Results are provided for development of refractory concrete based on modified alumina cement using chemical
industry waste. A quantitative ratio for mixed filler fractions, the effect of production factors on concrete strength, the dependence of its strength properties on form of filler, and solidification conditions are established.
It is shown that with respect to physical mechanical and engineering properties the concretes developed
is no worse than those existing in the market.With respect to all engineering properties this form of refractory
product may be recommended as lining for high-temperature units

de Arnaldo Araujo, A.

de Oliveira, Júlia Epischina Engrácia

Deserno, Thomas

Soiron, Michael

English

Publikationsserver der RWTH Aachen University

Computer-aided diagnostics of screening mammography using content-based image retrieval

Thomas M. Deserno

Michael Soiron

Júlia E. E. de Oliveira

Arnaldo de A. Araújo

Crossref

Vorozhbiyan, R. M.

Shabanova, G. N.

Korogodskaya, A. N.

Electronic National Technical University &quot;Kharkiv Polytechnic Institute&quot; Institutional Repository (eNTUKhPIIR)

HEAT-RESISTANT CONCRETE BASED ON ALUMINA CEMENTFROM SUBSTANDARD RAW MATERIALR. M. Vorozhbiyan,1 G. N. Shabanova,1,2 and A. N. Korogodskaya1Translated from Novye Ogneupory, No. 9, pp. 47 – 51, September, 2018.Original article submitted June 13, 2018.Results are provided for development of refractory concrete based on modified alumina cement using chemi-cal industry waste. A quantitative ratio for mixed filler fractions, the effect of production factors on concretestrength, the dependence of its strength properties on form of filler, and solidification conditions are estab-lished. It is shown that with respect to physicomechanical and engineering properties the concretes developedis no worse than those existing in the market. With respect to all engineering properties this form of refractoryproduct may be recommended as lining for high-temperature units.Keywords: alumina cement, refractory concrete, water-treatment sludge, catalyst support waste.INTRODUCTIONIt is possible to prepare assembled structures of any con-figuration from refractory concrete and this makes it possibleto obtain new structural solutions for heating units most ex-pedient from a heat engineering and production point of view[1]. Use of refractory concrete opens up considerable possi-bilities in industrialization of labor consuming work andmakes it possible thereby to reduce construction duration androutine repair of high-temperature units with a significant re-duction in cost and an increase in operating life. Use ofheat-resistant concrete is aimed at structural solutions forhigh-temperature industrial furnace elements, difficult tomake using individual refractories [3, 4]. In addition, refrac-tory concretes are use in various branches of industry [5 – 7].In view of the fact that the main component of refractoryconcrete is alumina cement it is expedient to us refractorybinder materials prepared by resource saving technology.RESEARCH MATERIALS AND METHODSIn order to prepare high-strength refractory concrete withthe required operating properties the optimum grain sizecomposition was selected for filler taking account ofstrength, density, and uniformity. The binder used was modi-fied alumina cement of optimum composition prepared onthe basis of water-treatment sludge and catalyst K-905 D2support waste in a ratio of 50:50 and having the best strengthproperties under different hardening conditions and times[Table 1) [8, 9].Grinding and careful mixing raw components was per-formed in a laboratory porcelain mill to complete passagethrough a screen No. 0063. The prepared mixture was driedin a laboratory drying cabinet at 100 – 105°C to completemoisture removal after which using the mixture in a hydrau-lic press under a pressure of 20 MPa specimens were com-pacted 50 mm in diameter and 50 – 70 mm thick. Specimenswere fired in a laboratory cryptolite furnace at 1380°C withisothermal exposure at the maximum temperature for 3 h.The rate of temperature increase with 50 – 70 °C/min. afterfiring specimens were subjected to rapid cooling. Clinker ofthe prepared cement was ground to complete passagethrough a screen