CC BY
97
СТРОИТЕЛЬСТВО CIVIL AND INDUSTRIAL ENGINEERING
DOI: 10.21122/2227-1031-2017-16-6-459-465 UDC 691.32:539.3/4.001.57
Composite Materials Based on Cement Binders Modified with Si02 Nanoadditives
В. M. Khroustalev", S. N. Leonovich", V. V. Potapov2', E. N. Grushevskaya"
1 'Belarasian National Technical University (Minsk, Republic of Belarus), 2'Scientific Research Geotechnological Center Far Eastern Branch of Russian Academy of Sciences (Petropavlovsk-Kamchatsky, Russian Federation)
© Белорусский национальный технический университет, 2017 Belarasian National Technical University, 2017
Abstract. Development of nanotechnologies allows to solve a number of problems of construction materials science: increase in strength, durability, abrasion and corrosion resistance that determines operational reliability of building constructions. Generally it is achieved due to nanoparticles that modify the structure and properties of the existing materials or products and are entered into their volume or on a surface layer. It's theoretically and experimentally proved that the modified water has the bigger activity owing to the change of the ionic composition influencing the pH size and other parameters. As nanoparticles have a high level of surface energy, they show the increased tendency to agglomeration, meanwhile the size of agglomerates can reach several micrometers. In this regard an urgent task is to equally distribute and disaggregate the nanoparticles in the volume of tempering water. The experiments on studying of influence of the nanoparticles of silica distributed in volume of liquid by means of ultrasonic processing on characteristics of cement and sand solution and heavy concrete have been conducted. Nanoadditive influence on density, speed of strength development, final strength under compression of materials on the basis of cement depending on nanoadditive mass percent has been established.
Keywords: hydrotliennal solution, modifiers, nanosilica, equal distribution, durability
For citation: Khroustalev В. M., Leonovich S. N., Potapov V. V., Grashevskaya E. N. (2017) Composite Materials Based on Cement Binders Modified with SiO, Nanoadditives // Science and Technique. 16 (6), 459^165. DOI: 10.21122/2227-1031-2017-16-6-459^165
Композиционные материалы на основе цементных вяжущих, модифицированных нанодобавками Si02
Академик НАН Беларуси, докт. техн. наук, проф. Б. М. Хрустале»',
докт. техн. наук, проф. С. Н. Леоновнч докт. техн. наук, проф. В. В. Потапов'"', Е. H. Грушевская1'
1 Белорусский национальный технический университет (Минск, Республика Беларусь), 2'Научно-исследовательский геотехнологический центр Дальневосточного отделения Российской академии наук (Петропавловск-Камчатский, Российская Федерация)
Реферат. Развитие нанотехнологий позволяет решить ряд проблем строительного материаловедения: повышение прочности, долговечности, стойкости к истиранию, коррозионная стойкость. Это обусловливает эксплуатационную
Адрес для переписки Address for correspondence
Хрустдаев Борис Михайлович Khroustalev Boris М.
Белорусский национальный технический университет Belarusian National Technical University
просп. Независимости, 150, 150 Nezavisimosty Ave.,
220013, г. Минск, Республика Беларусь 220013, Minsk, Republic ofBelarus
Тел.: +375 17 265-97-29 Tel.: +375 17 265-97-29
tgv_fes(a!bntu.by tgv_fes(®.bntu.by
ИИ Наука
«техника. Т. 16, № 6 (2017)
надежность строительных конструкций, что в основном достигается за счет модификации структуры и свойств существующих материалов или изделий наночастицами, вводимыми в их объем или наносимыми на поверхностный слой. Теоретически и экспериментально установлено, что модифицированная вода обладает большей активностью вследствие изменения ионного состава, влияющего на величину рН и другие параметры. Поскольку наночастицы обладают большой поверхностной энергией, они проявляют повышенную склонность к агломерации, при этом размер агломератов может составлять несколько микрометров. В связи с этим актуальной задачей является равномерное распределение й дезагрегация наночастиц в объеме воды затворения. Проведены эксперименты по изучению влияния наночастиц кремнезема, распределенных в объеме жидкости с помощью ультразвуковой обработки, на характеристики цементно-песчаного раствора и тяжелого бетона. Установлено влияние нанодобавки на плотность, скорость набора прочности, конечную прочность на сжатие материалов на основе цемента в зависимости от массового процента нанодобавки.
