Low-carbon cement-based grouting material and preparation method thereof

Abstract

The invention relates to a low-carbon cement-based grouting material, belongs to the technical field of building materials, and particularly relates to research and development of a low-carbon cementing material for highway roadbed reinforcement. According to the material, Portland cement is used as a matrix, cement is replaced with fly ash and slag powder to achieve high-value utilization of solid waste, a temperature response network is formed by combining polyurethane particles and a nano-encapsulated silicon dioxide phase change material, amination modified graphene oxide is introduced, surface amino groups of the amination modified graphene oxide and-NCO groups of polyurethane are crosslinked to enhance interface bonding force, and the thermal conductivity of the material is improved. And sodium sulfate excitation activation and polycarboxylic acid water reducer viscosity reduction effects are cooperated to form a low-carbon slurry with a low water-binder ratio and high impermeability. The material is suitable for repairing and reinforcing expressway roadbed cracks, carbon emission is reduced through industrial solid waste replacement, the temperature adaptability is improved through the nanometer phase change material, the crack resistance is enhanced through the polyurethane-graphene oxide network, and the dual low-carbon benefits of reducing construction energy consumption and prolonging the service life are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and more particularly to a low-carbon cement-based grouting material and a preparation method thereof. Background Art

[0002] Traditional cement-based grouting materials have the following technical defects in practical applications: First, the use of Portland cement is generally high (accounting for more than 60% of the base material), which generates a large amount of carbon dioxide emissions during the production process, and it is difficult to achieve effective carbon emission reduction through conventional industrial solid waste substitution; Second, when the amount of solid waste such as fly ash and slag added exceeds 30%, it is easy to lead to insufficient early strength of the slurry and increased bleeding rate, requiring the use of high-dose chemical stimulants, which increases costs; Third, existing materials are prone to microcracks in the alternating temperature environment of the roadbed. The interface bonding between conventional phase change materials and cement matrix is ​​weak, and the mismatch in thermal expansion coefficients leads to durability degradation. Fourth, polymer particles have poor compatibility with inorganic substrates, and physical mixing easily forms local agglomerations, which weakens the material's impermeability and self-healing properties.

[0003] The reasons for this are the low surface activity of solid waste particles, which limits their contribution to gelation; the insufficient stability of the phase change material packaging, which leads to core material leakage; and the lack of an effective interfacial chemical bonding mechanism to coordinate the performance of multiple components. These issues make it difficult for traditional materials to achieve a balance between low carbonization, durability, and construction adaptability. Summary of the Invention

[0004] An object of the present invention is to provide a low-carbon cement-based grouting material comprising the following components: Base material: composed of 35-45 parts by weight of Portland cement, 10-15 parts of fly ash, 25-35 parts of slag powder, 0.8-1.5 parts of polyurethane particles, 1.6-3.0 parts of nano-encapsulated silica phase change material, and 0.05-0.15 parts of amino-modified graphene oxide, wherein the fly ash and slag powder together account for 35%-50% of the total mass of the base material, the mass ratio of polyurethane particles to nano-encapsulated silica phase change material is 1:2-3, and the amino-modified graphene oxide is modified by grafting with ethylenediamine, and the surface amino groups form chemical crosslinks with the -NCO groups of the polyurethane particles; Sodium sulfate: 0.6%~1.0% of the total mass of the base material; Polycarboxylate water reducer: 0.2%~0.4% of the total mass of the base material.

[0005] Preferably, the surface of amino-modified graphene oxide is loaded with magnetic Fe3O4 nanoparticles to form a graphene oxide-Fe3O4 composite, and the added amount thereof is 0.05% to 0.15% of the total mass of the base material; The mass ratio of Fe3O4 nanoparticles to amino-modified graphene oxide is 1:0.5~1.0, and they are connected to the amino groups through coordination bonds.

[0006] Preferably, the base material further comprises 2 to 5 parts by mass of alkali-activated pretreated rice husk ash; Rice husk ash was soaked in a sodium hydroxide solution with a mass fraction of 5% to 8% and then dried and crushed to a particle size of ≤50 μm. Nano-encapsulated silica phase change material was adsorbed in its porous structure and its surface reacted with the hydration products of Portland cement to form CSH gel.

[0007] Provided is a method for preparing the low-carbon cement-based grouting material, comprising the following steps: S1. Preparation of amino-modified graphene oxide composite: Graphene oxide was dispersed in a buffer solution with a pH of 5.5-6.5, and ethylenediamine and EDC / NHS activator were added in a mass ratio of 1:8-12. The mixture was reacted at 40-50°C for 2-4 hours, and centrifuged to obtain amino-modified graphene oxide. When preparing the graphene oxide-Fe3O4 composite, amino-modified graphene oxide and Fe3O4 nanoparticles are dispersed in ethanol at a mass ratio of 1:0.3-0.6, and ultrasonicated for 30-60 minutes. The magnetic particles are loaded through the coordination between the amino groups and the metal ions on the Fe3O4 surface to obtain the graphene oxide-Fe3O4 composite. S2. Low carbon base material mixing: Portland cement, fly ash, slag powder and rice husk ash are dry-mixed for 3-5 minutes to form an inorganic matrix, and then amino-modified graphene oxide or graphene oxide-Fe3O4 composite is added and mixed until uniform; S3. Preparation of low carbon slurry: To the mixture in step S2, sodium sulfate solution, polycarboxylate water-reducing agent and nano-encapsulated silica phase change material were sequentially added, the water-binder ratio was controlled to be 0.28-0.32, and the mixture was stirred at 800-1200 r / min to form a slurry; S4, gradient dispersion molding: The polyurethane particles were added in two batches: 50% of the polyurethane particles were first added to the slurry and pre-reacted under low-speed stirring at 200-400 r / min, and the remaining 50% of the polyurethane particles were dispersed under high-speed shear at 600-800 r / min, and finally vibrated and formed under a magnetic field to form a three-dimensional interpenetrating network structure.