no. 008 [10, 11]. Completeness of occur-Refractories and Industrial Ceramics Vol. 59, No. 5, January, 20194781083-48771905905-0478 © 2019 Springer Science+Business Media, LLC1NTU, KhPI, Khar’kov, Ukraine.2gala-shabanova@ukr.netTABLE 1. Results of Physicomechanical Tests for Alumina CementBased on Catalyst Carrier WasteCatalyst carrierwaste : watertreatment sludgeM/SUltimate strength in compression, MPa,after solidification3 days 7 days 28 days50:50 0.31 58 62 6645:55 0.29 48 55 6040:60 0.30 48 50 5260:40 0.30 50 53 60DOI 10.1007/s11148-019-00257-6rence of synthesis of the main sinter minerals was monitoredby chemical and x-ray analysis methods (Fig. 1). It was es-tablished that the main phases are CaAl2O4 (0.4049, 0.3715,0.297, 0.2851, 0.2534, 0.2403 nm), CaAl4O7 (0.3509,0.2534, 0.2438, 0.2403, 0.2219, 0.2021 nm), and alsoNiAl2O4 (0.467, 0.2851, 0.2438, 0.2021 nm) [1].EXPERIMENTAL SECTIONThe filler used was high-alumina chamotte produced byPAO Kondrat’ev Refractory Plant and the cement:filler ra-tion equals 1:3.Concrete cubic specimens with a side of 2 cm were pre-pared by vibration compaction (L/S = 0.08). The optimumratio of grain sizes for the mixed filler fractions was deter-mined by an equation [1]dn/dn–1 = 0.226,where dnis average grain fine fraction diameter; dn–1is aver-age coarse grain fraction diameter.The quantitative ratio of mixed fractions of filler was de-termined by a simplex lattice experimental planning method.In order to describe the dependence of concrete properties onthe quantitative ratio of filler fractions an incomplete thirdorder polynomial was usedY = 1x1 + 2x2 + 3x3 + 12x1x2+ 13x1x3 + 23x2x3 + 123x1x2x3.The experimental planning matrix and results of mechan-ical property tests for concretes are provided in Table 2.From results of experimental data polynomial coefficientswere calculated expressing the dependence of strength andporosity on the quantitative and grain size ratio of filler frac-tions. Regression equations have the formY = 30·x1 + 41·x2 + 53·x3 + 14·x1x2+ 18·x1x3 + 16·x2x3 + 225·x1x2x3,Yn = 18.9·x1 + 18.0·x2 + 17.7·x3 – 1.0·x1x2– 1.6·x1x3 – 0.2·x2x3 – 7.8·x1x2x3.The adequacy of the equation was checked by means ofthe Student criterion and additional experimental specimensat control points. The regression equation was calculated bya TRIANGLE V.1.0 program with a variation step of10 wt.%. From results of calculations and mathematicaltreatment of an experiment simplex composition-strengthand composition-porosity diagrams were plotted (Fig. 2). Itwas established that in order to prepare high-strength con-crete the density and uniformity of the mixture required con-tained 10 – 35 wt.% fraction 1.25 – 0.63 mm, 15 – 45 wt.%Heat-Resistant Concrete Based on Alumina Cement from Substandard Raw Material 479Fig. 1. Line-diffraction pattern of alumina cement clinker preparedfrom water treatment sludge and catalyst carrier waste K-904 D2:CA is calcium monoaluminate CaAl2O4; CA2 is calcium dialuminateCaAl4O7; NiA is nickel spinel NiAl2O4.Fig. 2. Composition – ultimate strength in compression, MPa (a)and composition – open porosity, % (b ), diagrams for concretebased on alumina cement.TABLE 2. Experimental Planning MatrixPolynomialcoefficientFiller fraction Experimental datax1x2x3Y Ynultimate strengthin compression,MPaopenporosity, %1 1 0 0 30.0 18.92 0 1 0 41.0 18.03 0 0 1 53.0 17.712 0.5 0.5 0 39.0 18.213 0.5 0 0.5 46.0 17.923 0 0.5 0.5 51.0 17.8123 0.33 0.33 0.33 55.0 17.6Controlpoint0.5 0.3 0.2 49.0 17.80.63 – 0.315 mm, and 30 – 65 wt.% 0.315 – 0.50 mm. Fur-ther study of concretes was performed taking account of theoptimum filler grain size composition.In order to study the effect of different molding methodson the mechanical strength of concretes prepared on the basisof modified alumina cement cubic specimens were preparedwith a side of 5 cm. Results of studies showed (Fig. 3) thatthe most suitable is the vibration compaction method, mostappropriate for preparing large objects of complex configura-tion. Use of a compaction method makes it possible to pro-duce individual refractories.In order to determine the optimum ratio in concrete ofcement:filler an experiment was conducted on concrete cubicspecimens with a side of 4 cm prepared by vibration