Graphene oxide modified cement-based grouting material as well as preparation method and application thereof

Abstract

The invention relates to a graphene oxide modified cement-based grouting material as well as a preparation method and application thereof. The graphene oxide modified cement-based grouting material is prepared from cement, graphene oxide, silica fume, a polycarboxylate superplasticizer, an accelerator and water. The invention also provides a preparation method of the graphene oxide modified cement-based grouting material, which comprises the following steps: adding GO into an aqueous solution containing a polycarboxylic acid water reducer, stirring and then carrying out ultrasonic treatment to form a GO suspension; premixing silica fume and cement to obtain a dry mixture; and adding the GO suspension into the dry mixture, mixing and stirring, and then doping an accelerator to obtain the graphene oxide modified cement-based grouting material. The invention further provides application of the graphene oxide modified cement-based grouting material as a reinforcement treatment material for loose accumulation bodies and broken rock stratums. The GO modified grouting material solves the problem that the performance of a cement-based material is affected due to the fact that GO is not uniformly dispersed and larger aggregates are easily formed in the existing GO modified grouting material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering reinforcement materials, in particular to a graphene oxide modified cement-based grouting material and a preparation method and application thereof. BACKGROUND

[0002] Loose accumulation bodies formed by residual accumulation, alluvial-proluvial accumulation and landslide accumulation are widely distributed in the southwest mountainous area and the Three Gorges Reservoir area in China. Such loose accumulation bodies are prone to induce geological disasters such as landslides and debris flows under the action of rainfall or groundwater due to their loose structure, strong water permeability and easy deformation instability. For example, the accumulation bodies in the Tibet section of National Highway 318 and Jiuzhaigou have caused major disasters many times due to poor stability after the earthquake. In tunnel engineering, such strata are prone to cause problems such as instability of side and overhanging slopes, collapse of the working face and settlement of the foundation. Grouting technology has become an important means for reinforcing loose accumulation bodies due to its economic efficiency and convenient construction. However, traditional grouting materials have defects such as high brittleness and insufficient toughness, which cannot meet the engineering requirements.

[0003] To solve the above problems, domestic and foreign researchers have improved the performance of grouting materials by adding mineral admixtures (fly ash, silica fume, bentonite, etc.) and chemical admixtures (polyurethane, acrylamide, etc.). Mineral admixtures can improve the stability, strength and environmental benefits of the grout, but chemical admixtures can improve specific properties, but have problems such as insufficient strength and environmental pollution. In recent years, nanomaterials have become a research hotspot due to their unique reinforcing effect, among which graphene oxide (GO) is particularly outstanding. As a two-dimensional nanomaterial, GO has a large specific surface area and strong hydrophilicity, which can significantly improve the mechanical properties of cement-based materials: by optimizing the hydration process and pore structure, the compressive and flexural strengths are improved; by inhibiting crack propagation, the brittleness of the material is improved; at the same time, the frost resistance, impermeability and corrosion resistance are also enhanced. Studies have shown that GO modified grouting materials can achieve a synergistic improvement in strength and toughness while maintaining excellent construction performance, providing a new solution for the reinforcement of loose accumulation bodies.

[0004] However, although the addition of GO can significantly improve the performance of cement-based materials, studies have found that GO nanosheets can undergo chemical cross-linking with divalent cations (such as Ca 2+ ) in the cement matrix to form larger agglomerates. This cross-linking and agglomeration phenomenon reduces the uniformity of GO dispersion in the matrix, which in turn affects its improvement effect on the performance of cement-based materials (including fluidity, bleeding rate, stone formation rate and compressive strength, etc.), limiting the application of graphene oxide in grouting material engineering. SUMMARY

[0005] Therefore, the present application aims to provide a graphene oxide modified cement-based grouting material, a preparation method and application thereof, so as to solve the problem of uneven dispersion of GO in the existing GO modified grouting material, easy formation of larger agglomerates, and thus affecting the performance of the cement-based material (including fluidity, bleeding rate, stone rate, compressive strength and flexural strength).

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A graphene oxide modified cement-based grouting material, which is composed of cement, graphene oxide, silica fume, polycarboxylic acid water reducer, accelerator and water.

[0007] According to the above technical means, the active components of the silica fume react with Ca(OH)2 to generate C-S-H gel in the cement-based material, which not only consumes free Ca 2+ Prevents its combination with graphene oxide, and densifies the cement-based structure through the micro-particle filling effect. At the same time, the additional graphene oxide, polycarboxylic acid water reducer and accelerator, synergistically, significantly improve the mechanical strength, crack toughness and slurry stability of the grouting material. Effectively solve the problem of uneven dispersion of GO in the existing GO modified grouting material, easy formation of larger agglomerates, and thus affecting the performance of the cement-based material (including fluidity, bleeding rate, stone rate, compressive strength and flexural strength).

