Composite concrete containing nano silicon dioxide modified rubber powder and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to composite concrete containing nano silicon dioxide modified rubber powder and a preparation method, the composite concrete comprises the following raw material components by weight: 400-500 parts of 52.5 grade cement, 60-80 parts of fly ash, 600-700 parts of slag, 30-40 parts of silicon powder, 900-1000 parts of pebbles with a particle size of 5-25 mm, 200-300 parts of water, and 0.5-1.0 part of a water reducer. 2 to 20 parts of nano silicon dioxide modified rubber powder and 0.08 to 0.12 part of basalt fiber. The compatibility and interfacial strength between the rubber powder and a concrete matrix are greatly improved, the problem that existing rubber concrete is insufficient in freeze-thaw resistance is solved, meanwhile, the microstructure and compactness of the composite concrete are improved through the unique nano effect, and therefore the freeze-thaw cycle resistance of the composite concrete is remarkably improved, and the service life of the composite concrete is prolonged. The application scene of the rubber concrete is obviously widened, and the rubber concrete has more advantages especially in cold regions or constructional engineering needing to bear extreme weather conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to composite concrete containing nano-silica modified rubber powder and a preparation method thereof. Background Technique

[0002] Building materials are the general term for materials and products used in construction projects, structures, and buildings, and are the cornerstone of the construction industry; materials used in the construction of the main structure of construction projects, such as steel, cement, concrete, sand and gravel, etc. Among them, concrete is mixed by cement, sand, gravel and water in a certain proportion, and has high strength and durability, and is widely used in building structures such as foundations, beams, slabs, and columns. It has been found through research that adding rubber to concrete can effectively improve the toughness and impact resistance of concrete. However, due to the hydrophobic characteristics of the rubber surface, its compatibility is poor when mixed with cement-based materials, resulting in a decline in the mechanical properties of rubber concrete, especially in terms of strength and durability, which greatly limits the application of rubber in concrete.

[0003] In order to improve the compatibility between rubber and concrete, surface modification technology has been adopted at present, that is, active groups are introduced on the surface of rubber particles to enhance their bonding force with cement-based materials. For example, in the patent application CN111607054A - Amino-modified tire rubber powder / polyurethane composite material and its preparation method and application, swelling agent, concentrated sulfuric acid and amino-silane coupling agent are used to modify the waste tire rubber powder on the surface. Although it can improve the activity of rubber powder to a certain extent, the modification process is relatively complex, and the energy consumption and cost are relatively high, and it is difficult to meet the requirements of concrete for material strength, durability and environmental protection.

[0004] In the prior art, there are studies on the improvement of concrete strength by modified rubber powder. For example, in the patent application CN119118613A - A high-performance rubber concrete material and its preparation method, tetraethyl orthosilicate and methyltriethoxysilane are first used to modify rubber powder and rubber particles, and then calcium fluorosilicate, alumina, magnesium oxide and other raw materials are used to prepare a reinforcing agent, which solves the problem that the existing modified rubber powder is difficult to meet the requirements of concrete for material strength. However, the existing rubber concrete can only ensure the compressive, tensile and flexural strengths, but it is difficult to effectively ensure the freeze-thaw resistance, which limits the application scenarios and requirements to a certain extent. Therefore, a new technical solution is needed to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite concrete containing nano-silica modified rubber powder and a preparation method thereof, so as to solve the problems proposed in the above background technique that it is difficult to effectively ensure the freeze-thaw resistance of rubber concrete at the present stage, which limits the application scenarios and requirements to a certain extent.

[0006] To achieve the above object, the present invention provides the following technical solution: a composite concrete containing nano-silica modified rubber powder, and the raw material components of the composite concrete include, by weight: 400 - 500 parts of 52.5 grade cement, 60 - 80 parts of fly ash, 600 - 700 parts of slag, 30 - 40 parts of silica fume, 900 - 1000 parts of gravel with a particle size of 5 - 25 mm, 200 - 300 parts of water, 0.5 - 1.0 part of water reducing agent, 2 - 20 parts of nano-silica modified rubber powder, and 0.08 - 0.12 part of basalt fiber; wherein, the nano-silica modified rubber powder is prepared by grafting with a silane coupling agent and undergoing a condensation reaction with a silicate compound after activation and dispersion treatment of waste rubber powder as raw material, the water reducing agent is one of naphthalene series, amino sulfonic acid series, aliphatic, polycarboxylic acid series, and the diameter and length of the basalt fiber are 12 - 16 μm and 2 - 4 mm respectively.