compac-tion with L/S = 0.08. Results are given in Table 3 forphysicomechanical tests of concrete in relation to ratiowithin it of cement and filler. It is seen that with an increasein cement content the strength of solidified concrete in-creases, but conversely porosity decreases. This indicatesthat the cement added not only participates actively in form-ing concrete strength, but also leads to a reduction in poros-ity. The optimum ratio providing the required strength andeconomy for cement is cement:filler = 1:3.With subsequent use of the concrete developed in vari-ous branches comparative evaluation is required for the se-lected fillers. The fillers used were electromelted corundumand chamotte produced by PAO A. S. Berezhnyi UkraineSci.-Res. Institute of Refractories, high-alumina chamotteproduced by PAO Kondrat’ev Refractory Plant, and chips ofdeposits from furnaces for producing alumina cement. Con-crete specimens with a different filler prepared by vibrationcompaction were selected for mechanical strength under dif-ferent hardening conditions. The effect of form of filler andhardening conditions on concrete mechanical strength isshown in Fig. 4. Heat-resistant concretes based on filler ofhigh-alumina chamotte had the highest strength. Therefore,on the basis of alumina cement obtained from water-treat-ment sludge and catalyst support waste of the North DonetskAzot firm it is possible to obtain concrete with the beststrength properties and reduced open porosity, which makesit possible to employ them as a monolithic lining for ther-mally stressed sections of high-temperature units.Concrete thermomechanical properties were also stud-ied. Refractoriness of concrete based on electromelted corun-dum, measured by collapse of a pyrometric cone, comprised1750°C, for chamotte 1500°C, for high-alumina chamotte,1550°C, and a for deposit chips of 1650°C. Therefore, theconcrete obtained may be used in heating units at servicetemperatures up to 1500°C, depending on the filler selected.Concrete thermal shock resistance with different fillers(specimen cooling in air) comprises more than 20 cycles, re-taining more than 80% of the initial strength.Specimens of cylindrical shape were prepared in order todetermine the temperature for the start of concrete softening.Specimens C were prepared based on a corundum filler, andspecimen Ch based on chamotte; the binder used was experi-mental alumina cement (Fig. 5). Specimen dimensions aregiven in Table 4 and correspond to standard specifications.Specimens C and Ch were tested in a certified test unitaccording to GOST 4070–2000)ISO 1893–89) “Refractoryobjects. Method for determining deformation temperatureunder load.” Specimen deformation was measured by a dif-ferential method using differential measuring equipment pre-pared from single crystal corundum. During testing for eachof the specimens the load applied answered a pressure of0.02 ± 0.01 N/mm2. The rate of specimen temperature in-crease up to 300°C was not greater than 10°C/min, andabove 300°C it was 4.5°C/min. Test results: for specimen Ct0.6 = (1290 ± 10)°C, for specimen Ch t0.6 = (1230 ± 10)°C.measurement uncertainty for the temperature fort eh start ofsoftening was calculated in accordance with RMG 43–2001“State system providing measurement unification. Use ofguidance for expressing measurement uncertainty.”An important operating property of alumina concrete isthe degree of softening on heating. In order to study concrete480 R. M. Vorozhbiyan, G. N. Shabanova and A. N. KorogodskayaFig. 3. Effect of production factors on concrete strength: ) man-ual tamping; ) vibration compaction;) pressing.Fig. 4. Dependence of concrete strength on form of filler with hard-ening in moist air (a) and atmospheric conditions (b ): ) high-alumina chamotte;) chamotte;) electromelted corundum; ) de-posit chips.TABLE 3. Dependence of Concrete Strength and Porosity on Ce-ment:Filler RatioCement:fillerratioUltimate strength in compression, MPa, afterhardeningOpen poros-ity, %3 days 7 days 28 days1:9 25.3 27.3 40.2 18.01:4 28.8 37.4 50.8 17.81:3 33.4 48.6 57.9 17.41:2.3 35.1 49.2 58.2 17.2mechanical strength with action of elevated temperature cu-bic specimens were prepared with a side of 5 cm that weretested after 28 