[0008] Among them, graphene oxide, with its unique two-dimensional nanostructure and rich oxygen-containing functional groups, not only realizes uniform dispersion in the cement matrix through the polycarboxylic acid water reducer, but also promotes the cement hydration reaction, forms a multi-scale reinforced network structure, and significantly improves the compressive strength and flexural toughness of the material. The addition of silica fume further optimizes the microstructure of the material, and its active components react with the cement hydration products to generate additional C-S-H gel, while consuming free Ca 2+ Prevents its combination with GO, and realizes the synergistic reinforcement effect.

[0009] Preferably, the addition amount of graphene oxide is 0.03-0.06% of the total mass of cement and silica fume.

[0010] Preferably, the addition amount of silica fume is 5-10% of the total mass of cement and silica fume.

[0011] Preferably, the addition amount of polycarboxylic acid water reducer is 0-0.1% of the total mass of cement and silica fume.

[0012] Preferably, the addition amount of accelerator is 1-2% of the total mass of cement and silica fume.

[0013] Preferably, the addition amount of accelerator is 1.5% of the total mass of cement and silica fume.

[0014] Preferably, the water-cement ratio of the graphene oxide modified cement-based grouting material is 0.4-0.5.

[0015] The water-cement ratio is calculated according to the formula: water-cement ratio = weight of water / (weight of cement + weight of silica ash).

[0016] Preferably, the method for preparing graphene oxide comprises the following steps: The graphene oxide is obtained by sequentially subjecting flake graphite to chemical oxidation by concentrated sulfuric acid and potassium permanganate, and then placing it in water for ultrasonic treatment to exfoliate 2-4 layers. The exfoliated graphene oxide has 1-15 layers of graphite layers, a single layer thickness of 2-5 um, and a flake diameter of 20-40 um.

[0017] The concentrated sulfuric acid has a concentration of 98%. The flake graphite is sequentially immersed in concentrated sulfuric acid with a concentration of 98% and potassium permanganate solution with a concentration of 0.02 mol / L for 10 minutes, and then placed in pure water for ultrasonic treatment, so as to overcome the interlayer van der Waals force by mechanical force to achieve single-layer or few-layer exfoliation. The exfoliated product is graphene oxide, which has high exfoliation degree and good dispersibility in aqueous solution.

[0018] By using the product exfoliated from flake graphite as the raw material of graphene oxide, due to its high exfoliation degree, large aspect ratio, and good dispersibility in aqueous solution, when it is incorporated into the cement-based system, it can provide nucleation sites for the growth of hydration products, improve the mechanical properties of the cement-based material, and also improve the durability of the material.

[0019] Preferably, the accelerator is selected from alumina-silica clinker, and the method for preparing the alumina-silica clinker comprises the following steps: The alumina-silica clinker is obtained by calcining bauxite, soda ash and quicklime at a temperature of 1250-1300℃ for 1-2 hours; The fineness of the obtained alumina-silica clinker is less than 12.6%; The bauxite, soda ash (Na2CO3) and quicklime (CaO) are in a mass ratio of 50-70%:15-25%:10-25%; By selecting alumina-silica clinker as the accelerator, the setting time of the grouting material is effectively shortened, and the early strength development of the stone body is effectively promoted.

[0020] The chemical composition and content of the bauxite are as follows: aluminum oxide (Al2O3), content of 39%-80%; silicon dioxide (SiO2), content of 19%-60%; iron oxide (Fe2O3), content of 1%-2%.

[0021] Preferably, the cement is selected from P.O 42.5 grade Portland cement, and the loss on ignition is 2-4%.

[0022] Preferably, the loss on ignition of the cement is 3.2%.

[0023] Preferably, the specific surface area of the silica fume is 20-25 m 2 / g.

[0024] Preferably, the specific surface area of the silica fume is 22.1 m 2 / g.

[0025] Preferably, the water-reducing rate of the polycarboxylic acid water-reducing agent is 15-25%.

[0026] Preferably, the water-reducing rate of the polycarboxylic acid water-reducing agent is 19%.

[0027] The application also provides a preparation method of the graphene oxide modified cement-based grouting material as described in the application, comprising the following steps: adding graphene oxide (GO) into an aqueous solution containing a polycarboxylic acid water-reducing agent, stirring first and then ultrasonic treatment, to form a uniformly dispersed GO suspension; premixing silica fume and cement to ensure uniform mixing, to obtain dry mixture; slowly adding the GO suspension into the dry mixture, mechanically mixing and stirring until the fluidity of the slurry meets the standard, and then adding setting accelerator to adjust the setting time, to obtain the graphene oxide modified cement-based grouting material.

