RU2237642C1 - Composition for cellular concrete in non-autoclave hardening - Google Patents

Abstract

FIELD: building industry.

SUBSTANCE: invention relates to compositions of non-autoclave cellular concretes used for making building constructions, among them, safety building constructions designated for heat insulation of heated surfaces of industrial heat and electric equipments, for example, furnaces, boilers, steaming chambers, autoclaves. Invention provides preparing concrete with average density value less 128-133 kg/m³ due to increasing microporosity in interporous barriers of cellular concrete, reducing heat conductivity up to 0.067-0.070 Wt/m x degree and expanding field in using the cellular concrete. The composition for cellular concretes in non-autoclave hardening comprises the following components, wt.-%: cement, 6.4-6.8; water glass, 49.5-50.5; aluminum powder, 0.2-0.3; sodium hydroxide, 5.8-6.2; granulated polystyrene foam, 5.0-5.3; swollen vermiculite, 16.0-17.2; ferrosilicon, 13.9-14.1; diatomite, 0.8-1.0.

EFFECT: valuable properties of cellular concrete.

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Description

The invention relates to compositions of non-autoclaved cellular concrete used for the manufacture of building structures, including building envelopes intended for thermal insulation of heated surfaces of industrial thermal and electrical equipment, for example, furnaces, boilers, steaming chambers, autoclaves.

In addition, the invention can be used for the manufacture of structures designed for thermal insulation of the surfaces of pipelines of steam, gas, air, as well as for water conduits.

A known composition for the manufacture of heat-insulating material, including water glass, diatomaceous earth, sodium fluorosilicate, Portland cement and buckwheat husk (see, RF patent No. 2075210, Mcl 6: C 04 V 28/24, publ. 03/10/1997, "Composition for the manufacture of thermal insulation material").

The main disadvantage of the known composition is the low durability, frost and sulfate resistance due to the presence in the composition of the organic substance - buckwheat husk, which is largely susceptible to the destructive action of chemical and mechanical agents of the environment. Another disadvantage of the known composition is the relatively high average density of concrete due to insufficient microporosity in the inter-pore walls of the insulating material.

In addition, the disadvantage is the complexity of the preliminary processing of husks.

A known composition for producing a heat-insulating material, including a calcined siliceous component - diatomite, solid sodium hydroxide, silica fume, filler and water (see RF patent No. 2184099, Mcl 7: C 04 V 28/26, publ. June 27, 2002 g ., "Composition for obtaining insulating material").

A disadvantage of the known composition is the relatively high average density of concrete, equal to 131 - 205 kg / m ³ , due to insufficient microporosity in the inter-pore walls of the insulating material.

Another disadvantage is the technological complexity of preparing the insulating material.

The known composition of the heat-acid-resistant concrete mixture of non-autoclave hardening, consisting of siliceous opal-cristobalite rock, caustic soda and aggregate (see RF patent No. 2070872, Mkl. 6: 04 B 28/26, publ. 12/27/1996, , "A method of preparing a concrete mixture for the manufacture of acid and heat-resistant products").

The well-known concrete mixture intended for the manufacture of acid and heat-resistant products was prepared by mixing metasilicate sodium cristobalite suspension with standard Volsky sand or fireclay in a ratio of 1: 3. A suspension was prepared by dissolving opal-cristobalite rock in a solution of sodium hydroxide concentration of 100-150 g / l and partially transferring amorphous silica to the solution.

A disadvantage of the known concrete mixture is the high density of concrete, equal to more than 300 kg / m ³ , and insufficient microporosity of heat-resistant products. Another disadvantage is the high complexity of the leaching process opal-cristobalite rocks.

Since the thermal conductivity coefficient of finished products from this raw material reaches 0.16 W / m · deg., The heat-insulating properties of the concrete mixture do not allow to expand the scope of its application.

The closest analogue to the described invention is a composition for non-autoclaved aerated concrete, comprising a finely dispersed component, water glass, aluminum powder (see Russian application laid out No. 2000126457, M. Cl. 7: C 04 V 38/02, publ. 10.10.2002 G., “Composition for non-autoclaved cellular concrete”).