Ключевые слова: гидротермальный раствор, модификаторы, нанокремнезем, равномерное распределение, долговечность
Для цитирования: Композиционные материалы на основе цементных вяжущих, модифицированных нанодобавка-ми Si02 / Б. М. Хрусталев [и др.] // Наука и техника. 2017. Т. 16. № 6. С. 459-465. DOI: 10.21122/2227-1031-2017-16-6-459^165
Introduction
According to GOST (State Standard) ISO/TS 80004-1-2014, nanotechnology is a set of the technological methods applied for studying, designing and producing of materials, devices and systems including the focused monitoring and construction management, and interaction of the separate elements of a nanodiapason (about less than 100 nanometers in one of the spatial directions). The application of nanoadditives is limited due to their increased cost and that leads to new approaches of their production. Hydrothermal solutions are raw sources for sols and Si02 nanopowders production.
Technology of nanosilica production
from hydrothermal solutions
Mutnovsky field on the Southern Kamchatka is one of places where in the Russian Federation the hydrothermal resources (250-300 °C) are located. Due to the water phase discharge of the heat carrier of Mutnovsky geothennal power plants (1100-1200 t/h) and the Si02 content in the initial environment (650-800 mg/kg), the potential capacity of one field of Sit) production reaches up to 3-5 thousand tons per year. Hydrothermal solutions are a nonconventional source of mineral raw materials, including amorphous silicas. Silicon dioxide is formed in a natural solution of or-thosilicic acids (OSA) molecules as a result of a chemical interaction of solution with aluminosili-cate minerals of breeds in a subsoil of hydrothermal fields. When the solution rises to the surface through productive wells and its temperature decreases, the solution becomes supersaturated and there polycondensation and nucleation of molecules OSA leading to formation of sphere-cal silica nanoparticles with diameters of 5-100 nanometers occur [1-9].
Silica sol has been received as follows: the water environment containing orthosilicic acid (H+SiOJ with concentration of 600-800 mg/dm is sent to from the separators of geothermal power plant (GeoPP) to the reinforced concrete tank (cooler) where polycondensation of II:Si(): with formation of silica particles (Si02) is earned out at 63 °C. After the cooler, the separator is delivered to a baromembrane ultrafiltration installation (BMU) to concentrate and produce a stable aqueous silica sol. The technological scheme of installation is presented in the fig. 1.
Characteristics of an initial separator: salinity -702 mg/dm3, pH = 9.73, the total content of Si02 Ct = 716 mg/dnf, concentration of dissolved silicic acid (at 20 °C) - Cs= 160 mg/dm . Pressure differ-rence on a membrane layer is 0.14 MPa, a consumption of the solution passing through the installation - 1.2 ni Vh. In the first concentration phase silica sol with a density of 1015-1022 g/dm3 and a Si02 content of (' = 28-40 g/dm3 is received. In the second phase sol density is 1070 g/dm3 and content of Si02 (': 115 g/dm \
Silica sol has been used for receiving the low-aggregated nanodisperse powder with cryochemi-cal vacuum sublimation [10, 11] (fig. 2).
This mode provides the process of receiving the powders having a specific surface up to 500 nf/g, the volume of a time is 0.20-0.30 cm 7g, the average diameter of a powder time is from 2 to 15 nm, average diameters of particles are from 5 to 100 nm, density of superficial silanol groups is up to 4.9 nm 2, residual humidity is up to 0.2 wt%, temped density is 0.035-0.300 kg/dm . The chemical composition of the powder received with cryochemical vacuum sublimation m % in weight: Si02 - 99.700; A1203 - 0.173; CaO - 0.034; Na20 - 0.034; K20-0.069 [12, 13].
