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Sand-clay raw materials for silicate materials production.

INTRODUCTION

For the production of autoclave silicate materials by traditional technology as silica component used quartz sand, part of which is to strengthen then finely divided. Processes occurring at hydrothermal treatment processes in the system CaO-Si[O.sub.2]-[H.sub.2]O depend on the energy state of quartz.

Role of Ca (OH) 2 is loosened structure silica and on the basis thereof forming calcium hydrosilicates.

To expedite this process, the raw material is dispersed by means of grinding machines, and the hydrothermal treatment is used at high pressure. Reduce the consumption of energy in the grinding and hydrothermal treatment can be through the use of thermodynamically active materials. A special interest in the production technology of silicate products represent products with high chemical reactivity, which not only can replace the silica sand, but also to intensify the processes.

In this regard, it is of interest autoclave technology for producing silicate materials based on non-traditional construction industry argillaceous rocks, the specifics of which is unfinished processes of clay formation [17,18].

Clay products are one of the final phases of weathering of aluminosilicate rocks, the final stage of weathering which are predominantly kaolinitic clay montmorillonite and composition. These clays are used for the production of cement, ceramic materials, and can also be used to produce metal composites [7-16].

Mineral composition of rocks unfinished stage of clay formation is presented by such thermodynamically unstable compounds, such as [Ca.sup.2+]montmorillonite, disordered kaolinite, mixed-minerals, imperfect hydromica, fine quartz and amorphous phase. These rocks are not suitable for the production of cement and ceramic materials, but the mineral composition allows them to produce autoclave silicate materials [2].

These rocks are widespread, and in large quantities fall within the mining operations in mining. These rocks are in the dumps, which often occupy land suitable for agriculture. Consequently, the use of these species will not only expand the resource base of silicate materials, but also simultaneously solve the environmental problems related to the storage of industrial waste.

The aim is to explore the use of sand and clay soils as a feedstock for the production of energy-efficient autoclave silicate materials.

Methods:

Used for the study eolian-eluvial-diluvial clay rocks (clay loam) Quaternary. These rocks are widespread in the region of the Kursk Magnetic Anomaly.

Visually loam are loose brown rocks. The rock has a silty clay structure. Size and pelitic siltstone dominated particles (Table 1).

According to the chemical composition of the rocks belong to the category of acid with a high content of free silica (39.96 wt.%) (Table 2). Besides comprising fraction smaller than 0.005 mm is also contained significant amounts of free silica (33.60 wt.%).

The clay fraction rocks represented Ca2 + montmorillonite with d001 = 14,81-15,87 [Angstrom] (Fig. 1). These layers are easily replaced by mineral structure by polar organic molecules, so when saturated with ethylene glycol main interplanar distance increases. During calcining at 600 C [] for two hours reflexes characteristic d001 decreases to 9,99 [Angstrom], due to the fact that the interlayer water at this temperature is easily removed.

Series reflexes 9.99, 4.99 and 3.32 [Angstrom], whose values do not change either after saturation with ethylene glycol or after calcination, indicate the presence of rock hydromica. Interplanar distances that are multiples of 7.14 [Angstrom], which disappear during calcination for 2 h, allow the identification of kaolinite.

The binder component used quicklime lump lime activity 87.34%. As siliceous filler used quartz sand with a fineness modulus of 1.54. Si[O.sub.2] content was 92.4 wt. %.

Raw material mixtures were prepared with 8 % of the active content of CaO. Loam content in the raw mix was varied from 5 to 70 wt. %. As a control, use lime -sand feed mixture. The rock added to the feed mixture in the form of lime- sand- clay binder produced joint grinding rocks and lime to the specific surface of 500 [m.sup.2]/kg. Molding humidity raw mixture depended on the content of silt and was 7-10%. Sample--diameter cylinder and a height of 50 mm were molded at a compression pressure of 20 MPa. Autoclaving was performed at a vapor pressure of 1 MPa on the regime : the rise of the vapor pressure of 1.5 h, 6 h isothermal holding, and pressure steam for 1.5 hours.

The Main Part:

For samples subjected to autoclave treatment, determined the compressive strength, the average density and water absorption (Fig. 2).

Microscopic examination of thin sand-lime samples and samples containing 30 wc clay loam. % are shown in Fig. 3.

On the sand-lime samples and containing 30 wt. % loam, experiments were conducted to study the effect of time of autoclaving on the compressive strength. Time isothermal autoclaving varied from 2 to 8 hours. Results are presented in Table. 3.

The influence of the loam content on raw strength is determined (table 4). Active CaO content equaled 8 %. Molding humidity was 7-10%.

