CN109704662B - Nano silicon nitride reinforced cement-based material and preparation method thereof - Google Patents
Nano silicon nitride reinforced cement-based material and preparation method thereof Download PDFInfo
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Abstract
The invention provides a nano silicon nitride reinforced cement-based material and a preparation method thereof, which mainly comprises the following three steps: firstly, heat treatment of the nano silicon nitride material is carried out, and the nano silicon nitride material is subjected to heat treatment; then adding the heat-treated nano silicon nitride material into a high-efficiency dispersant to prepare a nano silicon nitride suspension; and finally, adding the nano silicon nitride suspension into a cement paste stirrer for stirring in a certain mode to prepare the nano reinforced silicon nitride cement-based material. The nano reinforced silicon nitride cement-based material prepared by the invention has simple preparation process and easy operation, and after the nano silicon nitride is added, the microstructure of cement paste is improved, the porosity is reduced, the defects of pores, cracks and the like in the cement paste are reduced, the compactness of the microstructure is improved, the mechanical property of the cement paste is greatly improved, the 28d compressive strength is improved by 24.6 percent when the nano silicon nitride is doped in 0.16 percent, and the 28 day flexural strength is improved by 19.8 percent.
Description
Technical Field
The invention belongs to the technical field of cement-based materials, and particularly relates to a nano silicon nitride reinforced cement-based material and a preparation method thereof.
Background
The cement-based material has unique characteristics such as good cementing property, high strength, good durability and the like, so that cement is one of the most widely applied building materials in the building material industry. But has significant disadvantages due to the physical properties of the cement itself. Because of the shrinkage of the cement in the curing process, the cement has a large number of defects such as pores, cracks and the like, has great weight and is easy to crack, and the durability of the cement is greatly reduced.
In view of the physical characteristics of cement and the defects in the application thereof, in order to enable the cement to have better performance and improve the strength and the durability when being applied to the building industry, the utilization of the nano material for modifying the cement becomes a hot point of research of current researchers, so that the physical filling effect of the nano material is expected to improve the microstructure of the cement, further improve the mechanical property of the cement-based material and improve the durability, at present, a simple and easy-to-operate method does not exist, and the mechanical property of the cement-based material can be effectively improved after the nano material is added.
Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.
Disclosure of Invention
The invention aims to provide a nano silicon nitride reinforced cement-based material and a preparation method thereof.
In order to achieve the above purpose, the invention provides the following technical scheme:
a preparation method of a nano silicon nitride reinforced cement-based material comprises the following steps:
s1 heat treatment of nano silicon nitride
Placing the nano silicon nitride into a heat-resistant container, placing the heat-resistant container into an oven for heating treatment to enable impurities on the surface of the nano silicon nitride to overflow, and taking out the nano silicon nitride after the heat treatment;
s2 dispersing treatment of nano silicon nitride
Adding water into the container, then putting the nano silicon nitride after heat treatment into the container, adding a dispersing agent into the container, and forming a suspension of the nano silicon nitride after the addition is finished; mechanically stirring the nano silicon nitride suspension, and performing ultrasonic dispersion after the mechanical stirring is finished;
s3 preparation of cement-based material
And (4) adding the nano silicon nitride suspension subjected to the ultrasonic dispersion treatment in the step (S2) into a stirrer, then adding water and cement into the stirrer to obtain a cement-based material mixed solution, and stirring the cement-based material mixed solution to obtain the nano silicon nitride reinforced cement-based material.
In the preparation method of the nano silicon nitride reinforced cement-based material, preferably, the heating temperature of the nano silicon nitride heating treatment in the step S1 is 325 to 375 ℃, and the heating time is 30 to 120 min.
In the above method for preparing a nano silicon nitride reinforced cement-based material, preferably, the dispersant in step S2 is a polycarboxylic acid water reducer;
preferably, the addition amount of the dispersing agent accounts for 0.01-0.5% of the mass of the cement.
