RU2448929C1 - Crude mixture and method of producing said mixture for nanostructured autoclave foamed concrete - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the industry of construction materials and can be used to produce heat insulation and structural-heat insulating autoclaved concrete for various purposes. In the method of producing a crude mixture for nanostructured autoclave foamed concrete, involving production of lime-silica binding material, subsequent mixing of the obtained lime-silica binding material, gypsum, a finely ground silica-containing component and a suspension of aluminium paste or powder in a mixer, the lime-silica binding material is obtained through combined dry milling of unslaked lime and quartz sand to specific surface area of 9000 cm²/g, and the finely ground silica-containing component is prepared by wet milling quartz sand to obtain a highly concentrated suspension with moisture content of 12-20% and content of particles smaller than 5 mcm of 30-50%, and subsequent dilution of the obtained suspension with water to density 1.75-1.80 kg/l, with the following ratio of components, wt %: said suspension (on dry substance) 62.5-72.5, said lime-silica binding material, with the following ratio of components, wt %: unslaked lime 75-85 and quartz sand 15-25, 25-35, gypsum 1.5-2.5, aluminium paste or powder 0.05-0.1, water to density 1.75-1.80 kg/l. The crude mixture for nanostructured autoclave foamed concrete is obtained using the method described above.

EFFECT: production of highly efficient heat insulating and heat-insulation construction autoclave foamed concrete with improved physical-mechanical and thermophysical properties.

2 cl, 2 dwg, 1 ex, 7 tbl

Description

The invention relates to the building materials industry and can be used for the manufacture of heat-insulating and structural heat-insulating concrete autoclaved for various purposes.

A known mixture for aerated concrete, including cement, lime, semi-aquatic gypsum, aluminum powder and water, additionally contains a water-soluble organosilicon water-repellent agent and lactam oil in the following ratio of components, wt.%: Cement - 50-55; lime - 3-5; semi-aquatic gypsum - 0.5-2.0; aluminum powder - 0.03-0.05; water-soluble organosilicon water-repellent agent - 0.05-0.1; lactam oil - 0.05-0.1; water is the rest. (RU 2191760 C1, (51) IPC7 C04B 38/02). The disadvantage of this analogue is the high consumption of cement and low physical and mechanical characteristics of the resulting material.

The known composition and method of producing aerated concrete, the composition contains cement, sand, aluminum powder, caustic soda and water, the sand contains unwashed and non-ground sand, in the following ratio of components, in wt.%: Cement - 15-50, specified sand - 31 -42, aluminum powder - 0.10-1.0, caustic soda - 0.05-0.45, water - the rest. A method of obtaining the aforementioned aerated concrete consists in dissolving an alkaline component in water, mixing the resulting solution, cement, sand and aluminum powder, pouring the mixture into a mold and keeping it for expansion and solidification, using caustic soda as an alkaline component, which is dissolved in water with a temperature of 65-90 ° C, then cement, unwashed and non-ground sand, aluminum powder are added to the solution with the simultaneous mixing of all components (RU 2255073 C1, (51) IPC7 C04B 38/02).

The known composition and method of producing aerated concrete include the inclusion of silica in the form of natural sand. Due to the characteristics of the hardening of the mixture by this composition, the microporosity of the cement stone is relatively small. The reduced microporosity of the material of the inter-pore walls is an obstacle to the production of aerated concrete with enhanced heat-insulating properties, while aerated concrete is mainly used in building exterior structures for thermal protection.

A known method of preparing a raw mix, including cement, sand, water, aluminum powder and lime, and sand in the form of sludge with a regulated particle size, the raw mix contains raw concrete in the composition of the sludge obtained by cutting the "hump" in the state of plastic strength A ₁ corresponding to the plastic strength A ₂ of raw concrete when cutting it into blocks of given sizes as A ₂ / A ₁ = 3.2-4.1, while the amount of water P _B in the preparation of the mixture is selected from the condition:

where P _B is the amount of water, kg; R _dry - the amount of dry materials, kg; R _sl.p - sand slurry consumption, l; R _{sl. G} - consumption of sludge obtained from the "hump" and wash water, l; B / T is the given water-solid ratio of the molding sand; In _sl.p - the amount of water in 1 liter of sand sludge, kg / l; B _{sl. G} - the amount of water in 1 liter of sludge obtained from the "hump", kg / l; B _al.s - the amount of water introduced with aluminum suspension, kg In the process of grinding, triethanolamine is introduced into the lime in an amount of 0.05% by weight of lime. (RU 2253567, C2, B28B 1/50, C04B 38/02). The disadvantage of this method is the low degree of mechanical activation of the siliceous component, as well as the high energy intensity and complexity of the technological design.

