Inorganic nanofiber reinforced concrete composite material and preparation method thereof

Abstract

The invention relates to the technical field of concrete composite materials, in particular to an inorganic nanofiber reinforced concrete composite material and a preparation method thereof.The inorganic nanofiber reinforced concrete composite material is prepared from cement, superfine slag powder, quartz sand, aluminum borate nanofibers, basalt microfibers, a silane coupling agent, nano-zinc oxide, a composite modifier and an accelerator; the quartz sand is subjected to phosphoric acid activation and plasma treatment, the fibers are subjected to ultrasonic dispersion, and the raw materials are subjected to dry mixing and wet mixing and then subjected to microwave vibration forming and curing. The concrete is high in compressive strength, good in impermeability, low in chloride ion diffusion coefficient, high in freeze-thaw resistance, rapid in early strength increase, good in construction performance and suitable for rapid construction, and the comprehensive performance of the concrete is superior to that of traditional fiber concrete.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete composite materials, in particular to an inorganic nanofiber reinforced concrete composite material and a preparation method thereof. BACKGROUND

[0002] In the field of construction engineering, concrete as a basic material faces many performance bottlenecks. The compressive strength of traditional concrete is limited, and the crack resistance is poor. Especially under long-term load or environmental action, microcracks are easily generated, which leads to a decrease in durability. Although the existing technology improves the performance by adding fibers, steel fibers have poor dispersibility in the matrix, which easily causes internal stress concentration and forms new defects. Non-metallic fibers have weak interfacial bonding force with the cement matrix, which limits the application of concrete in high-stress and large-span structures.

[0003] The durability problem of existing fiber concrete also needs to be solved. Although conventional admixtures can improve early strength, they often reduce the density of the matrix, resulting in insufficient impermeability and accelerated corrosion of steel bars due to chloride ion penetration. In freeze-thaw environments, the internal pore water of concrete expands due to ice formation, causing microstructure damage and significant strength loss, making it difficult to meet the long-term use requirements in cold regions or marine engineering. In addition, although the application of recycled aggregates can save resources, the old mortar attached to the surface leads to a weak interfacial transition zone and unstable overall performance.

[0004] The limitations of construction technology also restrict the development of materials. Traditional mixing methods cannot achieve uniform dispersion of nanoscale materials, and fibers are easily agglomerated during vibration molding, affecting the uniformity of mechanical properties. The long curing period and low early strength also increase the cost of project progress, especially in coal mine tunnels and other scenes that require rapid support, existing materials cannot meet the immediate load-bearing requirements. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the deficiencies of the prior art, the present application provides an inorganic nanofiber reinforced concrete composite material and a preparation method thereof.

[0007] (II) Technical solutions

[0008] The inorganic nanofiber reinforced concrete composite material comprises, by mass fraction: cement 70-85 parts, fly ash 25-40 parts, quartz sand 60-75 parts, aluminum borate nanofiber 10-18 parts, basalt microfiber 4-9 parts, silane coupling agent KH-590 5-8 parts, nano-zinc oxide 7-12 parts, composite modifier 6-11 parts, and accelerator 2-4 parts.

[0009] The composite modifier raw material comprises, by mass fraction, 2-5 parts of hydroxyapatite nanowires, 0.1-0.25 parts of magnesium acetate, and 3-6 parts of a diethanolamine solution with a mass fraction of 10-15%, and the reaction formula is: Mg(CH3COO)2+2H2O→Mg(OH)2+2CH3COOH, so that magnesium hydroxide whiskers are formed to enhance the toughness of the matrix.

[0010] Preferably, the cement is CEMIII type 42.5R grade slag portland cement, with a specific surface area of 450-500 m 2 / kg, and a free calcium oxide content of ≤1.0%.

[0011] Preferably, the aluminum borate nanofiber has a diameter of 80-150 nm, a length-diameter ratio of 120-200, and a surface grafted with an amino silane coupling agent, and the Zeta potential of the dispersion liquid in water is -30 to -45 mV.