Discussion:

The experimental data showed that the loam has a positive impact on increasing the strength of silicate materials. The optimum content of loam, corresponding to the maximum strength of the samples is 20-30 wt. %. Tensile samples increased from 20 to 32 MPa (1.6 times). When the content of the rock in an amount of 5 wt. % There is a slight decrease in strength.

The average density is increased from 1780 to 1980 kg/[m.sup.3] content of rock in an amount of 30 wt. %. Minimal water absorption (9.3%) corresponds to the content of 20 wt breed. %.

Microscopic examination of thin sand-lime samples showed that on the surface of quartz grains and on the contacts between them there are buildups of blurred nature (see Fig. 3a). Cementitious compounds are formed by the reaction of lime with fine and coarse quartz aggregate.

Quartz grains in samples with loam have virtually no contact with each other and uniformly distributed in the total weight of the amorphous (see Fig. 3b). Surface of many small particles of quartz corrode and edges surrounded by a gelatinous film. But large quartz grains almost unaffected by corrosion on the surface shows only slight traces of tumors.

From the data obtained it can be concluded that the lime-sand mixture in the presence of clay minerals the formation of cementitious compounds is primarily due to the interaction of calcium hydroxide with clay minerals and partially finely divided quartz. Coarse quartz lime virtually unresponsive.

Cementitious compound sand-lime (control) samples presented low-basic hydrosilicates calcium group CSH (B), detected by the exothermic effect at 835 [degrees]C in the thermogram and reflections 3,04, 2,80, 1,82 [Angstrom] on the radiograph (Fig. 4).

In the samples based on lime-clay binder also formed calcium hydrosilicates CSH (B). Offset exotherm to higher temperatures (870-880 [degrees]C) is probably due to the increase in the basic hydro calcium [22].

When the content of 5 wt. % loam in the raw mix is fixed hydrogarnets formation, the number of which with increasing content of rocks, judging by the increase in the intensity of the endothermic effect at 340 [degrees]C and reflections 5,00, 2,75, 2,00 [Angstrom], increases (see Fig. 4).

Changing the composition of tumors when injected into the lime-sand mixture of clay rocks is due to the reaction of calcium hydroxide with clay minerals and fine quartz [3].

In samples with 5 wt. % loam remains unbound calcium hydroxide (endo-effect at 520[degrees]C), which can be explained by insufficient to interact with it the clay fraction, as lime-sand mixture of clay and lime interacts mainly with clay minerals [17,18].

Accordingly, reduction in the strength at a content of 5 wt. % loam occurs as a result of reducing the number of tumors due to incomplete binding of lime.

Thermograms samples containing 50 wt. % Of the rock exhibit an endothermic effect at 530 [degrees]C, which indicates the appearance of unreacted clay minerals.

Consequently, the content of raw mixtures with 8 wt. % Active CaO loam amount shall not exceed 40 wt. %. In this case, the clay minerals rocks completely react with the lime. Contents of rock more than 40 wt. % leads to the appearance of unreacted clay minerals, which negatively affects the physical and mechanical properties of the finished products.

Consequently, the maximum allowable quantity of sand and shale in the raw mix determines the amount of clay content and the content of lime rock.

These data suggest that the clay minerals have a high reactivity to lime. This is due to the size and structure of clay minerals, which represent natural nanomaterials. Elementary layers and the space between them in clay minerals are nanoscale and possess a highly active surface [6].

Growth strength of the samples due to the formation of the microstructure stronger cementitious material by increasing the packing density of the material as well as synthesis hydrogarnets. Isometric crystals and plates hydrogarnets have low surface area and are microfiller which cemented submicrocrystalline gel phase of low-alkali hydro calcium. Growth medium density and the associated formation of a denser packing leads to lower water absorption. This is confirmed by the fact that the samples with a maximum average density corresponds to minimal water absorption (see Fig. 2).

With increasing exposure time, isothermal 2 to 8:00 strength sand-lime images increases from 9.8 to 24.4 MPa (2.5 times). According to differential thermal analysis of the samples, steamed with isothermal holding time 2:00, remains unbound calcium hydroxide, which completely disappears when the isothermal holding time 6 hours hence the rise in strength of sand-lime samples is determined by an increase in the degree of binding and lime, respectively by increasing the number of cementitious compounds [22].

Strength of the samples over lime-sand-clay binder after 2 h isothermal holding reaches 31.4 MPa and then remains practically unchanged. While calcium hydroxide is completely coupled. The rock due to clay component is highly reactive and accelerates the formation and crystallization of cementitious compound. This is possible due to the reduction in the duration of two times the hydrothermal treatment, thereby reducing energy consumption in the production of silicate materials.