In the method for preparing the nano silicon nitride reinforced cement-based material, preferably, the addition amount of the nano silicon nitride suspension in the step S3 is not more than 2% of the nano silicon nitride reinforced cement-based material;
preferably, the adding amount of the nano silicon nitride suspension in the step S3 is 0.01-0.2% of the nano silicon nitride reinforced cement-based material.
In the preparation method of the nano silicon nitride reinforced cement-based material, preferably, the nano silicon nitride suspension is mechanically stirred for 2min to 7min in step S2, and the ultrasonic dispersion time is not less than 30 min.
In the preparation method of the nano silicon nitride reinforced cement-based material, preferably, the rotation speed of the mechanical stirring of the nano silicon nitride suspension is 500r/min to 1000 r/min.
In the method for preparing a nano silicon nitride reinforced cement-based material, the water cement ratio of the water and the cement added into the mixer in the step S3 is preferably 0.28 to 0.40.
In the preparation method of the nano silicon nitride reinforced cement-based material, preferably, the cement-based material mixed solution is stirred in the step S3 in a manner of first slowly stirring for 120S at a rotation speed of 135r/min to 145r/min, then stopping stirring for 15S, then rapidly stirring for 120S at a rotation speed of 275r/min to 295r/min, and then stopping stirring.
In the method for preparing the nano silicon nitride reinforced cement-based material as described above, preferably, the average particle size of the nano silicon nitride in step S1 is 10nm to 30 nm.
A nano silicon nitride reinforced cement-based material prepared by the preparation method of the nano silicon nitride reinforced cement-based material.
Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:
the nano silicon nitride reinforced cement-based material provided by the invention is prepared by treating nano silicon nitride, then adding the treated nano silicon nitride into cement slurry according to a certain proportion, and adding additives and other materials, so that the physical and mechanical properties and durability of the cement-based material are improved; the nano silicon nitride reinforced cement-based material reduces the porosity, so that the microstructure is more compact, and the mechanical property of cement paste is improved; when the nano silicon nitride is doped by 0.16 percent, the 28d compressive strength is improved by 24.6 percent, and the 28-day flexural strength is improved by 19.8 percent.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:
FIG. 1 is a graph showing a comparison of compressive strengths at various ages of example 1 of the present invention and comparative example 1;
FIG. 2 is a graph showing a comparison of the compressive strengths at various ages of example 1 and comparative example 2 according to the present invention;
FIG. 3 is a graph showing a comparison of the compressive strengths at various ages of example 1 and comparative example 3 according to the present invention;
FIG. 4 is a graph showing a comparison of flexural strengths at various ages of example 1 and comparative example 1 according to the present invention;
FIG. 5 is a graph showing a comparison of flexural strengths at various ages of example 1 and comparative example 2 according to the present invention;
FIG. 6 is a graph showing the comparison of flexural strength between examples 1 and comparative example 3 according to the present invention at each age.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The preparation method of the nano silicon nitride reinforced cement-based material mainly comprises the following three steps: firstly, heat treatment of a nano silicon nitride material is carried out, and the nano silicon nitride material is subjected to heat treatment at a certain temperature for a certain time; then adding the heat-treated nano silicon nitride material into a high-efficiency dispersant to prepare a nano silicon nitride suspension; and finally, adding the nano silicon nitride suspension into a cement paste stirrer for stirring in a certain mode to prepare the nano reinforced silicon nitride cement-based material. The nano reinforced silicon nitride cement-based material prepared by the invention has simple preparation process and easy operation, and after the nano silicon nitride is added, the microstructure of cement paste is improved, the porosity is reduced, the defects of pores, cracks and the like in the cement paste are reduced, the compactness of the microstructure is improved, the mechanical property of the cement paste is greatly improved, the 28d compressive strength is improved by 24.6 percent when the nano silicon nitride is doped in 0.16 percent, and the 28 day flexural strength is improved by 19.8 percent.
