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ISSN 0020-1685, Inorganic Materials, 2017, Vol. 53, No. 9, pp. 973–979. © Pleiades Publishing, Ltd., 2017.Original Russian Text © K.S. Ivanov, E.A. Korotkov, 2017, published in Neorganicheskie Materialy, 2017, Vol. 53, No. 9, pp. 993–1000.

Effect of Sodium Silicate Slurries on the Propertiesof Alkali-Activated Materials

K. S. Ivanova, b, * and E. A. Korotkova, b

aInstitute of the Earth’s Cryosphere, Siberian Branch, Russian Academy of Sciences, ul. Malygina 86, Tyumen, 625000 RussiabTyumen State University, ul. Volodarskogo 6, Tyumen, 625003 Russia

*e-mail: [email protected] November 24, 2016; in final form, March 15, 2017

Abstract⎯We have studied the effect of water glass prepared by a wet-chemical process on the principal prop-erties of structural materials using alkali-activated mineral binders and determined the optimal hydrothermalleaching time for tripoli, corresponding to the maximum SiO2 concentration in the water glass slurry. We haveinvestigated the initial structure of the tripoli and the leaching-induced structural changes in its mineral com-ponent. The influence of three types of mixing agents has been analyzed in the context of the preparation ofmaterials: water glass in the form of slurry, water glass slurry filtrate, and the filtered-off insoluble residue ofthe slurry in the form of thick mass. The strength of the obtained materials increases in the following order:insoluble residue < filtrate < slurry. The present results demonstrate that the materials have high strengthcharacteristics and that water glass prepared by a wet-chemical process is potentially attractive for practicalapplication.

Keywords: water glass, tripoli, alkali activatedDOI: 10.1134/S0020168517090096

INTRODUCTIONWater glass is a multipurpose product which is used

in many industries and in the manufacture of variousmaterials: glass, ceramic, foam glass, composite bind-ers, concrete, and others. In a number of cases, hydro-thermal (wet-chemical) preparation of water glasswith the use of opal–cristobalite rocks allows one tomake the production process simpler and cheaper.Such rocks include diatomite, tripoli, and opoka withhigh contents of amorphous SiO2 varieties, whichallows for direct leaching, leading to the formation ofhydrated alkali silicates according to the scheme

(1)

where m is the silicate modulus (on the right-handside).

The hydrothermal process has a number of draw-backs: coloration of the final product and, in somecases, the necessity of boiling down to reach the presetdensity and the necessity of separating an insolubleprecipitate. The cause of the last drawback is thatopal–cristobalite rocks contain low-soluble quartzimpurities, clay minerals, zeolites, and organics,which leads to the formation of a colored water glassslurry (hereafter simply “slurry”). A negative effectmay also originate from the conversion of Al and Fecompounds into a soluble state, leading to gelation of

the product. Processes that use silica microparticlesand alkali-containing industrial waste are to someextent free from these drawbacks [1–3].

Even though the above-mentioned drawbacks pre-vent extension of hydrothermal water glass produc-tion, this process can be useful in a number of cases,for example, where slurries are used in the fabricationof foam glass-ceramics, sodium silicate binders, andother materials [4–6], as well as where an insolubleprecipitate can play a structure-forming role.

One potential application of slurries is the fabrica-tion of composite materials and concrete based onalkali-activated binders, which are mineral hydraulicbinders. Major components of such binders are alumi-nosilicate glasses (as a rule, blast-furnace slag and coalash), which are mixed with alkali solutions and waterglass. Such systems were first studied by Purdon [7].Further insight into their nature was provided byGlukhovskii. As a result these systems were named“alkali–alkaline earth aluminosilicate binders” andare thought to include blast furnace slag binders [8].Such systems exhibit the highest strength in the case ofmixing with water glass having a silicate modulus inthe range 1–2. In connection with this, the use of slur-ries in the preparation of alkali-activated materials isof practical interest.