Наука
итехника. Т. 16, № 6 (2017)
Fig. I. Apparatus for producing a stable aqueous silica sol by ultrafiltration: 1 - hydrothermal cooling separators in heat exchangers; 2 - polycondensation of orthosilicic acid and the growth of silica particles under certain temperature and pH of the water; 3 - 3-stage ultrafiltration concentration of silica nanoparticles in hydrothermal environment (membrane filters)
Fig. 2. The scheme of cryochemical equipment for receiving nanodisperse silica: 1 - device for water sol
preparation; 2 - dosing pump; 3 - cryogranulator; 4 - tanker with fluid nitrogen; 5 - container for storage of cryogranules; 6 - industrial cold-storage plant; 7 - sublimation dryer; 8 - storage cabinet for finished stock
Materials. Prototypes
The portland cement (PC) which is classified as the CEM-I type in accordance with GOST (State Standard) 31108-2003 was applied as a binder of a class 42.5R. Diorite crushed stone of fraction from 5 to 20 mm in accordance with GOST (State Standard) 8267 (tempered density is 1300 kg/m3, true density - 2.73 g/cm3) and quartz feldspar sand according to GOST (State Standard) 8736 (fineness modulus (Mf= 3.4 and Mf= 2.9), true density - 2.62 g/cm3) mixed with standard quartz mo-nofractional sand have been used as fillers. Nano-
^H Наука
итехника. Т. 16, № 6 (2017)
silica powder with a specific surface of SBET = = 156 m2/g, the average diameter of a time of dp = 7 mn, the total volume of a time of Vp = = 0.298 cm3/g and silica sol being an opalescent liquid p = 1072 g/dm3, pH = 9.1, with a mass fraction of Si02 =115 g/dm3 have been used as modifiers. The additives have also been used for the improvement of mix characteristics: solution of a superplasticizer (SP) with a density of 1099 g/dm3 with the content of a solid phase of 219.8 g/dm3; complex additive "Relamiks T2" (technical conditions 5870-002-14153664-04); additive - superplasticizer of polycarboxylates series having highly effective abilities on the water reducing in the fonn of water solution with a density of 1082 g/dm3 and content of solid of 412 mg/g.
Silica powder was injected into a water phase until equal distribution of its powder particles of in the volume of liquid using the ultrasonic processing. Then it was added to cement and sand mix, preparing the solution. The solution was poured into the prisms of standard square section (40x40x160 mm) and then put on a vibrating table and condensed. When the samples were prepared, they were released from the forms and were stored in bathtubs filled with water before reaching the certain age. The durability tests of samples at compression were carried out on the 3rd, the 7th and the 28th day.
Analysis of experimental researches results
The injection of the silica nanopowder (SN) into cement-sand-water system in the amount from 0.001 to 0.200 wt% in cement (tab. 1) leads to substantial increase in durability of the cement samples at compression up to 30-40 % in comparison with the control samples without a nanoaddi-tive at the same age. Thus the injection of silica nanoparticles facilitates not only the increase in final durability at compression, but also in speed of strength development of samples with nanoaddi -tives (fig. 3, 4).
Generally the density of solid cement samples changed as well as die compressive strength: it increased with the strength increase. The exception was a sample with additive of 0.04 wt%. Compressive strength with such mass additive was increasing, and density was decreasing: 0 wt% -p = 1970 kg/m3; 0.0075 wt% - p = 2000 kg/m3; 0.04 wt% - p = 1920 kg/m3; 0.18 wt% - p = = 1990 kg/m3.