Compared with the similar nano material, the nano silicon nitride has the following advantages: firstly, the nano silicon nitride has stable performance, mainly plays a physical filling role in the cement-based material and improves the density of the cement-based material; secondly, the nano silicon nitride has high hardness, is mostly used in products such as ceramics and the like, and can improve the strength and hardness of the cement-based material when added into the cement-based material; finally, the nanometer silicon nitride has high strength, so that the chloride ion permeation resistance of the cement-based material can be improved when the nanometer silicon nitride is added into the cement-based material.
The invention provides a preparation method of a nano silicon nitride reinforced cement-based material, which comprises the following steps:
s1 heat treatment of nano silicon nitride
Placing the nano silicon nitride into a heat-resistant container, placing the heat-resistant container into an oven for heating treatment to enable impurities on the surface of the nano silicon nitride to overflow, and taking out the nano silicon nitride after the heat treatment;
preferably, the heating temperature of the heating treatment of the nano silicon nitride in the step S1 is 325 to 375 ℃ (such as 330 ℃, 335 ℃, 340 ℃, 345 ℃, 350 ℃, 355 ℃, 360 ℃, 365 ℃, 370 ℃, 375 ℃) and the heating time is 30 to 120min (such as 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110 min).
S2 dispersing treatment of nano silicon nitride
Adding water into a container, then putting the nano silicon nitride after heat treatment into the container, adding a dispersing agent into the container, forming a suspension of the nano silicon nitride after the addition is finished, mechanically stirring the suspension of the nano silicon nitride, and performing ultrasonic dispersion after the stirring is finished.
Preferably, the rotation speed of the mechanical stirring of the nano silicon nitride suspension is 500r/min to 1000r/min (such as 550r/min, 600r/min and 650 r/min).
Preferably, the dispersing agent in the step S2 is a polycarboxylic acid water reducing agent; preferably, the dispersant is added in an amount of 0.01% to 0.5% (e.g., 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%) by mass of the cement.
Preferably, the nano silicon nitride suspension is mechanically stirred in step S2 for 2min to 7min (e.g., 3min, 4min, 5min, 6min), and the ultrasonic dispersion time is not less than 30 min.
Preferably, the average particle size of the nano silicon nitride is 10 nm-30 nm (such as 12nm, 14nm, 16nm, 18nm, 20nm, 22nm, 24nm, 26nm, 28nm and 30nm), the particle size is small, the nano silicon nitride is uniformly distributed after dispersion treatment, the specific surface area is large, the surface activity is high, the reinforcing effect of the cement-based material can be greatly improved when the nano silicon nitride is distributed in the cement-based material, the addition of the nano silicon nitride enables the microstructure of the cement paste to be more compact, the porosity to be reduced, and the defects of pores, cracks and the like in the cement paste to be reduced, so that the strength of the cement-based material is improved.
S3 preparation of cement-based material
And (4) adding the nano silicon nitride suspension subjected to the dispersion treatment in the step (S2) into a stirrer, then adding water and cement into the stirrer to obtain a cement-based material mixed solution, and stirring the cement-based material mixed solution to obtain the nano silicon nitride reinforced cement-based material.
Preferably, the adding amount of the nano silicon nitride suspension in the step S3 is not more than 2% of the nano silicon nitride reinforced cement-based material; preferably, the nano silicon nitride suspension added in step S3 accounts for 0.01% -0.2% (e.g. 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%) of the nano silicon nitride reinforced cement-based material; still preferably, the nano silicon nitride suspension added in step S3 accounts for 0.16% of the nano silicon nitride reinforced cement-based material.
Preferably, the water-cement ratio of the water and the cement added to the mixer in the step S3 is 0.28-0.40 (such as 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39).