[0028] Preferably, the ultrasonic treatment time is 10-20 min.

[0029] Preferably, the premixing time is 1-2 min.

[0030] Preferably, the mixing and stirring time is 3-5 min.

[0031] Preferably, the fluidity of the prepared graphene oxide modified cement-based grouting material is greater than 200 mm, the stone rate is greater than 99%, and the bleeding rate is less than or equal to 0.5%.

[0032] The application also provides an application of the graphene oxide modified cement-based grouting material as described in the application, and the graphene oxide modified cement-based grouting material is used for reinforcing treatment of loose bulk bodies and broken rock strata.

[0033] Preferably, the graphene oxide modified cement-based grouting material is used for tunnel support, slope reinforcement and geological disaster prevention.

[0034] The application has the following beneficial effects: The graphene oxide modified cement-based grouting material of the present application adopts ordinary Portland cement as the base, and by mixing graphene oxide, silica fume, polycarboxylate superplasticizer and accelerator as the admixture, the active components of silica fume in the cement-based material react with Ca(OH)2 to generate C-S-H gel, which not only consumes free Ca 2+ Prevent its combination with graphene oxide, and the cement-based structure is densified by the micro-particle filling effect, and the mechanical properties, slurry stability and crack resistance of the grouting material are significantly improved by the synergistic effect of graphene oxide, polycarboxylate superplasticizer and accelerator, GO is added into the slurry after being dispersed by the polycarboxylate superplasticizer, which effectively improves the dispersibility and hydration activity, and is suitable for reinforcement and treatment of poor geological conditions such as loose bulk body. The graphene oxide modified cement-based grouting material of the present application has high strength, high toughness and excellent construction performance, and can be widely applied to tunnel support, slope reinforcement and geological disaster prevention engineering, and is especially suitable for loose stratum grouting reinforcement requirements, and has popularization and application value in the field of geotechnical engineering reinforcement materials. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a flow degree determination result graph of the grouting material; Figure 2 is a stone rate and water separation rate determination result graph of the grouting material; Figure 3 is a compressive strength and flexural strength determination result graph of the grouting material; Figure 4 is a SEM graph of the corresponding test piece obtained after curing of the grouting material prepared in Comparative Example 1; Figure 5 is a SEM graph of the corresponding test piece obtained after curing of the grouting material prepared in Example 1; Figure 6 is a SEM graph of the corresponding test piece obtained after curing of the grouting material prepared in Example 2. DETAILED DESCRIPTION

[0036] The embodiments of the present application will be described below with reference to the preferred embodiments, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure in the specification. The present application can also be implemented or applied by different specific embodiments, and various modifications or changes can be made to the details in the specification based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, and are not intended to limit the protection scope of the present application.

[0037] The application provides a graphene oxide modified cement-based grouting material and a preparation method and application thereof, to solve the problem of uneven dispersion of GO in the existing GO modified grouting material, easy formation of larger agglomerates, and influence on the performance of the cement-based material (including fluidity, bleeding rate, stone rate, compressive strength and flexural strength).

[0038] The graphene oxide modified cement-based grouting material is composed of cement, graphene oxide, silica fume, polycarboxylic acid water reducer, accelerator and water.

[0039] The active components of the silica fume react with Ca(OH)2 to generate C-S-H gel in the cement-based material, which not only consumes free Ca 2+ Prevents its combination with graphene oxide, and densifies the cement-based structure through the micro-particle filling effect. At the same time, the addition of graphene oxide, polycarboxylic acid water reducer and accelerator significantly improves the mechanical strength, crack toughness and slurry stability of the grouting material. The problem of uneven dispersion of GO in the existing GO modified grouting material, easy formation of larger agglomerates, and influence on the performance of the cement-based material (including fluidity, bleeding rate, stone rate, compressive strength and flexural strength) is effectively solved.

[0040] The graphene oxide, with its unique two-dimensional nano structure and rich oxygen-containing functional groups, not only realizes uniform dispersion in the cement-based body through the polycarboxylic acid water reducer, but also promotes the cement hydration reaction to form a multi-scale reinforcing network structure, significantly improving the compressive strength and flexural toughness of the material. The addition of silica fume further optimizes the microstructure of the material, and the active components thereof react with the cement hydration products to generate additional C-S-H gel, while consuming free Ca 2+ Prevents its combination with GO, and realizes a synergistic reinforcing effect.