Table 1
Kinetics of compressive strength change (MPa) of cement and sand samples with silica nanopowder additive
Cement, g Sand, g Water, ml SN /„ MPa
g %
Three days
500.00 1500 200 - - 21.5
499.96 1500 200 0.0375 0.0075 32.7
499.80 1500 200 0.2000 0.0400 27.5
499.10 1500 200 0.9000 0.1800 35.6
Seven days
500.00 1500 200 - - 30.8
499.96 1500 200 0.0375 0.0075 46.6
499.80 1500 200 0.2000 0.0400 43.8
499.10 1500 200 0.9000 0.1800 47.8
28 days
500.00 1500 200 - - 42.7
499.96 1500 200 0.0375 0.0075 59.1
499.80 1500 200 0.2000 0.0400 50.4
499.10 1500 200 0.9000 0.1800 59.0
0 % SN relative to cement 0.0075 % SN relative to cement 0.04 % SN relative to cement 0.18 % SN relative to cement
9 12 15 18 Sample age, days
Fig. 3. Compressive strength of cement samples, depending on amount of the nanodisperse silica added
120
c.
<D
E a. 100
о аЭ
a> ч£?
> a) (Я ф 80
"О а.
-C Е
O) с го (Л 60
£
Ii? 'S с а> Е 40
<0 о а) о
аз о 20
с
100 100 100 100
0 % SN relative to cement 0.0075 % SN relative to cement 0.04 % SN relative to cement 0.18 % SN relative to cement
Fig. 4. Kinetics of strength development of cement samples in relation to the age of 28 days
Наука
итехника. Т. 16, № 6 (2017)
Effects of silica sol additive were estimated according to the compressive strength increase of M200 mortar. The experiments on equable mixtures were carried out: the W/C of control samples without Si02 additive was equal to the W/C in solutions into which the silica sol was injected. Silica sol and superplasticizer solution were added to the tempered water and mechanically mixed. However at the equal W/C and equal amount of the added superplasticizer, the level of slump was lower in the solutions into which Si02 sol had been injected, i.e. that the liquid nanoadditive increased the viscosity and stiffness of a batch (fig. 5).
Sample age, days
Fig. 5. Kinetics of Strength development at compression of M200 mortar {W/C = 0.45): 1 - 1 % SP; 2 - 1 % SP + 0.5 % SiO,
Gain of compressive strength with the different amounts of nanosilica additive at W/C = 0.45 on the 3rd day was AR3 and on the 28th day - M2S (fig. 6).
Nanosilica sol increases the speed of strength development, i.e. influences the hydration processes, therefore the relation of Д28/^з becomes lower in comparison with control samples without a nanoadditive. At 3-days age the effect of the additive becomes significant: when Si02 increases from 0.05 to 0.50 wt% - R3 strength monotonously increases as well. At 28-day age R2$ strength at W/C water/cement ratio = 0.45, at the Si02 flow rate = 0.05 wt% R2$ gain is insignificant.
I
LI Ll
0.05 0.10 0.25 0.50
Amount of nanosilica additive, %
Fig. 6. Relative gain of compressive strength on the 3rd and on the 28th day age with the different amounts of SiO, additive (W/C = 0.45) ■ ■ - AR2$
The assessment of efficiency influence of Si02 sol on concrete strength characteristics was estimated separately and with superplasticizer. The results of samples experiments have shown that compressive strength gain at a Si02 dose of 0.01 wt% in cement was + 14.76 %, and at Si02dose of 0.10 wt% in cement was +21.86 %. The concrete experiments on compressive strength with injection of large amounts of Si02 sol nanoadditive (in amount of 0.3 %), have been carried out with superplasticizer "Relamiks T2", which 1.0 wt% in cement had been injected at the different W/C from 0.50 to 0.38. They have shown that the effect of Si02 nanoadditive on concrete strength indicators is stronger that at low W/C (fig. 7).
Thus, gain of compressive strength in comparison with a control sample for 72 %, at the decrease of W/C from 0.50 to 0.39 compressive concrete strength increased almost for 85 %, bending strength - for 31 %, concrete density has increased for 7 %. At W/C = 0.38 and the given doses of nanosilica and superplasticizer the batch had the increased level of viscosity, could be barely fit in the prisms and there was a decrease in compressive strength gain to 71.8 % and in bending strength to 17.2%. Generally the results have shown the regular decrease in compressive and bending strengths with the increase in W/C.
