Cellular glass ceramic materials on the basis of zeolitic rock

Construction and Building Materials 36 (2012) 940–946

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Technical Note

Cellular glass ceramic materials on the basis of zeolitic rock S. Volland a,⇑, V. Vereshchagin b a b

Technical University Darmstadt, Institute of Concrete and Masonry Structures and Building Materials, Petersenstr. 12, 64287 Darmstadt, Germany Tomsk Polytechnic University, Department of Silicate Technology and Nanomaterials, 30, Lenin Avenue, 634050 Tomsk, Russia

a r t i c l e

i n f o

Article history: Received 6 July 2010 Received in revised form 15 May 2012 Accepted 4 June 2012 Available online 31 July 2012 Keywords: Lightweight aggregates Building materials Processing Raw materials Porous materials

a b s t r a c t This paper presents the results of investigations referring to a low-temperature technology for the production of cellular granulated materials on the basis of zeolitic rock. Using zeolitic rock from two different Russian deposits porous granulated materials were produced at process temperatures below 900 °C. Dolomite and chalk were used as carbonate expanding agents. The obtained material possesses a compressive strength of 8.8–15.7 MPa, and a bulk density of 570–690 kg/m3. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction The present day world economic situation urgently calls for a solution of a multitude of energy saving tasks, among which an increase of the energy efficiency of building enclosures like walls and roofs represents one of the prime problems. Today a great variety of highly efficient heat insulating materials is available, but the dilemma is in that their application must not degrade construction reliability. The answer to this problem is the application of easily available and inexpensive materials on a mineral basis with tolerably low pay-back time of their manufacture and use. A favorite among these is a cellular lightweight material on the basis of natural zeolitic rock, combining excellent heat insulation capability with good mechanical rigidity. Zeolites are alkali and/ or earth-alkali aluminosilicates, which show the phenomenon of foaming when heated to sufficiently high temperatures (1100– 1200 °C) [1]. The authors of [1] report having elaborated a technology that allows them to produce a porous material on the basis of zeolite containing minerals and a process temperature of 1100–1200 °C. The authors of [2–7] propose to use zeolite containing tuffs from Italy to produce light weight porous fillers and propose different technological parameters, still adhering to a high temperature process. The prime advantage of zeolite based porous heat-insulating materials over its competitors like fusible clays, vermiculite, and ⇑ Corresponding author. Tel.: +49 0615116125; fax: +49 06151165344. E-mail address: [email protected] (S. Volland). 0950-0618/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2012.06.039

perlite, is in that addition of adequate fusing agents to the raw mixture can substantially lower the process temperature and thus reduce energy consumption [8–10]. In this study, basic research was carried out to quantitate the influence of an addition of carbonate expanding agents on the properties of the porous granulated materials on the basis of zeolitic rocks from two Russian deposits.

2. Raw materials Zeolites are tectosilicates characterized by wide-meshed invested structures with big hollow cavities or canals containing big cations like Na+, Ca2+, K+, Ba2+ and Sr2+, and especially H2O molecules, called zeolite water. Loose bonds render the cations easily interchangeable. The zeolite water can be gradually driven out by moderate heating, without breaking down the aluminosilicate frame [1,12]. The investigations described hereafter used zeolitic rock originating from two Russian deposits: either from the Sakhaptinskoje deposit (Krasnoyarsk region) or from the Pegasskoje deposit (Kemerovo region). Sakhaptinskoje deposit: zeolite crystal dimensions in this rock cover a range from 1 to 20 lm. Apart from the zeolite target material (heulandite and clinoptillolite), the mineral composition comprises silica, plagioclases and clay minerals. The zeolite and montmorillonite weight fraction is in the range of 47–88%. Fig. 1 shows the XRD patterns of zeolitic rock from the Sakhaptinskoje deposit.

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Qz

Heu Cli

Heu Cli

Qz

Heu Cli Cl Mo Heu

Heu Cli Pl

Mo Heu Cli Pl

Qz Qz Qz Qz

15

20

25

30

35

Qz

40

Mo

45

Pl Mo

50

55

60

2θ Fig. 1. X-ray diffraction pattern (CuKa) for zeolitic rock from Sakhaptinskoje deposit Cli – clinoptillolite; Heu – heulandite; Qz – Quartz; Pl – plagioclases; Mo– montmorillonite.

2900 kg/m3. In the described investigations dolomite from the Tarabukinskoje deposit was used. The chemical properties are shown in Table 3. Chalk is a soft, white, porous sedimentary rock, a type of limestone, composed of the mineral calcite. The chemical composition of the chalk used in the present studies is listed in Table 4.