[0041] In some embodiments, the addition amount of graphene oxide is 0.03-0.06% of the total mass of cement and silica fume.

[0042] In some embodiments, the addition amount of silica fume is 5-10% of the total mass of cement and silica fume.

[0043] In some embodiments, the addition amount of polycarboxylic acid water reducer is 0-0.1% of the total mass of cement and silica fume.

[0044] In some embodiments, the addition amount of accelerator is 1-2% of the total mass of cement and silica fume.

[0045] In some embodiments, the water-cement ratio of the graphene oxide modified cement-based grouting material is 0.4-0.5.

[0046] The calculation formula of the water-cement ratio is: water-cement ratio = weight of water / (weight of cement + weight of silica fume).

[0047] In some embodiments, the method for preparing graphene oxide comprises the following steps: The flake graphite is sequentially subjected to chemical oxidation by concentrated sulfuric acid and potassium permanganate, and then placed in water for ultrasonic treatment, so as to overcome the interlayer van der Waals force by mechanical force to realize single-layer or few-layer exfoliation. The product after exfoliation is graphene oxide, which has 1-15 layers of graphite layers, a single-layer thickness of about 2-5 um, high exfoliation degree, a very large aspect ratio, and good dispersibility in aqueous solution with a particle size (D50) of 20-40 um.

[0048] In some embodiments, the accelerator is selected from alumina-silicate clinker. The method for preparing alumina-silicate clinker comprises the following steps: The bauxite, soda ash and quicklime are calcined at a temperature of 1250-1300℃ for 1-2 hours to obtain alumina-silicate clinker. The fineness of the obtained alumina-silicate clinker is less than 12.6%.

[0049] The bauxite, soda ash and quicklime are in a mass percentage of 50-70%: 15-25%: 10-25%.

[0050] In some embodiments, the cement is selected from P.O 42.5 grade Portland cement, and the loss on ignition is 2-4%.

[0051] In some embodiments, the loss on ignition of the cement is 3.2%.

[0052] In some embodiments, the specific surface area of the silica fume is 20-25 m 2 / g.

[0053] In some embodiments, the specific surface area of the silica fume is 22.1 m 2 / g.

[0054] In some embodiments, the water-reducing rate of the polycarboxylic acid water reducer is 15-25%.

[0055] In some embodiments, the water-reducing rate of the polycarboxylic acid water reducer is 19%.

[0056] In some embodiments, a method for preparing the graphene oxide modified cement-based grouting material according to any one of the above embodiments is also provided, comprising the following steps: The graphene oxide (GO) is added into an aqueous solution containing a polycarboxylic acid water reducer, and then stirred and ultrasonically treated to form a uniformly dispersed GO suspension; The silica fume and the cement are premixed to ensure uniform mixing, and a dry mixture is obtained; The GO suspension is slowly added into the dry mixture, and mechanically mixed and stirred until the slurry fluidity meets the standard, and then an accelerator is added to adjust the setting time, to obtain the graphene oxide modified cement-based grouting material.

[0057] In some embodiments, the time for ultrasonic treatment is 10-20 min.

[0058] In some embodiments, the time for premixing is 1-2 min.

[0059] In some embodiments, the time for mixing stirring is 3-5 min.

[0060] In some embodiments, the prepared graphene oxide modified cement-based grouting material has a fluidity greater than 200 mm, a stone rate greater than 99%, and a bleeding rate less than or equal to 0.5%.

[0061] In some embodiments, the graphene oxide modified cement-based grouting material is also provided for use as a reinforcing treatment material for loose bulk bodies and broken rock strata.

[0062] In some embodiments, the graphene oxide modified cement-based grouting material is used for tunnel support, slope reinforcement, and geological disaster prevention.

[0063] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the graphene oxide modified cement-based grouting material, its preparation method and application will be further described in detail below in combination with specific embodiments and drawings. Obviously, the specific embodiments described are only part of the embodiments of the present application, not all. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its applications. Based on the specific embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0064] Unless otherwise specified in the specific embodiments, the technology or conditions are carried out according to the technology or conditions described in the literature in the art or according to the product instructions. Unless otherwise specified, the reagents or instruments used are conventional products that can be obtained by purchase.

[0065] In the following examples, the cement used is P.O42.5 Portland cement produced by Wuxi Tian Shan Cement Co., Ltd., the composition and content of which are shown in Table 1.