[0007] Further, the specific preparation steps of the nano-silica modified rubber powder are as follows: S1. Place the waste rubber powder in a low-temperature plasma generator with an air atmosphere, carry out activation for 300 - 600 s at an air flow rate of 0.5 - 1.5 L / min and an activation power of 3 - 5 kW, then place it in an aqueous solution, and obtain an aqueous dispersion of activated rubber powder through ultrasonic dispersion for 1 - 2 h, wherein the particle size of the waste rubber powder is 80 - 200 mesh; S2. Add the silane coupling agent to the aqueous dispersion of the activated rubber powder obtained in S1, stir and react at 80 - 120 °C for 3 - 4 h to initiate the in-situ growth of subsequent nano-silica, carry out suction filtration and washing, and then redisperse it in an aqueous solution to obtain an aqueous dispersion of the coupling agent-modified rubber powder, wherein the mass ratio of the rubber powder to the silane coupling agent is 1:0.1 - 1:0.2, and the silane coupling agent is a silane coupling agent containing an epoxy group; S3. Add the ethanol solution of the silicate compound to the aqueous dispersion of the coupling agent-modified rubber powder obtained in S2, stir and react at 60 - 80 °C for 4 - 6 h, and obtain the nano-silica modified rubber powder after suction filtration, washing and drying, wherein the mass ratio of the rubber powder to the silicate compound is 1:0.5 - 1:1, and the silicate compound is one of methyl orthosilicate, ethyl orthosilicate, bis(trimethoxysilyl)ethane.

[0008] According to the above settings, the method for preparing the composite concrete containing nano-silica modified rubber powder is as follows: First, add specified amounts of gravel with a particle size of 5 - 25 mm, silica fume, slag, fly ash, nano-silica modified rubber powder, basalt fiber, and 52.5 grade cement into a mixer in sequence. After mixing evenly, obtain the first mixture. Then, add specified amounts of water and water reducer into the first mixture. After mixing evenly, obtain the second mixture. Finally, pour the second mixture into a test mold, place it on a vibrating table, and continuously vibrate and ram until the surface oozes slurry. After standing at room temperature for 48 h, obtain the composite concrete.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Through the design of introducing nano-silica modified rubber powder into the raw material components of the composite concrete, the present invention greatly improves the compatibility and interfacial strength between the rubber powder and the concrete matrix, effectively solves the problem of insufficient freeze-thaw resistance of the existing rubber concrete. After the composite concrete undergoes 300 freeze-thaw cycles, the mass loss rate is only 3%, and the dynamic elastic modulus retention rate can be as high as 60%, far superior to the performance of the existing rubber concrete. At the same time, through its unique nano-effect, the microstructure and compactness of the composite concrete are improved, thus significantly enhancing the freeze-thaw cycle resistance of the composite concrete, significantly broadening the application scenarios of rubber concrete, especially more advantageous in construction projects in cold regions or those that need to withstand extreme climate conditions. By adding basalt fiber, the toughness and crack resistance of the composite concrete are further enhanced, enabling the composite concrete to better maintain structural integrity when subjected to external forces, improving the safety and durability of buildings. 2. The present invention uses waste rubber powder as the raw material for preparing nano-silica modified rubber powder, realizing the recycling of waste resources, reducing environmental pollution, and conforming to the development concept of green, low-carbon, and sustainable. The nano-silica modified rubber powder is prepared through air plasma activation, silane coupling agent grafting, and silicate compound condensation reaction. Compared with traditional surface modification technologies, this preparation process is more concise and efficient, realizing the in-situ growth of nano-silica on the surface of rubber powder, avoiding complex chemical reaction steps and the use of high-energy-consuming equipment, reducing production costs, and improving the feasibility of industrial application. Utilizing the nucleation effect and filling effect of nano-silica, it not only promotes the hydration reaction of cement but also effectively fills and repairs the pores and cracks inside the composite concrete, thus significantly improving the overall performance and durability of the composite concrete after hardening. The compressive strength of the composite concrete can reach 84.2 MPa after 28 days, showing a significant improvement compared with unmodified rubber concrete, thus meeting the requirements of construction projects with higher strength requirements. 3. The present invention activates waste rubber powder through air plasma, making the surface of the waste rubber powder contain polar groups such as hydroxyl groups, carboxyl groups, and epoxy groups. Then, the silane coupling agent reacts with the active groups on the surface of the activated waste rubber powder to graft the silane coupling agent on the surface of the activated waste rubber powder. By using the condensation reaction of the silane coupling agent and the silicate precursor, the effect of in-situ polycondensation of the silicate compound on the surface of the rubber powder is improved, the grafting rate of nano-silica on the surface of the rubber powder is increased, the disordered precipitation of nano-silica is reduced, and the nano-silica grown in-situ on the surface of the nano-silica modified rubber powder is more uniformly distributed. The water-cement ratio at the rubber particle-mortar interface is reduced, thereby improving the interface strength, effectively avoiding the agglomeration phenomenon of nano-particles, and thus improving the overall performance of the composite material; 4. By precisely controlling the addition sequence and mixing process of raw materials, the present invention not only effectively avoids the agglomeration phenomenon and improves the uniformity of the materials, but also effectively avoids the decline of the performance of the composite concrete caused by premature or late reactions, ensures the smooth progress of the cement hydration reaction, and at the same time helps to improve the workability of the composite concrete, making the composite concrete easier to operate during pouring and vibration, reducing the formation of bubbles and pores. Adding raw materials in sequence can also enhance the interaction between different materials. For example, the nano-silica particles on the surface of the nano-silica modified rubber powder can chemically react with the cement hydration products to form chemical bonding, thereby improving the bonding strength between the rubber powder and the concrete matrix, ensuring the stable quality of the composite concrete prepared each time. By precisely controlling the addition sequence and mixing time of raw materials, the composite concrete prepared each time can have similar physical and chemical properties, meet the requirements of engineering applications, and provide a reliable technical guarantee for the large-scale production of the composite concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the preparation process of the composite concrete containing nano-silica modified rubber powder of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following examples are used to further illustrate the content of the present invention and do not limit the application of the present invention (the following parts are all parts by weight). Example 1:

[0012] This example provides a composite concrete containing nano-silica modified rubber powder. Nano-silica modified rubber powder is introduced into the raw material components of the composite concrete. In the preparation process of the nano-silica modified rubber powder, the coupling agent-modified rubber powder reacts through the epoxy group in the silane coupling agent and the surface active groups such as hydroxyl groups and carboxyl groups of the activated rubber powder. Therefore, the silane coupling agent includes but is not limited to γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and other silane coupling agents containing epoxy groups are also applicable.

[0013] The specific preparation process of nano-silica modified rubber powder is as follows: First, 10 g of waste rubber powder with a particle size of 80 mesh is treated under a low-temperature surface plasma with a power of 5 kW in an air atmosphere for 600 s, and then it is placed in 100 ml of aqueous solution and ultrasonically dispersed for 1 h to obtain an aqueous dispersion of activated rubber powder. Then, 2 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane is added to the aqueous dispersion of activated rubber powder, and the reaction is carried out at 80 °C for 3 h. After filtration and washing, it is redispersed in the aqueous solution to obtain an aqueous dispersion of coupling agent-modified rubber powder. Finally, 10 g of tetraethyl orthosilicate is added to 100 ml of the aqueous dispersion of coupling agent-modified rubber powder with a concentration of 0.1 g / ml, and the mixture is stirred at 60 °C for 4 h. After filtration, washing, and vacuum drying at 60 °C, nano-silica modified rubber powder (rubber powder@SiO2) is obtained. The nano-silica modified rubber powder prepared above is used in the preparation of composite concrete, and its specific preparation process is as follows: First, 948 parts of stones with a particle size of 5 - 25 mm, 35 parts of silica fume, 687 parts of slag, 70 parts of fly ash, 10 parts of nano-silica modified rubber powder, 0.10 part of basalt fiber, and 490 parts of 52.5 grade cement are sequentially added to a mixer and mixed evenly to obtain a first mixture. Secondly, 215 parts of water and 0.8 part of amino sulfonic acid-based water reducer are added to the first mixture and mixed evenly to obtain a second mixture. Then, the second mixture is filled into a test mold, placed on a vibrating table, and continuously vibrated and tamped until the surface shows slurry. After standing at room temperature for 48 h, composite concrete containing nano-silica modified rubber powder is obtained. Finally, the compressive strength of the prepared composite concrete is measured to be 66.3 MPa after standing for 7 days, and 84.2 MPa after standing for 28 days. After 300 freeze-thaw cycles, the mass loss rate of the composite concrete is 3.0%, and the dynamic elastic modulus retention rate is 60%. Example 2:

[0014] This example provides a composite concrete containing nano-silica modified rubber powder. Nano-silica modified rubber powder is introduced into the raw material components of the composite concrete. The specific preparation process of the nano-silica modified rubber powder is the same as that of the nano-silica modified rubber powder in Example 1, only the activation time is different, that is, 10 g of waste rubber powder with a particle size of 80 mesh is treated under a low-temperature surface plasma with a power of 5 kW in an air atmosphere for 300 s. Similarly, in this embodiment, the preparation process of the composite concrete is the same as that in Embodiment 1, only the dosages of the raw material components are different. That is, 900 parts of stones with a particle size of 5 - 25 mm, 40 parts of silica fume, 700 parts of slag, 80 parts of fly ash, 2 parts of nano-silica modified rubber powder (the nano-silica modified rubber powder prepared in this embodiment here), 0.12 parts of basalt fiber, 400 parts of 52.5-grade cement, 200 parts of water, and 0.5 parts of naphthalene-based water reducer are used. The compressive strength of the prepared composite concrete measured after standing for 7 days is 64.4 MPa, and the compressive strength measured after standing for 28 days is 80.5 MPa. After 300 freeze-thaw cycles, the mass loss rate of the composite concrete is 3.5%, and the dynamic elastic modulus retention rate is 59%. Embodiment 3:

[0015] This embodiment provides a composite concrete containing nano-silica modified rubber powder. Nano-silica modified rubber powder is introduced into the raw material components of the composite concrete. The specific preparation process of the nano-silica modified rubber powder is the same as that of the nano-silica modified rubber powder in Embodiment 1, only the activation power is different. That is, 10 g of waste rubber powder with a particle size of 80 mesh is treated for 600 s at a power of 3 kW in a low-temperature surface plasma with air as the atmosphere; Similarly, in this embodiment, the preparation process of the composite concrete is the same as that in Embodiment 1, only the dosages of the raw material components are different. That is, 1000 parts of stones with a particle size of 5 - 25 mm, 30 parts of silica fume, 600 parts of slag, 60 parts of fly ash, 20 parts of nano-silica modified rubber powder (the nano-silica modified rubber powder prepared in this embodiment here), 0.08 parts of basalt fiber, 500 parts of 52.5-grade cement, 300 parts of water, and 1.0 part of aliphatic water reducer are used. The compressive strength of the prepared composite concrete measured after standing for 7 days is 65.8 MPa, and the compressive strength measured after standing for 28 days is 82.3 MPa. After 300 freeze-thaw cycles, the mass loss rate of the composite concrete is 3.4%, and the dynamic elastic modulus retention rate is 59%. Embodiment 4:

[0016] This embodiment provides a composite concrete containing nano-silica modified rubber powder. Nano-silica modified rubber powder is introduced into the raw material components of the composite concrete. The specific preparation process of the nano-silica modified rubber powder is the same as that of the nano-silica modified rubber powder in Embodiment 1, only the dosage of γ-(2, 3-epoxypropoxy) propyltrimethoxysilane is different. That is, 1 g of γ-(2, 3-epoxypropoxy) propyltrimethoxysilane is added to the aqueous dispersion of the activated rubber powder; Similarly, in this embodiment, the preparation process of the composite concrete is the same as that in Embodiment 1, except for the nano-silica modified rubber powder. That is, the nano-silica modified rubber powder prepared in this embodiment is mixed with 948 parts of stones with a particle size of 5 - 25 mm, 35 parts of silica fume, 687 parts of slag, 70 parts of fly ash, 0.10 part of basalt fiber, and 490 parts of 52.5-grade cement in a mixer. The compressive strength of the prepared composite concrete measured after standing for 7 days is 65.1 MPa, and the compressive strength measured after standing for 28 days is 80.4 MPa. After 300 freeze-thaw cycles, the mass loss rate of the composite concrete is 3.3%, and the dynamic elastic modulus retention rate is 59%. Embodiment 5:

[0017] This embodiment provides a composite concrete containing nano-silica modified rubber powder. The nano-silica modified rubber powder is introduced into the raw material components of the composite concrete. The specific preparation process of the nano-silica modified rubber powder is the same as that in Embodiment 1, except for the amount of tetraethyl orthosilicate. That is, 5 g of tetraethyl orthosilicate is added to 100 ml of the aqueous dispersion of the coupling agent-modified rubber powder with a concentration of 0.1 g / ml. Similarly, in this embodiment, the preparation process of the composite concrete is the same as that in Embodiment 1, except for the nano-silica modified rubber powder. That is, the nano-silica modified rubber powder prepared in this embodiment is mixed with 948 parts of stones with a particle size of 5 - 25 mm, 35 parts of silica fume, 687 parts of slag, 70 parts of fly ash, 0.10 part of basalt fiber, and 490 parts of 52.5-grade cement in a mixer. The compressive strength of the prepared composite concrete measured after standing for 7 days is 64.9 MPa, and the compressive strength measured after standing for 28 days is 80.2 MPa. After 300 freeze-thaw cycles, the mass loss rate of the composite concrete is 3.2%, and the dynamic elastic modulus retention rate is 58%. Embodiment 6:

[0018] This embodiment provides a composite concrete containing nano-silica modified rubber powder. The nano-silica modified rubber powder is introduced into the raw material components of the composite concrete. The specific preparation process of the nano-silica modified rubber powder is the same as that in Embodiment 1. Similarly, in this embodiment, the preparation process of the composite concrete is the same as that in Embodiment 1, only the dosage of the nano-silica modified rubber powder is different. That is, 948 parts of stones with a particle size of 5 - 25 mm, 35 parts of silica fume, 687 parts of slag, 70 parts of fly ash, 20 parts of nano-silica modified rubber powder, 0.10 part of basalt fiber, and 490 parts of 52.5-grade cement are sequentially added to a mixer and mixed. The compressive strength of the prepared composite concrete measured after standing for 7 days is 64.1 MPa, the compressive strength measured after standing for 28 days is 80.0 MPa, the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 3.1%, and the dynamic elastic modulus retention rate is 60%. Embodiment 7:

[0019] This embodiment provides a composite concrete containing nano-silica modified rubber powder. The nano-silica modified rubber powder is introduced into the raw material components of the composite concrete, and the specific preparation process of the nano-silica modified rubber powder is the same as that in Embodiment 1; Similarly, in this embodiment, the preparation process of the composite concrete is the same as that in Embodiment 1, only the dosage of the nano-silica modified rubber powder is different. That is, 948 parts of stones with a particle size of 5 - 25 mm, 35 parts of silica fume, 687 parts of slag, 70 parts of fly ash, 2 parts of nano-silica modified rubber powder, 0.10 part of basalt fiber, and 490 parts of 52.5-grade cement are sequentially added to a mixer and mixed. The compressive strength of the prepared composite concrete measured after standing for 7 days is 65.6 MPa, the compressive strength measured after standing for 28 days is 82 MPa, the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 3.5%, and the dynamic elastic modulus retention rate is 58%.

[0020] Comparative Example 1: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Embodiment 1, but without adding nano-silica modified rubber powder. The compressive strength of the prepared composite concrete measured after standing for 7 days is 48 MPa, the compressive strength measured after standing for 28 days is 69 MPa, the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 18.2%, and the dynamic elastic modulus retention rate is 30%.

[0021] Comparative Example 2: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 5 parts of modified rubber powder prepared without adding silicate compounds and 5 parts of SiO2 (silicon dioxide) are directly used to replace the 10 parts of nano-silicon dioxide modified rubber powder prepared in Example 1. Here, SiO2 does not go through the activation and grafting steps, and the ethanol solution of silicate compounds is directly added to the aqueous dispersion for stirring reaction, and then obtained after suction filtration, washing and drying; The compressive strength of the prepared composite concrete measured after standing for 7 days is 40.1 MPa, the compressive strength measured after standing for 28 days is 51.5 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 17.3%, and the dynamic elastic modulus retention rate is 45%.

[0022] Comparative Example 3: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of modified rubber powder prepared without adding silicate compounds are directly used to replace the 10 parts of nano-silicon dioxide modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 42.6 MPa, the compressive strength measured after standing for 28 days is 53.2 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 16.9%, and the dynamic elastic modulus retention rate is 48%.

