Graphene cement additive, graphene-cement composite material and preparation method thereof

Abstract

This invention belongs to the field of graphene preparation, and discloses a graphene cement additive and its preparation method, as well as a graphene-cement composite material and its preparation method. The preparation method includes: preparing a stripping agent solution using pure water, bile salt anionic surfactants, and nonionic surfactants; then adding graphite raw materials and thoroughly mixing to obtain a graphite pre-stripping dispersion; subjecting the graphite pre-stripping dispersion to ultrasonic-assisted stripping dispersion in a water bath to obtain a graphene mixed dispersion system; centrifuging the graphene mixed dispersion system, taking the supernatant for dialysis to remove unstripped particles or thick graphite flakes, and obtaining the graphene cement additive. This invention uses pure water as a stripping agent and, by adding a small amount of surfactant, directly obtains the graphene cement additive through liquid-phase stripping. This method is not only non-toxic and harmless, but also yields graphene with good dispersibility. When the graphene cement additive is incorporated into cement, the compressive strength of the cement increases by more than 20%.

Description

Technical Field

[0001] This invention belongs to the field of graphene preparation technology, specifically relating to a method for preparing a liquid-phase exfoliated graphene cement additive and the graphene cement additive prepared therefrom, and also relating to a method for preparing a graphene-cement composite material and the graphene-cement composite material prepared therefrom. Background Technology

[0002] The continuous development of the construction industry and large-scale projects has placed higher and more demanding requirements on the performance of cement-based composite materials. However, the brittleness and low toughness of cement-based composite materials can no longer meet the current development requirements of the construction industry and large-scale projects, and at the same time, to a certain extent, it has limited the development and application of cement and its composite materials.

[0003] Graphene is a novel two-dimensional structural material composed of a single-layer sheet-like structure of six-membered rings formed by sp2 hybrid carbon atoms linked by covalent bonds (Electrochimica Acta, 2010, 56:491-500). It possesses excellent mechanical properties, being the hardest and strongest material known to date. As a novel high-performance nanomaterial, graphene exhibits unique mechanical properties and nanoscale effects, and has become a research hotspot in materials science. Previous studies have shown that incorporating optimized graphene into cement-based materials exhibits excellent reinforcing effects and improves the overall performance of cement-based materials.

[0004] Among the various methods for preparing graphene, liquid-phase exfoliation is relatively simple to operate, low in cost, and yields high-quality products. It is currently the only method capable of producing large quantities of graphene while maintaining its intact morphology and properties. This method involves dispersing graphite in a suitable solvent and then applying strong shear forces to overcome the van der Waals forces between the graphite layers, thereby exfoliating the graphene. The exfoliated graphene product obtained by this method can exist in the form of a dispersion or slurry, making transportation and reuse very convenient.

[0005] In current research on graphene preparation, organic solvents were initially used as exfoliation media (Advanced Functional Materials, 2009, 19:3680-95). However, organic solvents have drawbacks such as high toxicity, high cost, poor biocompatibility, and difficulty in separation. Therefore, water, as a colorless, odorless, non-toxic, harmless liquid with good renewability, is considered the most environmentally friendly solvent. Using water for graphene exfoliation is a crucial method for large-scale production and has promising industrial applications. However, due to the surface tension mismatch between graphene and water, ultrasonic or shear exfoliation of graphite raw materials in pure water often only yields micron-sized graphite fragments, making it difficult to obtain graphene. Therefore, research has found that adding an appropriate amount of surfactant to water to reduce its surface tension is currently an effective solution to the surface tension mismatch problem. Meanwhile, different surfactants exhibit varying degrees of effectiveness in exfoliating graphene due to their different structural properties. Based on their ionization state in water, surfactants can be broadly classified into ionic and nonionic types. Anionic surfactants are more commonly used due to their lower cost, but nonionic surfactants, under ultrasonic assistance, demonstrate superior dispersion / exfoliation performance of raw graphene in water compared to ionic surfactants (2011, carbon, 49:1653-62). Therefore, dispersion of graphene in surfactant / water systems may be the most promising approach, not only avoiding the use of toxic solvents but also reducing the aggregation of graphene sheets.