The objectives of this work were to study the effectof leaching products of opal–cristobalite rock opal–

( )⋅ +

= ⋅ +2 2

2 2 2

SiO H O 2NaOHNa O SiO · 1 H O, m n

m n

974

INORGANIC MATERIALS Vol. 53 No. 9 2017

IVANOV, KOROTKOV

cristobalite rock on the properties of alkali-activatedstructural materials and substantiate the use of slurriesas mixing agents.

THEORETICAL ANALYSISThe silicate modulus and SiO2 concentration in

water glass for the preparation of alkali-activatedmaterials have a significant effect on the properties ofthe final product. For example, ground blast-furnaceslag mixed with aqueous solutions of sodium meta-and orthosilicates with SiO2 concentrations in therange 200–400 g/L possess higher strength in compar-ison with disilicate [8].

The ability to ensure predetermined parameters inthe preparation of a slurry according to scheme (1) isdetermined by the percentage of active silica phases,including opal and cristobalite, in raw materials. Theirdissolution rate can be influenced by a variety of fac-tors. For example, the maximum dissolved SiO2 con-centration after leaching diatomite from the Irbit for-mation (Sverdlovsk oblast) can be reached by using a2 N NaOH solution, a diatomite : NaOH solution (S : L)weight ratio of 1 : 8, and holding at 90°C for 4 h. Suchparameters ensure a dissolved SiO2 yield of 45 wt %,whereas the total SiO2 content of the rock is 78.2 wt %.The use of less concentrated NaOH solutions (1 and1.5 N) leads to a reduction in SiO2 yield [9]. Treatmentof diatomite with a 7.8 N NaOH solution at 90 °C andS : L = 1 : 4 ensures a maximum SiO2 yield after 1.5 h[10]; that is, the rate of the slurry preparation processincreases.

Note the three most important factors that influ-ence SiO2 leaching at 90°C: the grain size of the opal–cristobalite rock, the NaOH solution concentration,and the S : L ratio. The second and third factors havethe strongest effect on the viscosity of the resultantslurry, that is, on the feasibility of using it as a mixingagent, and, hence, will have certain limits, whichshould be taken into account in preparing slurries.

As a result of leaching of opal–cristobalite rocks,the associated impurities in the form of layered andframework aluminosilicates may react with alkali toform synthetic zeolites. For example, detailed data onzeolite synthesis from kaolin via treatment with NaOH

solutions were presented by Breck [11]. Ruiz-Santa-quiterial et al. [12] reported products of alkaline treat-ment of clay to contain a new phase in the form of fau-jasite (synthetic zeolite). It seems likely that the syn-thesis of new phases in slurries will be influenced aswell by silicon–oxygen anions with various degrees ofpolycondensation [13].

New zeolites in slurries, in turn, have a chemicalaffinity for reaction products of aluminosilicate glassesand alkalies and, therefore, can be effective componentsacting as a crystalline seed, which would be expected tomake it possible to control structure formation processesin materials in a systematic way [14].

EXPERIMENTAL

In our studies, we used tripoli from the Sukhoi Logdeposit, Sverdlovsk oblast. The tripoli was dried at100°C to constant weight and ground into powder thatpassed through a sieve with an aperture size of0.16 mm. The chemical composition of the tripoli isindicated in Table 1.

The structure of the tripoli and its leaching prod-ucts was studied by scanning electron microscopy on aJEOL JSM-6510A (Japan). The phase composition ofthe starting materials and reaction products in thegranulated blast-furnace slag (GBFS)–sodium sili-cate mixing agent system was determined by X-ray dif-fraction on a DRON-6 diffractometer (wavelength of0.179 nm, Ni-filtered Cu Kα radiation). The phasespresent were identified using American MineralogistCrystal Structure Database data.

X-ray diffraction data indicate a rather high degreeof amorphization of the rock, as evidenced by the verybroad reflection in the angular range 2θ = 18°–26°(Fig. 1, scan 1). The crystalline phase having reflec-tions at 21.50° (0.413 nm) and 35.46° (0.253 nm) wasidentified as high cristobalite (β-cristobalite) (Fig. 1,scan 1). According to the above-mentioned database,the reflections from β-cristobalite at angles of 21.50°and 35.46° have the highest and second highest inten-sities: 100 and 19.1%, respectively (code 0017646).The observed reflections from β-cristobalite are con-sistent with previously reported data [15].