Pegasskoje deposit: Rock from this deposit contains up to 80% of zeolite (heulandite). Other components are hydromica, chalcedony, montmorillonite, and scattered crystals of magnetite and pyrite [1]. Fig. 2 shows the XRD patterns obtained for zeolitic rock from the Pegasskoje deposit. Table 1 summarizes the chemical compositions of zeolite rock from the Sakhaptinskoje and the Pegasskoje deposits [1]. To lower the fusion temperature of the mixture, soda ash was added as a fusion agent, the composition of which is given in Table 2 below. As a expanding agent, alternatively two carbonate additives were used in the production of granulated foam zeolite: dolomite and chalk. Dolomite rock is a sedimentary carbonate rock containing a high percentage of the mineral dolomite (90%). Theoretically dolomite contains: 47.9 wt.% CaCO3 and 45.65 wt.% MgCO3. The Mohs hardness is 3.5–4.0, and the density is of the order of 2800–

3. Investigations of the thermal behavior of raw mixes on the basis of zeolitic rock A TA-Instruments TG SDT Q600 thermogravimetric analyzer was used to determine the thermal behavior of raw mixes on the basis of zeolitic rock. In Fig. 3 the results of synchronous thermal analysis of the zeolitic rock of Sakhaptinskoje and Pegasskoje deposits is presented. A characteristic feature of zeolites is the gradual release of water upon moderate heating, occurring without damage to the aluminosilicate skeleton frame.

Qz Heu

Heu Heu Heu

Mo Heu

Heu Pl

Mo

Heu

Qz

15

20

25

30

35

40

Qz

Qz Mo

Qz

45

Mo

50

55

60

2θ Fig. 2. X-ray diffraction pattern (CuKa) for zeolitic rock from Pegasskoje deposit Cli – clinoptillolite; Heu – heulandite; Qz – Quartz; Pl – plagioclases; Mo – montmorillonite.

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Table 1 Chemical composition of the primary material. Origin of zeolite rock

Oxide content (wt.%)

Sakhaptinskoje deposit Pegasskoje deposit

SiO2

TiO2

Al2O3

Fe2O3

CaO

MgO

R2O

Loss on ignition

64.8 62.9

0.35 0.29

12.77 11.96

2.46 3.34

2.5 4.49

1.84 1.25

3.83 1.58

11.12 14.0

Table 2 Chemical composition of the soda ash. Na2CO3 (%)

Chloride (NaCl) (%)

Sulfate (R2SO4) (%)

Fe2O3 (%)

Insoluble residue (%)

Loss on ignition (270–300 °C) (%)

99.0

<0.5

<0.05

<0.003

<0.04

<0.8

Table 3 Chemical composition of the dolomite.

4. The influence of the carbonate expanding agent on the properties of granulated foam zeolites

SiO3

Al2O3

CaO

MgO

Fe2O3

2.0

1.5

34.0

18.0

0.23

Table 4 Chemical composition of the chalk. Oxide content (wt.%) SiO3

Al2O3

Fe2O3

CaO

MgO

SO3

Loss on ignition

1.48

0.53

0.37

55.38

0.25

–

42.27

The endothermic effects at 98.7 °C (Fig. 3a) and 103.2 oC (Fig. 3b) correspond to the release of adsorbed water. The subsequent rapid weight loss up to a temperature of about 400 °C can be attributed to the loss of interpackage water from montmorillonite and of zeolitic water from clinoptillolite and heulandite. The process is more pronounced for zeolite rock from the Pegasskoje deposit, a consequence of its specific mineralogical composition and the high zeolite content. Earlier investigations using zeolitic rock from the Sakhaptinskoje deposit had shown that the production of porous glass ceramic material is possible at a foaming temperature as low as 850 °C [8–10]. Fig. 4 shows again the results of the synchronous thermal analysis of a raw mix on the basis of Pegasskoje zeolitic rock, but in contrast to Fig. 3a, soda ash had now been added as a fusion agent. The endothermic effect at 114.2 °C (DTA) corresponds to the release of adsorbed water. The subsequent weight loss of 10.89% over the temperature interval from 400 to 700 °C can be attributed to water release from the zeolite, connected with the presence of Na+ and K+ cations, and of fixed water from the montmorillonite structure. If the temperature is further increased, chemical reactions start in the temperature interval 720 – 850 °C, characterized by the formation and the melt of a eutectic composition. The interaction of the soda ash with the silica leads to the formation of sodium-silicate and the liberation of CO2.