[0006] Therefore, how to further improve the exfoliation effect of graphene, reduce its cost to facilitate large-scale production without solvent residue, and then incorporate it into cement to enhance the mechanical strength of cement concrete is the current research focus. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention utilizes green and pollution-free pure water as a stripping agent. By adding a small amount of surfactant, graphene is obtained through an economical ultrasonic liquid-phase stripping process, which can be used as a cement additive. This reduces costs and increases production. The graphene is then further incorporated into cement to improve the mechanical properties of cement concrete.

[0008] According to a first aspect of the present invention, a method for preparing a liquid-phase exfoliated graphene cement additive is provided, comprising the following steps:

[0009] Step S1: Prepare a stripping agent solution using pure water, bile salt anionic surfactants and nonionic surfactants. Add graphite raw material to the prepared stripping agent solution and mix thoroughly to obtain a graphite pre-stripping dispersion.

[0010] Step S2: The graphite pre-exfoliated dispersion obtained in step S1 is subjected to assisted exfoliation and dispersion by ultrasonic treatment in a water bath to obtain a graphene mixed dispersion system.

[0011] Step S3: Centrifuge the graphene mixed dispersion system obtained in step S2, take the upper layer solution for dialysis, remove unpeeled particles or thick graphite sheets, and obtain graphene cement additive.

[0012] According to some embodiments of the present invention, in step S1, the bile salt anionic surfactant is one of sodium cholate (SC), sodium deoxycholate (SDC), sodium tauride deoxycholate (STC), and sodium deoxycholate (NaDC).

[0013] According to some embodiments of the present invention, in step S1, the nonionic surfactant is one of polyvinylpyrrolidone (PVP), fatty alcohol polyoxyethylene ether (AEO), amine oxide and alkyl polyglycoside (APG), and Tween 80.

[0014] According to some embodiments of the present invention, in step S1, the ratio of the bile salt anionic surfactant to the nonionic surfactant is 1:1 mg / mL.

[0015] According to some embodiments of the present invention, in the stripping agent solution, the concentration of the bile salt anionic surfactant is 1-10 wt%, and the concentration of the nonionic surfactant is 1-10 wt%.

[0016] According to some embodiments of the present invention, in step S1, the graphite raw material is one or more of graphite powder, natural graphite, natural flake graphite, spherical graphite, expandable graphite, graphite oxide powder, and directional pyrolytic graphite.

[0017] According to some embodiments of the present invention, in step S1, the concentration of graphite raw material in the prepared stripping agent solution is 0.1-20 wt%.

[0018] According to some embodiments of the present invention, in step S1, the stirring is magnetic stirring, the rotation speed is 500-2000 rpm, and the stirring time is 0.5-5 hours.

[0019] According to some embodiments of the present invention, in step S2, the mixture is stirred for 5 minutes every 30 minutes during the ultrasonic process.

[0020] According to some embodiments of the present invention, in step S2, the ultrasonic frequency range is 20-70 kHz, and the ultrasonic time is 0.5-12 hours.

[0021] According to some embodiments of the present invention, in step S3, the centrifugation speed is 5000-20000 rpm and the centrifugation time is 5-30 minutes.

[0022] According to a second aspect of the present invention, a graphene cement additive is provided, said graphene cement additive being prepared by the method described in the first aspect of the present invention.

[0023] According to a third aspect of the present invention, a method for preparing a graphene-cement composite material is provided, comprising the following steps:

[0024] Step S1: Prepare a stripping agent solution using pure water, bile salt anionic surfactants and nonionic surfactants. Add graphite raw material to the prepared stripping agent solution and mix thoroughly to obtain a graphite pre-stripping dispersion.

[0025] Step S2: The graphite pre-exfoliated dispersion obtained in step S1 is subjected to assisted exfoliation and dispersion by ultrasonic treatment in a water bath to obtain a graphene mixed dispersion system.