As a prototype, a cementless raw material mixture is selected for the manufacture of insulating aerated concrete containing ground quicklime, gypsum, aluminum powder, a siliceous component and water. As a siliceous component, ground and sieved bricks of silicate brick are used ground and sieved through a sieve No. 0.63, in the following ratio of components, parts by weight: specified quicklime 86-88; gypsum 2.7-2.76; aluminum powder 0.65-0.67; the specified battle of silicate brick 270-276; water 90-92 (RU 2385306, C04B 38/02). The disadvantage of this prototype is the use of a siliceous component with a relatively low specific surface area, which can serve as a serious obstacle to the occurrence of a full-fledged process of structure formation in the resulting material.

The closest way to prepare the raw material mixture for aerated concrete is a method of manufacturing foam concrete products, including the preparation of technical foam by mechanical treatment in a foam generator-mixer of an aqueous solution of a foaming agent, mixing it with a cementless nanostructured binder - a highly concentrated suspension of silica-containing raw materials, molding from the resulting foam and drying, characterized in that use the specified suspension with a particle content of less than 5 m km, constituting 20-50% and a moisture content of 12-20%, previously subjected to modification by the sequential introduction of an organo-mineral additive and a plasticizing additive. The technological operation to harden products is carried out by immersion with short-term exposure of the product after drying in an alkaline silicate solution with a density of 1.06-1.08 g / cm ³ for up to 3 minutes, depending on the type and overall dimensions of the products, or by surface treatment products by the aforementioned solution by irrigation and subsequent final drying (Pavlenko N.V., Cherevatova A.V., Strokova V.V. Features of obtaining a rational pore structure based on a nanostructured binder. - M.: Stroitelny materials. №10. 2009. S.33-36.). The disadvantage of this prototype is the inability to obtain by the proposed method a highly effective heat-insulating and structural cellular concrete without additional hardening operations.

One of the current trends in the development of the building materials industry is the creation of new and improvement of existing technologies that are associated with the production of nanosystems and the application of nanotechnological approaches.

Today, Portland cement is the main binder in the production of most types of building materials. Due to the increasing demand for effective binders, including non-hydration binders and hardening materials with high performance and environmental safety, both in production and in operation, the development and application of a new class of nanostructured binders capable of partially or completely replace cement in molding systems in the widest possible range of classes of building materials.

The directed formation of the structure of new materials based on nanosystems, the optimization of physicochemical production processes and the design of optimal technological solutions require a common scientifically based approach and a detailed study of the patterns and kinetics of structure formation of disperse systems during their technological processing and application. Equally important is the problem of uniform distribution of the active nanodispersed component in raw mixtures, which is especially important on a production scale.

The solution to this problem may lie not in introducing nanodispersed additives into the total mass, but in creating a nanostructured system in the composite mass itself in the process of technological redistribution - “in situ”.

The use of nanostructured binders will solve both the problem of aggregative stability and the problem of homogenization of nanodispersed active substances throughout the volume with the goal of stable structuring at all dimensional levels of organization of the composite.

The objective of the invention is the creation of a highly effective heat-insulating and heat-insulating structural autoclaved aerated concrete based on a fundamentally new type of cementless nanostructured binder with improved physicomechanical and thermophysical properties, the manufacture of technological, economical and environmentally friendly products for the construction of heat-efficient building envelopes of modern buildings.

In the inventive composition of the raw material mixture and the method of its production for nano-structured autoclaved aerated concrete, the following tasks were also set:

- the most fully use the effect of hydration hardening CaO and structure formation in the silicate system through the use of a siliceous component with a high degree of reaction interaction;

- to implement the possibility of mechanochemical activation of the siliceous component due to wet grinding on the principle of obtaining a highly concentrated binder suspension (HCBS).

- to obtain high-quality autoclave type hardening products with directionally adjustable properties.

