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Abylova Amina Zhanabaevna,, Karakalpak Scientific Research Institute of Natural Sciences of Karakalpak Branch of Academy of Sciences of the Republic of Uzbekistan, candidate, for a Degree, Chemistry Laboratory.
E-mail: [email protected] Turemutarov Sharibay Nauryzbaevich, Karakalpak Scientific Research Institute of Natural Sciences of Karakalpak Branch of Academy of Sciences of the Republic of Uzbekistan, Ph.D., in Chemistry, Head of Chemistry Laboratory
E-mail: [email protected] Uralbaeva Gulshat Bakhytbaevna, Karakalpak Scientific Research Institute of Natural Sciences of Karakalpak Branch of Academy of Sciences of the Republic of Uzbekistan, Laboratory Assistant, Chemistry Laboratory. E-mail: [email protected]
GYPSUM BINDERS BASED ON KARAKALPAKSTAN FIELD
Abstract: The gypsum materials of some Karakalpakstan fields was studied and such gypsum binding materials as the construction-grade, high-strength and estrich gypsums as well as the anhydrite cement were produced.
Keywords: gypsum, anhydrite cement, Karakalpakstan, gypsum minerals, binding material, thermal analysis.
Introduction. The gypsum binder manufacture from the large or small crystals of calcium sulfate di-is the most efficient one regarding the technical and hydrate CaSO4-2H2O. The transparent crystalline economic feasibility, in particular, in terms of the gypsum, gypsum spar, satin spar with satiny luster unit costs of the raw material, fuel, electric power (selenite) and granular gypsum are distinguished in and labor per the product unit. The reserves of the the rock appearance and fabric. The most pure kind initial natural raw material are unlimited as well as of the granular gypsum resembling the marble in ap-the gypsum-containing by-products for the gypsum pearance is called sometimes alabaster. The average and anhydrite binder manufacture. They include the density of the gypsum stone depends on the impu-natural calcium sulfate dehydrate, anhydride, clay- rity amount and type and is 2.2-2.4 g/cm3. gypsum as well as the industrial wastes consisting Study Subjects and Methods. The study sub-mainly of the anhydrous calcium sulfate or calcium ject in this work is the gypsum mineral - selenite of sulfate dihydrate, or their mixture [1, 464]. Karakalpakstan field, which is unrivaled throughout
The natural calcium sulfate dihydrate (gypsum Uzbekistan. In terms of the composition, it is close stone) is a rock of sedimentary origin formed mainly to the high-grade one; that is why it can be used to
produce the binding materials with high physical and mechanical properties.
The gypsum stone belongs to the rock of sedimentary origin; the content of the calcium sulfate dehydrate in it varies from 68.4 to 93.8%. Three specimens were sampled from three different Kara-kalpakstan fields respectively, and their complete silicate analyses was carried out. The study of the physical-chemical and mechanical properties was carried out in accordance with the requirements of GOSTs (State Standards) 23789-04 and 4013-82.
Discussion and Study Results. For study of the chemical and mineral composition of the specimens researched, the comprehensive analysis methods were used including the X-ray and differential thermal analyses (Table 1; Fig. 1).
It is known [2-3, 472] that the gypsum stone of 1st grade is used to manufacture the gypsum binders used in the whiteware, ceramic and medical industries as well as the white, architectural and expanding gypsum - alumina cement.
Table 1.- Chemical Analysis Results for the RK Gypsum Minerals
No. in order offield Field name Content in% on air-dry basis
SiO2 TiO2 Al O 2 3 Fe O 23 total Including MgO MnO CaO
Fe O 2 3 FeO
1. Kuskhanatau 2.88 0.015 0.45 0.25 < 0.25 0.40 0.01 30.51
2. Beltau 7.31 0.019 0.79 0.27 < 0.25 0.50 0.01 29.16
3. Khodzhakul 20.16 0.15 2.44 1.08 < 0.25 0.50 0.02 23.97
No. Field name Content in% on air-dry basis
Na2° K2O P2O5 SO3 total SO3 sulfate S sulfide Percentage of other impurities H2O 320° CO2
1. Kuskhanatau 0.10 0.11 0.048 44.67 44.61 20.49 19.63 0.55
2. Beltau 0.21 0.22 0.042 41.70 41.50 19.90 18.75 1.10
3. Khodzhakul 0.39 0.37 0.068 34.27 32.90 17.91 14.32 2.97
The results of the chemical and mineral analyses performed have demonstrated that the specimen (No. 1) sampled from Kuskhanatau field differs with the insignificant content of the harmful impurities. In terms of the basic oxide content (CaO, SO3, H20) in the amount of 93.8%, it meets the composition of the high-grade gypsum mineral, and the manufacture of the gypsum binding material with increased physical and mechanical properties is possible based on it for the whiteware, ceramic and medical industries. [4, 117-122]
The specimens from Beltau (No. 2) and Kho-dzhakul (No. 3) fields contain a large amount of
the clay impurities; it differ with the small amount of CaO and SO3. The total content of sulfate dihy-drate CaSO4-2H2O is 89.5 and 68.4%, respectively for 2nd and 3rd specimens. These minerals belong to the gypsum rock of the second rate, and the production of the materials with the increased physical and mechanical properties is possible based on them for the construction industry.