[0026] Step S3: Centrifuge the graphene mixed dispersion system obtained in step S2, take the upper layer solution for dialysis, remove unpeeled particles or thick graphite sheets, and obtain graphene cement additive.

[0027] Step S4: Add the graphene cement additive obtained in step S3 to the cement and mix to obtain a graphene-cement composite material.

[0028] According to some embodiments of the present invention, in step S4, the addition ratio of the graphene cement additive is 0.1-30 wt%.

[0029] According to a fourth aspect of the present invention, a graphene-cement composite material is provided, said graphene-cement composite material being prepared by the method described in the third aspect of the present invention.

[0030] By adopting the above technical solutions, the present invention has at least one of the following beneficial effects compared with the prior art:

[0031] 1. This invention uses a liquid phase exfoliation method to prepare graphene. This method is not only simple and easy to operate, but also can effectively separate graphite sheets and obtain a large amount of graphene in a short time. The obtained graphene is single-layer or few-layer, has good electrical and thermal conductivity, and excellent comprehensive performance, which is expected to realize the industrial preparation of graphene.

[0032] 2. This invention uses water as the exfoliating agent. Water, as a colorless, odorless, non-toxic, harmless liquid with good renewability, is considered the most environmentally friendly solvent. Using water to exfoliate graphene is an important means to achieve large-scale production and has good application prospects in industrialization.

[0033] 3. This invention employs bile salt anionic and nonionic surfactants to reduce the high surface tension of water. Anionic surfactants are inexpensive and have good dispersibility, while nonionic surfactants have good solubility. Their synergistic effect enables good dispersion of graphene. Furthermore, the residual surfactants can be directly added to cementitious materials as additives. The residual surfactants can also be grafted onto the graphene surface, further enhancing the hydrophilicity of graphene and ensuring its performance within the cement matrix, thus allowing graphene to form a better mixing system with cement. Therefore, there is no need for a surfactant removal step.

[0034] 4. The exfoliated graphene product obtained by this invention can exist in the form of dispersion or slurry, which is very convenient for transportation and reuse. It can be directly used as a cement additive. When it is added to the cement mortar, it has a good fusion effect with the cement and can reduce the agglomeration of graphene.

[0035] 5. The stripping agent and surfactant used in this invention are inexpensive and readily available. The liquid-phase stripping method used is simple to operate, highly efficient, and environmentally friendly. It can directly obtain graphene cement additives without secondary processing. When added to cement, it not only reduces the cost of directly adding graphene but also promotes the integration of graphene and cement. At the same time, according to GB / T 17671-2020 "Test Method for Strength of Cement Mortar (ISO Method)", the compressive strength of cement mortar at different ages is significantly improved, thus enhancing the mechanical properties of cement and meeting the needs of the construction industry. Attached Figure Description

[0036] Figure 1 A flowchart illustrating the preparation method of the liquid-phase exfoliated graphene cement additive provided by the present invention;

[0037] Figure 2 A flowchart illustrating the preparation method of the graphene-cement composite material provided by this invention;

[0038] Figure 3 A scanning electron microscope image of the graphene cement additive prepared in Example 1;

[0039] Figure 4 Transmission electron microscope (TEM) image of the graphene cement additive prepared in Example 1;

[0040] Figure 5 The X-ray powder diffraction spectrum of the graphene cement additive prepared in Example 1 is shown below.

[0041] Figure 6 This is a comparison chart of the compressive strength of the graphene-cement composite material prepared in Example 4 and the corresponding comparative example;

[0042] Figure 7 This is a comparison chart of the compressive strength of the graphene-cement composite material prepared in Example 5 and the corresponding comparative example;

