RU2433975C1 - Method of producing granular aggregate for concrete - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to production of construction materials and can be used in making concrete structures which are subjected to steam treatment during hardening, for civil and industrial construction. The method of producing granular aggregate for concrete, consisting of a core and cladding, involves formation of the core in the presence of liquid glass from a mixture of jointly ground foamed pearlite and sodium hydroxide, rolling the cladding on the surface of the core from jointly ground unslaked lime with sodium silicofluoride, curing the granules in a microwave field with specific power consumption of 41-86 J/cm3. ^ EFFECT: shorter production time, high activity of the granular aggregate, as well as high water impermeability of concrete structures and low heat conductivity thereof. ^ 1 ex, 2 tbl

Description

The invention relates to the production of building materials and can be used to obtain concrete building products subjected to heat and moisture treatment during hardening, for civil and industrial construction.

A known method of manufacturing a granular aggregate for concrete, consisting of a core and a protective shell. The core is made by granulation on a plate granulator of a mixture of dispersed silica-containing components - TPP ash (dispersion not less than 200 m ² / kg) and sludge from a biological wastewater treatment aeration station with a binder - ground lime (dispersion 500-600 m ² / kg) and gypsum ( with a brand name of at least 100 and a dispersion of at least 350 m ² / kg) in the ratio of the components of the mixture, respectively, 0.3: 0.5: 0.15: 0.05 by weight. After granulation, a 3-5 mm thick protective coating is applied to the core by wetting the core of the granule with liquid glass and dusting or pelletizing it on a disk or drum granulator with a dry, dusty mixture of lime, gypsum and mineral particulate filler (ash from a thermal power station, state district power station, loam, etc. ) in the ratio of the components of the mixture, respectively, 0.35: 0.10: 0.55 by weight. After the formation of the granules with the aim of curing, heat and moisture treatment is applied at a temperature of 90 ° C with isothermal exposure for one hour [RF Patent No. 2077517, cl. 6 C04B 20/10, 1993].

The disadvantage of this method of manufacturing granular aggregate is that it requires an increased cost of working time to cure: first, granular aggregate is subjected to heat and moisture treatment, then a molded building product including the above aggregate, as well as the resulting concrete building products subjected to heat and moisture treatment during hardening have low water resistance, strength and heat-insulating ability.

Closest to the proposed solution is a method of manufacturing aggregate for concrete in the form of granules with a size of 0.5-10.0 mm, consisting of a core and a shell, where the core is obtained by granulating a mixture of co-milled to a specific surface area of 150-250 m ² / kg silica-containing component - natural perlite and sodium hydroxide with a mass ratio of 0.70-0.95: 0.05-0.30 with a binder - an aqueous solution of sodium silicate with a density of 1.2-1.3 g / cm ³ in the amount of 0.1- 7.0% of the mixture, and the shell is formed on the surface of the core by rolling it into a dry, dusty a mixture of together ground quicklime with sodium silicofluoride at a mass ratio of 0.85-0.95: 0.05-0.15, followed by hardening to a strength of at least 0.12 MPa. [RF patent No. 2358937, cl. 7 C04B 28/04, 2007].

The disadvantages of the method of manufacturing a granular aggregate according to the prototype are the large time required for aging the obtained granules to set the required strength, which reduces production productivity, and also the fact that the reactions between natural perlite and alkali in the granule core during heat and moisture treatment of a concrete product do not occur in full, because different hardness of co-milled components does not allow to obtain sufficiently highly reactive homogeneous cores of granular aggregate for concrete, while in the finished concrete product up to 50-55 wt.% unreacted perlite is observed, which degrades the quality, does not allow to obtain the design indicators of strength, thermal conductivity and waterproofing characteristics obtained concrete building products.

The present invention solves the problem of expanding the arsenal of technical means for the production of cellular concrete with reduced thermal conductivity, allows to reduce production time, increase the reactivity of granular aggregate, reduce thermal conductivity, increase the strength characteristics of concrete building products subjected to heat and moisture treatment during hardening.