Preferably, the cement-based material mixed liquid is stirred in step S3 at a slow speed of 135 r/min-145 r/min (e.g., 136r/min, 137r/min, 138r/min, 139r/min, 140r/min, 141r/min, 142r/min, 143r/min, 144r/min) for 120S, and then stirred for 15S, and at a fast speed of 275 r/min-295 r/min (e.g., 276r/min, 277r/min, 278r/min, 279r/min, 280r/min, 281r/min, 282r/min, 283r/min, 284r/min, 285r/min, 286r/min, 287r/min, 288r/min, 289r/min, 290r/min, 291r/min, 292r/min, 293r/min, 294r/min) and then stopped.
Example 1
The invention provides a preparation method of a nano silicon nitride reinforced cement-based material, which comprises the following steps of: the method comprises the steps of placing a nano silicon nitride material into a corundum crucible, wherein the mass of the nano silicon nitride is 5g, the average particle size is 20nm, placing the nano silicon carbide into an oven, and carrying out heating treatment at 350 ℃ for 30min, wherein the surface of the nano silicon nitride material contains ammonium chloride in the processing and manufacturing process, and the ammonium chloride on the surface of the nano silicon nitride can overflow through the heating treatment.
The invention provides a preparation method of a nano silicon nitride reinforced cement-based material, which comprises the following steps on the basis of the above steps:
the first step is as follows: dispersion treatment of nano silicon nitride
Weighing 72g of water, adding 0.384g of nano silicon nitride after heat treatment, and then adding 0.096g of polycarboxylic acid water reducing agent, wherein the water reducing agent accounts for 0.04% of the cement by mass; pouring the mixture into a beaker in sequence, and then mechanically stirring the mixture for 2min at the rotating speed of 1000 r/min; and then ultrasonic dispersion is carried out for 30min under the condition of 250w of power to obtain the nano silicon nitride suspension.
The second step is that: preparation of nano silicon nitride cement base material slurry
When the nano silicon nitride cement-based material is prepared, the water-cement adding ratio is controlled to be 0.3, 72.480g of nano silicon nitride suspension and 240g of reference cement are sequentially added into a cement paste mixer, then the mixed solution is mixed at a slow speed of 120s at a rotating speed of 140r/min for 15s, then the mixed solution is quickly mixed at a rotating speed of 285r/min for 120s, and then the mixer is stopped to obtain nano silicon nitride cement-based material slurry.
In the embodiment, the doping amount of the nano silicon nitride accounts for 0.16 percent of the cement-based material.
The third step: preparation of nano silicon nitride cement-based material test piece
And (3) forming the prepared nano silicon nitride cement-based slurry in a 20mm multiplied by 20mm mould, vibrating on a vibrating table for 1min, sticking a preservative film after the nano silicon nitride cement-based slurry is condensed, placing the nano silicon nitride cement-based slurry in a constant temperature chamber, removing the mould after 24h, and placing the nano silicon nitride cement-based slurry in a 20 ℃ and 95% RH wet curing chamber for curing to obtain the nano silicon nitride cement-based slurry.
Then, the compressive strengths of the nano silicon nitride cement-based slurry in the embodiment at 1d, 3d, 7d and 28d were respectively tested, and the microstructures of the nano silicon nitride cement-based slurry at corresponding days were respectively tested by using a scanning electron microscope.
The strength test results are: the 1d compressive strength is 33.640 Mpa; the 3d compressive strength is 54.923 MPa; the 7d compressive strength is 65.256 MPa; the 28-day compressive strength is 101.172 MPa.
Microstructure analysis results: microstructure analysis of the nano silicon nitride cement-based slurry under 1d, 3d, 7d and 28d in the example shows that the structure is compact, no obvious bubbles are contained, and no obvious cracks are generated.
Example 2
In the embodiment, the heating temperature of the first step is replaced by 325 ℃ for heating treatment of the nano silicon nitride, the heating time is 50min, the average particle size of the nano silicon nitride is 30nm, 0.048g of the heat-treated nano silicon nitride is added, the addition amount of the water reducing agent is 0.24g, and the water reducing agent accounts for 0.1% of the cement by mass; 72.288g of nano silicon nitride suspension and 240g of reference cement are added in the second step, the doping amount of the nano silicon nitride in the cement-based material is 0.02% in the embodiment, and other method steps are the same as those in embodiment 1 and are not repeated herein.