[0008] Preferably, the preparation method of nano-encapsulated silicon dioxide phase change material comprises the following steps: A. Mix octadecane and ethyl orthosilicate in a mass ratio of 1:2-3, add 30%-50% of anhydrous ethanol and 0.5%-1% of PVP by volume of the mixture, and stir magnetically at 50-60°C for 30-40 minutes to form a uniform dispersion. B. Add 0.1 M hydrochloric acid to the dispersion to adjust the pH to 4-5, add APTES (10%-15% by mass of ethyl orthosilicate), and react at 60-70°C for 2-3 hours to form amino-modified core-shell particles; C. The amino-modified core-shell particles are dispersed in ethanol, and 5% to 8% of amino-modified nano-silica seeds are added, wherein the amino-modified nano-silica seeds are pretreated with a silane coupling agent, ultrasonically treated for 15 to 20 minutes, and vacuum-dried at 80 to 90° C. for 6 to 8 hours.

[0009] Preferably, step C further comprises: C1. Disperse the nano-silica seeds in anhydrous ethanol to form a suspension with a mass fraction of 3% to 5%, and ultrasonically disperse for 30 to 40 minutes at an ultrasonic power of 200 to 300 W. C2. Adding a silane coupling agent to the suspension after sonication in step C1 in an amount of 8% to 12% of the mass of the nano-silica seed crystals, and adding glacial acetic acid as a catalyst in an amount of 0.5% to 1% of the mass of the silane coupling agent; C3. In a constant temperature water bath at 40-50°C, stir mechanically at 300-400 r / min for 4-6 hours. C4. After the reaction is completed, centrifuge at 8000-10000 r / min for 15-20 minutes to collect the precipitate; C5. Wash the precipitate 3 to 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 60 to 70° C. for 12 to 15 hours to obtain amino-modified nano-silica seeds.

[0010] Preferably, the slurry mixed with polyurethane particles is injected into a mold and vibrated in a 0.5-1.0 T magnetic field with a vibration frequency of 20-40 Hz and an amplitude of 0.1-0.3 mm for 5-10 minutes.

[0011] Preferably, the buffer solution in step S1 is 2-morpholineethanesulfonic acid buffer, and the pH control accuracy is ±0.1.

[0012] Preferably, in step S1, the mass ratio of ethylenediamine to graphene oxide is 1:8-12.

[0013] Preferably, the silane coupling agent in step C2 is an aminosilane coupling agent, including one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane or γ-ureapropyltrimethoxysilane.

[0014] The present invention has at least the following beneficial effects: First, the present invention replaces part of the Portland cement by industrial solid waste such as fly ash, slag powder, and rice husk ash. In Example 2, CO2 emissions per unit volume are reduced by 55.9% compared with traditional materials. In Example 4, alkali-activated rice husk ash is further introduced, and CO2 emissions are reduced to 733 kg / m 3 , a decrease of 60.8%, achieving low-carbonization in the material production stage.

[0015] Second, the present invention utilizes the amino groups on the surface of amino-modified graphene oxide to form chemical crosslinks with the -NCO groups of polyurethane particles to construct an "organic-inorganic" interpenetrating network, enhance the cross-phase interface bonding force, effectively disperse stress, and significantly improve crack resistance. The present invention maintains a balance between low carbon and performance under high solid waste substitution through the "amino-modified graphene oxide-polyurethane" chemical crosslinking mechanism.

[0016] Third, the present invention reduces interface defects and improves matrix density by modifying nano-silica seeds with a silane coupling agent and then combining them with the silica shell through chemical bonding.

[0017] Fourth, the present invention utilizes the graphene oxide-Fe3O4 composite to further suppress thermal deformation of the specimen through the low thermal expansion characteristics of magnetic particles and the "magnetic network" constraint effect.

[0018] Fifth, the present invention utilizes Fe3O4 nanoparticles and modified nano-silica seeds as rigid fillers to fill pores and form a "rigid skeleton", thereby reducing porosity and inhibiting frost heave cracking.

[0019] Sixth, the present invention utilizes the dual adsorption-reaction properties of rice husk ash to stably load the phase change material and block the water penetration path through the gradient interface layer, significantly improving the durability of the roadbed under freeze-thaw cycles and rainwater erosion, and solving the problems of traditional grouting materials such as temperature control failure due to uneven dispersion of the phase change material and high porosity and easy water seepage due to the high porosity of the cement matrix.

[0020] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0022] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0023] EDC refers to 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide; NHS refers to N-hydroxysuccinimide; PVP refers to polyvinylpyrrolidone; and APTES refers to 3-aminopropyltriethoxysilane.