[0023] Comparative Example 4: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Example 1, except that the dosage of nano-silicon dioxide modified rubber powder is different. That is, 948 parts of stones with a particle size of 5 - 25 mm, 35 parts of silicon powder, 687 parts of slag, 70 parts of fly ash, 25 parts of nano-silicon dioxide modified rubber powder, 0.10 part of basalt fiber and 490 parts of 52.5 grade cement are sequentially added to a mixer for mixing. The compressive strength of the prepared composite concrete measured after standing for 7 days is 45.1 MPa, the compressive strength measured after standing for 28 days is 56.3 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 16.1%, and the dynamic elastic modulus retention rate is 49%.

[0024] Comparative Example 5: This comparative example provides a composite concrete, whose preparation process is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of modified rubber powder prepared without low-temperature surface plasma activation treatment are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 45.1 MPa, the compressive strength measured after standing for 28 days is 56.4 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 16.1%, and the dynamic elastic modulus retention rate is 48%.

[0025] Comparative Example 6: This comparative example provides a composite concrete, whose preparation process is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of modified rubber powder prepared by low-temperature surface plasma treatment for 900 s are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 47.3 MPa, the compressive strength measured after standing for 28 days is 59.2 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 15.8%, and the dynamic elastic modulus retention rate is 51%.

[0026] Comparative Example 7: This comparative example provides a composite concrete, whose preparation process is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of modified rubber powder prepared by low-temperature surface plasma activation treatment at an activation power of 8 kW are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 48.5 MPa, the compressive strength measured after standing for 28 days is 60.5 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 15.9%, and the dynamic elastic modulus retention rate is 50%.

[0027] Comparative Example 8: This comparative example provides a composite concrete, whose preparation process is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of modified rubber powder prepared without adding silane coupling agent for modification are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 47.4 MPa, the compressive strength measured after standing for 28 days is 59.2 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 16.0%, and the dynamic elastic modulus retention rate is 49%.

[0028] Comparative Example 9: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of the modified rubber powder prepared by modifying 3 g of silane coupling agent are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 49.6 MPa, the compressive strength measured after standing for 28 days is 62 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 15.9%, and the dynamic elastic modulus retention rate is 50%.

[0029] Comparative Example 10: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of SiO2 (silica) are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1. Here, SiO2 does not go through the activation and grafting steps, and the ethanol solution of silicate compound is directly added to the aqueous dispersion and stirred for reaction, and then obtained after suction filtration, washing and drying; The compressive strength of the prepared composite concrete measured after standing for 7 days is 48.4 MPa, the compressive strength measured after standing for 28 days is 60.4 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 18.0%, and the dynamic elastic modulus retention rate is 45%.

[0030] Comparative Example 11: This comparative example provides a composite concrete, the preparation process of which is the same as that of the composite concrete in Example 1, except that the modified rubber powder added is different. That is, 10 parts of the modified rubber powder prepared by modifying 15 g of silicate compound are directly used to replace the 10 parts of nano-silica modified rubber powder prepared in Example 1; the compressive strength of the prepared composite concrete measured after standing for 7 days is 46.7 MPa, the compressive strength measured after standing for 28 days is 58.4 MPa, and the mass loss rate of the composite concrete after 300 freeze-thaw cycles is 16.0%, and the dynamic elastic modulus retention rate is 49%.

[0031] The following is a statistical table of the compressive strength measured in Examples 1-7 and Comparative Examples 1-11, the mass loss rate measured after 300 freeze-thaw cycles, and the dynamic elastic modulus retention rate: ; As can be seen from the above table, for the composite concrete containing nano-silica modified rubber powder prepared in Examples 1-7, whether it is left standing for 7 days or 28 days, its compressive strength is superior to that of the composite concrete prepared in Comparative Examples 1-11. Moreover, for the composite concrete containing nano-silica modified rubber powder prepared in Examples 1-7, its mass loss rate and dynamic elastic modulus retention rate are also superior to those of the composite concrete prepared in Comparative Examples 1-11 after 300 freeze-thaw cycles. Therefore, introducing nano-silica modified rubber powder prepared by air plasma activation, silane coupling agent grafting and silicate ester compound condensation reaction into the raw material components of composite concrete can greatly improve the compatibility and interfacial strength between the rubber powder and the concrete matrix, effectively solve the problem of insufficient freeze-thaw resistance of existing rubber concrete, and at the same time, through the unique nano-effect of nano-silica modified rubber powder, improve the microstructure and compactness of the composite concrete, thus significantly improving the compressive strength and freeze-thaw cycle resistance of the composite concrete, and significantly broadening the application scenarios of rubber concrete, especially in cold regions or building projects that need to withstand extreme climate conditions, it has more advantages.