Na2 CO3 þ 2SiO2 ! Na2 SiO3 þ 2CO2 " Based on the chemical composition of the zeolitic rock from the Pegasskoje deposit (see Table 1), and taking into account the sodium oxide content introduced with the soda additive, the point of complete melting of the solid phase could be determined. The melt point of the mix has been identified and is marked by a letter B in Fig. 5. Using the ternary phase diagram for the system Na2O–Al2O3–SiO2 the start point of mix melting of the calculated composition could be determined as 732 °C (eutectic point T).

The objective of these investigations was to look into the influence of adding different carbonate expanding agents to the raw mix composition on the properties of the zeolite rock based porous granulated material. In accordance with the conditions of high temperature foaming, the formation of a homogeneous porous structure in the course of foaming silicate materials is conditioned by two main processes: the establishment of the pyroplastic state of a material with optimum viscosity and the release of gases that cause foaming of the material. Only when these two processes coincide, a cellular foam structure will be formed. As expanding agents, traditional carbonate additives were used, known to be employed also for the production of foam glass: dolomite and chalk. Using the recommended quantities for the production of foam glass as a guideline, the content of expanding agents in the raw mix was chosen as 1 wt.% [13]. For the preparation of the raw materials mix, the zeolitic rock was ground in a ball mill. After adding soda ash (see Table 4) to increase the alkali content, the mixture was fritted at 700 °C. The generated frit was then ground and an expanding agent was added. Then granules were formed from the so obtained intermediate product using a plate granulator. The granules were foamed in a muffle furnace, and afterwards cooled down. Table 5 summarizes the properties of the granulated materials (fraction 5–10 mm) obtained using zeolite rock from different deposits and alternatively chalk and dolomite expanding agents. The bulk density, the water adsorption and the particle strength of the so obtained foam zeolites were determined in accordance with the standardized Russian test method GOST 9758-86 [14]. According to this standard, the water absorption is defined as the difference in material mass between the dry state and after a 1 h immersion in water. The compressive strength of the porous granular material is determined in the following way: The material is filled into a cylinder of cross section area F. A piston is then enforced into the cylinder, until the material is compressed by 20 mm. With force P required to achieve this compression, the compressive strength Rcs results as

Rcs ¼ P=F;

ð1Þ

where P is the piston load necessary to compress the material by 20 mm, N; and F is the cross section area of the cylinder, cm2. Porosity of granules was calculated in accordance with the standardized Russian test method GOST 9758-86 [14] by the following formula:

P ¼ ð1  ðqrel =qtrue ÞÞ  100

ð2Þ

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DTG

3.05% 624.6°C 5.10J/g

403°C

622.1°C 0.05µV·min/mg

DTA

Mass (%)

85

662.19°C 29.35% 189.8°C

281.5°C 139.0J/g

70 98.7°C

296.8°C 1.56µV·min/mg

TG

0.25

0.5

0.00

0.0

-0.25

-0.5

-0.50

-1.0

-0.75

-1.5

1.99%

196.0J/g 3.62µV·min/mg

-2.0 1000

55 0

1.0

Heat flow (W/g)

100

Temperature difference (μV/mg)

(a)

200

400

600

800

Temperature (°C) 100

1.0

0.008

Mass (%)

5.49%

389.7°C

DTA 861.9°C 3.73J/g

0.006 131.8J/g 1.90µV·min/mg

665.8°C

95

886.4°C

0.004 178.1°C 103.2°C

1.88%

0.002 38.4°C 163.4J/g 38.5°C 2.45µV·min/mg

90 0

TG

1.77%

0.25

0.5

0.00

0.0

-0.25

-0.5

-0.50

-1.0

-0.75

-1.5

Heat flow (W/g)

DTG

Temperature difference (μV/mg)

(b)

-2.0

200

400

600

800

1000

Temperature (°C) Fig. 3. TG, DTA and DTG graphs of zeolitic rock from the Pegasskoje (a) and Sakhaptinskoje (b) deposits.

536.6°C 6.8J/g

1

793.5°C 62.3J/g 793.5°C 0.49µV·min/mg

DTG

19.13%

DTA

Mass (%)

578.0°C

80 821.7°C 930.2°C

13.07%

TG 4.63% 5.70%

60

0

0

-1

-1

-2

-2

-3

-3

114.2°C 89.9°C

0

200

Heat flow (W/g)

32.8°C 768.8J/g 32.8°C 11.30µV·min/mg

Temperature difference (μV/mg)

100

-4 400

600

800

1000

Temperature (°C) Fig. 4. TG, DTA and DTG graphs of zeolitic rock from the Pegasskoje raw materials with soda ash additive.