[0024] <Example 1> The preparation method of low-carbon cement-based grouting material comprises the following steps: S1. Preparation of amino-modified graphene oxide: 0.05 g of graphene oxide was dispersed in 50 mL of 2-morpholineethanesulfonic acid (MES) buffer (pH = 5.5 ± 0.1), and ethylenediamine (the mass ratio of ethylenediamine to graphene oxide was 1:12) and carbodiimide / N-hydroxysuccinimide activator were added. The mixture was reacted at 40°C for 4 hours and centrifuged to dry to obtain amino-modified graphene oxide. Aminated graphene oxide and Fe3O4 nanoparticles were dispersed in 200 mL of ethanol at a mass ratio of 1:0.5, ultrasonicated at 300 W for 30 minutes, and centrifuged to obtain a graphene oxide-Fe3O4 composite. S2. Nano-silica seed modification: C1: 5 g of nano-silica seeds were dispersed in 100 mL of 3% ethanol aqueous solution and ultrasonically dispersed at 200 W for 30 minutes to form a uniform suspension; C2: Add 0.4 g of γ-aminopropyltriethoxysilane (KH-550, accounting for 8% of the seed crystal mass) to the suspension, and add 0.002 g of glacial acetic acid (accounting for 0.5% of the silane coupling agent mass) as a catalyst; C3: Place the reaction bottle in a 40°C constant temperature water bath and mechanically stir at 300 rpm for 4 hours. C4: After the reaction, centrifuge at 8000 r / min for 15 minutes and discard the supernatant; C5: Wash the precipitate three times with anhydrous ethanol, centrifugation conditions are the same as above, and dry in a vacuum oven at 60°C for 12 hours to obtain amino-modified nano-silica seeds; Preparation of nano-encapsulated silica phase change materials: A: Mix 5 g of octadecane and 10 g of tetraethyl orthosilicate (mass ratio 1:2), add 0.075 g of polyvinyl pyrrolidone (0.5% of the total mass of the mixture), and stir magnetically at 50°C for 30 minutes until a uniform dispersion is formed; B: Ammonia was added dropwise to the dispersion to adjust the pH to 8. 1 g of 3-aminopropyltriethoxysilane (10% by mass of ethyl orthosilicate) was added at a rate of 2 drops / second. The sol-gel reaction was allowed to proceed at 60°C and 300 r / min for 3 hours to form amino-modified core-shell particles. C: The amino-modified core-shell particles were dispersed in 200 mL of anhydrous ethanol, and 2.5 g of modified nano-silica seeds (accounting for 5% of the mass of the amino-modified core-shell particles) were added. The particles were ultrasonically treated at 200 W for 15 minutes to allow the seeds to be uniformly adsorbed. The particles were then dried in a vacuum oven at 80°C for 8 hours to obtain a core-shell-seed composite phase change material. S2: 35 g of Portland cement, 10 g of fly ash, and 25 g of slag powder were put into a dry powder mixer and dry-mixed at 300 r / min for 3 minutes to form an inorganic matrix. 0.05 g of graphene oxide-Fe3O4 composite was added and mixed for another 5 minutes until uniform. S3: Add sodium sulfate aqueous solution (concentration 10%) accounting for 0.6% of the total mass of the base material to the inorganic matrix, then add polycarboxylate superplasticizer accounting for 0.2% of the total mass of the base material, and finally add 1.0g of phase change material. Control the water-binder ratio to 0.28 and stir at 800 r / min for 5 minutes to form a slurry; S4: Add 0.5g of polyurethane elastic particles in two times: 0.25 g was added for the first time and stirred at 200 r / min for 10 minutes at 25°C to allow the -NCO groups on the particle surface to pre-react with the amino groups of graphene oxide; The remaining 0.25 g was added after the stirring rate was increased to 600 r / min, and stirring was continued for 5 minutes to form a three-dimensional interpenetrating network structure by shear force gradient dispersion; S5: Inject into the mold, place in a 0.5 T magnetic field environment, set the vibration frequency to 20 Hz and the amplitude to 0.1 mm, and vibrate for 5 minutes.