The nano silicon nitride material prepared in this example was prepared in the same manner as in example 1, and then the compressive strengths of 1d, 3d, 7d and 28d were measured, and the microstructures of the nano silicon nitride cement-based slurry on the corresponding days were measured by using a scanning electron microscope.
The strength test results are as follows: the 1d compressive strength is 36.607 Mpa; the 3d compressive strength is 67.121 MPa; the 7d compressive strength is 69.280 MPa; the 28-day compressive strength was 86.229 MPa.
Microstructure analysis results: microstructure analysis is carried out on the nano silicon nitride cement-based slurry under 1d, 3d, 7d and 28d in the embodiment, and the slurry is found to be in a compact structure and has low pore content.
Example 3
In this embodiment, the first step is replaced by: adding 0.192g of heat-treated nano silicon nitride, wherein the adding amount of a water reducing agent is 0.24g, the mass ratio of the water reducing agent to the cement is 0.1%, the rotating speed of the nano silicon nitride for mechanical stirring is 1000r/min, the stirring time is 3min, and then the time for ultrasonic dispersion is 40 min; step two is replaced by: 72.432g of nano silicon nitride suspension and 240g of reference cement, wherein the doping amount of the nano silicon nitride accounts for 0.08 percent of the cement, and other method steps are the same as those in example 1 and are not repeated.
The nano silicon nitride material prepared in this example was prepared in the same manner as in example 1, and then the compressive strengths of 1d, 3d, 7d and 28d were measured, and the microstructures of the nano silicon nitride cement-based slurry on the corresponding days were measured by using a scanning electron microscope.
The strength test results are as follows: the 1d compressive strength is 37.109 Mpa; the 3d compressive strength is 58.734 MPa; the 7d compressive strength is 65.502 MPa; the 28-day compressive strength was 86.645 MPa.
Microstructure analysis results: microstructure analysis is performed on the nano silicon nitride cement-based slurry under 1d, 3d, 7d and 28d in the embodiment, and the results show that the structure is compact and the content of bubbles is low.
Example 4
In this embodiment, the first step is replaced by adding 0.48g of heat-treated nano silicon nitride, the adding amount of the water reducing agent is 0.48g, the mass ratio of the water reducing agent to the cement is 0.2%, and the mass ratio of the water reducing agent to the cement is 240g, in this embodiment, the doping amount of the nano silicon nitride to the cement-based material is 0.2%, and other method steps are the same as those in embodiment 1, and are not repeated herein.
The material prepared in this example was prepared into test pieces in the same manner as in example 1, and then the compressive strength of 1d, 3d, 7d and 28d was measured, and the microstructure of the nano silicon nitride cement-based slurry was measured by a scanning electron microscope on the corresponding days.
The strength test results are as follows: the 1d compressive strength is 46.291 Mpa; the 3d compressive strength is 67.925 MPa; the 7d compressive strength is 83.634 MPa; the 28-day compressive strength was 85.140 MPa.
Microstructure analysis results: microstructure analysis is performed on the nano silicon nitride cement-based slurry under 1d, 3d, 7d and 28d in the embodiment, and the results show that the structure is compact and the content of bubbles is low.
Comparative example 1
The difference between comparative example 1 and example 1 is that the nano silicon nitride in the first step and the second step is omitted, that is, the nano silicon nitride material is not doped in the cement-based material in the comparative example, 72g of water, 0.096g of water reducing agent and 240g of reference cement are weighed, and the other method steps are the same as those in example 1 and are not repeated herein.