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SiO2

Cristobalite

Quarz

B

Na2O·2SiO2 T

Na2O·SiO2

2Na2O·SiO2 3Al2O3·2SiO 2

Na2O

Na2O·Al2O3

Al2O3

Fig. 5. Equilibrium diagram of the system Na2O–Al2O3–SiO2 with fields of the primary crystalline phases, isotherms and temperatures of binary and ternary invariant points [11].

Table 5 Properties of granulated foam zeolite on the basis of zeolitic rock originating from different deposits and using carbonate expanding agents. Properties of granulated foam zeolite

Compressive strength (MPa) Water absorption (%) Bulk density (kg/m3) Relative density (kg/m3) True density (kg/m3) Granule porosity (%)

Zeolitic rock Sakhaptinskoje deposit

Pegasskoje deposit

Chalk

Dolomite

Chalk

Dolomite

15.7 2.1 696 1157 1921 40

8.8 3.3 665 912 1837 50

11.45 8.8 683 1025 2066 50

13.2 15.3 573 824 2046 60

where P is the total porosity, %; qrel the relative density, g/cm3; and qtrue is the true density, g/cm3. Table 6 shows that the granulates produced using 1 wt.% of dolomite as an expanding agent are characterized by a favorably low density, but rather high water absorption. Samples on the basis of zeolite rock from the Sakhaptinskoje deposit show water

absorption values from 2% to 4%, considerably lower than the corresponding values for samples prepared on the basis of zeolite rock from the Pegasskoje deposit. Both, quantity and structure of the expanding agent influence the structure of the granulated foam zeolite. The structure is characterized by the size and form of the cells, the quantity of

Table 6 Stability against silicate disintegration of granulated foam zeolite using different expanding agents. Samples name

Expanding agent

Materials weight before test (g)

Weight loss on the sieve after test (g)

Weight loss by steaming (%)

S-700,850 S-700,850 P-700,900 P-700,900

Dolomite Chalk Dolomite Chalk

2.022 3.397 2.703 5.410

1.961 3.309 2.636 5.302

3.0 2.6 2.5 2.0

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Fig. 6. Granular zeolite produced on the basis of raw materials the Pegasskoje deposit using (a) dolomite and (b) chalk as an expanding agent.

Samples of granulated zeolite based on raw materials from the two deposits have been tested for stability against silicate disintegration (alkali–silica reaction ASR). Firmness against silicate disintegration is tested by recording the weight loss of a sample before and after alternating steaming and cooling cycles. Granules are steamed during 3 h, and then immersed for 3 h in a water bath held at room temperature. These steaming and cooling cycles are repeated three times. After termination of this procedure, the samples are dried to constant weight and subsequently weighed. The sample weight loss Mc in percent upon steaming is calculated using the following formula:

interconnecting pores and the condition of dividing walls. The microscopic photographs of Fig. 6 show clearly that the samples have a porous structure. The most pronounced porosity of 60% (see also Table 7) is observed in the case, where the sample is based on zeolite rock from the Pegasskoje deposit with dolomite additive (Fig. 6a). It is important to note, however, that these samples show open and interconnecting pores, a feature that drastically increases material water absorption. The mineralogy of expanded granulates based on zeolitic rock from the Pegasskoje deposit was determined using X-ray power diffraction analysis, with the patterns for materials shows in Fig. 7. A considerable part of the material is amorphous – the crystalline phases are quartz, plagioclases and diopside.

Mc ¼ ððm1  m2 Þ=m1 ÞÞ100

where m1 is the sample weight before steaming, g; and m2 is the sample weight on the sieve after steaming, g. The weight loss is calculated as an average arithmetic value of the results of two parallel measurements for each material type [14]. The results of the steaming tests are summarized in Table 6. All measured values of the weight loss are below 3% and thus comply with the Russian standard GOST 9757-90 [15]. Table 7 shows the properties of expanded clay, in accordance with the standardized Russian request GOST 9757-90 and of granulated foam zeolite. Granulated foam zeolite meets the requirements and can be used, as well as expanded clay, as lightweight aggregates for concrete and as heat insulating filling.