[0025] <Example 2> The preparation method of low-carbon cement-based grouting material comprises the following steps: S1. Preparation of amino-modified graphene oxide and its composite: 0.10 g of graphene oxide was dispersed in 100 mL of MES buffer (pH = 6.0 ± 0.1), ultrasonically dispersed for 45 minutes, and ethylenediamine (ethylenediamine to graphene oxide mass ratio 1:10) and carbodiimide / N-hydroxysuccinimide activator were added. The mixture was reacted at 45°C for 3 hours and centrifuged to dry to obtain amino-modified graphene oxide. Aminated graphene oxide and Fe3O4 nanoparticles were dispersed in 200 mL of ethanol at a mass ratio of 1:0.45, ultrasonicated at 300 W for 45 minutes, and centrifuged to obtain a graphene oxide-Fe3O4 composite. Nano-silica seed modification: C1: 10 g of nano-silica seeds were dispersed in 250 mL of 4% ethanol aqueous solution and ultrasonically dispersed at 250 W for 35 minutes to form a uniform suspension. C2: Add 1g of γ-aminopropyltriethoxysilane (KH-550, accounting for 10% of the seed crystal mass) to the suspension, and add 0.0075g of glacial acetic acid (accounting for 0.75% of the silane coupling agent mass) as a catalyst; C3: Place the reaction bottle in a 45°C constant temperature water bath and mechanically stir at 350 rpm for 5 hours. C4: After the reaction, centrifuge at 9000 rpm for 18 minutes and discard the supernatant; C5: Wash the precipitate three times with anhydrous ethanol, centrifugation conditions are the same as above, and dry in a vacuum oven at 65°C for 13 hours to obtain amino-modified nano-silica seeds; Preparation of nano-encapsulated silica phase change materials: A: Mix 10g of octadecane and 25g of tetraethyl orthosilicate (mass ratio 1:2.5), add 0.26g of polyvinyl pyrrolidone (0.75% of the total mass of the mixture), and stir magnetically at 55°C for 35 minutes until a uniform dispersion is formed; B: Ammonia was added dropwise to the dispersion to adjust the pH to 8.5. 3.125 g of 3-aminopropyltriethoxysilane (12.5% ​​by mass of ethyl orthosilicate) was added at a rate of 2.5 drops / second. The sol-gel reaction was allowed to proceed at 65°C and 400 rpm for 2.5 hours to form amino-modified core-shell particles. C: The amino-modified core-shell particles were dispersed in 300 mL of anhydrous ethanol, and 13 g of modified nano-silica seeds (accounting for 6.5% of the mass of the amino-modified core-shell particles) were added. The particles were ultrasonically treated at 250 W for 20 minutes to uniformly adsorb the seeds, and then dried in a vacuum oven at 85°C for 7 hours to obtain a core-shell-seed composite phase change material. S2. 40 g of Portland cement, 12.5 g of fly ash, and 30 g of slag powder were put into a dry powder mixer and dry-mixed at 300 rpm for 4 minutes to form an inorganic matrix. 0.10 g of graphene oxide-Fe3O4 composite was added and mixed for 5 minutes until uniform. S3. Add a sodium sulfate aqueous solution (concentration 10%) accounting for 0.8% of the total mass of the base material to the inorganic matrix, then add a polycarboxylate water reducer accounting for 0.3% of the total mass of the base material, and finally add 2.0g of phase change material, control the water-binder ratio to 0.30, and stir at a high speed of 1000 r / min for 6 minutes to form a slurry; S4. Add 1.0g of polyurethane elastic particles in two steps: 0.5 g was added for the first time and stirred at 300 r / min at 28 °C for 12 minutes to allow the -NCO groups on the particle surface to pre-react with the amino groups of graphene oxide; The remaining 0.5 g was added after the stirring rate was increased to 700 r / min, and stirring was continued for 8 minutes to form a three-dimensional interpenetrating network structure by shear force gradient dispersion; S5. Inject the mold and place it in a 0.75T magnetic field environment. Set the vibration frequency to 30Hz and the amplitude to 0.2mm, and vibrate for 8 minutes.

[0026] <Example 3> The preparation method of low-carbon cement-based grouting material comprises the following steps: S1. Preparation of amino-modified graphene oxide and its composite: 0.15 g of graphene oxide was dispersed in 150 mL of MES buffer (pH = 6.5 ± 0.1), ultrasonically dispersed for 60 minutes, and then ethylenediamine (ethylenediamine to graphene oxide mass ratio 1:8) and carbodiimide / N-hydroxysuccinimide activator were added. The mixture was reacted at 50°C for 2 hours and centrifuged to dry to obtain amino-modified graphene oxide. Aminated graphene oxide and Fe3O4 nanoparticles were dispersed in 300 mL of ethanol at a mass ratio of 1:0.6, ultrasonicated at 300 W for 60 minutes, and centrifuged to obtain a graphene oxide-Fe3O4 composite. Nano-silica seed modification: C1: 15 g of nano-silica seeds were dispersed in 300 mL of 5% ethanol aqueous solution and ultrasonically dispersed at 300 W for 40 minutes to form a uniform suspension. C2: Add 1.8g of γ-aminopropyltriethoxysilane (KH-550, accounting for 12% of the seed crystal mass) to the suspension, and add 0.018g of glacial acetic acid (accounting for 1% of the silane coupling agent mass) as a catalyst; C3: Place the reaction bottle in a 50°C constant temperature water bath and mechanically stir at 400 rpm for 6 hours; C4: After the reaction is completed, centrifuge at 10,000 rpm for 20 minutes and discard the supernatant; C5: Wash the precipitate with anhydrous ethanol 4 times, centrifugation conditions are the same as above, and dry in a vacuum oven at 70°C for 15 hours to obtain amino-modified nano-silica seeds; Preparation of nano-encapsulated silica phase change materials: A: Mix 15g of octadecane and 45g of tetraethyl orthosilicate (mass ratio 1:3), add 0.6g of polyvinyl pyrrolidone (1% of the total mass of the mixture), and stir magnetically at 60°C for 40 minutes until a uniform dispersion is formed; B: Ammonia was added dropwise to the dispersion to adjust the pH to 9. 6.75 g of 3-aminopropyltriethoxysilane (15% by mass of ethyl orthosilicate) was added at a rate of 3 drops / second. The sol-gel reaction was allowed to proceed at 70°C and 500 rpm for 2 hours to form amino-modified core-shell particles. C: The amino-modified core-shell particles were dispersed in 400 mL of anhydrous ethanol, 28 g of modified nano-silica seeds (accounting for 8% of the mass of the amino-modified core-shell particles) were added, and ultrasonic treatment was performed at 300 W for 20 minutes to uniformly adsorb the seeds. The particles were then dried in a vacuum oven at 90°C for 6 hours to obtain a core-shell-seed composite phase change material. S2. 45 g of Portland cement, 15 g of fly ash, and 35 g of slag powder were put into a dry powder mixer and dry-mixed at 300 rpm for 5 minutes to form an inorganic matrix. 0.15 g of graphene oxide-Fe3O4 composite was added and mixed for another 5 minutes until uniform. S3. Add 1.0% of the total mass of the base material to the inorganic matrix with a sodium sulfate aqueous solution (concentration 10%), then add 0.4% of the total mass of the base material to the polycarboxylate water-reducing agent, and finally add 3.0g of the phase change material. Control the water-binder ratio to 0.32 and stir at 1200 rpm for 8 minutes to form a slurry. S4. Add 1.5g of polyurethane elastic particles in two steps: 0.75 g was added for the first time and stirred at 400 r / min at 30°C for 15 minutes to allow the -NCO groups on the particle surface to pre-react with the amino groups of graphene oxide; The remaining 0.75 g was added after the stirring rate was increased to 800 r / min, and stirring was continued for 10 minutes to form a three-dimensional interpenetrating network structure by shear force gradient dispersion; S5. Inject the mold and place it in a 1.0T magnetic field environment. Set the vibration frequency to 40 Hz and the amplitude to 0.3 mm. Vibrate and mold for 10 minutes.