Table 1. Chemical composition of components, wt %

SiO2 СaO Al2O3 MgO Fe FeO Fe2O3 TiO2 MnO K2O Na2O SO3 LoI

Tripoli

76.7 0.7 7.7 1.2 – 0.9 4.8 0.3 – 0.4 0.6 0.6 6.1

GBFS

38.2 38.6 10.5 7.6 – – 0.1 0.8 0.3 0.7 0.6 2.0 0.1

WMSTs

47.2 19.3 7.4 13.7 6.2 3.8 – 0.9 – – – – 1.5


EFFECT OF SODIUM SILICATE SLURRIES ON THE PROPERTIES 975

The phases present in the tripoli were identified asquartz (reflections at 26.65°, 36.56°, 39.49°, 40.41°,and 50.17°), montmorillonite (19.60° and 34.67°), andillite (whose reflections are similar to those frommontmorillonite).

In this case, high cristobalite is not an independentmineral phase but is a structural element of this silicaform. Its reflections are rarely encountered in X-raydiffraction patterns of opal–cristobalite rocks. Lowcristobalite (α-cristobalite), with characteristic reflec-tions at 0.400–0.404 and 0.248 nm, is present morefrequently, indicating the onset of opal crystallization.The presence of high cristobalite can be accounted forin terms of the metastable state of many siliceous min-erals, which often exist beyond their thermodynamicstability limits [16].

Scanning electron microscopy results confirm thatthe tripoli contains an opal–cristobalite component inthe form of loose spheres on the order of 1–2 μm insize (Fig. 2a). According to Sen’kovskii [16], this is aso-called lepispherical structure: the outer part of thespheres bristles up with lussatite (disordered cristob-alite) crystallites. We also identified remnants of dia-tom skeletons about 20–30 μm in size (Fig. 2b) andclay mineral impurities in the form of f lakes.

Slurries were prepared using a 4.3 N NaOH solu-tion. The tripoli and NaOH solution in the ratio S : L =1 : 4.4 were mixed in cylindrical stainless steel vessels.The S : L ratio and NaOH solution concentration werechosen under the assumption that the tripoli con-tained about 50 wt % amorphous SiO2. Theoretically,after leaching this yields a slurry of water glass havinga silicate modulus of unity (metasilicate), with a SiO2concentration of 100 g/L.

The vessels were covered with lids and the mixturewas leached under the following conditions: heatingover a period of 30 min, holding at 95°C with stirringevery 10 min, and natural cooling to a temperature of22 ± 2°C. Next, using an MPW-251 laboratory centri-fuge (Poland) at a rotation rate of 5000 rpm, the slurrywas separated into two components: water glass and aninsoluble residue (in the form of viscous mass). Thecentrifugation time was 5 min. To determine the SiO2concentration in solution and the silicate modulus asfunctions of holding time at 95°C, the water glass wasanalyzed by a high-speed method [17].

The aluminosilicate component of the material wasGBFS whose chemical composition is indicated inTable 1. The slag was comminuted in a vibratory millto a specific surface area of 300 m2/kg. Its X-ray dif-fraction pattern (not presented here) showed no dis-cernible ref lections, suggesting that it had a predomi-nantly amorphous structure.

As a filler material, we used bulk titanomagnetitedressing waste from the Kachkanar Mining ProcessingPlant (Kachkanar, Sverdlovsk oblast) in the form ofwet magnetic separation tailings (WMSTs). Thechemical composition of the waste is indicated inTable 1. According to X-ray diffraction results, themain constituent in the mineralogical composition ofthe filler are magnetite, diopside, and quartz.