Table 7 Properties of expanded clay in accordance with the standardized Russian request GOST 9757-90 and granulated foam zeolite. Expanded clay

Granulated foam zeolite

Compressive strength (MPa)

Bulk density (kg/m3)

Compressive strength (MPa)

Bulk density (kg/m3)

2–2.5 2.5–3.3 3.3–4.5 4.5–5.5

500 600 700 800

8.8 11.45 13.2 15.7

665 683 573 696

ð3Þ

Pl

Qz

Pl

Pl Di

Di

Pl

Qz

Qz

15

20

25

30

35

Qz

40

Qz

Pl Di

Pl

45

50

Pl

Qz Di

55

60

2θ Fig. 7. X-ray diffraction pattern (CuKa) for expanded granules from zeolitic rock Qz – Quartz; Pl – plagioclases; Di– Diopside.

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5. Summary and conclusions The investigations described in this article have shown that melting of a raw mix on the basis of zeolite rock from the Pegasskoje deposit requires a substantially higher temperature than melting of a raw mix using Sakhaptinskoje zeolite rock. Two types of gas-forming agents were used: dolomite and chalk. The best material properties were obtained for the granulated foamed zeolite samples based on zeolite rock from the Sakhaptinskoje deposit combined with a dolomite expanding agent. The porosity of the granulated foam zeolite using different types of expanding agents always exceeded 50%. The obtained foam zeolite is stable against silicate disintegration, the steaming weight loss never exceeding a value of 3%. The compressive strength and bulk density of granulated foam zeolite meet the requirements of standardized Russian specifications, and the material can be used, as well as expanded clay, as lightweight aggregates for concrete and as heat insulating filling. Acknowledgements Research focusing on the use of zeolitic rock in the production of lightweight aggregates was performed within the program ‘‘Mikhail Lomonosov’’ and was financed by the German academic exchange service and the Ministry of Education and Science of the Russian Federation. References [1] Ovtscharenko GI, Sviridova VA, Kasanzeva KL. Zeolites in the building materials. Barnaul: Altai State Technical University Publishing House; 2000.

[2] Doldi M, Cappelletti P, Cerri G, Gennaro M, Gennaro R, Langella A. Zeolitic tuffs as raw materials for lightweight aggregates. Key Eng Mater 2004;264– 268:1431–4. [3] Gennaro R, Dondi M, Colella A, Langella A. Use of high zeolite-bearing as raw material for the preparation of lightweight aggregates. In: Proceeding of the 7th European conference on advanced materials and processes. EUROMAT 2001; 2001. p. 1–7. [4] de Gennaro R, Cappelletti P, Cerri G, de’ Gennaro M, Dondi M, Langella A. Zeolitic tuff as raw material for lightweight aggregates. Appl Clay Sci 2004;25:71–81. [5] de Gennaro R, Cappelletti P, Cerri G, de’ Gennaro M, Dondi M, Langella A. Neapolitan yellow tuff as raw material for lightweight aggregates in lightweight structural concrete production. Appl Clay Sci 2005;28:309–19. [6] de Gennaro R, Cappelletti P, Cerri G, De’ Gennaro M, Dondi M, Graziano SF, Langella A. Campanian ignimbrite as raw material for lightweight aggregates. Appl Clay Sci 2007;37:115–26. [7] de Gennaro R, Cappelletti P, D’Amore M, Colella A, de’ Gennaro M, Dondi M, et al. Use of zeolite-rich rocks and waste materials for the production of structural lightweight concretes. Appl Clay Sci 2008;41:61–72. [8] Vereshchagin VI, Sokolova SN. Forming of porous structure of the granular glass ceramic material from zeolitic rocks with alkaline additions. Glass Ceram 2006;7:17–9. [9] Mueller A, Vereshchagin VI, Sokolova SN. Characteristics of lightweight aggregates from primary and recycled raw materials. Constr Build Mater 2008;22:703–12. [10] Vereshchagin VI, Sokolova SN. Granulated foam glass-ceramic material from zeolitic rocks. Constr Build Mater 2008;22:999–1003. [11] Schairer JF, Bowen NL. Am J Sci 1956;254:129–95. [12] Breck D. Zeilitic molecular sieves. Moskow: Mir Publishing House; 1976. [13] Demidovich BK. Penosteklo. Minsk: Nauka i tekhnika; 1975. [14] GOST 9758-86. Porous inorganic aggregates for civil engineering. Test methods. Izdatelstvo standartov. Moscow: Publishing House; 1987. p. 60. [15] GOST 9757-90. Artificial porous gravel, crushed stone and sand. Specifications. Izdatelstvo standartov. Moscow: Publishing House; 1986. p. 30.