days of hardening. Isothermal exposure for2 h at a prescribed temperature with rapid cooling in air. Thefiller used was chamotte and high-alumina chamotte, i.e.,materials exhibiting the closest matrix affinity for cement anfiller. Test results for concretes with action elevated tempera-ture are shown in Fig. 6. Concrete with different fillers onheating behaves approximately the same. Concrete based onfiller of high-alumina chamotte loses strength up to 9.6% ofthe initial value, but concrete based on chamotte loses up to20% of the initial strength. The greatest increase in the de-gree of loss of concrete strength is observed in the range400 – 800°C that is explained by removal of crystallizationwater from calcium hydroaluminate and aluminum hydrox-ide, and also recrystallization of hexagonal calciumaluminate, which facilitates occurrence of internal stressesand insignificant concrete weakening. Above 800°C weaken-ing slows down, and above 1000°C sintering of the binderand its reaction with filler commence, which facilitates a sig-nificant increase in strength with formation of a dense ce-ramic structure. Loss of strength for concrete based on nor-mal alumina cement with traditional fillers in the test temper-ature range exceeds 28% and may reach 40%, which ishigher by a factor of 2 – 4 than for the concrete developed.CONCLUSIONIt has been established that concretes prepared on the ba-sis of modified alumina cement have a number of advantagescompared with existing analogs and are characterized byequal setting time, high initial strength, and absence of a sig-nificant loss of strength after 28 days of hardening. Theseconcretes may be used for preparing both a large lining ofcomplex configuration, and also individual refractories withan operating temperature above 1500°C. It has been estab-lished that with respect to high-temperature operating prop-erties the concretes developed are no worse than the bestoverseas analogs and are promising refractory materials foruse in various industries.REFERENCES1. R. M. Vorozhbiyan, G. N. Shabanova, and S. M. Korogodskaya,“Alumina cements based on CaO–NiO–Al2O3,” NovyeOgneupory Tekhn. Keram., No. 11/12, 11 – 14 (2012).2. R. Vorozhbiian, H. Shabanova, T. Ryshchenko, “Alumina ce-ment on chemical industry wastes,” 19 InternationalBaustofftagung, 16 – 18 September, 2015, Tagungsbericht,Band 2, Weimar, Bundesrepublik, Deutschland (2015).3. M. T. Mel’nik and N. Sh. Shapovalova, Refractory Cements [inRussian], Vysshaya Shkola, Kiev (1984).4. T. V. Kuznetsova and I. Talaber, Alumina Cement [in Russian]Stroiizdat, Moscow (1988).5. O. O. Pashchenko, V. P. Serbin, and O. O. Starchevs’ka, ViscousMaterials [in Ukrainian], Vishcha Shkola, Kiev (1995).6. A. A. Pashchenko, cement Theory [in Russian], Budevel’nik,Kiev (1991).7. M. T. Mel’nik and N. N. Shapalova, “Refractory concrete basedon alumina cement with addition of active alumina,”Ogneupory, No. 10, 56 – 57 (1974).8. R. M. Vorozhbiyan, G. N. Shabanova, A. N. Korogodskaya, etal., “Basis of possible use of nickel catalyst waste in the produc-tion of alumina cement,” Zbirnik, Nauk. Prats’ VATUkrNDIVognetriviv im A. S. Berezhnogo, No. 112, 223 – 229(2012).9. R. M. Vorozhbiyan, G. N. Shabanova, and A. N. Korogodskaya,“Questions of using water cleaning waste in alumina cementmanufacture,” Visnik NTU KhGP, No. 27, 164 – 173 (2011).10. R. M. Vorozhbiyan, G. M. Shabanova, A. M. Korohods’ka, etal., Equal characteristics of aluminum oxide cements with theuse of approaches employed in chemical plants, Zb. NaukovykhPrats’ PAT UkrNDIVognetriviv im. A. S. Berezhnogo, No. 113,86 – 93 (2013).11. R. M. Vorozhbiyan, G. M. Shabanova, A. M. Korohods’ka, andT. D. Ryshchenko, High-efficiency specialized viscous materi-als based on alkali-earth oxides, Zb. Nauk. Prats’ Ukrains’k.Derzh. Akad. Zaliz. Transportu, No. 138, 27 – 32 (2011).Heat-Resistant Concrete Based on Alumina Cement from Substandard Raw Material 481Fig. 5. Test specimens (without visible damage).TABLE 4. Specimen Technical parametersSpecimen identificationdesignationSpecimen size, mmdiameter thicknessC 36.0 50.9Ch 35.8 52.9Fig. 6. Dependence of concrete strength on temperature and formof filler : ) high-alumina chamotte )electromelted corundum;) deposit chips.