[0012] Preferably, the quartz sand is activated by a 10-15% phosphoric acid solution at room temperature for 5-8 h, so that a calcium phosphate coating is formed on the surface, with a thickness of 5-10 μm and a crushing index of ≤15%.

[0013] Preferably, the preparation steps of the composite modifier are as follows: hydroxyapatite nanowires are mixed with deionized water at a mass ratio of 1:15, magnesium acetate is added and ultrasonically treated for 3-4 h at a frequency of 60-80 kHz, diethanolamine solution is added dropwise and ultrasonic treatment is continued for 25-35 min, hydrothermal reaction is carried out at 190-210°C for 14-18 h, and then centrifugation, isopropanol washing, and vacuum drying at 70°C are performed.

[0014] Preferably, the basalt microfiber has a diameter of 15-20 μm and a length of 10-20 mm, and is treated with a silane coupling agent KH-690, and the mass ratio of the basalt microfiber to the aluminum borate nanofiber is 1:2.5-1:4.

[0015] Preferably, the preparation method of the inorganic nanofiber reinforced concrete composite material comprises the following steps:

[0016] S1: plasma treatment of aggregate: the quartz sand is placed in a plasma treatment device and treated in an argon atmosphere for 5-10 min at a power of 100-150 W, and then a silane coupling agent is immediately added and stirred at a high speed of 1000-1200 r / min for 20-25 min;

[0017] S2: ultrasonic dispersion of nanofiber: the aluminum borate nanofiber and the basalt microfiber are added to deionized water in a proportion to prepare a dispersion liquid with a solid content of 3-4%, and 1-1.5% of a polyether type dispersant is added and treated by power ultrasonic for 4-6 times, each time for 15-20 min;

[0018] S3 Gradient mixing stirring: first, dry mixing cement, fly ash and nano zinc oxide for 5-8 min, then wet mixing S2 fiber dispersion liquid and water for 7-10 min, and then adding S1 treated aggregate, composite modifier and accelerator, stirring at 600-800 r / min for 5-7 min until uniform;

[0019] S4 Microwave assisted curing: pouring the mixture into a mold, vibrating at a frequency of 2.45 GHz for 1.5-2.5 min, covering with polytetrafluoroethylene film for 12-18 h, then moving into a microwave curing chamber for 3-5 d, and finally curing at room temperature for 28 d.

[0020] Preferably, the S1 plasma treatment can increase the surface roughness of quartz sand by 30-50%, enhancing the mechanical interlocking strength with the cement matrix.

[0021] Preferably, the nano zinc oxide is added in the S3 wet mixing process to react with the cement hydration products to form ZnO-C-S-H composite gel, and the reaction formula is:

[0022] Ca(OH)2+SiO2+ZnO+H2O→CaO·SiO2·ZnO·nH2O

[0023] Preferably, the microwave curing in S4 can make the 3d compressive strength of the composite material ≥30 MPa, the 28d compressive strength ≥140 MPa, the impermeability grade ≥P14, and the chloride ion diffusion coefficient ≤3×10 -12 m 2 / s, meeting the requirement of strength loss rate ≤5% after 500 freeze-thaw cycles in GB / T 50082-2009.

[0024] (Three) Beneficial technical effects

[0025] Compared with the existing technology, the beneficial effects of the present application are:

[0026] 1. The aluminum borate nanofiber and basalt microfiber form a multi-level reinforcing network, combined with the modification treatment of silane coupling agent, making the compressive strength of the composite material reach more than 140 MPa, improving the crack resistance, effectively solving the problems of insufficient strength and crack propagation of traditional materials. The magnesium-oxygen coordination network generated by the reaction of hydroxyapatite nanotubes in the composite modifier and magnesium acetate strengthens the interfacial bonding between aggregate and cement matrix, reduces the chloride ion diffusion coefficient to less than 3×10 -12 m 2 / s, and the impermeability grade reaches more than P14, significantly improving the durability.