The technical result is achieved in that a method of manufacturing a granular aggregate for concrete, consisting of a core and a shell, comprising forming a core in the presence of liquid glass from a mixture of co-milled natural perlite and sodium hydroxide, rolling the shell onto the surface of the core from co-milled quicklime with sodium silicofluoride, curing of granules, according to the proposed solution, pre-expanded perlite is used as perlite, and curing of granules is carried out in a microwave le with a specific energy consumption of 41-86 J / cm ³ .

Component Feature:

1. As a binder used Portland cement ZAO Belgorodcement according to GOST 10178-85 of the following mineralogical composition, wt.%: C ₃ S - 66.8; C ₂ S - 17.4; C ₃ A - 4.0; C ₄ AF - 11.8. The fineness of grinding is 345 m ² / kg. The normal density of the cement paste according to GOST 310.4-81 is 27.12%. The activity during steaming is 38.9 MPa, the activity during normal storage at the age of 28 days is 44.2 MPa.

2. As a silica-containing component for the manufacture of the core aggregate used dust caught by cyclones during the expansion of crushed perlite Mukhor-Talinsky deposits. The chemical composition of perlite dust, wt.%: SiO ₂ - 71.7; Al ₂ O ₃ - 14.4, Fe ₂ O ₃ - 1.7, TiO ₂ - 0.6, CaO - 0.8; MgO - 1.9; R ₂ O - 8.9. Currently, perlite dust is not used; its removal to a landfill pollutes the environment.

3. Sodium hydroxide according to GOST 2263-79.

4. Sodium silicofluoride Na ₂ SiF ₆ according to TU 6-09-1461-91.

5. As a lime-containing component for the manufacture of a protective envelope for the aggregate, quicklime construction lime was used by JSC "Building Materials", Belgorod in accordance with GOST 9179-77.

6. As a fine aggregate of concrete mixtures used natural quartz Volsky sand according to GOST 6139-2003.

7. Tap water in accordance with GOST 23732-79.

8. When granulating a mixture of perlite dust with sodium hydroxide on a plate granulator, an aqueous solution of liquid glass according to TU 2385-001-54824507-2000 with a density of 1.2-1.3 g / cm ^{3 was} used as a binder.

To obtain cores of a granular aggregate, perlite dust was dosed with sodium hydroxide by the gravimetric method in a ratio of 0.70-0.95: 0.05-0.30. The resulting mixture was loaded into a ball mill and grinding was carried out to a specific surface of 150-250 m ² / kg. The resulting mixture was fed to a standard plate granulator, where when spraying an aqueous solution of water glass with a density of 1.2-1.3 g / cm ³ received core aggregates of a given size.

The obtained core aggregates were directed to the formation of a protective shell by pelletizing in a drum mixer, to which ground lime and sodium silicofluoride were also fed together with their mass ratio of 0.85-0.95: 0.05-0.15, i.e. similar to the method described in the patent of the Russian Federation No. 2358937.

The obtained granules were sent for curing in a resonator of a microwave oven (microwave field) with a specific energy consumption of 41-86 J / cm ³ and a frequency of 150-314 MHz for 8-17 minutes. The hardening time was selected based on the maximum values of the strength characteristics of the granules. The energy intensity of the processing of granules can be changed as the frequency of the microwave field, and the speed of the conveyor belt.

The strength of the granular aggregate was controlled by crushing in a cylinder according to GOST 9758-86.