Heat-resistant concrete based on alumina cement from substandard raw material

Library of National Technical University "Kharkiv Polytechnic Institute"

HEAT-RESISTANT CONCRETE BASED ON ALUMINA CEMENT
FROM SUBSTANDARD RAW MATERIAL
R. M. Vorozhbiyan,1 G. N. Shabanova,1,2 and A. N. Korogodskaya1
Translated from Novye Ogneupory, No. 9, pp. 47 – 51, September, 2018.
Original article submitted June 13, 2018.
Results are provided for development of refractory concrete based on modified alumina cement using chemi-
cal industry waste. A quantitative ratio for mixed filler fractions, the effect of production factors on concrete
strength, the dependence of its strength properties on form of filler, and solidification conditions are estab-
lished. It is shown that with respect to physicomechanical and engineering properties the concretes developed
is no worse than those existing in the market. With respect to all engineering properties this form of refractory
product may be recommended as lining for high-temperature units.
Keywords: alumina cement, refractory concrete, water-treatment sludge, catalyst support waste.
INTRODUCTION
It is possible to prepare assembled structures of any con-
figuration from refractory concrete and this makes it possible
to obtain new structural solutions for heating units most ex-
pedient from a heat engineering and production point of view
[1]. Use of refractory concrete opens up considerable possi-
bilities in industrialization of labor consuming work and
makes it possible thereby to reduce construction duration and
routine repair of high-temperature units with a significant re-
duction in cost and an increase in operating life. Use of
heat-resistant concrete is aimed at structural solutions for
high-temperature industrial furnace elements, difficult to
make using individual refractories [3, 4]. In addition, refrac-
tory concretes are use in various branches of industry [5 – 7].
In view of the fact that the main component of refractory
concrete is alumina cement it is expedient to us refractory
binder materials prepared by resource saving technology.
RESEARCH MATERIALS AND METHODS
In order to prepare high-strength refractory concrete with
the required operating properties the optimum grain size
composition was selected for filler taking account of
strength, density, and uniformity. The binder used was modi-
fied alumina cement of optimum composition prepared on
the basis of water-treatment sludge and catalyst K-905 D2
support waste in a ratio of 50:50 and having the best strength
properties under different hardening conditions and times
[Table 1) [8, 9].
Grinding and careful mixing raw components was per-
formed in a laboratory porcelain mill to complete passage
through a screen No. 0063. The prepared mixture was dried
in a laboratory drying cabinet at 100 – 105°C to complete
moisture removal after which using the mixture in a hydrau-
lic press under a pressure of 20 MPa specimens were com-
pacted 50 mm in diameter and 50 – 70 mm thick. Specimens
were fired in a laboratory cryptolite furnace at 1380°C with
isothermal exposure at the maximum temperature for 3 h.
The rate of temperature increase with 50 – 70 °C/min. after
firing specimens were subjected to rapid cooling. Clinker of
the prepared cement was ground to complete passage
through a screen no. 008 [10, 11]. Completeness of occur-
Refractories and Industrial Ceramics Vol. 59, No. 5, January, 2019
478
1083-48771905905-0478 © 2019 Springer Science+Business Media, LLC
1
NTU, KhPI, Khar’kov, Ukraine.
2
gala-shabanova@ukr.net
TABLE 1. Results of Physicomechanical Tests for Alumina Cement
Based on Catalyst Carrier Waste
Catalyst carrier
waste : water
treatment sludge
M/S
Ultimate strength in compression, MPa,
after solidification
3 days 7 days 28 days
50:50 0.31 58 62 66
45:55 0.29 48 55 60
40:60 0.30 48 50 52