Claims

1. A composite concrete containing nano-silica modified rubber powder, characterized in that, The raw material components of the composite concrete include, by weight: 400 - 500 parts of 52.5 grade cement, 60 - 80 parts of fly ash, 600 - 700 parts of slag, 30 - 40 parts of silica fume, 900 - 1000 parts of stones with a particle size of 5 - 25 mm, 200 - 300 parts of water, 0.5 - 1.0 part of water reducer, 2 - 20 parts of nano-silica modified rubber powder, and 0.08 - 0.12 part of basalt fiber; among them, the nano-silica modified rubber powder is prepared by grafting with a silane coupling agent and carrying out a condensation reaction with a silicate compound after activating and dispersing waste rubber powder as raw materials.

2. The composite concrete containing nano-silica modified rubber powder according to claim 1, characterized in that The specific preparation steps of the nano-silica modified rubber powder are as follows: S1. Place the waste rubber powder in a low-temperature plasma generator for activation, then place it in an aqueous solution, and obtain an aqueous dispersion of activated rubber powder through ultrasonic dispersion for 1 - 2 h. S2. Add the silane coupling agent to the aqueous dispersion of the activated rubber powder obtained in S1, stir and react to initiate the in-situ growth of subsequent nano-silica, carry out suction filtration and washing, and then redisperse it in an aqueous solution to obtain an aqueous dispersion of the coupling agent-modified rubber powder. S3. Add an ethanol solution of the silicate compound to the aqueous dispersion of the coupling agent-modified rubber powder obtained in S2, stir and react, and obtain the nano-silica modified rubber powder after suction filtration, washing, and drying.

3. A composite concrete containing nano-silica modified rubber powder according to claim 2, characterized in that, In S1, the particle size of the waste rubber powder is 80 - 200 mesh.

4. A composite concrete containing nano-silica modified rubber powder according to claim 2, characterized in that, In S1, the atmosphere of the low-temperature plasma generator is air, the air flow rate is 0.5 - 1.5 L / min, the activation time is 300 - 600 s, and the activation power is 3 - 5 kW.

5. A composite concrete containing nano-silica modified rubber powder according to claim 2, characterized in that, In S2, the mass ratio of the rubber powder to the silane coupling agent is 1:0.1 - 1:0.2, where the silane coupling agent is a silane coupling agent containing an epoxy group, the stirring reaction temperature is 80 - 120 °C, and the stirring reaction time is 3 - 4 h.

6. A composite concrete containing nano-silica modified rubber powder according to claim 2, characterized in that In S3, the mass ratio of the rubber powder to the silicate compound is 1:0.5 - 1:1, where the silicate compound is one of methyl orthosilicate, ethyl orthosilicate, and bis(trimethoxysilyl)ethane, the stirring reaction temperature is 60 - 80 °C, and the stirring reaction time is 4 - 6 h.

7. A composite concrete containing nano-silica modified rubber powder according to claim 1, characterized in that, The water reducer is one of naphthalene series, amino sulfonic acid series, aliphatic, and polycarboxylic acid series, and the diameter and length of the basalt fiber are 12 - 16 μm and 2 - 4 mm respectively.

8. The preparation method of a composite concrete containing nano-silica modified rubber powder according to any one of claims 1 to 7, characterized in that, The specific steps are as follows: First, add the specified amount of stones with a particle size of 5 - 25 mm, silica fume, slag, fly ash, nano-silica modified rubber powder, basalt fiber, and 52.5 grade cement to the mixer in sequence, and obtain the first mixture after mixing evenly; then, add the specified amount of water and water reducer to the first mixture, and obtain the second mixture after mixing evenly; finally, pour the second mixture into a test mold, place it on a vibrating table, continuously vibrate and tamp until the surface oozes slurry, and let it stand at room temperature for 48 h to obtain the composite concrete.

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