RU2651720C2 - Method of producing nanomodified additive for construction purpose - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method consists in the production of a nanomodified additive for the construction purposes, characterized in that cement is sprayed in the synthesis chamber together with the particles of the metal oxide catalyst for the synthesis of carbon nanomaterials (NiO/MgO) and, through the chamber-precipitator pre-purged with inert gas, is deposited on the desktop-disc connected with a rotation drive, then the heating is switched on to the temperature of 630-670°C, and a continuous supply of propane-butane mixture (hydrocarbon gas) and the withdrawal of gaseous products of pyrolysis are performed, and at the end of the chemical deposition process the finished product-cement with the carbon nanotubes synthesized on the surface is cooled, and then the disc rotating drive is switched on, the finished product is moved with a scraper through the window made in the lower part of the synthesis chamber to the auger hopper, the drive of which is switched on simultaneously with the disc rotating drive. Belgorod M500 D0 cement or other cement, including cement with additives, and a metal oxide catalyst for the synthesis of carbon nanomaterials (NiO/MgO) at the ratio of catalyst to cement being of 1:5 can be used in the feedstock.

EFFECT: reducing the cement consumption by increasing the activity of the additive, while maintaining the strength characteristics of concrete, simplifying the technology and reducing energy costs.

2 cl, 1 tbl, 3 dwg

Description

The method relates to the production of nanomodifying additives for construction purposes, in particular, can be used to obtain modifiers of cementitious building materials (substances) in the manufacture of block and monolithic concrete.

Currently, carbon nanostructures are being actively developed and are finding practical use; interest in these objects is caused by their high operational properties, such as exceptional tensile strength, high elastic modulus, and a number of other important indicators. The most difficult when using nanomodifying additives is their uniform distribution in the matrix of the final building material. Due to the high agglomeration ability, they cannot be easily and uniformly dispersed; in order to overcome these forces, multistage and labor-intensive processes are required to overcome them. A successful solution to this problem will open up new possibilities for creating nanostructured building composites with improved functional characteristics.

A known method of preparation of nanomodified cement, which consists in joint grinding of the original cement with superplasticizer (RF patent No. 2515345, IPC С04В 40/00, 2014). According to the method, cement with superplasticizer is subjected to shock activation in an aerodynamic device at an acceleration of 35-40 g and a frequency of 20,000-25,000 beats / sec. Moreover, the amount of superplasticizer is 10-15% by weight of cement. Then, the resulting nanomodifier of cement in an amount of 2-4% by weight of the cement is mixed with the original cement in a diaphragm mixer. This method uses an installation comprising an activation chamber, a mixing chamber and a loading and unloading device. Moreover, the activation chamber is made aerodynamic, and the mixing chamber is equipped with primary and secondary diaphragms.

The disadvantage of this method is the high energy costs and a rather complicated scheme for implementing the entire process as a whole due to two-stage processing of the material: grinding with subsequent processing in a mixing plant.

Partially, these disadvantages are eliminated in the method of production of nanocement (Application WO 2014148944, IPC B82Y 30/00, B82B 1/00, C04B 7/12, C04B 7/52, 2014). A method for the production of nanocement involves the mechanochemical activation of dispersed Portland cement grains in the presence of a polymer modifier with a sodium naphthalene sulfonate content of at least 60 wt. %, mineral siliceous additives containing SiO ₂ not less than 30 wt. %, and gypsum stone with the formation of continuous nanoshells - capsules with a thickness of 20-100 nm on Portland cement grains from sodium naphthalene sulfonate structured with calcium cations, while the mechanochemical activation of Portland cement is combined with grinding materials to a specific surface of 300-900 m ² / kg and carried out in a ball mill and nanocement receive the specified method in the following ratio of the starting components, wt. %:

Portland cement or Portland cement clinker 30.0-90.0 Gypsum stone 0.3-6.0 Specified Polymer Modifier 0.6-2.0 Specified siliceous additive Rest

The method allows to increase the construction and technical properties of cement to classes 72.5-82.5, reduce its cost, radically reduce specific fuel costs, emissions of NOx, SO ₂ and CO ₂ . However, this method requires the use of additional components, namely plasticizing additives, subjected to additional subsequent mechanical activation.