Example. Preparation of granular aggregate cores. Perlite dust (8 kg) and sodium hydroxide (2 kg), i.e. in a ratio of 0.80: 0.20 by weight of the milling in the mill to a specific surface of 200 m ² / kg The obtained powder material was fed to a plate granulator. An aqueous solution of sodium silicate was applied to the surface of the powder by spraying.

table 2 Physico-mechanical properties of concrete building products after heat and moisture treatment No. p / p The mass ratio of unreacted perlite in granules after heat-moisture treatment of concrete to the original, wt.% Teplopro
water content, W / (m · K) Waterproof grade concrete
value The limit of compressive strength, MPa Notes one 5.1 0.29 B8 39.7 - 2 9.6 0.37 B6 32.3 Part of the pores has a non-spherical shape, which reduces the strength of concrete samples 3 8.4 0.39 AT 6 33.9 Part of the pores has a non-spherical shape, which reduces the strength of concrete samples four 14.3 0.71 B3 27.0 Pores have a disordered structure due to the low strength of the granular aggregate 5 10,2 0.50 B3 27,2 Pores have a disordered structure due to the low strength of the granular aggregate 6
(prototype) 48.9 0.38 AT 6 34.9 -

density of 1.25 g / cm ³ in an amount of 4% relative to the mass of the core aggregate. The rotation speed and the angle of inclination of the granulator plate controlled the diameter of the resulting cores, which in this case was 4.4-4.5 mm (similar to the method described in RF patent No. 2358937).

Obtaining a protective shell on the nuclei. The resulting cores were sent for dusting with a powder of lime (9 kg), ground together with sodium silicofluoride (1 kg), i.e. in a ratio of 0.90: 0.10 to obtain granules with a size of 5.0 mm Dusting was performed in a drum mixer (similar to the method described in RF patent No. 2358937).

The obtained granules were sent for curing into the resonator of a microwave oven with a specific energy consumption of 74 J / cm ³ and a frequency of 270 MHz for 10 minutes. The temperature of the granules at the outlet is 95 ° C, the conveyor speed is 8 cm / min.

Part of the obtained granular aggregate was tested for strength by compression in a cylinder according to GOST 9758, the strength was 2.92 MPa; the rest was used in the preparation of concrete mixtures for the manufacture of standard samples of building products.

Preparation of concrete mix. The components were dosed by the weight method: 2 kg of Portland cement (20 wt.%), 2.5 kg of quartz sand (25 wt.%) And 3.5 kg (35 wt.%) Of granular aggregate were mixed in a screw mixer until homogeneous and added 2 kg (20 wt.%) Of water.

Samples were formed in the traditional way by filling in standard forms 2FK-100 according to GOST 10181-2000. The exposure time in the forms is 6 hours.

Heat and moisture treatment of all concrete samples was carried out in a steaming chamber at atmospheric pressure according to the 2 + 6 + 2 mode and isothermal exposure temperature of 90 ° C, thus, the concrete mixture was prepared, samples were molded and their heat and moisture treatment was performed according to the known method [Gershberg O.A. Technology of concrete and reinforced concrete products. - M: Stroyizdat, 1971, S. 98-102, 305-313].

Product samples were tested for strength (according to GOST 10180), thermal conductivity (according to GOST 7076-99) and water resistance (according to GOST 12730.5-84) were determined. The ratio of the mass of unreacted perlite in granules after heat and moisture treatment of concrete to the initial one was determined as the ratio of the residual mass of perlite in granules after heat and moisture treatment of concrete to the initial mass of perlite in the granule before its introduction into the concrete mix (in mass percent), the lower the value, the higher reactivity of core aggregate granules.

In the same way, wall concrete products with other characteristics of granular aggregates were obtained due to the variation of the parameters of the microwave field during curing. The content of granules in concrete mixtures 1-6 was constant and amounted to 35 wt.%. When forming a granular aggregate to obtain comparable results, the following conditions were fulfilled: the ratio between perlite and sodium hydroxide by weight in the core of the granule is 0.80: 0.20; the ratio between lime and sodium silicofluoride in the protective shell of the granule by weight is 0.90: 0.10; the amount of an aqueous solution of sodium silicate in relation to the mass of the core aggregate - 4.0%; the diameter of the granules is 5 mm. The test results of the physico-mechanical properties of the obtained concrete building products are given in table 2, mixtures 1-6.

