RU2497780C1 - Raw material mixture for obtaining porous filler - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of building material and can be applied in production of artificial porous fillers for light concretes and heat-insulating fillings. Raw material mixture for obtaining porous filler includes silica-containing rock and gas-former, as gas-former, it contains mixture of aluminium oxide and silicon carbide with the following component ratio, wt %: silica-containing rock - 95.0-96.0, aluminium oxide 3.0-4.9, silicon carbide 0.1-1.0.

EFFECT: increase of porous filler strength by reduction of filler agglomeration with reduction of its water-absorption and heat-conduction.

4 ex, 1 tbl

Description

The invention relates to the production of building materials and can be used in the manufacture of artificial porous aggregates for lightweight concrete and insulating fillings.

As aggregates for lightweight concrete, natural and artificial bulk porous materials with a bulk density of not more than 1200 kg / m ³ with a grain size of up to 5 mm (sand) and not more than 1000 kg / m ³ with a grain size of 5 ... 40 mm (gravel, gravel).

Expanded porous aggregates are expanded clay and its varieties (shungizite, ash gravel, clay clay expanded clay, etc.), agloporite, slag pumice, granulated slag, expanded perlite and vermiculite. They are specially obtained in the form of gravel, crushed stone and sand as a result of heat treatment of clay, ash, slag and other mineral raw materials.

Known raw material mixture for the manufacture of porous aggregate (AS USSR No. 1805117, IPC С04В 18/06, publ. 03/30/1993), consisting of siliceous rock (tripoli, diatomite, flask), alkaline hydroactivator, nitrates and nitrites of alkali metals sodium fluoride.

The main feature of the known raw material mixture is that the compound used for foaming siliceous rocks to produce porous aggregate is production waste.

The lack of raw mix according to A.S. No. 1805117 is the need to introduce in addition to the alkaline hydroactivator obtained from the spent soda solution, additionally expensive deficient additives are alkali metal nitrates and sodium fluoride.

Closest to the proposed one is a raw material mixture for producing a porous aggregate (RF patent No. 1813080, IPC С04В 14/04, 18/04, publ. 04/30/1993), including silica-containing rock as a filler and ferrosilicon slag as a blowing agent .

The disadvantage of the raw mix according to the patent of the Russian Federation No. 1813080 is its lack of strength, due to the fact that at high firing temperatures (1180-1250 ° C) the possibility of sintering of aggregate granules is not excluded.

The technical problem solved by the invention is to increase the strength of the porous aggregate by reducing sintering of the aggregate while reducing its water absorption and thermal conductivity.

The problem is solved in that in the raw material mixture to obtain a porous filler, as in the prototype, a silica-containing rock and a blowing agent are used. In this case, unlike the prototype, a mixture of aluminum oxide and silicon carbide is used as a blowing agent in the following ratio of components, wt.%:

Silica-bearing rock 95.0-96.0 Aluminium oxide 3.0-4.9 Silicon carbide 0.1-1.0

The use of a mixture of alumina and silicon carbide with a predominance of alumina as a blowing agent will reduce sintering. It has been experimentally established that when the claimed ratio of the components, there is a decrease in contact between the aggregate granules. During sintering, aluminum oxide is squeezed onto the surface of the granules, enveloping them. Since the melting point of alumina is 3000 ° C, which is much higher than the temperature of the firing of the aggregate, sintering of the granules does not occur, and the resulting porous material has increased strength.

In addition, it is possible to increase the foaming temperature, which will increase the foaming coefficient, and this, in turn, leads to a decrease in bulk mass and lower coefficients of water absorption, heat conductivity.

Porous aggregate using the proposed raw material mass is obtained as follows.

Silica-containing rock (or its waste) is crushed in a ball mill. The crushed rock is mixed with alumina and silicon carbide in the following ratio of components, wt.%:

Siliceous rock 95.0-96.0 Aluminium oxide 3.0-4.9 Silicon carbide 0.1-1.0

Spherical granules of a given size from 5 to 15 mm in diameter are obtained from the raw material mixture on a plate granulator. Raw granules are dried at 100 ° C for 30 minutes, heated to 600 ° C for 5 minutes and fired at a foaming temperature of 1120-1250 ° C for 10 minutes. As a result of thermochemical reactions of oxidation of silicon carbide, gaseous products are released and mineral raw materials expand during firing. In this case, during the firing process, the material of the granules goes into a pyroplastic state, and alumina tends to the surface of the granules, preventing their sintering. The expanded masses are cooled in the refrigerator, where they are cooled and heat is recovered.