The X-ray phase analysis of the gypsum specimens was carried out using diffractometer DRON-3,0 with the filtered copper radiation under 22 kW voltage, 14 mA strength of current, 2 degree/min meter disk speed.
Figure 1. Gypsum stone X-ray diagrams for Karakalpak field: 1 - Kuskhanatau, 2 - Beltau, 3 - Khudzhakul
The X-ray phase analysis of specimen No. 1 (Fig. 4) has demonstrated the sufficient purity of this selenite; reflexes: 7.16; 4.04; 3.67; 3.00; 2.81; 2.61; 2.16; 2.03; 1.88; 1.75; 1.61; 1.34. A meet those of the calcium sulfate dihydrate. In specimens No. 2 and No. 3 (Fig. 5-6), reflexes: 7.16; 4.21; 3.67; 3.00; 2.81; 2.61; 2.16; 2.03; 1.88; 1.75; 1.61; 1.34. A meet those of the calcium sulfate dihydrate, reflexes: 12.04; 3.21; 2.47; 2.23 - those of the quartz, 3.46; 2.53; those of the kaolin and 3.15; 2.76; 1.86 meet the calcite lines [5, C. 19-24].
The differential thermal analysis of the gypsum specimens was carried out using the derivatograph of "Paylik-Paylik-Erday" system with 9-10 degree/min speed and 0.132-0.155 g weighed amount, with galvanometer sensitivity as T - 900, TG (Russian: Tr) - 200, DTA (Russian: ATA) 1/10, DTG (Russian: ATr) - 1/10. The recording was carried out under atmospheric conditions. The holder was 7 mm diameter platinum crucible without cover. Al2O3 was used as the reference.
The gypsum calcination was performed as per gypsum process design using the rotary kilns. The rotary kilns are the continuously operating units assuring the compact flow chart. The crushed gypsum stone with 10-20 mm and 20-35 mm fraction sizes is calcined in the rotary kilns [6, 56-62].
The gas inlet temperature at the drying drum with direct flow reaches about 900 °C, and with counter flow - 600-700 °C. Prior to entering the kiln, the gases are diluted with the air up to required 170-200 °C temperature. At the drum outlet, the gas temperature is 160-180 °C with direct flow, and about 100 °C in case of the counter flow.
The calcined grit is milled up to the residue on screen No. 02 not more than 10-12%. The milling often takes place using the single chamber or double-chamber ball mills.
The gypsum manufacturing processes with its calcination within the rotary kilns are continuous; that is why their automatic control is performed
with ease. This method of the gypsum manufacture is very cost effective.
The fuel consumption varies within 45-50 kg, that of the electric power is 15-20 kW-h per 1 t.
The testing of the physical and chemical properties of the produced gypsum binders carried out
according to GOST U23789-04 (Table 2) demonstrates the possibility of their use for the manufacture of the construction, high-strength and estrich gypsums as well as the anhydrite cement.
a b c
Figure 2. The differential thermal analysis of the gypsum specimens of the Karakalpak field: a - Kuskhanatau, b - Beltau, c - Khudzhakul
Table 2.- Physical and mechanical parameters of the gypsum binders
No. Name of parameter GB (gypsum binder) based on specimen No. 1 GB based on specimen No. 2 GB based on specimen No. 3
1. Milling fineness, screening residue 0.2% 2 6 6.2
2. B/G normal consistency,% 57 51 46
3. Setting time: beginning, min. end, min. 6 12 7 19 9 16
4. Ultimate compression strength in 2 hours, kgf/cm2 73 51 35
5. Ultimate tensile strength under bending, kgf/cm2 34 24 16
6. Binder grade G-7 G-5 G-3
7. Metal impurities content, mg 3 4 8
8. Volume dilatation, 0.4 0.3 0.4
9. Impurities, which are insoluble in the hydrochloric acid,% 0.8 0.9 2.8
The study results for the binder materials have shown that specimen No. 1 meets grade G-7BIII, which is characterized by the normally setting properties and fine milling, and specimen No. 2 of grade G-5BII is characterized by the normally setting properties and medium milling.
The gypsum binders of grade G-3BII, which are characterized by the normally setting properties and medium milling, were produced from specimen No. 3.
Conclusion. The study of the physical and chemical properties of the gypsum binding materials pro-
duced based on the Karakalpakstan gypsum minerals demonstrates the possibility to use these minerals for manufacture of such binders as the construction, high-strength and estrich gypsums as well as the anhydrite cement.
The introduction of the minerals studied into the construction material manufacture is cost effective as the binding materials are produced using the low temperature calcination and fine milling of the raw material with no waste and consequently, the prime cost of the materials will be relatively low.
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