[0027] Comparative Example 1 The preparation method of the low-carbon cement-based grouting material uses amino-modified graphene oxide instead of the graphene oxide-Fe3O4 complex. The rest of the preparation method is completely consistent with Example 2.

[0028] Comparative Example 2 In the preparation method of the low-carbon cement-based grouting material, the nano-silica seeds were not modified with a silane coupling agent in step C (i.e., steps C1 to C5 were omitted), and untreated nano-silica seeds (accounting for 6.5% of the mass of the amino-modified core-shell particles) were directly used. The rest of the preparation method was exactly the same as in Example 2.

[0029] Comparative Example 3 The preparation method of the low-carbon cement-based grouting material does not add the graphene oxide-Fe3O4 composite, and the rest of the preparation method is completely consistent with Example 2.

[0030] Comparative Example 4 The preparation method of the low-carbon cement-based grouting material does not add modified nano-silica seeds, and the rest of the preparation method is completely consistent with Example 2.

[0031] <Experimental test> (I) Sample preparation The grouting materials were prepared according to the specific steps of Examples 1 to 3 and Comparative Examples 1 to 4. Three parallel specimens with a size of 40 mm × 40 mm × 160 mm were prepared for each group of samples. The performance test was carried out after 28 days of standard curing.

[0032] (2) Test indicators and methods 1. Use a microcomputer-controlled universal material testing machine (loading rate 0.5 MPa / s) to test the compressive strength and flexural strength according to GB / T 17671-1999 "Test Method for Cement Mortar Strength", and take the average value of three specimens; 2. Freeze the specimen at ~20℃ for 4 hours and thaw at 50℃ for 4 hours as one cycle. Record the number of cycles when cracks appear on the specimen surface or the mass loss exceeds 5%. Test the number of freeze-thaw cycles. 3. Test the specimens using a thermomechanical analyzer (TMA, heating rate 5°C / min, test temperature range: ~20°C~60°C) to calculate the coefficient of linear thermal expansion (CTE, unit: 10 -6 / ℃); 4. Use a differential scanning calorimeter (DSC, heating rate 10°C / min, nitrogen atmosphere) to record the temperature at which the core material octadecane begins to leak (i.e., the temperature at which an abnormal exothermic peak appears on the DSC curve) to test the heat leakage temperature of the phase change material.