The proposed technological solution allows the use of not only glassy volcanic rocks (perlite, vitrosite, ashes or vitroclastic tuffs), but widespread igneous rocks of acidic and medium composition (granites, diorites, dacites, andesites, etc.) without preliminary melting to obtain glass granules (raw materials for foam glass). Such rocks have a low melting point; therefore, a porous material can be made from a mixture based on them by single heating (combining the processes of its melting and foaming).

This gives a two-fold reduction in energy costs compared with the production of Azerite or the production of foam glass according to the traditional two-stage technology.

An important new element of the proposed solution is the possibility of using large-tonnage waste from igneous rocks for the production of building material (screenings from crushing to gravel, dump tailings and slimes of mining and processing plants), and not specially welded glass granules from scarce materials.

An example of a specific manufacture of a porous aggregate from the inventive feedstock.

The feedstock is delivered by automobiles and fed to the receiving hoppers, then the charge components are dosed to obtain the desired dosage of the blowing agent, at the same time, electromagnetic separation of the feedstock occurs along the conveyor belt to remove metal impurities. In the first drying drum, the raw materials are dried and mixed for the first time. Then, the charge is fed to vibrocentrifugal mills, where the disintegration and mechanochemical activation of the mixture takes place to the necessary condition. Granular pellets are formed on dish-shaped granulators, which are fed into a drying chamber, where granules are blown on a mesh conveyor by a constant stream of heated air. Air heating to a temperature of 400-450 ^{° C} is carried out by pre its passage through the cooling elements of the furnace and selecting from them of heat. The heated granules fall into the lower part of the apparatus, where they are fed into the kiln with a distribution device. Heated granules moved in a monolayer ring hearth are additionally heated with metal heaters to a temperature of 1180C. After firing, the granules fall into the refrigerator, where they are cooled and heat is recovered.

Examples of the specific composition of the raw mix.

Composition 1.

albitofir - 67%

diabase - 28%

aluminum oxide - 4.5%

silicon carbide - 0.5%

In this composition, albitophyre and diabase are siliceous rocks.

Composition 2.

Granite - 95%

Alumina - 4%

Silicon Carbide - 1%

In this composition, granite is a silica-containing rock. When using this mixture, the strength of the obtained material increases.

Composition 3.

Diorite - 96%

Alumina - 3.5%

Silicon Carbide - 0.5%

In this composition, diorite is a silica-containing rock. When using this mixture, the processing temperature is reduced.

The most important consumer properties of the product obtained from the proposed raw mix:

- high compressive strength;

- low thermal conductivity;

- low water absorption;

- high soundproof properties;

- high resistance to low temperatures;

- incombustibility, non-toxicity.

For the manufacture of porous aggregate from the claimed mass, it is possible to use large-tonnage waste of siliceous rocks - waste from the production of crushed stone in the form of screenings stored in heaps and in the form of dusty screenings stored in slurry pools. At the same time, production waste can also be used as a blowing agent. For example, aluminum oxide is contained in the waste from the Achinsk Alumina Refinery, and silicon carbide is contained in the waste from the Volzhsky Abrasive Plant. The required percentage of ingredients in this case is obtained by dosing.

Thus, in the manufacture of building material from the inventive raw material mixture, mining waste that pollutes the environment is utilized.

In addition, the resulting material is both thermal insulation and structural material, providing significant savings.

The proposed raw material mass makes it possible to produce lightweight building heat-insulating material in the form of blocks of standard sizes, which makes it possible to use it as a traditional masonry material, and its thermotechnical and strength characteristics make it possible to reduce the consumption of ordinary brick by a factor of five, with constant thermal protection of structures, which reduces the cost of building 20-30% of jobs.

The main characteristics of the material obtained from the inventive raw mix are shown in table 1.

Table 1 Tested Requirements GOST 9758-86 Compressive Strength in the Cylinder 12.9 kg / cm ² , 1.3 MPa not lower than 1.0 MPa Water absorption 2-8% no more than 30% Resistance to silicate decomposition 3.1% loss on boiling not more than 5% Thermal conductivity, W / m * K 0.06-0.30 Alkaline Resistance 35 mmol / l limit value 50 mmol / l

Claims (1)

The raw material mixture to obtain a porous aggregate, including silica-containing rock and a gasifier, characterized in that as a gasifier it contains a mixture of aluminum oxide and silicon carbide in the following ratio of components, wt.%:
Silica-bearing rock 95.0-96.0 Aluminium oxide 3.0-4.9 Silicon carbide 0.1-1.0