The invention is also aimed at improving the competitiveness of the obtained gas-silicate autoclave products as a result of a 1.8-2 times increase in compression compared to industrial products, improving the technology and expanding the arsenal of means for producing gas-silicate autoclave products.

These tasks are achieved by a method of obtaining a raw mixture for nanostructured autoclaved aerated concrete, including obtaining a lime-siliceous binder, subsequent mixing in the mixer of the obtained lime-siliceous binder, gypsum, a suspension of aluminum paste or powder and a finely ground silica-containing solution, according to which we obtain a lime-based component containing lime, -silica binder is carried out by joint dry grinding of quicklime and quartz sand to ud Flax surface of 9000 cm ² / g and the preparation from fine silica-containing component is effected by wet grinding of quartz sand, to obtain a highly concentrated suspension humidity of 12-20% and the content of particles less than 5 microns 20-50%, followed by dilution with water and the resulting suspension to a density of 1.75 -1.80 kg / l, with the following ratio of components, wt.%:

specified suspension (on dry matter) 62.5-72.5 specified lime-silica binder, at a ratio of components quicklime 75-85 and quartz sand 15-25, 25-35 gypsum 1.5-2.5 aluminum paste or powder 0.05-0.1 water up to a density of 1.75-1.80 kg / l

Tasks are also achieved by the raw material mixture for nanostructured autoclaved aerated concrete, obtained by the above method and including calc-siliceous binder, gypsum, aluminum powder or paste and a finely ground silica-containing component, according to the proposed solution, a highly concentrated 20-20% concentrated suspension of 20% is used as a silica-containing component a particle content of less than 5 microns 20-50% obtained by wet grinding of quartz sand, in the following ratio of components, wt.%: the specified su a suspension (on dry matter) 62.5-72.5, the specified lime-silica binder, with a ratio of components, wt.%: lime 75-85 and quartz sand 15-25, 25-35, gypsum 1.5-2, 5, aluminum paste or powder 0.05-0.1, water to a density of 1.75-1.80 kg / l.

Examples of specific performance.

Case Study 1

To obtain a silicate mixture and test its suitability for the production of autoclaved aerated concrete, a number of operations were performed in accordance with the claimed composition of the raw mixture and the method for its preparation for nanostructured autoclaved aerated concrete.

Cement is not a required component of aerated concrete. It was found that the addition of cement increases the strength of aerated concrete, frost resistance and accelerates the setting of a cellular mixture.

In the presented composition of the cementless raw material mixture and the method for its preparation, it is planned, due to the presence of the nanodispersed component in the finely ground silica-containing component, to make it possible to optimize the structure formation processes in the resulting material and, accordingly, significantly increase the physicomechanical and operational characteristics.

For the production of aerated concrete, environmentally friendly mineral raw materials are used: sand, lime, gypsum, aluminum paste or powder and water.

To obtain a lime-silica binder, sand of the Karnaukhovsky deposit was used, with a content of 92.65% SiO ₂ , the chemical composition of which is shown in Table 1, and meets the requirements of GOST 8736-93 “Sand for construction work. Technical conditions. "

Also used quicklime lump lime, the characteristics of which are given in table 2 and satisfy GOST 9179-77 "Building lime. Technical conditions "; gypsum according to GOST 4013 and water according to GOST 23732, table 3.

To obtain a lime-silica binder, lime and sand were ground dry in a ball mill to a specific surface of 9000 cm ² / g.

As a silica raw material for producing a finely ground silica-containing component in the form of a highly concentrated suspension of silica-containing raw materials, in this case, the same sand of the Karnaukhovsky deposit was used.

To obtain a highly concentrated suspension of silica-containing raw materials, wet grinding was carried out in a ball mill with a stepwise loading of the material, observing the basic principles for the preparation of highly concentrated suspensions (Pivinsky Yu.E. Ceramic binders and ceramic concrete. / Yu.E. Pivinsky. - M .: Metallurgy, 1990. 270. from.).