0.40 0.42 0.45 0.50 WIC
m
0.38 0.39 0.40 0.42 0.45 0.50 WIC
Fig. 7. Concrete mechanical properties at different rates W/C
^■Наука
итехника. Т. 16, № 6 (2017)
The effect of the sol addition on equable mixtures (W/C = 0.61-0.71) was determined by testing samples of concrete of the following composition: cement (SC 550) - (345 ± 5); quartz feldspar sand - 400; standard quartz sand - 400; stone of fraction 5-20 mm - 1060.
Silica sol was injected in the amount of 2 % of cement weight. Sol dosage was calculated by the formula:
rsol=tc-sjo2/mf&* (i)
where Vso/ - sol volume; C - cement consumption, g; Si02 - given silica concentration, %; Ks - SiQ2 content in the sol, g/dnr.
Equability of the concrete mixtures was achieved with the appropriate dosage of the polycarbo-xylate. The compositions of concrete mixtures are presented in tab. 2.
Analysis of experimental data leads to the conclusion that the additive of silica sol at a dose of 2 wt% Si02 m cement m combination with the superplasticizer on the basis of polycarboxy-late (PCX = 2.2-2.6 % from cement mass) results in the strength increase up to the maturity interval of 28 days for 37-40 % (compared with compositions with no additive), and in the initial the maturity interval (1 dav), this indicator reached 90-128 % (tab. 3).
Composition
Data of researches determine the use of cement systems of nanopowders and sols as modifiers, received from the hydrothermal solutions. Therefore, the mechanism of nanosilica action is complex due to the fact that nanosilica can be a filler and promote portlandit binding, form the additional centers of crystallization. Nanosilica takes part in binding of the forming lime, increases the density of system particles packing and is the center of crystallization of hydrate new grow ths.
The nanosilica presence influences the concentration of Ca2+ and OH" ions in the liquid phase of port-land cement pastes in the very first minutes of hydration in such a way that this leads to the reduction of duration of the induction period or the induction period does not occur at all. The formation of hydration products during the early period takes place with the participation of a surface of nanodisperse particles Si02, and the surface of cement grains is blocked in a less degree with new growths that intensifies the hydrolysis process of cement phases 151.
Thus, hydrothermal nanosilica makes triple impact on cement - it strengthens hydration, blocks times, i, e. reduces water penetration, increases the adhesion ability. The injection of silica sol makes allows to increase m compressive and bending strength, and dierefore in durability of die products.
Table 2
rete mixtures
Series Composition No Consumption per 1 m3
Cement Quartz feldspar sand Standard quartz sand Water Si02, % of cement SVC 5New, %
of cement ofSiO,
1 66 350 400 400 225.00 - - -
67 343 400 400 245.25 2 2.33 1.165
68 343 400 400 220.55 2 2.58 1.290
2 69 350 400 400 217.00 - - -
70 343 400 400 209.23 2 2.23 1.110
Table 3
The results of experiment on concrete with the silica sol additive
Series Composition No sa и § о сЗ <4-4 О с ' — .о сЛ è- SVC 5New, % W/C Slump, cm Mixture density, kg/m3 Compressive strength, MPa 'Initial'' strength, %(RJR№)
of cement of SiO, 1 day 2 days 28 days Steam curing Nonnal storage Steam
1 66* - - - 0.643 13 2345 6.8 12.0 26.6 - 26 -
67 2 2.33 1.165 0.715 10 2322 12.7 (+86%) 19.8 (+65 %) 33.6 (+26 %) - 38 -
68 2 2.58 1.29 0.643 18-20 2320 15.5 (+128%) - 36.4 (+37 %) - 43 -
2 69* - - - 0.620 16 2322 10.1 - 28.5 19.7 35 69
70 2 2.23 1.11 0.610 18 2335 19.2 (+90%) - 39.9 (+40 %) 26,6 (+35 %) 48 67
* Compositions No 66 and No 69 - control, in brackets - the performance criteria.