[0033] The test results are shown in Table 1 below: Table 1 Performance test of the test pieces prepared in each group of Examples 1 to 3 and Comparative Examples 1 to 4 According to the data in Table 1, in terms of strength, among Examples 1 to 3, Example 2 (65.8 MPa / 11.2 MPa)> Example 3 (58.9 MPa / 9.8 MPa)> Example 1 (52.3 MPa / 8.5 MPa). Analysis shows that the increase in the amount of graphene oxide and Fe3O4 composite can enhance the material network structure, but excessive use (such as in Example 3) may lead to uneven dispersion or increase the burden on the matrix, resulting in a decrease in strength. In terms of freeze-thaw cycles, Example 2 (350 times)> Example 3 (320 times)> Example 1 (280 times). Analysis shows that the increase in the amount of modified seed crystals (Example 2 accounts for 6.5% of the amino-modified core-shell particles) improves the material density and interfacial bonding strength, thereby enhancing the freeze-thaw resistance. In terms of thermal expansion coefficient, Example 2 (6.5×10 -6 / ℃) is the lowest, indicating that it has the best thermal stability, which may be related to the synergistic temperature regulation effect of nano-encapsulated silica phase change material and the composite; Compared with Example 2, the strength of Comparative Example 1 decreased, indicating that the Fe3O4 nanoparticles promoted the uniform dispersion of graphene oxide through magnetic effects and formed a "magnetic network" to enhance the continuity of the matrix. After the nanoparticles were missing, the interface defects increased and the strength decreased, while the freeze-thaw cycles decreased, indicating that the rigid particle filling effect of Fe3O4 can reduce the porosity and improve the freeze-thaw resistance. The thermal expansion coefficient increased, indicating that the low thermal expansion characteristics of Fe3O4 can inhibit the thermal deformation of the matrix. After the nanoparticles were missing, the thermal stability of the material decreased. The above shows that the introduction of the Fe3O4 complex is crucial to improving strength, durability and thermal stability. Compared with Example 2, the strength of Comparative Example 2 decreased, indicating that the surface of the unmodified seed crystal lacked active groups and was bonded to the matrix (silica shell) by physical adsorption. The interfacial bonding force was weak and it easily became a stress concentration point. The freeze-thaw cycle was reduced, indicating that the modified seed crystal formed a chemical bond through the silane coupling agent, improved the interfacial compatibility, and inhibited the propagation of cracks during the freeze-thaw process. The unmodified seed crystal was easy to fall off, resulting in structural degradation. The thermal expansion coefficient increased, indicating that the modified seed crystal formed a "rigid skeleton" with the matrix to constrain thermal deformation. The interface slip of the unmodified seed crystal increased thermal expansion. The above shows that seed crystal modification is a key step in improving interfacial bonding strength and material durability. Compared with Example 2 and Comparative Example 1, the strength of Comparative Example 3 is greatly reduced, indicating that the amino-modified graphene oxide forms chemical bonds with polyurethane (-NCO) and cement hydration products through amino groups (-NH2), thereby enhancing cross-phase interface connection. The non-amino-modified graphene oxide relies solely on physical adsorption, with weak binding force, and the freeze-thaw cycle is sharply reduced, indicating that amino modification can improve the dispersibility of graphene oxide in the polar matrix and reduce defects caused by agglomeration. The non-amino material is prone to agglomeration to form large-sized defects, accelerating freeze-thaw damage, and the thermal expansion coefficient surges, indicating that the amino-modified graphene oxide restricts the thermal motion of the matrix molecules through hydrogen bonds, while the non-amino material lacks such an effect and has significant thermal deformation. The above shows that amino modification is a necessary condition for graphene oxide to exert its reinforcing effect; Compared with Example 2 and Comparative Example 2, the strength of Comparative Example 4 decreases, indicating that the nano-silica seeds can fill the pores as "nano-fillers" and improve the density of the matrix. After they are omitted, the internal porosity of the material increases, the bearing capacity decreases, and the freeze-thaw cycles decrease, indicating that even if the seeds are not modified, they can still hinder the expansion of cracks by physical filling. After they are omitted, the matrix is ​​more likely to produce through cracks due to frost heave, and the thermal expansion coefficient increases, indicating that the high elastic modulus of the seeds can inhibit the thermal expansion of the matrix. After they are omitted, the thermal deformation ability of the material is significantly enhanced. The above shows that the introduction of nano-silica seeds (regardless of whether they are modified) plays a fundamental role in improving the density and rigidity of the material, but the effect is better after modification.

[0034] <Example 4> The preparation method of low-carbon cement-based grouting material comprises the following steps: S1. Alkali-activated rice husk ash pretreatment: 100 g of rice husk ash was added with 6% sodium hydroxide solution (liquid-to-solid ratio 3:1) and soaked for 24 h. After filtration, the product was washed with deionized water until neutral, dried at 80 °C for 12 h, and crushed to a particle size of ≤50 μm; 5 g of alkali-activated pretreated rice husk ash was mixed with 1.5 g of nano-encapsulated silica phase change material (prepared in Example 2) and stirred at 300 r / min for 30 minutes to allow the phase change material to be adsorbed in the pores of the rice husk ash.

[0035] S2. Base material mixing: 40 g of Portland cement, 12 g of fly ash, 30 g of slag powder, and 5 g of rice husk ash with phase change material adsorption were put into a dry powder mixer and dry mixed at 300 rpm for 4 minutes; 0.10 g of graphene oxide-Fe3O4 composite (prepared in Example 2) was added and mixing was continued for 5 minutes until uniform.

[0036] S3. Preparation of slurry: Add 0.8% of sodium sulfate aqueous solution (concentration 10%) and 0.3% of polycarboxylic acid water-reducing agent to the base material, control the water-binder ratio to 0.30, and stir at a high speed of 1000 r / min for 6 minutes to form a slurry.

[0037] S4, polyurethane step-by-step dispersion: 0.5 g of polyurethane particles (prepared in Example 2) were added for the first time, and stirred at a low speed of 300 r / min for 12 minutes at 28°C; The remaining 0.5 g of polyurethane particles was added under high-speed stirring at 700 r / min and stirring was continued for 8 minutes.

[0038] S5, vibration molding: injection into the mold, vibration frequency 30 Hz, amplitude 0.2 mm, vibration molding for 8 minutes, standard curing for 28 days.

[0039] Comparative Example 5 The preparation method of the low-carbon cement-based grouting material omits the rice husk ash pretreatment step and directly uses untreated rice husk ash (without adsorption of phase change material). The rest is the same as in Example 4.

[0040] Comparative Example 6 The preparation method of the low-carbon cement-based grouting material is the same as Example 4 except that rice husk ash is not added.

