on a copolymer of vinyl acetate, ethylene and vinyl chloride, causes reduction of the size of crystals, while the crystals turn elongated. The crystal-to-crystal contact area increases; therefore, it is likely that the strength of the hardening agent goes up.
B. It has been demonstrated that the X-ray analysis can be applied to simulate the shape and habitus of crystals.

DOI: 10.22227/1997-0935.2012.4.140 - 144

References
  1. Korneev V.I., Zozulya P.V., Medvedeva I.N., Bogoyavlenskaya G.A., Nuzhdina N.I. Retsepturnyy spravochnik po sukhim stroitel'nym smesyam [Book of References and Recipes of Dry Building Mixtures]. St. Petersburg, Kvintet Publ., 2010, 308 p.
  2. Izotov V.S. Khimicheskie dobavki dlya modifikatsii betona [Chemical Additives to Modify the Concrete]. Moscow, Paleotip Publ., 2006, 244 p.
  3. Mishra R.K., Flatt R.J., Heinz H. Molecular Understanding of Directional Surface and Interface Tensions of Gypsum and Calcium Sulfate Hemihydrate. Proceedings of the XIII ICCC International Congress on the Chemistry of Cement, Madrid, Spain, 3-8 July, 2011.
  4. Kristallograficheskaya i kristallokhimicheskaya baza dannykh dlya mineralov i ikh struk-turnykh analogov [Crystallographic and crystal-chemical database of minerals and their structural counterparts]. Available at: http://database.iem.ac.ru/mincryst/rus. Date of access: 04.02.2012.

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STUDY OF CRYSTALLIZATION OF CALCIUM SULFATE DIHYDRATE THAT HAS POLYMER ADDITIVES

Vestnik MGSU 7/2012
  • Ustinova Yuliya Valer'evna - Moscow State University of Civil Engineering (MSUCE) +7 (499) 183-32-92, Moscow State University of Civil Engineering (MSUCE), 26 Yaroslavskoe shosse, Moscow, 129337, Russian Federation; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
  • Sivkov Sergey Pavlovich - D. Mendeleyev University of Chemical Technology of Russia (MUCTR) 8 (495) 496-92-38, D. Mendeleyev University of Chemical Technology of Russia (MUCTR), 20 Geroev Panfilovtsev str., Moscow, 125047, Russian Federation; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .
  • Aleksashin Valeriy Mikhaylovich - All- Russian Scientific Research Institute of Aviation Materials Candidate of Technical Sciences, Senior Researcher, +7 (499) 263-89-02, All- Russian Scientific Research Institute of Aviation Materials, 7 Radio St., Moscow, 105005, Russian Federation; This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Pages 130 - 135

Currently, functional additives represented by many classes of substances and compounds, including polymers of different origin, are widely used in the production of dry mixtures based on gypsum binders. However, the impact of these additives produced on the formation of calcium sulfate dihydrate (CaSO42H2O) crystals in the course of the hardening of gypsum binders, is not quite clear. Therefore, the research is aimed at the clarification of the processes of growth and formation of calcium sulfate dihydrate crystals in the presence of functional additives based on polymers of different origin. The research is composed of the following stages.
At the first stage, calcium sulfate dihydrate crystals were synthesized both in the pure form and with additives. The additives included super plasticizers based on sulfonated melamine-formaldehyde resin (SMF), methylcellulose (MC) and polymer powder based on copolymer of vinyl acetate, ethylene and vinyl chloride (VAEVC). At the second stage, X-ray analysis of the synthesized crystals was performed to identify potential patterns of influence produced by polymer additives onto the shape and size of calcium sulfate dihydrate crystals. At the third stage, thermal analysis and electron microscopy methods were applied to synthesized crystals.
The research suggests the following conclusions:
A. It is identified that additives based on polymers of different origin affect processes of crystallization, the size and shape of crystals.
B. The X-ray diffraction analysis has proven that molecules of polymer additives do not penetrate into the gypsum structure and the chemical composition of the product does not change.
C. Methods of thermal analysis have proven that the introduction of polymer additives does not produce any adverse impact on the stability of gypsum crystals, if exposed to temperature fluctuations.
D. The major impact produced onto crystallization is the one of the super plasticizer based on the sulfonated melamine-formaldehyde resin.

DOI: 10.22227/1997-0935.2012.7.130 - 135

References
  1. Korneev V.I., Zozulya P.V., Medvedeva I.N. Retsepturnyy spravochnik po sukhim stroitel’nym smesyam [Cookbook of Dry Building Mixtures]. St. Petersburg, 2010, RIA Kvintet Publ., 308 p.
  2. Izotov V.S. Khimicheskie dobavki dlya modifikatsii betona [Chemical Additives to Modify Concrete]. Moscow, Paleotip Publ., 2006, 244 p.
  3. Batrakov V.G. Modifitsirovannye betony. Teoriya i praktika [Modified Concretes. Theory and Practice]. Moscow, 1998, 768 p.
  4. Mishra R. K., Flatt R. J., Heinz H. Molecular Understanding of Directional Surface and Interface Tensions of Gypsum and Calcium Sulfate Hemihydrate. Proceedings of the XIII ICCC International Congress on the Chemistry of Cement. Madrid, Spain, 3-8 July, 2011.
  5. Butt Yu.M., Sychev M.M., Timashev V.V. Khimicheskaya tekhnologiya vyazhushchikh materialov [Chemical Technology of Binding Materials]. Moscow, Vyssh. shk. Publ.,1980, 472 p.

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