The core of the granular aggregate according to the patent of the Russian Federation No. 2358937 was made from co-ground natural perlite and sodium hydroxide; kept after manufacture for curing at 19 ° C in dry conditions for 7 hours.

Analysis of the test results of the properties of samples of concrete building products shown in table 2, shows the following.

1. Introduction to the composition of the concrete mixture of granular aggregate manufactured by the present method, the use for curing its microwave field with a frequency of 150-314 MHz and specific energy consumption of 41-86 J / cm ³ , replacing natural perlite with pre-expanded allows you to get durable waterproof concrete construction products with reduced thermal conductivity, while, due to the exclusion of the process of long exposure of the filler for hardening, the time of its manufacture is reduced to 20-30 minutes, significantly increasing creases core reactivity.

2. The decrease in specific energy consumption to 41 J / cm ³ and the frequency of the microwave field to 150 MHz during curing of the granular aggregate leads to the appearance of deformations and a decrease in its strength due to softening of the core, the reactivity of the aggregate is reduced. Concrete samples prepared using this aggregate are characterized by increased thermal conductivity, reduced strength and water resistance (mixture 2, Table 2), this composition is accepted as boundary.

A further decrease in the aforementioned parameters of the microwave field leads to a significant decrease in the physical and mechanical properties of concrete building products, therefore, the composition of the mixture 4 is beyond the scope of the proposed method for the manufacture of granular aggregate for concrete.

3. An increase in the specific energy consumption to 86 J / cm ³ and the frequency of the microwave field to 314 MHz during curing of the granular aggregate leads to a decrease in its strength, the appearance of deformations of spherical nuclei, zonal swelling due to overheating and intensive removal of moisture from the core of the granule, a decrease aggregate reactivity. Concrete samples prepared using the obtained aggregate are characterized by increased thermal conductivity, reduced strength and water resistance (mixture 3, Table 2), this composition is accepted as boundary.

A further increase in the aforementioned parameters of the microwave field leads to a significant decrease in the physico-mechanical properties of concrete building products and granular aggregate due to its expansion, therefore, the composition of mixture 5 is beyond the scope of the inventive method for manufacturing granular aggregate for concrete.

With the optimal characteristics of the microwave field used to cure the granular aggregate (mixture 1, table 1), the resulting concrete building products have the following advantages compared to the known ones:

1) strength indicators increase by 12-14%, thermal conductivity decreases by 23%, the water resistance mark increases from B6 to B8 due to more complete dissolution of the core material and, therefore, more dense impregnation of the concrete surrounding the granule;

2) the obtained granular aggregate according to the claimed method does not require large expenditures of time for manufacturing, due to this, labor costs are reduced when obtaining structural and heat-insulating concrete building products.

When using granular aggregates obtained with the boundary parameters of the microwave field (mixtures 2 and 3, Table 1), the resulting concrete building products practically retain the brand for water resistance and strength characteristics comparable to the similar properties of the prototype.

Replacing natural perlite with waste from the production of expanded perlite in the manufacture of granular aggregate for concrete can significantly increase the performance of mills used for the joint grinding of perlite and alkali, or use screw mixers instead. The presence of expanded perlite in the core provides the necessary capillary porosity, which allows the free exit of the generated water vapor.

Utilization of bulk waste of expanded perlite production that cannot be used will not only improve the environment, but also produce high-quality environmentally friendly structural and heat-insulating concrete with good consumer characteristics.

Claims (1)

A method of manufacturing a granular aggregate for concrete, consisting of a core and a shell, comprising forming a core in the presence of liquid glass from a mixture of co-milled natural perlite and sodium hydroxide, rolling the shell onto the surface of the core from co-milled quicklime with sodium silicofluoride, curing the granules, characterized in that pre-expanded perlite is used as perlite, and the curing of granules is carried out in a microwave field with a specific energy consumption of 41-86 J / cm ³ .