Thus, the presented methods are characterized by the use of surface mechanical activation of the initial components of the mixture, aimed at the transition of particles from one phase of the structure of the substance to a smaller one. In turn, this process, even in the presence of plasticizing additives, does not affect the processes of structure formation.

The closest to the claimed method in terms of features is a patent of the Republic of Belarus (BY 18547 IPC С04В 7/48, B82Y 40/00, 2014), which consists in obtaining carbon nanotubes on cement particles in the process of cement production (prototype). The method is as follows. Limestone and clay are first crushed in a crusher, then dried in a tumble dryer to a moisture content of about 1% and ground in a mill to produce raw flour. To obtain raw flour of a certain chemical composition, it is sent to mixing silos, where additional raw flour with obviously low or high CaCO ₃ content is served. In silos, flour is mixed with compressed air. The prepared flour is fed into the heat exchanger system, where it is preheated with flue gases coming out of the furnace moving towards it. The flour residence time in cyclone heat exchangers does not exceed 25-30 s. In this case, the raw meal has time to warm up to a temperature of 700-800 ° C and is completely dehydrated and partially (by 20-25%) decarbonized, which leads to the partial formation of an intermediate product in the form of cement clinker. From the heat exchangers, the material is fed into the furnace, where a further reaction of the formation of cement clinker takes place with its heating to a temperature of 1100 ° C. From the furnace, cement clinker is fed into the synthesis chamber, in which it is blown with propane-butane at atmospheric pressure for 5-15 minutes (depending on the required concentration of carbon nanotubes). In this case, the growth of nanotubes occurs on the particles of cement clinker due to chemical vapor deposition. The obtained carbon nanotubes are fairly evenly distributed on the surface of the particles of cement clinker, which eliminates the need for additional mixing of the mixture. Then the resulting composite cement material is poured into the refrigerator and after cooling, grinding the clinker and mixing with gypsum in the mill, they are sent to the warehouse.

However, the method is characterized by high energy costs, increased consumption of the propane-butane mixture due to the insufficient catalytic activity of the components of the cement clinker and a large park of the required hardware design, the whole process, which, in turn, leads to a high final cost of the resulting modifier.

The technical result consists in reducing the consumption of cement by increasing the activity of the additive while maintaining the strength characteristics of concrete, simplifying the technology and reducing energy costs.

The technical result is achieved by the method of obtaining a nanomodified additive for construction purposes, characterized in that the cement is sprayed in the synthesis chamber together with the particles of the metal oxide catalyst for the synthesis of carbon nanomaterials (NiO / MgO) and, through a pre-blown inert gas, the precipitating chamber is deposited on the working table connected to the rotation drive - disk, then include heating to a temperature of 630-670 ° C and produce a continuous supply of propane-butane mixture (hydrocarbon gas) and the removal of gaseous uktov pyrolysis, and at the end of the chemical deposition finished product - cement with carbon nanotubes synthesized on the surface is cooled, after which include

  a disk rotation drive, the finished product is scraper shifted through a window made in the lower part of the synthesis chamber into a screw hopper, the drive of which is turned on simultaneously with the disk rotation drive.

The composition of the feedstock uses: Belgorod cement M500 D0 or other binders for construction purposes (also cements with and without additives), a metal oxide catalyst for the synthesis of carbon nanomaterials (NiO / MgO) with a catalyst to cement ratio of 1: 5. Preliminary preparation of the starting materials is carried out in a mixing plant with a duration of the mixing process of 20 ± 5 min and a stirrer speed of 60 rpm.

The synthesis process on a matrix of binder and metal oxide catalyst took place in the reactor shown in FIG. one

The list of items shown in the drawing.