[0027] 2. The plasma treatment in the preparation process increases the surface roughness of the aggregate, improves the mechanical interlocking strength, and accelerates the crystallization of hydration products by combining with microwave curing technology, so that the 3d compressive strength breaks through 30 MPa, meeting the rapid construction demand. The composite gel formed by the nano zinc oxide and the cement hydration product fills the pores and refines the crystal structure, so that the strength loss rate of the material after 500 freeze-thaw cycles is less than 5%, and the material is suitable for harsh environments. The method ensures the uniform dispersion of the nanofiber through gradient mixing stirring and pulse vibration process, has good construction performance, and the microstructure of the substrate after forming is dense, and the comprehensive performance is better than that of the existing fiber reinforced concrete, and has a wide application prospect in the fields of marine engineering, nuclear facilities and the like. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a preparation method flow chart of the inorganic nanofiber reinforced concrete composite material according to the present application;

[0029] Figure 2 is a 3d compressive strength and 28d compressive strength fold line comparison graph of the examples and the comparative examples;

[0030] Figure 3 is a flexural strength and splitting tensile strength columnar comparison graph of the examples and the comparative examples;

[0031] Figure 4 is a radar comparison graph of the durability and micro performance data of the concrete composite material of the examples and the comparative examples after being unified dimension. DETAILED DESCRIPTION

[0032] According to Figures 1 to 4 , the specific embodiments of the present application are as follows:

[0033] Example 1: High impermeability inorganic nanofiber reinforced concrete

[0034] 1. Raw material components (mass parts)

[0035] Cement: 70 parts, CEMIII type 42.5R slag portland cement, specific surface area 450 m 2 / kg;

[0036] Slag powder: 30 parts, S95 grade, specific surface area 400 m 2 / kg;

[0037] Quartz sand: 60 parts, activated by 10% phosphoric acid solution for 5h, surface calcium phosphate coating thickness 8μm;

[0038] Aluminum borate nanofiber: 12 parts, diameter 100nm, aspect ratio 150, modified by KH-590;

[0039] Basalt microfiber: 5 parts, diameter 15 μm, length 10 mm, KH-690 treatment;

[0040] Silane coupling agent: 5 parts, KH-590, 2% of the mass of the aggregate;

[0041] Nano zinc oxide: 7 parts, particle size 50 nm;

[0042] Composite modifier: 6 parts, 3 parts of hydroxyapatite nanowires, 0.1 parts of magnesium acetate, and 4 parts of 12% diethanolamine solution;

[0043] Accelerator: 3 parts, aluminate type accelerator.

[0044] 2. Preparation steps

[0045] S1 Aggregate plasma treatment:

[0046] The quartz sand was placed in an argon atmosphere with a pressure of 15 Pa and treated with a power of 100 W for 8 min. Immediately, a silane coupling agent was added, and stirring was performed at 1000 r / min for 20 min. The surface roughness was increased by 40%.

[0047] S2 Nanofiber ultrasonic dispersion:

[0048] The aluminum borate nanofiber and basalt microfiber were added to deionized water to form a 3% dispersion liquid, 1% polyether dispersant was added, and ultrasonic treatment was performed at 40 kHz and a power of 800 W for 4 times, each time for 15 min, with a Zeta potential of -35 mV.

[0049] S3 Gradient mixing and stirring:

[0050] The cement, slag powder, and nano zinc oxide were dry mixed for 5 min, the dispersion liquid was added, the water-binder ratio was 0.23, and wet mixing was performed for 7 min. Then, the treated aggregate, composite modifier, and accelerator were added, and stirring was performed at 500 r / min for 5 min.

[0051] S4 Microwave-assisted curing:

[0052] After the mixture was poured into the mold, microwave vibration was performed at 2.45 GHz and a power of 5 kW for 1.5 min. The mixture was covered with a polytetrafluoroethylene film and cured for 12 h. Then, it was moved to a 60°C microwave curing room for 3 d, and cured at room temperature until 28 d.