[0043] Figure 8 This is a comparison chart of the compressive strength of the graphene-cement composite material prepared in Example 6 and the corresponding comparative example. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] According to a first aspect of the present invention, a method for preparing a liquid-phase exfoliated graphene cement additive is provided. For example... Figure 1 As shown, the preparation method of liquid-phase exfoliated graphene cement additive includes the following steps: Step S1: Prepare an exfoliating agent solution using pure water, bile salt anionic surfactant, and nonionic surfactant. Add graphite raw material to the prepared exfoliating agent solution and mix thoroughly to obtain a graphite pre-exfoliated dispersion. Step S2: Perform assisted exfoliation and dispersion of the graphite pre-exfoliated dispersion obtained in Step S1 using ultrasonic water bath to obtain a graphene mixed dispersion system. Step S3: Centrifuge the graphene mixed dispersion system obtained in Step S2, take the upper layer solution for dialysis, remove unexfoliated particles or thick graphite flakes, and obtain the graphene cement additive.

[0046] In some embodiments, in step S1, the bile salt anionic surfactant can be one of sodium cholate (SC), sodium deoxycholate (SDC), sodium taurodeoxycholate (STC), and sodium deoxycholate (NaDC), and the nonionic surfactant can be one of polyvinylpyrrolidone (PVP), fatty alcohol polyoxyethylene ether (AEO), amine oxide and alkyl polyglycoside (APG), and Tween 80. In some embodiments, preferably, in step S1, the ratio of bile salt anionic surfactant to nonionic surfactant can be 1:1 mg / mL. Preferably, in the stripping agent solution, the concentration of bile salt anionic surfactant can be 1-10 wt%, and the concentration of nonionic surfactant can be 1-10 wt%. In this document, the concentration of bile salt anionic surfactant refers to the percentage of the mass of bile salt anionic surfactant to the total mass of the stripping agent solution, and the concentration of nonionic surfactant refers to the percentage of the mass of nonionic surfactant to the total mass of the stripping agent solution. Specifically, in the stripping agent solution, the concentrations of bile salt anionic surfactants and nonionic surfactants can both be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value between them.

[0047] In some embodiments, in step S1, the graphite raw material can be one or more of graphite powder, natural graphite, natural flake graphite, spherical graphite, expandable graphite, graphite oxide powder, and directional pyrolytic graphite.

[0048] In some embodiments, preferably, in step S1, the concentration of the graphite raw material in the prepared stripping agent solution can be 0.1-20 wt%. Specifically, the concentration of the graphite raw material in the prepared stripping agent solution can be 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, or any value between these values.

[0049] In some embodiments, preferably, in step S1, the stirring can be magnetic stirring at a speed of 500-2000 rpm for a stirring time of 0.5-5 hours. Specifically, the speed can be 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm or any value therein, and the stirring time can be 0.5h, 1h, 2h, 3h, 4h, 5h or any value therein.

[0050] In some embodiments, preferably, in step S2, the mixture is stirred for 5 minutes every 30 minutes during the ultrasonic process. This helps to eliminate the adhesion of graphite to the stirrer, allowing the graphite to be better dispersed in the solution, thereby achieving homogeneity in the graphite exfoliation. In some embodiments, preferably, in step S2, the ultrasonic frequency range is 20-70 kHz, and the ultrasonic time is 0.5-12 hours. Specifically, the ultrasonic frequency range can be 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, or any value between these ranges, and the ultrasonic time can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, or any value between these ranges.

[0051] In some embodiments, preferably, in step S3, the centrifugation speed is 5000-20000 rpm, and the centrifugation time is 5-30 minutes. Specifically, the centrifugation speed can be 5000 rpm, 10000 rpm, 15000 rpm, 20000 rpm, or any value between them, and the centrifugation time can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, or any value between them.

[0052] According to a second aspect of the present invention, a graphene cement additive is provided, which is prepared by means of the method described in the first aspect of the present invention.