The choice of the concentration of the system at the first grinding stage was carried out taking into account the packing coefficient of the source material and its other characteristics, as well as the overall dimensions of the mill. In the first grinding stage, usually all of the liquid calculated from the final suspension concentration is introduced. The duration of this stage of the process, depending on many factors, ranges from 1 to 5 hours. In this case, the duration of this stage of the process was 2 hours. The degree of dispersion should be such that the average particle size is at least 10-20 times less than the size of the material introduced during the next loading. Optimal results, as a rule, can be obtained in the case when dispersion is achieved at the first grinding stage, characterized by a significant (up to 30-50%) content of particles of the fraction less than 5 microns. In this case, the suspension is as if compressed, accelerating the process of subsequent grinding after the introduction of the next portion of the material.

With stepwise loading of the material, as the volume concentration increases, the effective density of the grinding media decreases and the humidity increases significantly. Due to a gradual decrease in the volumetric liquid content and an increase in the friction forces, the process temperature increases, which largely determines the rheological properties of the system directly in the grinding process, as well as the properties of a highly concentrated suspension of silica-containing raw materials after grinding. So, with increasing temperature, the overall viscosity of the system decreases significantly, its fluidity increases, as well as dilatant properties, which allows the grinding process to be carried out at elevated concentrations.

After wet grinding, the resulting highly concentrated suspension of silica-containing raw materials had a moisture content of 14.0%, with a particle content of less than 5 microns 42%.

Then, the resulting suspension was diluted with water to a density of 1.80 kg / L.

A comparative analysis of the effectiveness of wet sand grinding by the HCBS method showed that even at the initial stage of grinding, the finely ground component obtained by the HCBS method has a higher degree of dispersion of solid particles with a more developed surface morphology and, therefore, a significantly higher reactivity, which ultimately confirmed by a significant improvement in the technical and operational characteristics of silicate material (Fig. 1 - the results of a comparative analysis of the fineness of fine-grained the component obtained by the method ECCU and plant cuttings; Figure 2 - comparative data on the microstructure).

In the HCBS system, as a result of mechanochemical activation of the main solid phase, about 1-3% of nanoscale particles are formed already at the grinding stage. The presence of nanoparticles in HCBS has a complex positive effect. The latter concerns both the microstructure and technological aspects of HCBS production, as well as the technical and operational characteristics of the materials obtained on their basis. In addition, when wet grinding, mills consume less electricity, their productivity is 10-15% more.

With the introduction of HCBS instead of quartz slurry, the strength increased by 50% compared with the factory composition.

Further, the raw material mixture for aerated concrete was obtained by mixing the prepared finely ground silica-containing component - a substitute for sludge, a calcareous-silica binder and gypsum.

Next, an aqueous suspension of a blowing agent (aluminum paste or powder) was introduced into the already prepared mixture.

In this case, we used an aqueous suspension of aluminum paste GPB-2 that meets the requirements of GOST 5494 (table 4).

The process of gas formation occurs as a result of the chemical interaction of aluminum with calcium hydroxide by the reaction:

2Al + 3Ca (OH) ₂ + 6H ₂ O = 3CaO · Al ₂ O ₃ · 6H ₂ O + 3H ₂

The released hydrogen swells the mineral composition, which, hardening, preserves the cellular structure.

Next, the prepared raw material mixture for autoclaved aerated concrete was fed to the molding section.

The required estimated amount of the constituent components of the molding sand (for the experimental composition and factory analogue) at a density of the final product of 500 kg / m ³ and a productivity of 1080 m ³ per day (378,000 m per year); the consumption of materials is given in tables 5, 6.

According to the developed compositions, cube samples 100 × 100 × 100 mm in size were formed. Next, the samples at a temperature of 183 ° C and an overpressure of 10 atmospheres according to the regime: pressure start-up - 2 hours, isothermal exposure - 6 hours, pressure relief - 2 hours. Next, the cube samples were tested for strength, density and water absorption, frost resistance, vapor permeability, thermal conductivity . The test results are presented in table 7.

When using the specified finely ground silica-containing component in the form of a highly concentrated suspension, it becomes possible to increase the production efficiency of silicate autoclaved pressed materials by optimizing the grain composition of the initial mixture by controlling the content of a certain amount of nanosized particles in the system; to establish the relationship between the method of grinding the binder component, the rate of formation of calcium hydrosilicates and their type in silicate systems; by increasing the degree of dispersion (1.5 times) of the binder components achieved by wet grinding according to the HCBS principle, a higher degree of amorphization and mechanical activation of particles, significantly reduce the temperature and pressure during autoclaving and increase the physicomechanical characteristics by 40-50% material.