[0053] Example 2: High-strength weather-resistant composite material

[0054] 1. Raw material components (mass parts)

[0055] Cement: 80 parts, CEMIII type 42.5R cement, specific surface area 480 m 2 / kg;

[0056] Slag powder: 35 parts, S105 grade, specific surface area 450 m 2 / kg;

[0057] Quartz sand: 65 parts, 15% phosphoric acid activation for 6h, coating thickness 10 pm;

[0058] Aluminum borate nanofiber: 15 parts, diameter 120 nm, aspect ratio 180, modified with KH-590;

[0059] Basalt microfiber: 7 parts, diameter 18 pm, length 15 mm, treated with KH-690;

[0060] Silane coupling agent: 7 parts, 2.5% of the mass of the aggregate;

[0061] Nano zinc oxide: 10 parts, particle size 60 nm;

[0062] Composite modifier: 8 parts, 4 parts of hydroxyapatite nanowire, 0.15 parts of magnesium acetate, 5 parts of 15% diethanolamine solution;

[0063] Accelerator: 4 parts.

[0064] 2. Preparation steps

[0065] S1 Aggregate treatment:

[0066] Plasma treatment parameters: argon pressure 20 Pa, power 120 W, treatment time 10 min, stirring speed of silane coupling agent 1100 r / min, time 22 min.

[0067] S2 Nanofiber dispersion:

[0068] Solid content of the dispersion 3.5%, polyether type dispersant 1.2%, 50 kHz ultrasonic (power 900 W) treatment 5 times, each time 20 min, Zeta potential -40 mV.

[0069] S3 Mixing and stirring:

[0070] Wet mixing time 8 min (700 r / min), dry mixing time 6 min, final stirring speed 600 r / min, time 6 min.

[0071] S4 Curing process:

[0072] Microwave vibration power 6 kW, time 2 min, microwave curing chamber temperature 70°C, humidity 92%, curing for 4d, normal temperature curing for 28d.

[0073] Example 3: Ultra-high performance engineering composite material

[0074] 1. Raw material components (parts by mass)

[0075] Cement: 85 parts, CEM III type 42.5R cement, specific surface area 500 m2 / kg. 2

[0076] Slag powder: 40 parts, S105 grade, specific surface area 480 m2 / kg. 2

[0077] Quartz sand: 75 parts, activated with 15% phosphoric acid for 8h, coating thickness 12μm.

[0078] Aluminum borate nanofiber: 18 parts, diameter 150nm, aspect ratio 200, modified with KH-590.

[0079] Basalt microfiber: 9 parts, diameter 20μm, length 20mm, treated with KH-690.

[0080] Silane coupling agent: 8 parts, 3% of the mass of the aggregate.

[0081] Nano zinc oxide: 12 parts, particle size 80nm.

[0082] Composite modifier: 11 parts, 5 parts of hydroxyapatite nanowires, 0.25 parts of magnesium acetate, 6 parts of 15% diethanolamine solution.

[0083] Accelerator: 4 parts

[0084] 2. Preparation steps

[0085] S1 Aggregate treatment:

[0086] Plasma treatment power 150W, argon pressure 20Pa, treatment time 10min, silane coupling agent stirring speed 1200r / min, time 25min.

[0087] S2 Nanofiber dispersion:

[0088] Dispersion solid content 4%, polyether type dispersant 1.5%, 50kHz ultrasonic treatment (power 1000W) 6 times, 20min each time, Zeta potential -45mV.

[0089] S3 Mixing and stirring:

[0090] Dry mixing 8min, wet mixing 10min (800r / min), final stirring speed 800r / min, time 7min.

[0091] S4 Curing process:

[0092] Microwave vibration power 8kW, time 2.5min, microwave curing chamber temperature 80℃, humidity 95%, curing 5d, normal temperature curing 28d.