60:40 0.30 50 53 60
DOI 10.1007/s11148-019-00257-6
rence of synthesis of the main sinter minerals was monitored
by chemical and x-ray analysis methods (Fig. 1). It was es-
tablished that the main phases are CaAl2O4 (0.4049, 0.3715,
0.297, 0.2851, 0.2534, 0.2403 nm), CaAl4O7 (0.3509,
0.2534, 0.2438, 0.2403, 0.2219, 0.2021 nm), and also
NiAl2O4 (0.467, 0.2851, 0.2438, 0.2021 nm) [1].
EXPERIMENTAL SECTION
The filler used was high-alumina chamotte produced by
PAO Kondrat’ev Refractory Plant and the cement:filler ra-
tion equals 1:3.
Concrete cubic specimens with a side of 2 cm were pre-
pared by vibration compaction (L/S = 0.08). The optimum
ratio of grain sizes for the mixed filler fractions was deter-
mined by an equation [1]
dn/dn–1 = 0.226,
where d
n
is average grain fine fraction diameter; d
n–1
is aver-
age coarse grain fraction diameter.
The quantitative ratio of mixed fractions of filler was de-
termined by a simplex lattice experimental planning method.
In order to describe the dependence of concrete properties on
the quantitative ratio of filler fractions an incomplete third
order polynomial was used
Y = 1x1 + 2x2 + 3x3 + 12x1x2
+ 13x1x3 + 23x2x3 + 123x1x2x3.
The experimental planning matrix and results of mechan-
ical property tests for concretes are provided in Table 2.
From results of experimental data polynomial coefficients
were calculated expressing the dependence of strength and
porosity on the quantitative and grain size ratio of filler frac-
tions. Regression equations have the form
Y = 30·x1 + 41·x2 + 53·x3 + 14·x1x2
+ 18·x1x3 + 16·x2x3 + 225·x1x2x3,
Yn = 18.9·x1 + 18.0·x2 + 17.7·x3 – 1.0·x1x2
– 1.6·x1x3 – 0.2·x2x3 – 7.8·x1x2x3.
The adequacy of the equation was checked by means of
the Student criterion and additional experimental specimens
at control points. The regression equation was calculated by
a TRIANGLE V.1.0 program with a variation step of
10 wt.%. From results of calculations and mathematical
treatment of an experiment simplex composition-strength
and composition-porosity diagrams were plotted (Fig. 2). It
was established that in order to prepare high-strength con-
crete the density and uniformity of the mixture required con-
tained 10 – 35 wt.% fraction 1.25 – 0.63 mm, 15 – 45 wt.%
Heat-Resistant Concrete Based on Alumina Cement from Substandard Raw Material 479
Fig. 1. Line-diffraction pattern of alumina cement clinker prepared
from water treatment sludge and catalyst carrier waste K-904 D2:
CA is calcium monoaluminate CaAl2O4; CA2 is calcium dialuminate
CaAl4O7; NiA is nickel spinel NiAl2O4.
Fig. 2. Composition – ultimate strength in compression, MPa (a)
and composition – open porosity, % (b ), diagrams for concrete
based on alumina cement.
TABLE 2. Experimental Planning Matrix
Polynomial
coefficient
Filler fraction Experimental data
x
1
x
2
x
3
Y Yn
ultimate strength
in compression,
MPa
open
porosity, %
1 1 0 0 30.0 18.9
2 0 1 0 41.0 18.0
3 0 0 1 53.0 17.7
12 0.5 0.5 0 39.0 18.2
13 0.5 0 0.5 46.0 17.9
23 0 0.5 0.5 51.0 17.8
123 0.33 0.33 0.33 55.0 17.6
Control
point
0.5 0.3 0.2 49.0 17.8
0.63 – 0.315 mm, and 30 – 65 wt.% 0.315 – 0.50 mm. Fur-
ther study of concretes was performed taking account of the
optimum filler grain size composition.
In order to study the effect of different molding methods
on the mechanical strength of concretes prepared on the basis
of modified alumina cement cubic specimens were prepared
with a side of 5 cm. Results of studies showed (Fig. 3) that
the most suitable is the vibration compaction method, most
appropriate for preparing large objects of complex configura-
tion. Use of a compaction method makes it possible to pro-
duce individual refractories.
In order to determine the optimum ratio in concrete of
cement:filler an experiment was conducted on concrete cubic
specimens with a side of 4 cm prepared by vibration compac-
