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Abstract

Содержание

Introduction

An important part of the sustainable development of modern society is environmental safety and protection of the environment. The greatest danger in relation to human health and protection of the environment present waste tonnage, 95 % of which is produced and accumulated in Donetsk, Dnepropetrovsk, Zaporozhye, Lugansk regions of Ukraine with the highest density of mining, metallurgical, chemical and electric power industries. Volumes of waste generation and accumulation is much higher than other European countries [1].

In particular, to date, in the Donetsk region about 600 heaps, which occupy more than 3.5 hectares. Of 77 507 dumps burn about 100 heaps considered already blown. Thus, with a single blade for burning average night stands out in the atmosphere of carbon monoxide of 4–5 t. and from 600 to 1100 kg of sulfur dioxide, a slight amount of hydrogen sulfide, nitrogen oxides and other products of combustion. In this case the use amount of industrial waste is negligible – 6.5 % of their yield.

Fancy pile Donetsk: Golden Deer Fancy pile Donetsk: Stone the devil

Figure 1 – Fancy piles Donetsk: Golden Deer and Stone the devil

Heaps negative impacton the air, groundwater and surface water, soils, flora and fauna [2]. The problem of waste has a number of serious environmental and economic aspects and calls for urgentaction to resolve it.

1. Actuality of the topic

Given the current environmental and economic situation seems to be promising heaps involvement to economic turnover as powerful and almost bargain mineral base stocks which are more than sufficient for creating a highly profitable processing industries over many decades. Accumulation of waste minimization and returning them to production in order to extract valuable components and use them as secondary resources is the basic direction of state policy in the field of environmental protection, using natural resources and environmental safety [3].

It is known that using waste in 2–3 times lower than that of natural materials. Fuel consumption by using certain types of waste is reduced by 10–40 %, and the specific investment by 30–50 %.

Studies in recent years, domestic and foreign scientists [4, 5] show that the problem of waste from coal mining and coal washing in the production of building materials and products remains relevant and requires further development in this direction.

Burned breed

Figure 2 – Burned breed

2. Purposes and objectives of the study

There was tasked to identify ways of solving the ecological problems which associated with the accumulation of rocks in mine tailings. Purpose – to increase the level of utilization of burned rocks on the example of waste heaps Donetsk regionby improving the composition of the binder containing as an active ingredient hydraulically burned rocks.

Development activities for complex processing of rocks mine waste heaps will solve a number of pressingp roblems [6]:

3. Origin, meaning and application of burned rocks in the construction industry

Under the influence of the atmosphere and sulfur compounds as well as the inclusion of coal available in the rock ignite spontaneously in significant amounts, providing that considerable amounts of heat and harmful living organisms sulfide, carbon dioxide and other gases.

The product resulting from the blown blade thus, called burnt rock.

To the fall waste heaps different in mineralogical composition of rocks that are exposed to natural roasted at different temperatures and, consequently, have different degrees of roasting.

Burnt rocks represent hydraulic additive capable of processing after the runners in the presence of water and an activator (lime, cement) or after grinding mill acquire properties of hydraulic binder, that is having the ability to grasp and harden under water.

Burnt rocks are treated as natural component of a special kind of cement, nature harvested in huge quantities. Being finely ground and mixed with lime and other additives, they form view clinkerless cement similar. Such tsemyanochny cement is known to mankind as the most ancient form of hydraulic binder, is widely used in the construction of all ages and peoples. The clay of the ancient cement consisted of artificially burnt and milled clay, often battle of bricks, tiles and various ceramic products.

Photomicrographs of the surface of particles of burnt rocks of different fractions (X 2000) animation: 3 frames , 7 cycles of repetition , 134 kilobytes

Figure 3 – Photomicrographs of the surface of particles of burnt rocks of different fractions (X 2000). Reference: [7]
(animation: 3 frames, 7 cycles of repetition, 134 kilobytes)
(particle size: slide 1 – <0,63 mm; slide 2 – 2,5–5 mm; slide 3 – >20 mm).

Before invention of Russian inventor engineer Yegor Cheliev in 1820 (four years before the English patent John Aepdina in Portland) method for producing artificial cement raw mix all construction in Russia was conducted in the lime-glinitny, cement. Study mortarswich was taken from the walls of the monuments of ancient architecture XI and XII centuries and Sophia of Polotsk cathedrals found that, along with sand and lime in oily solutions added tsemyanku and crushed brick, and it was one of the reasons for the longevity of ancient building materials. According to archival data lime-cement clay in Moscow began to produce not less than 200 years ago. First burnt rocks were used in the construction in 1923 in Donetsk and Kuznetsk basins.