[0053] According to a third aspect of the present invention, a method for preparing a graphene-cement composite material is provided. For example... Figure 2As shown, the preparation method of graphene-cement composite material includes the following steps: Step S1: Prepare a stripping agent solution using pure water, bile salt anionic surfactant, and nonionic surfactant; add graphite raw material to the prepared stripping agent solution and mix thoroughly to obtain a graphite pre-stripping dispersion; Step S2: Perform assisted stripping dispersion of the graphite pre-stripping dispersion in Step S1 using ultrasonic water bath to obtain a graphene mixed dispersion system; Step S3: Centrifuge the graphene mixed dispersion system obtained in Step S2, take the supernatant and dialyze it to remove unstripped particles or thick graphite flakes to obtain a graphene cement additive; Step S4: Add the graphene cement additive obtained in Step S3 to cement and mix to obtain a graphene-cement composite material. Steps S1-S3 here are the same as steps S1-S3 described in the first aspect of the present invention, and will not be repeated here.

[0054] In some embodiments, preferably, in step S4, the addition ratio of graphene cement additive is 0.1-30 wt%. Specifically, the addition ratio of graphene cement additive can be 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or any value between these values.

[0055] According to a fourth aspect of the present invention, a graphene-cement composite material is provided, which is prepared by the method described in the third aspect of the present invention.

[0056] The present invention will be described in detail below through specific embodiments. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0057] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0058] The present invention will now be described in detail with reference to specific embodiments.

[0059] Preparation Examples of Graphene Cement Additives

[0060] Example 1

[0061] A method for preparing a liquid-phase exfoliated graphene cement additive includes the following specific steps:

[0062] 1) Prepare a 1 wt% aqueous solution of sodium cholate (SC) and polyvinylpyrrolidone (PVP) in pure water. Disperse 10 g of graphite powder in 90 g of the solution to obtain a 10 wt% graphite solution. Stir the solution for 2 h at 1000 rpm using a magnetic stirrer to ensure thorough mixing. Then, pack the obtained graphite pre-exfoliation dispersion into a sealed container.

[0063] 2) The above pre-exfoliated graphite dispersion was subjected to ultrasonication at room temperature for 6 hours for assisted exfoliation and dispersion. The ultrasonic frequency was set to 60kHz, and the mixture was stirred for 5 minutes every 30 minutes during the ultrasonication process to obtain a graphene mixed dispersion system.

[0064] 3) Centrifuge the graphene mixed dispersion system using a centrifuge with a speed of 18,000 rpm and a centrifugation time of 10 minutes. Take the upper layer solution for dialyzing to remove unpeeled particles or thick graphite flakes to obtain graphene cement additive.

[0065] Example 2

[0066] A method for preparing a liquid-phase exfoliated graphene cement additive includes the following specific steps:

[0067] 1) Prepare a 10wt% aqueous solution of sodium cholate (SC) and polyvinylpyrrolidone (PVP) in pure water. Disperse 1g of graphite powder in 999g of the solution to obtain a 0.1wt% graphite solution. Stir the solution for 2 hours at 1000rpm using a magnetic stirrer to ensure thorough mixing. Then, pack the obtained graphite pre-exfoliation dispersion into a sealed container.

[0068] 2) The above pre-exfoliated graphite dispersion was subjected to ultrasonication at room temperature for 6 hours for assisted exfoliation and dispersion. The ultrasonic frequency was set to 60kHz, and the mixture was stirred for 5 minutes every 30 minutes during the ultrasonication process to obtain a graphene mixed dispersion system.

[0069] 3) Centrifuge the graphene mixed dispersion system using a centrifuge with a speed of 18,000 rpm and a centrifugation time of 10 minutes. Take the upper layer solution for dialyzing to remove unpeeled particles or thick graphite flakes to obtain graphene cement additive.

[0070] Example 3

[0071] A method for preparing a liquid-phase exfoliated graphene cement additive includes the following specific steps:

[0072] 1) Prepare a 5wt% aqueous solution of sodium deoxycholate (SDC) and fatty alcohol polyoxyethylene ether (AEO) in pure water. Disperse 1g of graphite powder in 99g of the solution to obtain a 1wt% graphite solution. Stir the solution for 3 hours at 1000rpm using a magnetic stirrer to ensure thorough mixing. Then, pack the obtained graphite pre-exfoliation dispersion into a sealed container.