[0066] Table 1 shows the composition and content of P.O42.5 Portland cement In the following examples, the preparation method of graphene oxide includes the following steps: The flake graphite is sequentially soaked in 98% concentrated sulfuric acid and 0.02 mol / L potassium permanganate solution for 10 minutes to realize chemical oxidation, and then is placed in pure water for ultrasonic treatment, so as to overcome the interlayer van der Waals force by mechanical force to realize the exfoliation of 2-4 layers. The exfoliated product is graphene oxide, which has 1-15 layers of graphite layers, a single layer thickness of about 2-5 um, a high degree of exfoliation, a great aspect ratio, good dispersibility in aqueous solution, and a flake diameter of 20-40 um.

[0067] The physical parameters of the graphene oxide are shown in Table 2.

[0068] Table 2 is the physical parameters of GO The silica fume used in the following examples is produced by Henan Pulin Foundry Material Co., Ltd., which has the characteristics of high activity and fine particles, and the physical parameters are shown in Table 3.

[0069] Table 3 is the product parameter of silica fume The polycarboxylic acid water reducing agent used in the following examples is produced by Kelly Chemical Industry, which has the advantages of high water reducing rate, good dispersibility, and small addition amount, and the physical parameters are shown in Table 4.

[0070] Table 4 is the product parameter of polycarboxylic acid water reducing agent The accelerator used in the following examples is mainly composed of alumina clinker, The preparation method of the alumina clinker comprises the following steps: The bauxite, soda ash and quicklime are calcined at a temperature of 1280℃ for 1.5 hours to obtain the alumina clinker; The fineness of the obtained alumina clinker is <12.6%; The bauxite, soda ash (Na2CO3) and quicklime (CaO) are 60%, 20% and 20% by mass percentage.

[0071] The obtained alumina clinker has the remarkable characteristics of short setting time and fast early strength development, and the physical parameters are shown in Table 5.

[0072] Table 5 is the product parameter of accelerator Example 1 A preparation method of a graphene oxide modified cement-based grouting material, The graphene oxide modified cement-based grouting material is composed of cement, graphene oxide, silica fume, polycarboxylate superplasticizer, accelerator and water, the mass ratio of cement, graphene oxide (GO), silica fume, polycarboxylate superplasticizer and accelerator is 95:0.06:5:0.1:1.5, and the water-cement ratio is 0.4. The preparation method comprises the following steps: S1, adding GO into the water solution containing polycarboxylate superplasticizer, stirring first and then ultrasonic treatment for 15 min to form a uniformly dispersed GO suspension; S2, slowly adding the GO suspension into cement, mechanically mixing and stirring for 4 min, and then adding accelerator to adjust the setting time to prepare the graphene oxide modified cement-based grouting material.

[0073] Example 2 A preparation method of a graphene oxide modified cement-based grouting material, The graphene oxide modified cement-based grouting material is composed of cement, graphene oxide, silica fume, polycarboxylate superplasticizer, accelerator and water, the mass ratio of cement, graphene oxide (GO), silica fume, polycarboxylate superplasticizer and accelerator is 90:0.06:10:0.1:1.5, and the water-cement ratio is 0.4. The preparation method comprises the following steps: S1, adding GO into the water solution containing polycarboxylate superplasticizer, stirring first and then ultrasonic treatment for 15 min to form a uniformly dispersed GO suspension; S2, pre-mixing silica fume and cement in proportion for 1-2 min to ensure uniform mixing to obtain dry mixture; S3, slowly adding the GO suspension into the dry mixture, mechanically mixing and stirring for 4 min until the slurry fluidity meets the standard, then adding accelerator to adjust the setting time to prepare the graphene oxide modified cement-based grouting material.

[0074] Example 3 A preparation method of a graphene oxide modified cement-based grouting material, The graphene oxide modified cement-based grouting material is composed of cement, graphene oxide, silica fume, polycarboxylate superplasticizer, accelerator and water, the mass ratio of cement, graphene oxide (GO), silica fume, polycarboxylate superplasticizer and accelerator is 90:0.03:10:0.1:1.5, and the water-cement ratio is 0.4. The preparation method comprises the following steps: S1, adding GO into the water solution containing polycarboxylate superplasticizer, stirring first and then ultrasonic treatment for 15 min to form a uniformly dispersed GO suspension; S2, pre-mixing silica fume and cement in proportion for 1-2 min to ensure uniform mixing to obtain dry mixture; S3, slowly add the GO suspension into the dry mixture, mechanically mix for 4 min until the slurry fluidity meets the standard, then incorporate the accelerator to adjust the setting time, and prepare the graphene oxide modified cementitious grouting material.

[0075] Comparative Example 1 A method for preparing a cementitious grouting material, wherein the graphene oxide modified cementitious grouting material is composed of cement and water, and the water-cement ratio is 0.4; The method for preparing, comprising the following steps: S1, mix the cement and water in proportion, mechanically stir for 4 min, and prepare the pure cementitious grouting material.

