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Abylova Amina Zhanabaevna,, Doctor of Technical (PhD), Senior Researcher, chemistry laboratory, Karakalpak Scientific Research Institute of Natural Sciences of Karakalpak Branch of the Academy of Sciences of the Republic of Uzbekistan E-mail: [email protected] Turemuratov Sharibay Nauryzbaevich, Ph.D., in Chemistry, Head of chemistry laboratory Karakalpak Scientific Research Institute of Natural Sciences of Karakalpak Branch of the Academy of Sciences of the Republic of Uzbekistan
E-mail: [email protected] Bekbosynova Rysgul Zhyemuratovna, Junior Researcher, chemistry laboratory Karakalpak Scientific Research Institute of Natural Sciences of Karakalpak Branch of the Academy of Sciences of the Republic of Uzbekistan
DEVELOPMENT OF TECHNOLOGY FOR PRODUCING CEMENTITIOUS COMPOSITES BASED ON GYPSUM MINERALS IN KARAKALPAKSTAN
Abstract. The chemical, physico-mechanical properties of gypsum minerals of various deposits of Karakalpakstan are investigated. Studied the colloid-chemical basis for the production ofbinders. Based on gypsum minerals, gypsum binders such as building gypsum, high-strength gypsum and extreme gypsum, as well anhydrite cement.
Keywords: gypsum mineral, building gypsum, marl, Karakalpakstan, glauconite, bentonite, high-strength gypsum, binders.
Introduction. Research on the development of new gypsum binders was carried out taking into account the specific features in the chemical and min-eralogical compositions of natural gypsum minerals in the deposits of Karakalpakstan, as well as their basic colloidal chemical characteristics.
Building gypsum is an airy binder. This type of gypsum binder can not be used for structures in contact with water, which is associated with the solubility in water of two-water gypsum formed during hardening of binders. When the gypsum is dried, its strength is restored again. As a result of the studies, the possibility of increasing water resistance by add-
ing small amounts of some surfactants to gypsum, a mixture of finely ground lime or cement, and clay minerals was established. In the literature there is evidence of an increase in water resistance when or-ganosilicon and other substances are added to gypsum [1, 464; 2, 27-36].
Study Subjects and Methods. The study subject in this work is the gypsum minerals of various deposits of Karakalpakstan and mineral fillers, which is unrivaled throughout Uzbekistan. In composition, it is close to high-grade, therefore, it can be used to obtain binders with high physico-mechanical properties.
Gypsum stone belongs to sedimentary rock; the content of calcium hydrogen sulfate in it varies from 68.4 to 93.8%. Three samples were taken for the study - from three different deposits of Karakalpak-stan, respectively, and their full silicate analysis was carried out. The study of the physicochemical and mechanical properties of gypsum binders was carried out respectively with the requirements of GOST 23789-79 and 4013-82 [3; 4].
Discussion and study results. To obtain building gypsum from natural raw materials, the following operations were carried out: crushing, grinding and firing, depending on the performance of which the following technological schemes for the production Table 1.- Physico-mechanical
of binders are possible: the first is the firing of previously crushed gypsum stone with subsequent grinding; the second - grinding previously purified from impurities of natural raw materials into a powder of the required dispersion with subsequent firing.
The study results showed that the use of the second method of obtaining gypsum binders is more profitable from an economic point of view, because this greatly reduces the time of firing gypsum stone, due to which a reduction in energy costs is achieved. It should also be noted differences in technological characteristics i.e. as a finished product. The technological characteristics of gypsum based on gypsum minerals of Karakalpakstan are given in (table 1). properties of gypsum binders
No Name of parameter Urge No. 1 Raushan No. 2 Aybuyir No. 3 Kushana-tau No. 4 Beltau No. 5 Khujakul No. 6
1. Milling fineness, screening residue 0,2% 2 3 8 2 6 6.2
2. Normal density W/G,% 52 52 57 57 51 46
3. Setting time beginning, min end, min 4 10 6 15 7 16 6 12 7 19 9 16
4. Ultimate compressive strength in 2 hours, kgf/cm2 105 84 64 73 51 35
5. Ultimate tensile strength under bending, kgf/cm2 42 39 34 34 24 16
6. Binder grade G-10 G-8 G-6 G-7 G-5 G-3
7. Metal impurities content, mg 2 3 4 3 4 8
8. Volume dilatation 0.2 0.4 0.3 0.4 0.3 0.4
9. Impurities, which are insoluble in the hydrochloric acid,% 0.5 0.8 0.9 0.8 0.9 2.8
As shown by the data given in (tablel). binders based on the Urge and Raushan deposits possess higher technological properties. To increase the operational characteristics, as well as the water resistance of gypsum binders based on them, it is
Table 2.- Physico-mechanical properties
sufficient to use WSP additives (waste from soda production) in the amount of 5 and 8%, respectively. The use of sand dune, WSP, marl also improves the water resistance of gypsum based on other studied samples several times (table. 2). of gypsum binders of the Urge deposit
No Name of parameter GВ + d/sand GВ + marl GВ + limestone GВ + ben-tonit GВ + glau-conite GВ+ WSP
1 2 3 4 5 6 7 8
1. Milling fineness, screening residue 0,2% 5 3 2 3 6 2
1 2 3 4 5 6 7 8
2. Normal density W/G,% 52 58 52 47 49 59
3. Setting time beginning, min 5 2 2 3 6 2
end, min 17 12 16 19 21 15
4. Ultimate compressive strength in 2 hours, kgf/cm2 106 122 113 54 72 143
5. Ultimate tensile strength under bending, kgf/cm2 38 53 49 21 27 58
6. Binder grade G-10 G-12 G-11 G-5 G-7 G-14
7. Metal impurities content, mg 8 7 5 7 9 6
8. Volume dilatation 0.4 0.3 0.3 0.4 0.4 0.2
Impurities, which are in-
9. soluble in the hydrochloric acid,% 1.7 1.1 0.9 1.3 1.9 2.0
The obtained experimental results make it possible to recommend gypsum minerals from the Urge and Raushan deposits for the production of gypsum, used mainly for the production of gypsum and gypsum concrete products for the interior of buildings, as well as for the production of gypsum-gypsum plaster mortars. On the basis of other gypsum minerals, it is also possible to obtain building gypsum with satisfactory technological characteristics [5, 117-122].