Based on the studies, it can be concluded that the nanostructured silicate autoclave material is highly technological and promising, since, according to preliminary estimates, the duration of the quenching period is actually reduced by 2 times and, accordingly, a significant reduction in the energy intensity of the autoclave treatment mode is possible, which will give an additional economic effect on existing production .

Table 1 The chemical composition of the sand of the Karnaukhovsky field Compound SiO ₂ Na ₂ O + K ₂ O Al ₂ O ₃ SO ₃ Fe ₂ O ₃ Cao MgO Cl ₂ clay p.p.p. Content% 92.65 traces 1.72 0.19 0.06 0.69 0.69 traces traces 1.23

table 2 Characteristics of quicklime Indicators Value The content of active CaO + MgO,%, not less 85 MgO content,% no more 5 Content of unburnt lime,% no more 7 Blanking rate, min twenty

Table 3 Basic requirements for mixing water Names Indicators pH 6-8 Rigidity, not less 18 ° dH Chlorides, not less than mg / liter 500 Sulfates, not less than mg / liter 200

Table 4 Technical characteristics of gas paste for concrete Gas paste for concrete GPB-1 GPB-2 Mass fraction of active aluminum,%, not less 75-80 80-85 Sieve residue,%, no more (grid numbers in accordance with GOST 6613) +008 1,0 1,0 +0056 - - +0045 15.0 5,0 Wettability with water Yes Yes

Table 5 Consumption of materials, factory composition Name of material Consumption, wt.%: Consumption for 1080 m ³ per day Consumption of 378,000 m ³ per year Sand 65.5 383.4 t 134.2 thousand tons Cement 15.7 91.8 t 32.13 thousand tons Lime 15.7 91.8 t 32.13 thousand tons Gypsum 2,8 16.2 t 5.67 thousand tons Aluminum paste 0.15 0.864 t 302.4 t Water 0.05 270 m ³ 94.5 thousand m ³ 12 bar steam 150 kg 162000 kg 56.7 thousand tons Electric power 30 kWh 32,400 kWh 11340 thousand kWh Mold grease 0.15 L 162 l 56.7 thousand liters Grinding bodies for a mill 1-3 kg / t of sand depending on the fineness of grinding - -

Table 6 Consumption of materials, experimental composition Name of material Consumption, wt.%: Consumption for 1080 m ³ per day Consumption of 378,000 m ³ per year Sand 72.5 475.2 t 173.5 thousand tons Cement - - - Lime silica binder:
lime 85 wt.%
sand 15 wt.% 25.9 91.8 t 32.13 thousand tons Gypsum 1,5 16.2 t 5.67 thousand tons Aluminum paste 0.1 0.864 t 302.4 t Water up to a density of 1.75 kg / l 12 bar steam 150 kg 162000 kg 56.7 thousand tons Electric power 30 kWh 32,400 kWh 11340 thousand kWh Mold grease 0.15 L 162 l 56.7 thousand liters Grinding bodies for a mill 1-3 kg / t of sand depending on the fineness of grinding - -

Claims (2)

1. A method of obtaining a raw material mixture for nanostructured autoclaved aerated concrete, comprising obtaining a lime-siliceous binder, subsequent mixing in the mixer of the obtained lime-siliceous binder, gypsum, a suspension of aluminum paste or powder and a finely ground silica-containing component, characterized in that by co dry grinding of quick lime and quartz sand to a specific surface of 9000 cm ² / g and the preparation tonkomolo silica-containing component is carried out by wet grinding quartz sand to obtain a highly concentrated suspension with a moisture content of 12-20% and a particle content of less than 5 microns 20-50%, and then diluting the resulting suspension with water to a density of 1.75-1.80 kg / l, in the following the ratio of components, wt.%:
specified suspension (on dry matter) 62.5-72.5
the specified lime-silica binder, with a ratio of components, wt.%:
quicklime 75-85 and quartz sand 15-25 25-35 gypsum 1.5-2.5 aluminum paste or powder 0.05-0.1 water up to a density of 1.75-1.80 kg / l 2. The raw material mixture for nanostructured autoclaved aerated concrete obtained by the method according to claim 1.

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