1. upper case;

2. lower case;

3. site of dispensing of the catalyst and binders;

4. heater;

5. a pipe for supplying hydrocarbon gas;

6. pipe outlet of gaseous pyrolysis products;

7. precipitation chamber;

8. gas distribution device;

9. window;

10. desktop;

11. desktop drive;

12. scraper;

13. screw hopper for finished products.

The synthesis reactor comprises an upper housing 1, a lower housing 2, and a catalyst and binder dosing unit 3, a heater 4, a hydrocarbon gas supply pipe 5, a discharge pipe of gaseous pyrolysis products 6 are installed on the upper housing 1, and a precipitation chamber 7 and gas distribution device 8. In the lower case 2, a window 9 is made and a worktable 10 is installed, connected to the drive of the worktable 11, which interacts with the scraper 12. Under the window 9, a screw hopper for finished products 13 is installed.

The synthesis process on a matrix of a binder and metal oxide catalyst was carried out according to the well-known scheme for the production of carbon nanomaterials by gas-phase chemical deposition. The raw materials used were: Belgorod cement M500 D0 or other binders for construction purposes (also cements with and without additives) and a metal oxide catalyst for the synthesis of carbon nanomaterials (NiO / MgO) with a catalyst to cement ratio of 1: 5. Preliminary preparation of the starting materials is carried out in a mixing plant with a duration of the mixing process of 20 ± 5 min and a stirrer speed of 60 rpm.

The reactor synthesis chamber, formed by the upper case 1 and the lower case 2, is flushed with inert gas (argon) through the hydrocarbon gas supply pipe 5 with discharge through the pipe outlet of gaseous pyrolysis products 6, cement or other binders for construction purposes are sprayed in the synthesis chamber together with metal oxide particles synthesis of carbon nanomaterials using a catalyst metering unit and binders 3 and, through a precipitation chamber, are deposited on a working table connected to the rotation drive 11, made in ide drive, then turn on the heaters 4, which are heated until 630-800 ° C, and then produce a continuous supply of hydrocarbon gas (propane-butane mixture) through a pipe for supplying hydrocarbon gas 5 to a gas distribution device 8 with a discharge through the pipe for removing gaseous pyrolysis products 6, which provides the maximum concentration of hydrocarbon gas over the deposited material. At the end of the gas-phase chemical deposition process (the duration of the process is 90 ± 20 min), the product, together with the nanotubes synthesized on the surface of the particles, is cooled, then the rotation drive 11 of the working table 10 is turned on, the finished product is scraper 12 is moved through the window 9 made in the lower part of the synthesis chamber into the screw a hopper 13, the drive of which (not shown) is included simultaneously with the drive rotation of the disk.

Studies to verify the effect of the obtained modifier on the quality and functional properties of the building material were carried out on fine-grained concrete samples according to GOST 26633-91, according to the operation diagram shown in FIG. 2. At the same time, according to the scheme presented in the prototype, a modifier was obtained, which was also tested to verify the effectiveness of the obtained concrete. The tests were carried out on samples of fine-grained concrete. The properties of fine concrete are determined by the same factors as conventional concrete. However, fine-grained cement-sand concrete has some features due to its structure, which is characterized by high uniformity and fine grain, high content of cement stone, the absence of a hard stone skeleton, increased porosity and specific surface area of the solid phase. The following materials were used: cement Belgorod M500 D0, sand, water.

The ratio of the initial components of the mixture for one batch was, g:

Sand 1056 Cement 704 Water 373

Water-cement ratio W / C = 0.53.

The manufacturing process of modified samples was carried out in the following order: sand, cement and the resulting modifier were poured into the mixer tank and mixed in the dry state for 10 minutes without adding water. Then, mixing water was introduced into the resulting mixture, and the mixture was stirred for 7-10 minutes. Further, the obtained fine-grained concrete was evenly distributed in demountable forms (size 4 × 4 × 16 cm) made of corrosion-resistant material, the inner surface of which was previously treated with mineral oil. The resulting samples were removed from the molds after 24 hours. Testing of samples of modified fine-grained concrete was carried out after the final curing of the material at the age of 28 days. The strength of the samples was determined in accordance with GOST 1080-2012, the testing machine - IP-500M-auto. The test results are shown in FIG. 3.