[0093] Comparative example: traditional fiber concrete (without nano modification)​​

[0094] 1. Raw material difference

[0095] No addition of aluminum borate nanofiber, composite modifier, nanometer zinc oxide;

[0096] Basalt fiber dosage 15 parts (unmodified), cement 80 parts, quartz sand 70 parts, accelerator 4 parts, water-cement ratio 0.25.

[0097] 2. Preparation process

[0098] The aggregate was not subjected to plasma treatment and was directly mixed;

[0099] Mechanical stirring (400 r / min) was used for 10 min for fiber dispersion, without ultrasonic treatment;

[0100] Curing method: normal temperature thin film curing for 28 d, without microwave assistance.

[0101] The mechanical properties of the concrete composite materials of the examples and the comparative examples were compared, as shown in the following table:

[0102] Table 1

[0103] Performance indicators Example 1 Example 2 Example 3 Comparative example 3d compressive strength (MPa) 32.5 35.8 38.2 18.3 28d compressive strength (MPa) 142.6 156.3 168.9 78.5 Flexural strength (MPa) 16.8 18.5 20.3 8.2 Split tensile strength (MPa) 8.5 9.2 10.1 4.3 Elastic modulus (GPa) 48.6 51.2 53.8 32.5

[0104] Table 1 shows that the mechanical properties of the examples are better than those of the comparative examples: the 3d compressive strength reaches 32.5-38.2 MPa, which is 1.77-2.09 times that of the comparative examples, meeting the rapid construction requirements; the 28d compressive strength is as high as 142.6-168.9 MPa, which is 81.5%-115.2% higher than that of the comparative examples, and the flexural, splitting tensile strength and elastic modulus are also doubled, which is due to the synergistic effect of the multi-level reinforcing network of aluminum borate nanofiber and basalt microfiber and microwave curing, fully reflecting the significant improvement effect of inorganic nanofiber reinforcement technology on the mechanical properties of concrete.

[0105] The durability and micro properties of the concrete composite materials of the examples and the comparative examples were compared, as shown in the following table:

[0106] Table 2

[0107]

[0108]

[0109] The data in Table 2 show that the durability and microstructure of the examples are far superior to the comparative examples: the impermeability grade reaches P14-P18, the chloride ion diffusion coefficient is only 13.5%-19.9% of that of the comparative examples, the strength loss rate after 500 freeze-thaw cycles is less than 5%, and the applicability of the material in harsh environments is significantly improved; on the micro level, the interface transition zone thickness is reduced by more than 75%, the fiber agglomeration rate is controlled to be less than 1.2%, and the absolute value of Zeta potential is more than 35 mV, which confirms the key role of plasma treatment, ultrasonic dispersion and other processes and composite modifiers in optimizing the microstructure of the material and improving the macro durability.

[0110] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An inorganic nanofiber reinforced concrete composite material, characterized in that: The raw materials include, by mass: 70-85 parts of cement, 25-40 parts of fly ash, 60-75 parts of quartz sand, 10-18 parts of aluminum borate nanofiber, 4-9 parts of basalt microfiber, 5-8 parts of silane coupling agent KH-590, 7-12 parts of nano zinc oxide, 6-11 parts of composite modifier, and 2-4 parts of accelerating agent; The composite modifier raw materials include, by mass, 2-5 parts of hydroxyapatite nanowires, 0.1-0.25 parts of magnesium acetate, and 3-6 parts of a diethanolamine solution with a mass fraction of 10-15%. The reaction formula is: Mg(CH3COO)2+2H2O→Mg(OH)2+2CH3COOH, forming magnesium hydroxide whiskers to enhance the toughness of the matrix.

2. The inorganic nanofiber reinforced concrete composite material according to claim 1, characterized in that: The cement is CEMIII type 42.5R grade slag silicate cement with a specific surface area of ​​450-500m 2 / kg, free calcium oxide content ≤1.0%.