The cement-based material prepared in the comparative example was prepared in the same manner as in example 1, and then the compressive strengths of 1d, 3d, 7d and 28d were measured, respectively, and the microstructures of the nano silicon nitride cement-based slurry on the corresponding days were measured by using a scanning electron microscope, respectively.
The strength test results are as follows: the 1d compressive strength is 33.251 MPa; the 3d compressive strength is 53.047 MPa; the 7d compressive strength is 64.807 MPa; the 28d compressive strength is 81.182 MPa.
Microstructure analysis results: the inside of the test block has micro-cracks and air holes, and the tissue density is not high.
Comparative example 2
The difference between the comparative example 2 and the example 1 is that the heating temperature of the heat treatment of the nano silicon nitride is 200 ℃, the heating time is 30min, and the other method steps are the same as the example 1 and are not repeated herein.
The cement-based material prepared in the comparative example was prepared in the same manner as in example 1, and then the compressive strengths of 1d, 3d, 7d and 28d were measured, respectively, and the microstructures of the nano silicon nitride cement-based slurry on the corresponding days were measured by using a scanning electron microscope, respectively.
The strength test results are as follows: the 1d compressive strength is 34.927 MPa; the 3d compressive strength is 56.607 MPa; the 7d compressive strength is 65.393 MPa; the 28d compressive strength is 72.021 MPa.
Microstructure analysis results: the test block in this comparative example had significant air bubbles on the surface, and a small amount of small air bubbles were also contained in the middle of the broken test block.
Comparative example 3
Comparative example 3 differs from example 1 in that the nano silicon nitride was not subjected to the heat treatment, 0.120g of the nano silicon nitride was added without the heat treatment, and the second step was replaced with: 72.600g of nano silicon nitride suspension and 240g of reference cement, and the other steps of the method are the same as those of the embodiment 1, which are not described herein again, and the doping amount of the nano silicon nitride accounts for 0.04% of the cement-based material.
The nano silicon nitride material prepared in this example was prepared in the same manner as in example 1, and then the compressive strengths of 1d, 3d, 7d and 28d were measured, and the microstructures of the nano silicon nitride cement-based slurry on the corresponding days were measured by using a scanning electron microscope.
The strength test results are as follows: the 1d compressive strength is 36.758 Mpa; the 3d compressive strength is 56.706 MPa; the 7d compressive strength is 72.788 MPa; the 28-day compressive strength was 77.599 MPa.
Microstructure analysis results: the test block in this comparative example had a large amount of bubbles and had significant cracks.
The nano silicon nitride cement-based slurries prepared in the above examples and comparative examples were subjected to a flexural strength test of 28d, and the compressive strength and flexural strength in comparative examples 1, 2, and 3 were compared with those in example 1, and the results of the data obtained are shown in table 1 below.
TABLE 1 compression and flexural strengths of cement-based slurries in various examples and comparative examples
As can be seen from the table, in example 1, compared with comparative example 1, the compressive strength of the cement-based slurry prepared by adding the nano silicon nitride is improved by 24.60% in 28 days, and the flexural strength of the cement-based slurry prepared by adding the nano silicon nitride is improved by 19.8% in 28 days; the compressive strength and flexural strength in example 2 and example 3 were also superior to those in comparative example 1, indicating that the addition of nano-silicon nitride significantly enhanced the compressive strength and flexural strength of the cement-based material.
Comparing with the example 2, the heating temperature of the heat treatment of the added nano silicon nitride in the comparative example 2 is 200 ℃, and the compression strength and the flexural strength are also lower than those of the corresponding examples 1-4, which shows that the heat treatment temperature of the nano silicon nitride has a great influence on the performance of the cement-based slurry.
Compared with the addition of the nano silicon nitride after the heat treatment, the strength of the nano silicon nitride without the heat treatment in the comparative example 3 is obviously reduced, which shows that the strength of the cement-based material slurry can be greatly reduced by adding the nano silicon nitride without the heat treatment.