The particle size composition of the WMSTs wasdetermined by sieving. The following size fractions wereobtained (wt %): 5 mm, 0.2; 2.5 mm, 1.3; 1.25 mm, 8.9;0.63 mm, 24.1; 0.315 mm, 37.3; 0.14 mm, 21.5; <0.14 mm,6.7. The bulk and true densities of the material were1540 and 3320 kg/m3, respectively.

Fig. 1. X-ray diffraction patterns of (1) tripoli from Sukhoi log, (2) the insoluble residue of the slurry, and (3) a synthetic stonefrom GBFS and the slurry: C = β-cristobalite, I = illite, M = montmorillonite, Q = quartz.

30 50402010

1

2θ, deg

2

3

MM

MM

M

M

M

M

MM

C

C

Q

QQ

QQQQQ

QQQQ

Q

Q

976


IVANOV, KOROTKOV

GBFS–sodium silicate mixing agent binder sys-tems were prepared and their physicomechanicalproperties were assessed according to standard meth-ods of testing cement (EN 196). Mixtures for thepreparation of an alkali-activated composite materialwere made manually in a spherical bowl: to three partsby weight of WMSTs was added one part of GBFS.After mixing, a sodium silicate component wasadded—slurry, water glass, or the insoluble residue—and the system was again mixed.

The amount of the sodium silicate component wasadjusted so that the amount of Na2O in the mixture

was 5% of the weight of GBFS. When necessary, waterwas added to the mixture to ensure that they had equalmobilities (consistencies), which corresponded to aVebe time of 30 s according to the EN 12350-3 methodof testing concrete mixtures.

The mixtures were consolidated by vibration insteel molds 4 × 4 × 16 cm in dimensions. The vibrationamplitude and frequency of the vibrating table were

0.5 mm and 3000 min–1, respectively. After 30 min, thesamples in the molds were heat-treated in saturatedwater vapor at atmospheric pressure and a temperatureof 90°C for 12 h. Uniform heating and cooling to roomtemperature took 2 h. The samples were then with-drawn from the molds and stored for 28 days at a tem-perature of 22 ± 2°C and relative humidity of 60 ± 5%.

The weight and dimensions of the samples weredetermined with an accuracy of 0.1 g and 0.5 mm,respectively. The average density was rounded to

1 kg/m3. The bending and compressive strength of thesamples was determined according to EN 196-1. Waterabsorption was evaluated as the difference between thesample weight after saturation with water and the ini-tial sample weight relative to the initial sample weight.The result was rounded to 0.1%. To determine waterabsorption, the samples were immersed in distilledwater so that its surface was 50 ± 5 mm above theupper sample face.

The water resistance of the samples was quantifiedby the softening coefficient: the ratio of the bendingstrength of the samples after saturation with water tothe initial bending strength.

The frost resistance of the samples was assessed bya rapid test method in conformity with the RussianFederation State Standard GOST 10060.2. To thisend, the samples were saturated with an aqueous 5%NaCl solution and control specimens were tested inbending. The main samples were subjected to cyclicfreezing (in air at –18 ± 1°C) and thawing (in a 5%aqueous NaCl solution at 18 ± 2°C), followed bybending tests after every five cycles. The frost resis-tance of the samples corresponded to the maximumnumber of freezing–thawing cycles at which the com-pressive strength decreased by no more than 5% com-pared to control specimens.

Fig. 2. Scanning electron microscopy images of the (a, b)starting tripoli and (c, d) insoluble residue (after washingwith water).

55 μm

1010 μm

1010 μm

5050 μm

5 μm

10 μm

10 μm

50 μm

(b)

(c)

(d)

(a)



RESULTS AND DISCUSSION

The tripoli leaching time was optimized by deter-mining the SiO2 concentration in the clear part of the

slurry after holding at 95°C. In particular, at the S : Lratio and NaOH solution concentration used, themaximum SiO2 concentration is reached in 1 h and is

160 g/L, and the silicate modulus of the slurry is 1.37.Increasing the leaching time to 4 and 8 h causes no sig-nificant changes in SiO2 concentration, so we are led

to conclude that the leaching process takes 1 h.