tion with L/S = 0.08. Results are given in Table 3 for
physicomechanical tests of concrete in relation to ratio
within it of cement and filler. It is seen that with an increase
in cement content the strength of solidified concrete in-
creases, but conversely porosity decreases. This indicates
that the cement added not only participates actively in form-
ing concrete strength, but also leads to a reduction in poros-
ity. The optimum ratio providing the required strength and
economy for cement is cement:filler = 1:3.
With subsequent use of the concrete developed in vari-
ous branches comparative evaluation is required for the se-
lected fillers. The fillers used were electromelted corundum
and chamotte produced by PAO A. S. Berezhnyi Ukraine
Sci.-Res. Institute of Refractories, high-alumina chamotte
produced by PAO Kondrat’ev Refractory Plant, and chips of
deposits from furnaces for producing alumina cement. Con-
crete specimens with a different filler prepared by vibration
compaction were selected for mechanical strength under dif-
ferent hardening conditions. The effect of form of filler and
hardening conditions on concrete mechanical strength is
shown in Fig. 4. Heat-resistant concretes based on filler of
high-alumina chamotte had the highest strength. Therefore,
on the basis of alumina cement obtained from water-treat-
ment sludge and catalyst support waste of the North Donetsk
Azot firm it is possible to obtain concrete with the best
strength properties and reduced open porosity, which makes
it possible to employ them as a monolithic lining for ther-
mally stressed sections of high-temperature units.
Concrete thermomechanical properties were also stud-
ied. Refractoriness of concrete based on electromelted corun-
dum, measured by collapse of a pyrometric cone, comprised
1750°C, for chamotte 1500°C, for high-alumina chamotte,
1550°C, and a for deposit chips of 1650°C. Therefore, the
concrete obtained may be used in heating units at service
temperatures up to 1500°C, depending on the filler selected.
Concrete thermal shock resistance with different fillers
(specimen cooling in air) comprises more than 20 cycles, re-
taining more than 80% of the initial strength.
Specimens of cylindrical shape were prepared in order to
determine the temperature for the start of concrete softening.
Specimens C were prepared based on a corundum filler, and
specimen Ch based on chamotte; the binder used was experi-
mental alumina cement (Fig. 5). Specimen dimensions are
given in Table 4 and correspond to standard specifications.
Specimens C and Ch were tested in a certified test unit
according to GOST 4070–2000)ISO 1893–89) “Refractory
objects. Method for determining deformation temperature
under load.” Specimen deformation was measured by a dif-
ferential method using differential measuring equipment pre-
pared from single crystal corundum. During testing for each
of the specimens the load applied answered a pressure of
0.02 ± 0.01 N/mm
2
. The rate of specimen temperature in-
crease up to 300°C was not greater than 10°C/min, and
above 300°C it was 4.5°C/min. Test results: for specimen C
t0.6 = (1290 ± 10)°C, for specimen Ch t0.6 = (1230 ± 10)°C.
measurement uncertainty for the temperature fort eh start of
softening was calculated in accordance with RMG 43–2001
“State system providing measurement unification. Use of
guidance for expressing measurement uncertainty.”
An important operating property of alumina concrete is
the degree of softening on heating. In order to study concrete
480 R. M. Vorozhbiyan, G. N. Shabanova and A. N. Korogodskaya
Fig. 3. Effect of production factors on concrete strength: ) man-
ual tamping; ) vibration compaction;) pressing.
Fig. 4. Dependence of concrete strength on form of filler with hard-
ening in moist air (a) and atmospheric conditions (b ): ) high-