As can be seen from the data presented, the nanomodifying additive can increase the strength of the starting material by at least 20%.

Example 1

The synthesis of carbon nanomaterials (CNM) on a matrix of binder for construction purposes was carried out using the technology of gas-phase chemical deposition of crystalline nanocarbon on metal catalysts. The propane-butane mixture was chosen as the carbon source. The choice of this gas mixture was due to previous experience in using these components in the synthesis of carbon materials of the Taunit series. Cement particles were used in this experiment without the use of additional processing. For this, weighed portions of cement (300 g) and metal oxide catalyst (60 g) in the quantities shown were mixed in a mixing unit, the duration of mechanical stirring lasted for 20 minutes, and the number of revolutions of the mixer was 60 rpm. Then the resulting mixture was applied to the working table of the reactor. The synthesis process on a matrix of binder and metal oxide catalyst was carried out according to the well-known scheme for producing carbon nanomaterials by gas-phase chemical deposition and included the following stages: inert gas purging of the reactor (argon) in order to displace atmospheric air from the reactor cavity, heating the reaction zone of the reactor (650 ± 20 ° С ), the supply of hydrocarbon gas (propane-butane mixture), the pyrolysis process (90 min), cooling, unloading the finished product. The yield of the finished product was 600 g.

Example 2

Checking the influence of factors of temperature and gas treatment of cement particles.

The experiment was carried out similarly to Example 1, but without the use of a catalyst, the technology of synthesis of carbon nanotubes and nanofibers on silica particles was taken as the basis. After synthesis, it should be noted that the obtained substance did not have significant differences from the starting components. The increase in the mass fraction of the substance was insignificant, which allowed us to conclude that the described procedure for producing carbon nanomaterials would not allow obtaining this material in the required quantities. Experimental studies on the effect of this additive on the physicomechanical characteristics of fine-grained concrete did not give positive results; there was no increase in the strength of modified samples.

Example 3

Choosing the best catalyst / binder ratio. The experiment was carried out similarly to Example 1, a distinctive factor was the variation of the catalyst / binder parameters, during which a significant effect of this parameter on the yield of the final product was found. In order to identify the optimal ratio, experimental synthesis was carried out, the range of catalyst / binder ratios was chosen as follows: from 0.5 to 0.1. After this experiment, the optimal catalyst / binder ratio was found to be 0.2. With this ratio of components, the maximum yield of the product was reached, which amounted to 25% relative to the initial mass of the substance.

The test results are shown in FIG. 3 and in table 1.

The invention provides a reduction in cement consumption by increasing the activity of the additive while maintaining the strength characteristics of concrete. At the same time, technology is simplified and energy costs are reduced.

Claims (2)

 1. A method of producing a nano-modified additive for construction purposes, characterized in that the cement is sprayed in the synthesis chamber together with particles of a metal oxide catalyst for the synthesis of carbon nanomaterials (NiO / MgO) and, through a pre-blown inert gas, the precipitating chamber is deposited on a worktable-disk connected to a rotation drive then turn on heating to a temperature of 630-670 ° C and produce a continuous supply of a propane-butane mixture (hydrocarbon gas) and removal of gaseous pyrolysis products, and at the end of the process chemical deposition process, the finished product - cement with carbon nanotubes synthesized on the surface is cooled, after which the disk rotation drive is turned on, the finished product is scrapped through the window made in the lower part of the synthesis chamber into the screw hopper, the drive of which is switched on simultaneously with the disk rotation drive. 2. The method according to p. 1, characterized in that the composition of the feedstock uses: Belgorod cement M500 D0 or other cements, including cements with additives, and a metal oxide catalyst for the synthesis of carbon nanomaterials (NiO / MgO) with a catalyst to cement ratio of 1: 5.

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