In the X-ray diffraction pattern of the insoluble res-idue of the slurry after h of heat treatment and wash-ing (Fig. 1, scan 2), reflections from β-cristobalite andthe broad reflection in the angular range 2θ = 18°–26°, corresponding to amorphous SiO2, are missing.

This attests to dissolution of the opal–cristobalitecomponent of the tripoli and the formation of a waterglass slurry.

Electron microscopic data for the insoluble residueare consistent with its X-ray diffraction pattern. InFigs. 2c and 2d, one can see quartz grains and the claycomponent of the tripoli, which has a layered, f lakystructure. There is no SiO2 in the form of spheres or

diatom skeletons, which suggests that such structuresdissolved in the alkali solution.

Thus, the insoluble residue of the slurry is a mix-ture consisting predominantly of minerals present inthe tripoli before leaching: quartz, montmorillonite,and illite. No products of reaction of clay mineralswith NaOH in the form of synthetic zeolites weredetected. It seems likely that the formation of suchproducts was hindered by the presence of silicateanions with various degrees of polymerization (in con-trast to the initial assumption).

Table 2 presents the main properties of the GBFS–sodium silicate mixing agent binder system. The insol-uble residue and water glass were obtained by centri-fuging the slurry after 1 h of hydrothermal treatment.All of the mixing agents were added in amounts equiv-alent in terms of Na2O content, which ensured a

GBFS : Na2O weight ratio of unity. This reflects on

the different percentages of GBFS and the mixingagent (Table 2).

The almost twofold increase in the onset time andend point of the setting of the mixtures on the insolu-ble residue is due to the addition of water necessary forensuring identical viscosities of the mixtures. Dilution

of the insoluble residue inevitably leads to a reductionin total hydroxide ion concentration and, as a conse-quence, to a reduction in the activity of the binder,which shows up as an increase in setting time and analmost a factor of 2 decrease in bending strength. Thesetting times of mixtures on the slurry and the waterglass obtained from it depend little on the nature of themixing agent.

The reaction products of binder mixtures (slurryand GBFS) in the form of a synthetic stone wereinvestigated by X-ray diffraction. The diffraction pat-tern of the sample on water glass has no well-definedreflections and is essentially identical to that of GBFS,suggesting that the reaction products are X-ray amor-phous, that is, have a disordered, cryptocrystallinestructure.

Figure 1 shows the X-ray diffraction pattern of thesample on the slurry (scan 3). In addition to reflec-tions characteristic of montmorillonite, illite, andquartz, there is a reflection at 29.1° (0.303 nm), whichpoints to a crystalline nature of the stone. However, wefailed to identify the synthesized hardening product.

As seen from Table 2, the material on the slurry hasthe highest strength. This may be due not only to thepresence of an additional microfiller in the form ofparticles of the insoluble residue of the slurry, whichcontributes to a more ordered packing of fine compo-nents of the binder system, but also to the strengthen-ing effect of reaction products forming in the sampleson the slurry.

Table 3 summarizes the main properties of thealkali-activated composite materials prepared usingthree types of mixing agent. The samples on the insol-uble residue have a reduced average density, which isdue to the higher content of clay fractions. As a result,such a mixture requires additional water for reaching agiven consistency, which in turn produces additionalporosity in the material after hardening.

The increased porosity of the material on the insol-uble residue is also evidenced by the fact that its waterabsorption is twice that of the samples on the slurryand water glass (Table 3). All this influences thestrength characteristics of the material on the insolu-ble residue: the bending (6.2 MPa) and compressive(46 MPa) strength of the samples is almost a factor of2 lower than that of the samples prepared using theslurry and water glass. As in the case of the binder mix-tures, the lower strength of the samples on the insolu-

Table 2. Properties of the composite binder

No. Mixing agentGBFS/mixing agent

ratio

Setting interval (hours–minutes) Compressive strength,

MPaonset end point

1 Slurry 70/30 1–00 3–00 77.2

2 Water glass 71/29 1–05 3–00 72.0

3 Insoluble residue 66/34 1–55 6–30 40.4

978


IVANOV, KOROTKOV

ble residue is caused as well by the lower hydroxide ionconcentration as a result of the dilution of the mixturewith water in order to reach a given consistency.