High-strength gypsum differs from gypsum in larger crystals of non-fibrous structure, as a result of which it has less water demand.
To obtain this type of binder, heat treatment of gypsum crushed stone was carried out in a self-steaming autoclave at temperatures of 120-125 °C for 3-5 hours. With this treatment, recrystalliza-tion of two-water gypsum into a coarse-crystalline semi-aquatic a-modification, consisting of long needle-like transparent crystals. After steaming, the crushed stone is unloaded from the autoclave and is dried, then milled. The high-strength gypsum obtained as a result of these operations has the following characteristics (Table 3).
Table 3.- High Strength Plaster Test Results
No Name of parameter Indicators of gypsum binder from the Raushan field Indicators of gypsum binder from the Raushan field+10% glauconite
1. Milling fineness, screening residue 0,2% 8 5
2. Normal density W/G,% 58 52
3. Setting time beginning, min end, min 5 14 6 17
4. Ultimate compressive strength in 2 hours, kgf/cm2 199.7 98.9
5. Ultimate tensile strength under bending, kgf/cm2 77 55
6. Binder grade G-23 G-19
7. Metal impurities content, mg 2 2
8. Volume dilatation 0.2 0.4
The experiments showed that based on the gypsum minerals of the Raushan deposit, it is possible to obtain high-strength gypsum binders by the above method without the additional cost of chemicals, setting stabilizers, etc. The use ofmarl or lime in the amount of4-6 or 3-5%, respectively, of sample No. 3 in the grinding process contributes to obtaining a high-strength binder with relatively high technological parameters. Such results were also obtained for samples No. 3 and 4.
Anhydrite binders are obtained by firing at temperatures above 600 °C. Known methods for
producing such binders also without firing method - grinding natural anhydride with hardening activators.
In studies, anhydrite cement was obtained by calcining gypsum at 650-700 °C and then grinding it finely together with additives. Soda waste, sodium hydrogen sulfate, and vitriol in various mass ratios were used as additives.
The main technological characteristics of anhydrite binders based on the studied samples are shown in (table 4).
Table 4.- Characterization of anhydrite binders based on test samples
No Characteristic Sample No. 1 Sample No. 2
1. Specific surface of CaSO4, cm2/g 1030...1080 1010.1071
2. Content of the main substance,% 95 97
3. H2O total content,% 1.2 0.94
4. The content of residual sulfuric acid,% 0.03 0.005
5. Sieve composition of anhydrite 100% < 60 um 100% < 60 um
6. Specific surface area, cm2/g 1600 1560
7. H2O total / H2O crystal,% 0.7/0.7 1.2/1.2
The water requirement of anhydrite binders to obtain a test of normal density is 23-36%. Of these samples, high calcined gypsum based on samples No 4 and 5 are characterized by the slowest setting and hardening. The setting begins not earlier than 3 hours from the start of mixing. Anhydrite gypsum based on sample No 6 has more unsatisfactory properties.
High-fired gypsum based on samples No 1 and 3 have high technological characteristics and can be used to obtain mortars and concrete, for the manufacture ofartificial marble and other construction needs.
Physico-mechanical and indicators of pilot batches of gypsum binders confirm that they correspond to the results of laboratory tests and satisfy the requirements for gypsum binders used in the construction of various structures [6, 19-2; 7, 56-62].
Conclusion. The study of the physico-chemical and physico-mechanical properties of gypsum bind-
ers derived from gypsum minerals in Karakalpakstan shows the possibility of using these minerals for the production of binders such as building, high strength and estrich gypsum, as well as anhydrite cement.
The introduction of the studied minerals is economically effective, since the binders are obtained with low-temperature firing and fine grinding of raw materials without waste and, accordingly, the cost of materials will be relatively low.
The influence of various microfillers and their concentrations on the technological properties of the resulting gypsum binders.
Developed gypsum compositions differing in technological properties.
Developed physical and colloidal-chemical bases for obtaining high-strength gypsum binder based on gypsum minerals Raushan, suitable as a binder for the construction industry.
References:
1. Volzhensky A. V. Mineral binders.-M.: Stroyizdat, 1986.- 464 p.
2. Dvorcin L. I., Dvorcin O. L. Mineral building binders.- M.: Infra-Engineering, 2011.- P. 27-36.
3. GOST 4013-82. Gypsum and gypsum-anhydrite stone for the production of binders. Technical conditions - M.: 07/01/1983.
4. GOST 23789-79. Cementing gypsum. Methods of eating.- M.: 07/01/1980.
5. Abylova A. Zh., Turemuratov Sh. N., Khamraev S. S. Obtaining a variety of gypsum binders based on gypsum minerals of the Republic of Karakalpakstan // Actual problems of modern science.- M., 2014.-No. 5.- P. 117-122.
6. Abylova A. Zh., Turemuratov Sh. N., Khamraev S. S. Obtaining binders based on gypsum minerals of the Ustyurt deposit // Chemistry technology and control control.- T., 2015.- No. 1.- P. 19-24.
7. Abylova A. Zh., Khamraev S. S. Cementing materials based on gypsum minerals of the Republic of Karakalpakstan // Chemical industry.- M., 2016.- No. 2.- P. 56-62.