[0076] Detection analysis 1) Flowability, stone rate and bleeding rate test The grouting materials prepared in Example 1, Example 2, Example 3 and Comparative Example 1 are respectively subjected to flowability test, stone rate test and bleeding rate test.

[0077] Wherein, the flowability test steps of the grouting material are as follows: (1) Preparation Instrument preparation: prepare a truncated cone mold (upper inner diameter 100±0.5 mm, lower inner diameter 70±0.5 mm, height 60±0.5 mm), glass plate (400 mm×400 mm×5 mm), cement mortar mixer, electronic balance, stopwatch, steel ruler, etc.

[0078] Sample preparation: weigh not less than 2000 g of grouting material sample.

[0079] Equipment wetting: wipe the glass plate, truncated cone mold, stirrer and stirring pot with a wet cloth to make the surface wet but not with water droplets.

[0080] (2) Stir the grouting material Pour the sample into the stirring pot, add water according to the recommended water amount of the manufacturer, and stir for 3 minutes from the start of water addition.

[0081] (3) Pour into the truncated cone mold Pour the stirred slurry into the truncated cone mold quickly and scrape it flat with a spatula.

[0082] (4) Lift the truncated cone mold and time Lift the truncated cone mold in the vertical direction and start the stopwatch at the same time.

[0083] (5) Measure the flowability Within 30 seconds after lifting the truncated cone mold, measure the maximum diameters of the two directions perpendicular to each other of the flowing slurry with a steel ruler, and take their average value as the initial flowability.

[0084] The results of the flowability test are shown in Table 5 and Table 6. Figure 1

[0085] The stone rate test procedure is as follows: (1) Experimental preparation Environmental conditions: The laboratory temperature should be controlled at 20 ℃±2 ℃, and the relative humidity should be greater than 50%.

[0086] Instrument equipment: A measuring cylinder with a volume of 250 mL is used, which should meet the requirements of the current national standard "Laboratory Glass Instrument Measuring Cylinder" GB / T 12804 in terms of material, shape and size, and the measuring cylinder should be equipped with a sealing cover.

[0087] (2) Sample preparation Prepare the simultaneous grouting material sample according to the relevant provisions of the current industry standard "Standard for Testing Methods of Basic Properties of Building Mortar" JGJ / T 70.

[0088] (3) Initial state measurement Place the measuring cylinder on a horizontal surface, and fill the grouting material slurry 200 mL±5 mL into the measuring cylinder. After standing for 1 minute, measure and record the scale value a0 corresponding to the initial slurry surface, and then cover the measuring cylinder tightly.

[0089] (4) Standing and measurement Standing for 3 hours: After standing for 3 hours, measure the scale value a1 corresponding to the bleeding surface and the scale value a2 corresponding to the slurry surface, respectively, and calculate the bleeding rate.

[0090] Standing for 3 days: Continue to stand until 3 days, and measure the scale value a3 corresponding to the surface of the hardened slurry.

[0091] (5) Stone rate calculation The stone rate (HR3) is calculated according to the formula shown in formula (I): HR3= (a3 / a0) x 100 (I) In formula (I), HR3 is the 3-day stone rate (%), accurate to 0.1; a3 is the scale value (mL) corresponding to the surface of the hardened slurry after standing for 3 days. a0 is the scale value (mL) corresponding to the initial grouting material slurry surface.

[0092] The bleeding rate test procedure is as follows: (1) Experimental preparation Instrument equipment: Select 250 mL measuring cylinder, pipette, stopwatch, electronic balance, glass sheet, etc.

[0093] Environmental conditions: The test should be carried out under constant temperature and humidity conditions, and the temperature is generally (20±2) ℃, and the relative humidity is greater than 50%.

[0094] ​(2) Test steps Measuring the grouting material slurry: a graduated cylinder is used to measure the grouting material slurry V0, for example, 200 mL.

[0095] Standing and precipitating: the graduated cylinder is covered with a glass sheet and placed in a constant temperature and humidity box for standing.

[0096] Reading data: read the scale V between the upper clear water and the lower precipitated colloid every 5 minutes until the reading is stable (the last three readings are exactly the same).

[0097] The water separation rate is calculated according to the formula (II) as follows: δ=[(V0-V) / V0]×100% (II) In formula (II), V0 represents the initial volume of the grouting material; V represents the scale between the upper clear water and the lower precipitated colloid after stabilization, and δ represents the water separation rate (%).

[0098] The stone rate and water separation rate test results are shown in Figure 2 and Table 6.