[0041] Grouting materials were prepared according to the specific steps of Example 4 and Comparative Examples 5-6. Three parallel specimens were prepared for each group of samples, with a size of 40 mm × 40 mm × 160 mm. After 28 days of standard curing, performance tests were conducted to detect compressive strength, flexural strength, number of freeze-thaw cycles, and water permeability coefficient. The water permeability coefficient was measured using a concrete permeameter, and its calculation formula is: , where Q is the amount of water that penetrates, L is the thickness of the specimen, A is the penetration area, t is the time, and ΔP is the water pressure difference. The test results are shown in the following table: Table 2 Performance test of the test pieces prepared in Example 4 and Comparative Examples 5-6 According to the data in Table 2, the water permeability coefficient of Example 4 (1.2×10 -8 m / s) is only 31.6% of that in comparative example 5, and the anti-permeability is significantly improved, indicating that the alkali-activated rice husk ash significantly reduces the pore penetration by adsorbing the phase change material and forming a CSH gel layer; The number of freeze-thaw cycles in Example 4 (340 times) increased by 61.9% compared to Comparative Example 5 (210 times), and the freeze-thaw resistance was significantly enhanced, indicating that the gradient interface layer effectively inhibited the crack propagation caused by frost heave stress. The compressive strength of Example 4 (63.2 MPa) is 15.5% higher than that of Comparative Example 5, which may be due to the reaction of active silicon in rice husk ash with cement to form a dense structure, while the flexible phase change material relieves stress concentration.

[0042] <Low carbon performance test> To verify the low-carbon characteristics of the material, the CO2 emissions per unit volume and the low-carbon efficiency index of the cementitious material were calculated for Example 2, Example 4, Comparative Example 3, and Comparative Example 5. The traditional grouting material (cement content: 100%) was used as the control group. The specific test process and data are as follows: 1. CO2 emissions per unit volume (raw material production stage) Principle: According to the carbon emission factors in the production process of each raw material, the CO2 emissions per unit mass of grouting material are calculated, and the emissions per unit volume are converted into the density of the material. The calculation formula is: CO2 (kg / m 3 )=∑(m i ×CF i )×ρ, where m i Refers to the mass proportion of each raw material (%); Cf i Refers to the carbon emission factor of raw materials (kgCO2 / kg), Portland cement: 0.85, fly ash: 0.1, slag powder: 0.05, rice husk ash: 0.02, other auxiliary materials (such as polyurethane, nanomaterials): carbon emissions can be ignored (accounting for <1%); ρ refers to the material density (taken as 2200 kg / m 3 , based on conventional values ​​for cement-based materials), where waste residue refers to fly ash + slag powder + rice husk ash.

[0043] 2. Low carbon efficiency index of cementitious materials Definition: CO2 emission reduction per unit of cementitious material (Portland cement + waste slag), reflecting the low-carbon benefit of replacing cement with waste slag. Low-carbon efficiency index = [(cement usage of traditional materials − cement usage of sample) × CF 水泥 ] / Total mass of sample cementitious material, unit: kgCO2 / kg cementitious material.

[0044] The test results are shown in Table 3 below: Table 3 Low carbon performance test of the specimens prepared in each group According to the data in Table 3, in terms of CO2 emissions per unit volume, Example 4 reduces CO2 emissions by 13.3% (733 vs 845 kg / m 3 In Comparative Example 5, due to the poor adsorption of untreated rice husk ash, the phase change material did not effectively fill the pores, and the amount of adhesive needed to be increased. The emission was slightly higher than that of Example 4 (741 vs 733 kg / m 3In terms of low-carbon efficiency index, Example 4 has the highest index (0.52), indicating that 0.52 kg of CO2 emissions can be reduced per kilogram of cementitious material. The volcanic ash effect of rice husk ash significantly improves the utilization rate of waste residues. However, since Comparative Example 3 does not add the graphene oxide-Fe3O4 composite, the interface bonding force of the cementitious material is weak, and the amount of cement needs to be increased (the actual replacement rate remains unchanged). Therefore, the index is the same as that of Example 2, but the mechanical properties are reduced (see Table 1). Therefore, it can be shown that the combined use of fly ash, slag, and rice husk ash of the present invention maximizes the potential of solid waste to replace cement (total replacement rate of 56.4%). Compared with the traditional grouting material in the control group, the CO2 emission of Example 4 was reduced by 60.8% (733 vs 1870 kg / m 3 ), the low-carbon efficiency index reaches 0.52, indicating the core feature of the "low-carbon cement-based" of the present invention; Compared with the traditional grouting material in the control group, the untreated rice husk ash in comparative example 5 has limited actual emission reduction effect due to the failure to adsorb phase change material, indicating the necessity of the "alkali excitation pretreatment" of the rice husk ash of the present invention.

[0045] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. Low carbon cement-based grouting material, characterized in that: Includes the following components: Base material: composed of 35-45 parts by weight of Portland cement, 10-15 parts of fly ash, 25-35 parts of slag powder, 0.8-1.5 parts of polyurethane particles, 1.6-3.0 parts of nano-encapsulated silica phase change material, and 0.05-0.15 parts of amino-modified graphene oxide, wherein the fly ash and slag powder together account for 35%-50% of the total mass of the base material, the mass ratio of polyurethane particles to nano-encapsulated silica phase change material is 1:2-3, and the amino-modified graphene oxide is modified by grafting with ethylenediamine, and the surface amino groups form chemical crosslinks with the -NCO groups of the polyurethane particles; Sodium sulfate: 0.6%~1.0% of the total mass of the base material; Polycarboxylate water reducer: 0.2%~0.4% of the total mass of the base material.