4. Physical and mechanical properties of burned rocks

Physical and mechanical properties of burned rocks depend on the degree of roasting. There are currently no reliable methods for predicting and assessing the firing burned rocks in mine waste heaps, as it depends on many factors: the content of the coal in the original rock and the rate of combustion in the combustion zone depth slagheap, combustion environment.

Upon firing rocks in aluminosilicate minerals is undergoing profound changes, especially in kaolinite, which largely determines the mechanical properties and chemical (hydraulic) activity burnt rocks. The result selffiring mine rock forming minerals conversion is primarily kaolinite with metakaolinite form which with increasing temperature partially converted into mullite and dissolves oxides. In addition, burning also exposed sandstones, which are cemented quartz grains. In this known that ability silica (β-quartz) to polymorphic transformations during heating. In this way, at the temperature of 573 °C the transition happens β-quartz in the α-modification, which in way temperature rising to 870 °C undergoes a change in crystal lattice with the transition into tridymite and then at the temperature of over 1000 °C in kristabolit. When the firing temperature is over 1200 °C produces the corresponding window, which reduces the reactivity of the burnt rock.

However, the use of waste coal in the production of knitting is recommended to use only well-blown rock. At the same time, it is known that, even within a single degree of roasting waste heap is very heterogeneous rock, which greatly restricts the volume of its utilization. In the literature, there are practically no information on the effect of different contents of harmful impurities in the overburden (sulfur compounds, clay, unburned carbon particles) on the properties of binders based on them.

Properties burned rocks determined by the conditions of formation: the composition of the mineral part, firing temperature and the composition of the gaseous medium during combustion. All of these factors ultimately determine the scope of burnt rocks.

Rocks have the following chemical composition: losses on ignition (1,61–5,66), SiO2 (40,17–56,47), Al2O3 (8,74–19,74), Fe2O3 (4,62–8,39), FeO (0,07–3,85), CaO (1,55–13,88), MgO (1,45–5,4), SO3 (0,94–2,37), K2O (0,64–1,78), Na2O (0,32–0,89) [8].

5. Planned bottom

On clay raw materials for the production of Portland cement are no established standard specifications. However, based on practical experience, the following indicative requirements for chemical composition of clay rocks, determining their appropriateness for use: amount of CaO is not limited; permissible content of MgO depends on its content in lime component and limiting conditions for Portland cement clinker with MgO content of not more than 5 %, and for magnesium Portland – not more than 10 %; amount of SiO2, Al2O3, Fe2O3 in combination with lime component must deliver the required values of the coefficient of saturation, silica and alumina modules in the raw mix and clinker (including the possibility of introducing corrective additives). Desirably, Na2O and K2O in an amount not exceeding 3–4 %, and SO3 was not more than 1 %. Increase of SiO2 additive achieved with high level of flint in its composition substances – tripoli, flasks, diatomite. Insufficient amount in the raw mix iron oxide additive compensated cinders, iron ore; high level of clay and terrestrial in its composition additive (bauxite) can improve the content of alumina in the clinker [9].

The virtual absence of carbonaceous particles allows the addition of clinker burning rocks as hydraulically active component during grinding. Using burnt rocks as an active mineral additives is possible thanks to their pozzolanic activity.

It is believed [10] that the pozzolanic activity due to the presence of burnt rocks several active ingredients:

The presence of these substances in violation of burned rock explains the molecular bonds of water aluminosilicate source rocks during firing, as well as activation of quartz due to violations of the surface and the dispersion of particles in pyrolysis process.

The above-mentioned active substances can react following types:

Al2O3·2SiO2 + Ca(OH)2 + nH2O ↔ CaO·Al2O3·2SiO2·nH2O;

γ-Al2O3 + Ca(OH)2 + nH2O ↔ CaO·Al2O3·nH2O;

SiO2 + nCa(OH)2 + mH2O ↔ nCaO·SiO2·pH2O;

mCaO·Al2O3·nH2O + pSiO2 + Fe2O3 ↔ mCaO·(Al, Fe)2O3·pSiO2·nH2O.

The purpose was to study the effect of additives on the burning rock strength cement. For this was to study the strength of blended cement burning rocks of different amounts and different factions. In particular, the paper samples to be tested with an integrated binder content burnt rock 10, 20, 30, 40 % portland cement clinker – the rest. Molding samples is done via the vibro. Load testing samples made in accordance with GOST 310.4-81 Cements. Methods for determination of flexural strength and compression. In accordance with this can be analyzed according to the compressive strength of samples of complex binder amounts to be added additives burnt rock and its size fractions.

Conclusions

In this way, using waste coal can develop new complex binder. The main purpose of the work was to improve waste management in the form of coal burned rocks coal heaps by improving the binder.

References

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