The composition additionally contains caustic soda, granulated polystyrene foam, expanded vermiculite, ferrosilicon, and cement as the binder and finely divided component, with the following ratio of components, wt.%:

Cement 6.4-6.8

Liquid glass 49.5-50.5

Aluminum powder 0.2-0.3

Caustic soda 5.8-6.2

Granular polystyrene foam 5.0-5.3

Expanded vermiculite 17.0-18.0

Ferrosilicon 13.9-14.1

The formation of a cellular structure occurs within 3-20 minutes. The foaming time depends on the temperature of the liquid glass solution with caustic soda. At a temperature of 20 ° C, foaming begins after 1-3 minutes, and at a temperature of 8-10 ° C, foaming occurs after 5-6 minutes. Physico-mechanical properties of the products obtained on the basis of the prototype are as follows: the coefficient of thermal conductivity is 0.07 W / m · deg, average density of 128-133 kg / m ³ .

A disadvantage of the known composition for non-autoclaved aerated concrete is a relatively high average density due to insufficient microporosity in the inter-pore partitions of aerated concrete.

The technical task of the invention is to obtain concrete of average density below 128-133 kg / m ³ by increasing microporosity in the inter-pore walls of cellular concrete, in reducing thermal conductivity to 0.067-0.070 W / m · deg, as well as in expanding the scope of cellular concrete.

The problem is solved in that the proposed composition for non-autoclaved aerated concrete, including cement, water glass, aluminum powder, caustic soda, granulated polystyrene foam, expanded vermiculite, ferrosilicon, according to the invention additionally contains diatomite, in the following ratio, wt.%:

cement 6.4-6.8

water glass 49.5-50.5

aluminum powder 0.2-0.3

caustic soda 5.8-6.2

granular polystyrene foam 5.0-5.3

expanded vermiculite 16.0-17.2

ferrosilicon 13.9-14.1

diatomite 0.8-1.0

The proposed composition for cellular concrete differs from the known composition in the content of a new component and its quantitative content - diatomite, as well as a new quantitative ratio of one of the known components - expanded vermiculite.

The manufacturing process of the composition includes the following basic operations: dissolving sodium hydroxide in liquid glass by mixing and then grinding and mixing in a ball mill the remaining dry components - aluminum powder, diatomite, cement, granulated polystyrene foam, expanded vermiculite, ferrosilicon.

Mixing of the dry components is carried out for 15-20 minutes, which ensures the formation of a uniform average specific surface area and, as a result, uniformity of the resulting cellular structure of the composition. By the end of mixing, the specific average surface of the co-milled mixture is in the range of 3000-4000 cm ² / g.

In the process of mixing and grinding dry components, some of them are activated, for example cement, and the mixture is prepared for interaction with a solution of caustic soda and water glass.

The combination of components such as sodium hydroxide solution, ferrosilicon and liquid glass in the mixture provides exotherm of the foaming process and the formation of pores.

The combination of components such as aluminum powder and ferrosilicon in a mixture contributes to a significant intensification of foaming and to obtain a given porosity of concrete with increasing exotherm of the process of interaction with caustic soda and liquid glass.

The combination in a mixture of granular polystyrene foam, expanded vermiculite, cement and diatomite, a decrease in density to 120-125 kg / m ³ and a maximum increase in microporosity in the inter-pore walls of aerated concrete.

In this case, apparently, the microporosity of diatomite helps to reduce the average density and thermal conductivity relative to the properties of the prototype.

The presence of diatomite in the mixture at a given ratio of components allows to stabilize the structure formation after pouring the crude mixture into the mold, helps to intensify microporosity in the inter-pore partitions of aerated concrete, which allows to obtain aerated concrete with specified thermal insulation properties.

The proposed ratio of components provides those optimal thermal insulation properties of the composition, beyond which there is an increase in density and an increase in the coefficient of thermal conductivity.

The amount of water glass, equal to 49.5-50.5% of the total mass of the obtained composition, provides the composition with the completeness of an exothermic reaction in the interaction of solutions of water glass and caustic soda with a dry mixture of aluminum powder and ferrosilicon.

The amount of caustic soda solution equal to 5.8-6.2 of the total weight of the composition, among other indicators, for example, such as the temperature of the solution, allows you to provide a specified amount of foaming sewn into the form of a crude mixture of the composition.

As shown by laboratory tests of the proposed composition, the crude mixture, heated by the heat of the exothermic reaction, is dried in the form for 20-25 minutes without additional energy consumption.

The increase in the content of caustic soda solution to 6.3-6.5% of the total weight of the composition, reduces the volume of foaming and increases the density, which reduces the thermal insulation resistance of the resulting cellular concrete.

The amount of aluminum powder, equal to 0.2-0.3% of the total weight of the composition, ensures uniform foaming at the beginning of the pore formation process.