[0099] Table 6 is the test results of flowability, stone rate and water separation rate From Figure 1 , Figure 2 and Table 6, it can be seen that the prepared graphene oxide-based modified cement-based grouting material has a flowability of 200-300 mm, and is not less than 200 mm, which indicates that the grouting material has excellent injectability and meets the pumping requirements. At the same time, the prepared graphene oxide-based modified grouting material maintains excellent consolidation characteristics, and the stone rate is stably maintained at a high level of 99%, and the ultra-low water separation rate within the range of 0.5% is realized, which indicates that the graphene oxide modified cement-based grouting material slurry has high stability.

[0100] 2) Compression, bending and SEM electron microscope scanning tests The specific operation steps are: the grouting materials prepared in Example 1, Example 2, Example 3 and Comparative Example 1 are poured into a cylindrical mold with a diameter of 50 mm x height of 100 mm and a three-way test mold with a size of 40 mm x 40 mm x 160 mm, and then placed in a standard curing box with a temperature of 25℃ and a humidity of about 95%, and after curing for 28 days, the test pieces are obtained, and the test pieces are subjected to compression and bending tests, and the test pieces cured for 28 days are broken and ground for SEM electron microscope scanning test.

[0101] The compression strength test steps are as follows: Test piece preparation: After taking the test piece from the curing site, test it in time. Before testing, clean the surface of the test piece, measure the size, and check its appearance. Calculate the bearing area of the test piece.

[0102] Install the test piece: Place the test piece on the lower pressing plate or lower base plate of the testing machine. The bearing surface of the test piece should be perpendicular to the top surface during molding, and the center of the test piece should be aligned with the center of the lower pressing plate or lower base plate of the testing machine.

[0103] Load and record: Start the testing machine. When the upper pressing plate approaches the test piece or the upper base plate, adjust the ball seat to ensure that the contact surface is evenly pressed. The compression test should be continuous and uniform, with a loading speed of 0.25-1.5 kN / s. When the test piece approaches failure and starts to deform rapidly, stop adjusting the testing machine throttle until the test piece fails, then record the failure load.

[0104] The compressive strength is calculated according to the formula (III) as follows: fcu=F / A (Ⅲ) In formula (III), fcu is the compressive strength (MPa), F is the failure load (N), and A is the bearing area of the test piece (mm 2 ).

[0105] Result processing: The arithmetic mean of the three parallel test values of the test piece in the same example or comparative example is taken as the average compressive strength of the test piece, accurate to 0.1 MPa.

[0106] The bending strength test procedure is as follows: Equipment preparation: Use a universal testing machine or a dedicated bending strength tester to ensure accurate calibration of the equipment.

[0107] Test piece installation: Place the test piece cured to the specified age on the support frame of the testing machine and test it using the three-point bending method.

[0108] Load test: Load the test piece at a rate of 1 mm / min until it fails, and record the maximum load at failure.

[0109] The bending strength is calculated according to the formula (IV) as follows: R1=(1.5×F1×L) / b 3 (Ⅳ) In formula (IV), R1 is the bending strength (unit: MPa), F1 is the failure load (unit: N), L is the center distance of the support cylinder (unit: mm), and b is the side length of the square cross section of the test piece (unit: mm), usually 40 mm.

[0110] Result processing: the arithmetic mean of the three parallel test pieces of the same example or comparative example was calculated, and the result was accurate to 0.1 MPa. If there were more than ±10% of the average value in the three strength values, they should be removed and the average value should be calculated again.

[0111] The compressive strength, the bending strength and the SEM electron microscope scanning results are as shown in Figures 3 to 6 and Table 7.

[0112] Table 7 is the determination result of the compressive strength and the bending strength From Figure 3 and Table 7, it can be known that the graphene oxide-based cement-based grouting material prepared in the application can achieve 36.4 MPa and 12.2 MPa of the 28d compressive strength and the bending strength respectively, which proves that the grouting material of the application can significantly improve the structural strength and the overall stability of the loose accumulation body and realize effective reinforcement.

[0113] From Figures 4 to 6 comparative analysis, it can be known that the single graphene oxide modification makes the hydration product form a dense sheet structure with enhanced mechanical properties, and the generation of silicon-rich gel after the incorporation of silica fume promotes the product to change into a rod / cylinder structure filling the voids, and the synergistic effect of the two significantly improves the material density. Thus, it is proved that the graphene oxide-based cement-based grouting material prepared in the application greatly improves the toughness and strength of the stone body.