A great role in the technology of production of silica brick has raw strength, which for raw lime -sand mixture is 0.4-0.5 MPa. However, this strength is not enough to completely eliminate the defects in the molding process and transportation of products. In addition to traditional raw materials difficult to hollow molded products. Therefore, the problem of increasing raw strength is very important [5].

Strength on the basis of raw lime-sand mixture was 0.43 MPa. Sandy loam at a content of 20-50 wt. % Increases the strength of raw 3-4. Using clay rocks in the production of silica brick will improve the formability of the raw mixture to increase the strength of raw and, accordingly, reduce the flaws in the molding process. Increasing raw strength will facilitate release hollow products.

The introduction the sandy lime-sand mixture produces a body-colored brown materials. The color intensity increases with the content of sandy loam. When the content of the latter in the amount of 30-40 wt. % Color samples reaches saturation hue source loam. Frost resistance of the materials obtained is 35-50 cycles of freezing and thawing.

Conclusion:

Thus, unfinished stage sand- clay rocks of clay formation can be used as energy-efficient raw material for autoclave silicate materials. Due to the nanoscale clay mineral contained in the species and fine-dispersed qartz destruction of siliceous raw material mixture components is accelerated, and as a result, neoplasms synthesis is accelerated. This reduces twice the isothermal aging time of the product in the autoclave.

Prerequisite for the use of clay rocks as raw material for autoclave silicate materials is their polymineral composition. Lime content shall be sufficient to fully interact with clay minerals contained in the raw mix since unreacted clay minerals may have a negative effect on the strength of silicate materials.

Argillaceous rocks should be thoroughly mixed with lime. It can be achieved by the use of lime- clay and sand binder, obtained by lime and rock co- grinding.

Further research in this direction is to study the influence of minerals making up the clay rocks on the formation of a cementitious compound and, therefore, the properties of silicate materials. This will determine the rational composition of raw mixtures within fluctuations of the material composition of clay rocks of different deposits.

ARTICLE INFO

Article history:

Received 15 April 2014

Received in revised form 22 May 2014

Accepted 25 May 2014

Available online 15 June 2014

REFERENCES

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(1) Anatoliy Nikolaevich Volodchenko, (2) Natalya Petrovna Lukutsova, (1) Ekaterina Olegovna, Prasolova, (1) Valery S. Lesovik, (1) Anna Alexandrovna Kuprina

(1) Belgorod State Technological University named after VG. Shukhov, Russia, 308012, Belgorod, Kostyukov str., 46

(2) Bryansk State Technological Academy of Engineering Russia, 308012, Bryansk, Stanke Dimitrova str., 3

Corresponding Author: Anatoliy Nikolaevich Volodchenko, Belgorod State Technological University named after V.G. Shukhov, Russia, 308012, Belgorod, Kostyukov str., 46

Table 1: Granulometric composition of loam.

The content of fractions wt. % Sieve size, mm

more then 2,0    2,0-0,5   0,5-0,1   0,1-0,05

0,21              0,51      1,46       4,70

more then 2,0    0,05-0,01   0,01-0,005   0,005-0,001

0,21               34,46       10,23         10,94

Table 2: Chemical composition of sandy wt. %.

Si[O.sub.2]   Si[O.sub.2]   [Al.sub.2]
total         free          [O.sub.3]     Ti[O.sub.2]

66,97         39,96         12,75         0,92

Si[O.sub.2]   [Fe.sub.2]
total         [O.sub.3]    CaO     MgO     [K.sub.2]O

66,97         5,33         1,38    4,20    1,60

Si[O.sub.2]                 Loss on
total         [Na.sub.2]O   ignition.   Sum

66,97         0,44          6,34        99,93

Table 3: Compressive strength of silicate materials depending
on the time of the isothermal aging.

                        Compressive strength (MPa) at
Composition             the isothermal holding time, h
of the
samples            2         3       4       6       8

Lime-sand samples           9,8    10,7    13,4     20

Containing 30 wt. % loam   31,4    32,1    32,8    31,5

Table 4: Strength on the basis of raw clay rocks.

Compressive strength (MPa) at a content
of sandy loam, wt. %

5        10      20      30      40
0,53    0,71    1,23    1,58    1,70
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Author:Volodchenko, Anatoliy Nikolaevich; Lukutsova, Natalya Petrovna; Olegovna, Ekaterina; Prasolova; Leso
Publication:Advances in Environmental Biology
Article Type:Report
Date:Jun 1, 2014
Words:2956
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