The cement-based slurry test block prepared in the comparative examples 2-3 has bubbles on the surface, and the cement-based slurry prepared from the nano silicon nitride which is not subjected to heat treatment in the comparative example 3 has obvious cracks, and the nano silicon nitride can reduce the content of the bubbles after heat treatment at a proper temperature because the surface of the nano silicon nitride contains impurity components, and after XRD analysis, the surface of the nano silicon nitride contains ammonium chloride, and after heat treatment, the ammonium chloride can be removed, so that the content of the bubbles in the slurry test block is greatly reduced, defects such as pores and cracks caused by the bubbles are eliminated, and the compactness of a microstructure is increased, thereby improving the compressive strength and the breaking strength of the material.
In summary, the following steps: according to the nano silicon nitride reinforced cement-based material, nano silicon nitride is added in the preparation process of cement-based slurry, the nano silicon nitride is subjected to heat treatment and dispersion treatment, then the nano silicon nitride is added into the cement slurry according to a certain proportion, and materials such as additives and the like are added, so that the physical and mechanical properties (compressive strength and flexural strength) and durability of the cement-based material are improved; the nano silicon nitride reinforced cement-based material has a compact microstructure, and reduces the porosity, so that the mechanical property of cement paste is greatly enhanced; when the nano silicon nitride is doped by 0.16 percent, the 28d compressive strength is improved by 24.6 percent, the 28-day flexural strength is improved by 19.8 percent, and the cement-based material slurry has compact structure and no defects such as internal cracks.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A preparation method of a nano silicon nitride reinforced cement-based material is characterized by comprising the following steps:
s1 heat treatment of nano silicon nitride
Placing the nano silicon nitride into a heat-resistant container, placing the heat-resistant container into an oven for heating treatment, wherein the heating temperature is 325-375 ℃, the heating time is 30-120 min, so that impurities on the surface of the nano silicon nitride overflow, and taking out the nano silicon nitride after the heat treatment;
s2 dispersing treatment of nano silicon nitride
Adding water into the container, then putting the nano silicon nitride after heat treatment into the container, adding a dispersing agent into the container, and forming a suspension of the nano silicon nitride after the addition is finished; mechanically stirring the nano silicon nitride suspension, and performing ultrasonic dispersion after the mechanical stirring is finished;
the dispersant is a polycarboxylic acid water reducer, and the addition amount of the dispersant accounts for 0.01-0.5% of the mass of the cement;
s3 preparation of cement-based material
Adding the nano silicon nitride suspension subjected to the ultrasonic dispersion treatment in the step S2 into a stirrer, then adding water and cement into the stirrer to obtain a cement-based material mixed solution, and stirring the cement-based material mixed solution to obtain a nano silicon nitride reinforced cement-based material;
the addition amount of the nano silicon nitride suspension accounts for 0.01-0.2% of that of the nano silicon nitride reinforced cement-based material.
2. The method for preparing nano silicon nitride reinforced cement-based material according to claim 1, wherein the nano silicon nitride suspension is mechanically stirred for 2min to 7min and the ultrasonic dispersion time is not less than 30min in step S2.
3. The method of claim 2, wherein the nano silicon nitride reinforced cement-based material is mechanically agitated at a speed of 500r/min to 1000 r/min.
4. The method of claim 1, wherein the water-cement ratio of water to cement added to the mixer in step S3 is 0.28 to 0.40.
5. The method of claim 1, wherein the step S3 is performed by stirring the mixture of the cement-based materials at a slow speed of 135 r/min-145 r/min for 120S, stopping stirring for 15S, then stirring at a fast speed of 275 r/min-295 r/min for 120S, and then stopping stirring.
6. The method of claim 1, wherein the average particle size of the nano silicon nitride particles in step S1 is 10nm to 30 nm.
7. A nano silicon nitride reinforced cement-based material prepared by the method of preparing a nano silicon nitride reinforced cement-based material according to any one of claims 1 to 6.
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