The highest strength is offered by the samples onthe slurry (88 MPa). The strength of the samples onwater glass is slightly lower (82 MPa). In the formercase, this seems to be due to the addition of an extramicrofiller from the insoluble residue of the slurry,which leads to a more ordered arrangement of thebinder particles. Similar behavior is observed in thecase of the binder mixture samples (Table 2) whenwater glass and the slurry are used as mixing agents. How-ever, an opposite picture is observed in the case of thebending strength of the samples: 12.4 against 11.6 MPa.The origin of this discrepancy is not yet clear.

The highest water resistance is offered by the sam-ples on water glass, which are free from clay impurities.In comparison with the samples on water glass, the useof the slurry and insoluble residue reduces the soften-ing coefficient of the samples from 1 to 0.9 and 0.87,respectively.

The softening coefficient of the samples is seen tobe directly related to their water absorption: as the lat-ter increases, the softening coefficient decreases.Thus, an increase in the content of the insoluble resi-due in the material leads to an increase in its porosity,because it is then necessary to add an extra amount ofwater during mixing. An increase in porosity systemat-ically leads to a decrease in the softening coefficient ofthe samples.

The frost resistance of the samples is also directlyrelated to their water absorption. The number of freez-ing–thawing cycles for the materials on the slurry,water glass, and insoluble residue was 260, 290, and40, respectively. These frost resistance parameters ofthe samples indirectly characterize their capillary poros-ity, which increases, like water absorption (Table 3), inthe following order: water glass < slurry < insolubleresidue. An increase in the content of the insolubleresidue in the samples leads to an increase in their cap-illary porosity and water absorption, which has a neg-ative effect on the ability of the material to withstandfreezing–thawing cycles without strength loss.

CONCLUSIONS

It has been shown that the optimal hydrothermalleaching time necessary for complete dissolution of

the opal–cristobalite component of tripoli at 95°Cusing a 4.3 N NaOH solution with an S : L ratio of 1 :4.4 is 1 h.

Using the proposed scheme, we have obtainedmixing agents for the preparation of alkali-activatedmaterials: slurry, water glass, and the insoluble residueof the slurry in the form of viscous mass (after centrif-ugation). The strength of the samples depends signifi-cantly on the nature of the mixing agents, even thoughthey were added in equivalent amounts in terms ofNa2O. The compressive strength decreases in the

order slurry > water glass > insoluble residue: 77.2,72.0, and 40.4 MPa, respectively, for mixing agent–GBFS binder mixtures and 88, 82, and 46 MPa forcomposite materials using WMSTs.

The decrease of compressive strength in this ordercan be accounted for by the absence of a microfiller inthe form of the insoluble residue of the slurry in thecase of the use of water glass and by the addition of anextra amount of water for ensuring a given mixtureconsistency in the case of the preparation of sampleson the insoluble residue. The latter leads to an increasein the capillary porosity of the samples and their waterabsorption in the order water glass < slurry < insolubleresidue, causing a decrease in the softening coefficientand frost resistance of the samples on the slurry andinsoluble residue.

Given that the compressive strength of the sampleson the insoluble residue reaches 46 MPa (with a bend-ing strength of 6.2 MPa) and that the insoluble residueis a by-product of the wet-chemical preparation ofwater glass, we envisage that using it in the preparationof binder mixtures and related materials will be eco-nomically justified. At the same time, the high contentof insoluble clay fractions requires additional mea-sures to reduce the capillary porosity of the materialsdue to the increased water requirement of moldingcompounds.

REFERENCES

1. Rusina, V.V. and Korda, E.V., Principles of water glasspreparation from anthropogenic raw materials, TsementPrimen., 2012, no. 3, pp. 108–114.