alumina chamotte;) chamotte;) electromelted corundum; ) de-
posit chips.
TABLE 3. Dependence of Concrete Strength and Porosity on Ce-
ment:Filler Ratio
Cement:filler
ratio
Ultimate strength in compression, MPa, after
hardening
Open poros-
ity, %
3 days 7 days 28 days
1:9 25.3 27.3 40.2 18.0
1:4 28.8 37.4 50.8 17.8
1:3 33.4 48.6 57.9 17.4
1:2.3 35.1 49.2 58.2 17.2
mechanical strength with action of elevated temperature cu-
bic specimens were prepared with a side of 5 cm that were
tested after 28 days of hardening. Isothermal exposure for
2 h at a prescribed temperature with rapid cooling in air. The
filler used was chamotte and high-alumina chamotte, i.e.,
materials exhibiting the closest matrix affinity for cement an
filler. Test results for concretes with action elevated tempera-
ture are shown in Fig. 6. Concrete with different fillers on
heating behaves approximately the same. Concrete based on
filler of high-alumina chamotte loses strength up to 9.6% of
the initial value, but concrete based on chamotte loses up to
20% of the initial strength. The greatest increase in the de-
gree of loss of concrete strength is observed in the range
400 – 800°C that is explained by removal of crystallization
water from calcium hydroaluminate and aluminum hydrox-
ide, and also recrystallization of hexagonal calcium
aluminate, which facilitates occurrence of internal stresses
and insignificant concrete weakening. Above 800°C weaken-
ing slows down, and above 1000°C sintering of the binder
and its reaction with filler commence, which facilitates a sig-
nificant increase in strength with formation of a dense ce-
ramic structure. Loss of strength for concrete based on nor-
mal alumina cement with traditional fillers in the test temper-
ature range exceeds 28% and may reach 40%, which is
higher by a factor of 2 – 4 than for the concrete developed.
CONCLUSION
It has been established that concretes prepared on the ba-
sis of modified alumina cement have a number of advantages
compared with existing analogs and are characterized by
equal setting time, high initial strength, and absence of a sig-
nificant loss of strength after 28 days of hardening. These
concretes may be used for preparing both a large lining of
complex configuration, and also individual refractories with
an operating temperature above 1500°C. It has been estab-
lished that with respect to high-temperature operating prop-
erties the concretes developed are no worse than the best
overseas analogs and are promising refractory materials for
use in various industries.
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Heat-Resistant Concrete Based on Alumina Cement from Substandard Raw Material 481
Fig. 5. Test specimens (without visible damage).
TABLE 4. Specimen Technical parameters
Specimen identification
designation
Specimen size, mm
diameter thickness
C 36.0 50.9
Ch 35.8 52.9
Fig. 6. Dependence of concrete strength on temperature and form
of filler : ) high-alumina chamotte )electromelted corundum;
) deposit chips.


de A Araujo, Arnaldo

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Heat-resistant concrete based on alumina cement from substandard raw material

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Heat-resistant concrete based on alumina cement from substandard raw material

Abstract

Similar works

Full text

Available Versions

Publikationsserver der RWTH Aachen University

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Electronic National Technical University &quot;Kharkiv Polytechnic Institute&quot; Institutional Repository (eNTUKhPIIR)

Library of National Technical University "Kharkiv Polytechnic Institute"

RWTH Publications

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Publikationsserver der RWTH Aachen University

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