3. The inorganic nanofiber reinforced concrete composite material according to claim 1, characterized in that: The aluminum borate nanofiber has a diameter of 80-150 nm and an aspect ratio of 120-200, an aminosilane coupling agent is grafted onto the surface, and the Zeta potential of the dispersion in water is -30 to -45 mV.

4. The inorganic nanofiber reinforced concrete composite material according to claim 1, characterized in that: The quartz sand is activated by a 10-15% phosphoric acid solution at room temperature for 5-8 hours, and a calcium phosphate coating is formed on the surface thereof with a thickness of 5-10 μm and a crushing index of ≤15%.

5. The inorganic nanofiber reinforced concrete composite material according to claim 1, characterized in that: The preparation steps of the composite modifier are as follows: hydroxyapatite nanowires and deionized water are mixed in a mass ratio of 1:15, magnesium acetate is added, and ultrasonic treatment is performed for 3-4 hours at a frequency of 60-80 kHz, diethanolamine solution is added dropwise, and ultrasonic treatment is continued for 25-35 minutes, hydrothermal reaction is carried out at 190-210° C. for 14-18 hours, and the mixture is centrifuged, washed with isopropanol, and vacuum dried at 70° C.

6. The inorganic nanofiber reinforced concrete composite material according to claim 1, characterized in that: The basalt microfiber has a diameter of 15-20 μm and a length of 10-20 mm, is treated with a silane coupling agent KH-690, and has a mass ratio of 1:2.5-1:4 to the aluminum borate nanofiber.

7. A method for preparing the inorganic nanofiber reinforced concrete composite material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1 Aggregate Plasma Treatment: Place the quartz sand in a plasma treatment device and treat it in an argon atmosphere for 5-10 minutes at a power of 100-150W. Immediately after treatment, add the silane coupling agent and stir at a high speed of 1000-1200 r / min for 20-25 minutes. S2 Nanofiber Ultrasonic Dispersion: Aluminum borate nanofibers and basalt microfibers are added to deionized water in proportion to prepare a dispersion with a solid content of 3-4%. 1-1.5% of a polyether dispersant is added and the dispersion is treated with high-power ultrasonic treatment for 4-6 times, each time for 15-20 minutes. S3 gradient mixing: first dry mix cement, fly ash and nano zinc oxide for 5-8 minutes, then add S2 fiber dispersion and water and wet mix for 7-10 minutes, then add S1 treated aggregate, composite modifier and accelerator, and stir at 600-800r / min for 5-7 minutes until uniform; S4 Microwave-assisted curing: Pour the mixture into the mold, vibrate with microwaves at a frequency of 2.45 GHz for 1.5-2.5 minutes, cover with polytetrafluoroethylene film and cure for 12-18 hours, then move into a microwave curing room for 3-5 days, and finally cure at room temperature for 28 days.

8. The method for preparing the inorganic nanofiber reinforced concrete composite material according to claim 7, characterized in that: The plasma treatment in S1 can increase the surface roughness of the quartz sand by 30-50%, thereby enhancing the mechanical bite strength with the cement matrix.

9. The method for preparing an inorganic nanofiber reinforced concrete composite material according to claim 7, wherein: Nano zinc oxide is added during the wet mixing process in S3 to react with cement hydration products to form ZnO-CSH composite gel. The reaction formula is: Ca(OH)2+SiO2+ZnO+H2O→CaO·SiO2·ZnO·nH2O.

10. The method for preparing an inorganic nanofiber reinforced concrete composite material according to claim 7, wherein: The microwave curing in S4 can make the composite material have a 3d compressive strength of ≥30MPa, a 28d compressive strength of ≥140MPa, an impermeability grade of ≥P14, and a chloride ion diffusion coefficient of ≤3×10 -12 m 2 / s, meeting the requirement of GB / T50082-2009 that the strength loss rate of 500 freeze-thaw cycles is ≤5%.

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