2. The low-carbon cement-based grouting material according to claim 1, characterized in that: The surface of graphene oxide is modified by amino and loaded with magnetic Fe3O4 nanoparticles to form a graphene oxide-Fe3O4 composite, with the addition amount being 0.05% to 0.15% of the total mass of the base material; The mass ratio of Fe3O4 nanoparticles to amino-modified graphene oxide is 1:0.5~1.0, and they are connected to the amino groups through coordination bonds.

3. The low-carbon cement-based grouting material according to claim 1, characterized in that: The base material also includes 2 to 5 parts by weight of alkali activated pretreated rice husk ash; Rice husk ash was soaked in a sodium hydroxide solution with a mass fraction of 5% to 8% and then dried and crushed to a particle size of ≤50 μm. Nano-encapsulated silica phase change material was adsorbed in its porous structure and its surface reacted with the hydration products of Portland cement to form CSH gel.

4. The method for preparing the low-carbon cement-based grouting material according to any one of claims 1 to 3, wherein: The following steps are involved: S1. Preparation of amino-modified graphene oxide composite: Graphene oxide was dispersed in a buffer solution with a pH of 5.5-6.5, and ethylenediamine and EDC / NHS activator were added in a mass ratio of 1:8-12. The mixture was reacted at 40-50°C for 2-4 hours, and centrifuged to obtain amino-modified graphene oxide. When preparing the graphene oxide-Fe3O4 composite, amino-modified graphene oxide and Fe3O4 nanoparticles are dispersed in ethanol at a mass ratio of 1:0.3-0.6, and ultrasonicated for 30-60 minutes. The magnetic particles are loaded through the coordination between the amino groups and the metal ions on the Fe3O4 surface to obtain the graphene oxide-Fe3O4 composite. S2. Low carbon base material mixing: Portland cement, fly ash, slag powder and rice husk ash are dry-mixed for 3-5 minutes to form an inorganic matrix, and then amino-modified graphene oxide or graphene oxide-Fe3O4 composite is added and mixed until uniform; S3. Preparation of low carbon slurry: To the mixture in step S2, sodium sulfate solution, polycarboxylate water-reducing agent and nano-encapsulated silica phase change material were sequentially added, the water-binder ratio was controlled to be 0.28-0.32, and the mixture was stirred at 800-1200 r / min to form a slurry; S4, gradient dispersion molding: The polyurethane particles were added in two batches: 50% of the polyurethane particles were first added to the slurry and pre-reacted under low-speed stirring at 200-400 r / min, and the remaining 50% of the polyurethane particles were dispersed under high-speed shear at 600-800 r / min, and finally vibrated and formed under a magnetic field to form a three-dimensional interpenetrating network structure.

5. The method for preparing the low-carbon cement-based grouting material according to claim 4, wherein: The preparation method of nano-encapsulated silicon dioxide phase change material comprises the following steps: A. Mix octadecane and ethyl orthosilicate in a mass ratio of 1:2-3, add 30%-50% of anhydrous ethanol and 0.5%-1% of PVP by volume of the mixture, and stir magnetically at 50-60°C for 30-40 minutes to form a uniform dispersion. B. Add 0.1 M hydrochloric acid to the dispersion to adjust the pH to 4-5, add APTES (10%-15% by mass of ethyl orthosilicate), and react at 60-70°C for 2-3 hours to form amino-modified core-shell particles; C. The amino-modified core-shell particles are dispersed in ethanol, and 5% to 8% of amino-modified nano-silica seeds are added, wherein the amino-modified nano-silica seeds are pretreated with a silane coupling agent, ultrasonically treated for 15 to 20 minutes, and vacuum-dried at 80 to 90° C. for 6 to 8 hours.

6. The method for preparing the low-carbon cement-based grouting material according to claim 5, wherein: Step C also includes: C1. Disperse the nano-silica seeds in anhydrous ethanol to form a suspension with a mass fraction of 3% to 5%, and ultrasonically disperse for 30 to 40 minutes at an ultrasonic power of 200 to 300 W. C2. Adding a silane coupling agent to the suspension after sonication in step C1 in an amount of 8% to 12% of the mass of the nano-silica seed crystals, and adding glacial acetic acid as a catalyst in an amount of 0.5% to 1% of the mass of the silane coupling agent; C3. In a constant temperature water bath at 40-50°C, stir mechanically at 300-400 r / min for 4-6 hours. C4. After the reaction is completed, centrifuge at 8000-10000 r / min for 15-20 minutes to collect the precipitate; C5. Wash the precipitate 3 to 4 times with anhydrous ethanol, and then dry it in a vacuum drying oven at 60 to 70° C. for 12 to 15 hours to obtain amino-modified nano-silica seeds.

7. The method for preparing a low-carbon cement-based grouting material according to claim 4, wherein: The slurry mixed with polyurethane particles is injected into the mold and vibrated in a 0.5-1.0 T magnetic field with a vibration frequency of 20-40 Hz and an amplitude of 0.1-0.3 mm for 5-10 minutes.

8. The method for preparing a low-carbon cement-based grouting material according to claim 4, wherein: The buffer solution in step S1 is 2-morpholineethanesulfonic acid buffer, and the pH control accuracy is ±0.

1.

9. The method for preparing a low-carbon cement-based grouting material according to claim 4, wherein: In step S1, the mass ratio of ethylenediamine to graphene oxide is 1:8-12.

10. The method for preparing a low-carbon cement-based grouting material according to claim 6, wherein: The silane coupling agent in step C2 is an aminosilane coupling agent, including one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane or γ-ureapropyltrimethoxysilane.

Images