2. Karnaukhov, Yu.P., Belykh, S.A., Lebedeva, T.A., andKudyakov, A.I., Fabrication of porous materials forenclosing structures from cellular loaded water glass, Izv.Vyssh. Uchebn. Zaved., Stroit., 2003, no. 2, pp. 59–63.

Table 3. Properties of the alkali-activated composite material (GBFS + WMSTs + mixing agent)

No. Mixing agentAverage density,

kg/m3

Bending strength,

MPa

Compressive

strength, MPa

Water absorption,

wt %

Softening

coefficient

1 Slurry 2550 11.6 88.0 1.4 0.90

2 Water glass 2560 12.4 82.0 1.2 1.00

3 Insoluble residue 2505 6.2 46.0 3.6 0.87



3. Glebov, M.P., Lokhova, N.A., Sharova, V.V., andPatramanskaya, S.V., Application of anthropogeniccellulose production eff luents in the fabrication of asemidry-pressed wall material, Izv. Vyssh. Uchebn.Zaved., Stroit., 2001, no. 1, pp. 49–53.

4. Ivanov, N.K., Radaev, S.S., and Shorokhov, S.M.,Structure formation in water glass- and opal rock-basedsystems, Stroit. Mater., 1998, no. 8, pp. 24–25.

5. Ivanov, N.K., Suvorov, S.A., and Sklyanov, S.V., Fab-rication of building materials based on opal rocks fromTyumen and Sverdlovsk oblasts, Izv. Vyssh. Uchebn.Zaved., Stroit., 2002, no. 5, pp. 43–46.

6. Ivashchenko, Yu.G. and Strakhov, A.V., Properties of asodium silicate binder prepared by hydrothermal syn-thesis from silicitic rocks, Vestn. Saratovsk. Gos. Tekh-nol. Univ., 2010, vol. 4, no. 1 (49), pp. 193–200.

7. Purdon, A.O., The action of alkali on blast-furnaceslag, J. Soc. Chem. Ind., London, 1940, vol. 59, no. 53,pp. 191–202.

8. Shchelochnye i shchelochno-shchelochnozemel’nyegidravlicheskie vyazhushchie i betony (Alkali andAlkali–Alkaline Earth Hydraulic Binders and Con-crete), Kiev, 1979.

9. Balayan, M.A. and Balekaev, A.G., Properties of sili-ceous solutions based on Ural diatomites, Glass Ceram.,1988, vol. 45, no. 9, pp. 325–327.

10. Filippovich, E.N., Khatsrinov, A.I., and Egorova, T.V.,Optimization of Inza diatomite processing for thepreparation of crystalline sodium silicates, Vestn. Kaz.Gos. Univ., 2010, no. 8, pp. 272–276.

11. Breck, D.W., Zeolite Molecular Sieves: Structure, Chem-istry and Use, New York: Wiley, 1973.

12. Ruiz-Santaquiterial et al., Clay reactivity: Productionof alkali activated cements, Appl. Clay Sci., 2013,vol. 73, pp. 11–16.

13. Ivanov, N.K., Ivanov, K.S., and Radaev, S.S., Degreeof polymerization and alkalinity of water glasses, Tekh.Tekhnol. Silikatov, 2015, no. 4, pp. 12–18.

14. Krivenko, P.V., Skurchinskaya, Zh.V., and Sido-renko, Yu.A., New generation of blast furnace slagbinders, Tsement, 1991, no. 11, pp. 4–8.

15. Barth, T., The cristobalite structures. I. High-cristob-alite, Am. J. Sci., 1932, vol. 23, pp. 350–356.

16. Sen'kovskii, Yu.N., Litogenez kremnistykh tolshch yugo-zapada SSSR (Lithogenesis of Siliceous Masses in theSouthwest of the USSR), Kiev, 1977.

17. Sokolovich, V.E., Rapid method of determining themodulus of sodium silicate solution, Glass Ceram.,1963, vol. 20, no. 9, pp. 471–472.

Translated by O. Tsarev

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