The amount of expanded vermiculite, equal to 16.0-17.2% of the total mass of the resulting composition, affects the microstructure of the cementitious substance and increases its thermal insulation properties. The amount of ferrosilicon, equal to 13.9-14.1% of the total weight of the composition, also allows you to adjust the thermal conductivity index along with other components.

The amount of granulated polystyrene foam, equal to 5.0-5.3% of the total weight of the composition, provides stabilization of pore formation in a predetermined range of pore sizes.

The amount of cement, equal to 6.4-6.8% of the total mass of the obtained composition, affects the strength and heat resistance.

The amount of diatomite, equal to 0.8-1.0% of the total mass of the obtained composition, significantly affects the total porosity of aerated concrete, since natural diatomite has a predominantly closed porosity of up to 85%, partially preserved during its grinding and contributing to the formation of microporosity in inter-pore partitions of cellular concrete. As laboratory tests have shown, the proposed quantitative diatomite content in the range of 0.8-1.0% of the total mass of the obtained composition allows to obtain the necessary thermal insulation properties: average density of 120-125 kg / m ³ and thermal conductivity in the range of 0.067-0.070 W / m ·hail.

The formulation of the proposed composition and the raw material mixture selected as a prototype are shown in table 1.

The thermal insulation properties of cellular concrete are given in table 2.

Changing the limiting contents of these components, for example, increasing them above the maximum value, affects the physicomechanical properties of concrete, for example, the consistency of the molding mixture. In this case, there is an increase in the viscosity of the mixture, which reduces the volume of the foamed material, and therefore worsens the physical and mechanical properties: increases the average density to 160 kg / m ³ and the thermal conductivity to 0.10 W / m · deg.

The decrease in the limiting contents of the components of the composition in excess of the minimum set leads to a decrease in the viscosity of the molding sand, worsening the indicators of heat resistance and thermal insulation.

As can be seen from table 2, the proposed composition has a fairly low coefficient of thermal conductivity, equal to 0.067-0.070 W / m · deg. and an average density in the range of 120-125 kg / m ³ .

Consumer properties and performance indicators of products manufactured according to the proposed recipe meet the requirements of GOST 254-85-89 “Cellular concretes”.

The proposed composition for non-autoclaved aerated concrete not only allows the manufacture of products superior in their heat-insulating and consumer properties to the raw material mixture selected as a prototype, but also provides the possibility of the appearance on the market of building materials of cellular concrete products not inferior to the best samples in their consumer properties non-autoclaved aerated concrete products.

The proposed composition for cellular concrete is prepared as follows. A solution of sodium hydroxide in an amount of 6.4-6.8 wt.% Dissolved in 49.5-50.5 wt.% Water glass by stirring the solution. Dry components: cement, diatomite, aluminum powder, granular polystyrene foam, expanded vermiculite and ferrosilicon are mixed in a ball mill for 15-20 minutes.

The dry components are crushed to form an averaged homogeneous specific surface with a co-milled mixture of 3000-4000 cm ² / g. Dosed dry components are mixed manually or in any forced-action mixer of the sparkless version with a solution of liquid glass and caustic soda for 1 minute. The crude mixture is poured into the prepared forms. The formation of a cellular structure occurs within 3-20 minutes. The foaming time also depends on the temperature of the liquid glass solution with caustic soda. At a temperature of 20 ° C, foaming begins after 1-3 minutes, and at a temperature of 8-10 ° C, foaming occurs after 5-6 minutes.

The foaming process is exothermic and after 20-25 minutes the product is dried.

The proposed composition for cellular concrete non-autoclaved hardening allows in comparison with the prototype

- reduce the average density of concrete to 120 kg / m ³ ;

- reduce the coefficient of thermal conductivity of finished building products from cellular concrete to 0.067 W / m · deg and thereby increase the thermal insulation properties;

- at the same time expand the scope of cellular concrete;

- to exclude energy costs for thermo-humid autoclave processing of molded products.

Claims (1)

Composition for non-autoclaved aerated concrete, including cement, water glass, aluminum powder, caustic soda, polystyrene foam, expanded vermiculite, ferrosilicon, characterized in that it additionally contains diatomite in the following ratio, wt.%: Cement 6.4 - 6.8 Liquid glass 49.5 - 50.5 Aluminum powder 0.2 - 0.3 Caustic soda 5.8 - 6.2 Granular polystyrene foam 5.0 - 5.3 Expanded vermiculite 16.0 - 17.2 Ferrosilicon 13.9 - 14.1 Diatomite 0.8 - 1.0