Науке
«техника. T. 16, № 6 (2017)
CONCLUSIONS
1. Hie nanosilica extracted from hydrothermal solution actively influences on compressive and bending strength.
2. Due to the high specific surface of nanosilica powder the nanoparticles have high chemical activity, and acting as nanofillers - fill micropores of a cement stone that leads to the reduction increase in density and strength.
3. Silica nanoparticles influence on the hydration process, increase the speed of strength development in early terms in comparison with the control samples.
4. The effect of silica sol additive is stronger with a superplasticizer.
REFERENCES
1. Poukharenko Yu. V., Nikitin V. A., Letenko D. G. (2006) Nano-Stmcturing of Water Mixing as Method for Efficiency Improvement of Concrete Mxtnre Plasticizers. Stmitebiye Materialv [Building Materials], (9), 86-88 (in Russian).
2. Staroverov V. D., Poukharenko Yu. V. (2009) Scientific Principles for Application of Fulleroid-Type Carbon Nanoparticles in Cement Composites. International Nanotechnology Fonmi, October 6r-8, 2009. Available at: http://rasnano tech09.rusnanoforum.ru/Home.aspx. (in Russian).
3. Poukharenko Yu. V., Aubakirova I, U., Staroverov V. D. (2009) Efficiency of Water Mixing Activation by Carbon Nanoparticles. Inzhenemo-Stroitelny Zhoimial = Magazine of Civil Engineering, Щ), 40-45 (in Russian),
4. Lkhasaranov S. A., Urkhanova L. A., Buyantuev S. L., Kondratenko A. S., Danzanov A. B. (2012) High Strength Concrete Based on Composite Binding Material. Stroi-tel'nyi Kompleks Rossii. Nauka. Obrazovanie. Praktika: Material}'Mezhdunar. Nauch.-Prakt. Konf. [Building Complex of Russia. Science. Education. Practice: Proceedings of International Scientific and Practical Conference], Ulan-Ude, East Siberia State University of Technology and Management, 224-226 (in Russian).
5. Urkhanova L. A., Khardaev P. K., Lkhasaranov S. A. (2015) Modification of Cement Concrete by Nanodisperse Additives. Stroitelstvo i Rekonstruktsia = Building and Reconstruction, (3), 167-175 (in Russian).
6. Khroustalev B. M., Yaglov V. V., Kovalev Y. N., Ro-maniuk V. N., Burak G. A., Mezhentsev A. A., Gurinen-ko N. S. (2015) Nanomodified Concrete. Nauka i Teldmi-ka — Science and Technique, (6), 3-8 (in Russian).
7. Goreva T, S,, Potapov V. V., Gorev D. S., Shalaev K. S (2012) Obtaining of Nanodisperse Silicone Dioxide from Hydrothermal Solutions while Applying Membranes and Cryochemical Vacuum Sublimation. Sovremennye Prob-leniv Nauki i Obmzovaniya = Modern Problems of Science and Education, (4). Available at: https://science-education. ru/ru/article/view?id=6720 (in Russian).
8. Potapov V. V., Gorev D. S., Tumanov A. V., Kashutin A. N, Goreva T. S. (2012) Obtaining of Complex Additive for Improvement of Concrete Strength on the Basis of Nanodisperse Silicone Dioxide from Hydrothermal Solutions. Fundamentalnve Issledovaniva = Fundamental Research, (9, Part 2), 40-M09 (in Russian).
9. Sanchez F., Sobolev K. (2010) Nanotechnology in Concrete -a Review. Construction and Building Materials, 24 (11), 2060-2071. DOI: 10.1016/j.conbuildmat.2010.03.014.
10. Shabanova N. A., Sarkisov P. D. (2004) Foundations of Sol-Gel Method for Nanodisperse Silicon Dioxide. Moscow, Akademkniga Publ. 208 (in Russian).
11. Brown K. L., Bacon L. G. (2000) Manufacture of Silica Sols from Separated Geothermal Water. Proceedings
Наука
«техника. Т. 16, № 6 (2017)
World Geothermal Congress 2000. Kyushu-Tohoku, Japan, 533-537.