[0114] In summary, the graphene oxide modified cement-based grouting material of the present application uses ordinary Portland cement as the basis, by adding graphene oxide, silica fume, polycarboxylic acid water reducer and accelerator and other admixtures, which significantly improves the mechanical properties, slurry stability and crack toughness of the grouting material, GO is dispersed by polycarboxylic acid water reducer and then added to the slurry, which effectively improves its dispersibility and hydration activity, and is suitable for reinforcement and treatment of loose bulk body and other adverse geological conditions. The graphene oxide modified cement-based grouting material of the present application has high strength, high toughness and excellent construction performance, and can be widely used in tunnel support, slope reinforcement and geological disaster prevention engineering, especially suitable for loose stratum grouting reinforcement requirements. Among them, ordinary Portland cement and silica fume are used as the main cementing component, polycarboxylic acid water reducer, graphene oxide (GO) and accelerator are used as the key modified material, and the early strength and later durability of the grouting material are significantly improved through the synergistic effect of cement and silica fume; the polycarboxylic acid water reducer effectively improves the fluidity and stability of the slurry, reduces the water-cement ratio while ensuring good pumpability, which is beneficial to control the setting time of the grouting material and improve the density of the stone body, meet the engineering requirements of loose bulk body reinforcement; graphene oxide improves the mechanical properties and durability of cement-based materials; accelerator shortens the setting time of the slurry, and the early strength develops quickly to achieve the purpose of quick setting of concrete in repair or well and roadway, and has popularization and application value in the field of geotechnical engineering reinforcement materials.

[0115] The above examples are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent replacement or transformation made by those skilled in the art on the basis of the present application is within the protection scope of the present application.

Claims

1. A graphene oxide modified cement-based grouting material, characterized in that: It consists of cement, graphene oxide, silica fume, polycarboxylate water reducer, accelerator and water.

2. The graphene oxide modified cement-based grouting material according to claim 1, wherein The added amount of graphene oxide is 0.03-0.06% of the total mass of cement and silica fume; And / or, the amount of silica fume added is 5-10% of the total mass of cement and silica fume; And / or, the addition amount of the polycarboxylate water reducer is 0-0.1% of the total mass of cement and silica fume; And / or, the addition amount of the accelerating agent is 1-2% of the total mass of cement and silica fume.

3. The graphene oxide modified cement-based grouting material according to claim 1, wherein The water-cement ratio of the graphene oxide modified cement-based grouting material is 0.4-0.

5.

4. The graphene oxide modified cement-based grouting material according to claim 1, characterized in that The method for preparing graphene oxide comprises the following steps: Graphene oxide is obtained by chemically oxidizing flake graphite with concentrated sulfuric acid and potassium permanganate in sequence, and then exfoliating 2 to 4 layers in water through ultrasonic treatment. The graphene oxide obtained after peeling has 1 to 15 graphite layers, a single layer thickness of 2 to 5 μm, and a sheet diameter of 20 to 40 μm.

5. The graphene oxide modified cement-based grouting material according to claim 1, wherein The accelerating agent is selected from alumina clinker; The method for preparing the alumina clinker comprises the following steps: Calcine bauxite, soda ash and quicklime at a temperature of 1250-1300°C for 1-2 hours to obtain alumina clinker; The fineness of the obtained alumina clinker is <12.6%; The bauxite, soda ash and quicklime are calculated in percentage by mass as follows: 50-70%: 15-25%: 10-25%.

6. The graphene oxide modified cement-based grouting material according to claim 1, characterized in that: The cement is selected from P.O42.5 grade Portland cement with a loss on ignition of 2-4%; And / or, the specific surface area of ​​the silica fume is 20-25m 2 / g; And / or, the water reduction rate of the polycarboxylate water reducer is 15-25%.

7. A method for preparing a graphene oxide modified cement-based grouting material according to any one of claims 1 to 6, characterized in that: The following steps are involved: Graphene oxide (GO) was added to an aqueous solution containing a polycarboxylate superplasticizer, stirred, and then ultrasonicated to obtain a GO suspension. Premixing silica fume with cement to obtain a dry mix; The GO suspension is added to the dry mix, mixed and stirred, and then an accelerating agent is added to obtain a graphene oxide modified cement-based grouting material.

8. The preparation method according to claim 7, characterized in that The ultrasonic treatment time is 10 to 20 minutes; And / or, the premixing time is 1 to 2 minutes; And / or, the mixing and stirring time is 3 to 5 minutes.

9. The preparation method according to claim 8, characterized in that The prepared graphene oxide modified cement-based grouting material has a fluidity greater than 200 mm, a stone formation rate greater than 99%, and a water separation rate less than or equal to 0.5%.

10. Use of the graphene oxide modified cement-based grouting material according to any one of claims 1 to 6, characterized in that: The graphene oxide modified cement-based grouting material is used for reinforcing loose accumulations and broken rock formations.

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