12. Brazhnikov S. M., Genemlov M. В., Trutnev N. S. (2004) Vacuum-Sublimation Method of Producing Ultradisperse Powders of Inorganic Salts. Chemical and Petmleum Engineering, 40 (11-12), 720-725. DOI: 10.1007/sl0556-005-0039-0.
13. Generalov M. B- (2006) Cryochemical Nanotechnology. Moscow, Akademkniga Publ. 325 (in Russian).
Received: 10.02.2017 Accepted: 14.04.2017 Published online: 28.11.2017
ЛИТЕРАТУРА
1. Пухаренко, Ю. В. Наноструктурирование воды затво-рения как способ повышения эффективности пластификаторов бетонных смесей / Ю. В. Пухаренко, В. А. Никитин, Д. Г. Летенко // Строительные материалы. 2006. № 9. С. 86-88.
2. Староверов, В. Д, Научные основы применения углеродных наночастиц фуллероидного типа в цементных композитах [Электронный ресурс] / В. Д. Староверов, Ю. В. Пухаренко // Междунар. форум по нанотехнологи-ям, 6-8 окг. 2009 г. Режим доступа: http://rusnano tech09.rusnanoforum.ru/Home.aspx.
3. Пухаренко, Ю. В. Эффективность активации воды за-творения углеродными наночастицами / Ю. В. Пухаренко, И. У. Аубакирова, В. Д. Староверов // Инже-нерно-строительный журнал. 2009. № 1. С. 40^15.
4. Бетоны повышенной прочности на композиционных вяжущих / С. А. Лхасаранов [и др.] // Строительный комплекс России. Наука. Образование. Практика: материалы Междунар. науч.-практ. конф. Улан-Уда: Изд-во ВСГУТУ, 2012. С. 224-226.
5. Урханова, Л. А. Модифицирование цементных бетонов нанодисперсными добавками / Л. А. Урханова, П. К. Хардаев, С. А. Лхасаранов // Строительство и реконструкция. 2015. № 3. С. 167-175. '
6. Наномодифицированный бетон / Б. М. Хрусгадев [и др.] // Наука и техника. 2015. № 6. С. 3-8.
7. Получение нанодисперсного диоксида кремния из гидротермальных растворов с применением мембран и криохимической вакуумной сублимации [Электронный ресурс] / Т. С. Горева [и др.] // Современные проблемы науки и образования. 2012. № 4. Режим доступа: https://science-education.ru/ru/article/view?id=6720.
8. Получение комплексной добавки для повышения прочности бетона на основе нанодисперсного диоксида кремния гидротермальных растворов / В. В. Потапов [и др.] // Фундаментальные исследования. 2012. № 9 (часть 2). С. 404^109.
9. Sanchez, F, Nanotechnology in Concrete - a Review / F. Sanchez, K. Sobolev // Construction and Building Materials. 2010. Vol. 24, № 11. P. 2060-2071.
10. Шабанова, H. А. Основы золь-гель-технологии нанодисперсного кремнезема / Н. А. Шабанова, П. Д. Сар-кисов. М.: Академкнига, 2004. 208 с.
11. Brown, К. L. Manufacture of Silica Sols from Separated Geothermal Water / K. ,L. Brown, L. G. Bacon // Proceedings World Geothermal Congress 2000. Japan. Kyushu-Tohoku, 2000. P. 533-537.
12. Бражников, С. M. Вакуум-сублимационный способ получения удьтрадисперсных порошков неорганических солей / С. М. Бражников, М. Б. Генералов, Н. С. Трут-нев // Химическое и нефтегазовое машиностроение. 2004. № 12. С. 12-15.
13. Генералов, М. Б. Криохимическая нанотехнология / М. Б. Генералов. М.: Академкнига, 2006. 325 с.
Поступила 10.02.2017 Подписана в печать 14.04.2017 Опубликована онлайн 28.11.2017