[0073] 2) The above pre-exfoliated graphite dispersion was subjected to ultrasonication at room temperature for 8 hours for assisted exfoliation and dispersion. The ultrasonic frequency was set to 60 kHz, and the mixture was stirred for 5 minutes every 30 minutes during the ultrasonication process to obtain a graphene mixed dispersion system.

[0074] 3) Centrifuge the graphene mixed dispersion system using a centrifuge with a speed of 18,000 rpm and a centrifugation time of 20 minutes. Take the upper layer solution for dialyzing to remove unpeeled particles or thick graphite flakes to obtain graphene cement additive.

[0075] Example 4

[0076] A method for preparing a liquid-phase exfoliated graphene cement additive includes the following specific steps:

[0077] 1) Prepare a 5wt% aqueous solution of sodium deoxycholate (SDC) and fatty alcohol polyoxyethylene ether (AEO) in pure water. Disperse 20g of graphite powder in 80g of the solution to obtain a 20wt% graphite solution. Stir the solution for 3 hours at 1000rpm using a magnetic stirrer to ensure thorough mixing. Then, pack the obtained graphite pre-exfoliation dispersion into a sealed container.

[0078] 2) The above pre-exfoliated graphite dispersion was subjected to ultrasonication at room temperature for 8 hours for assisted exfoliation and dispersion. The ultrasonic frequency was set to 60 kHz, and the mixture was stirred for 5 minutes every 30 minutes during the ultrasonication process to obtain a graphene mixed dispersion system.

[0079] 3) Centrifuge the graphene mixed dispersion system using a centrifuge with a speed of 18,000 rpm and a centrifugation time of 20 minutes. Take the upper layer solution for dialyzing to remove unpeeled particles or thick graphite flakes to obtain graphene cement additive.

[0080] Preparation Examples of Graphene-Cement Composite Materials

[0081] Example 5

[0082] The graphene cement additive prepared in Example 1 was added to cement at a ratio of 2 wt%, and the mixture was mixed to obtain a graphene-cement composite material.

[0083] Example 6

[0084] The graphene cement additive prepared in Example 2 was added to cement at a ratio of 1.5 wt%, and the mixture was mixed to obtain a graphene-cement composite material.

[0085] Example 7

[0086] The graphene cement additive prepared in Example 3 was added to cement at a ratio of 2.5 wt%, and the mixture was mixed to obtain a graphene-cement composite material.

[0087] Example 8

[0088] The graphene cement additive prepared in Example 1 was added to cement at a ratio of 0.1 wt%, and the mixture was mixed to obtain a graphene-cement composite material.

[0089] Example 9

[0090] The graphene cement additive prepared in Example 1 was added to cement at a ratio of 15 wt%, and the mixture was mixed to obtain a graphene-cement composite material.

[0091] Example 10

[0092] The graphene cement additive prepared in Example 1 was added to cement at a ratio of 30 wt%, and the mixture was mixed to obtain a graphene-cement composite material.

[0093] Testing and characterization of graphene cement additives

[0094] The graphene cement additives prepared in the above embodiments were tested and characterized using the following methods: The microstructure of the prepared graphene cement additives was characterized using scanning electron microscopy and transmission electron microscopy. The crystal structure of the material was determined using X-ray powder diffraction.

[0095] Figure 3 The image shows a scanning electron microscope (SEM) image of the graphene cement additive prepared in Example 1. The results show that the graphene cement additive exhibits a relatively loose structure with no obvious stacking between the layers.

[0096] Figure 4 The image shown is a transmission electron microscope (TEM) image of the graphene cement additive prepared in Example 1. The results show that the graphene cement additive exhibits a thin-layer structure with fewer than 10 layers.

[0097] Figure 5 The X-ray powder diffraction spectrum of the graphene cement additive prepared in Example 1 shows that the 002 peak of the graphene cement additive has a low intensity and is relatively broad, which also confirms the thin-layer structure of the graphene cement additive.

[0098] Performance characterization of graphene-cement composites

[0099] After the prepared graphene-cement composite mortar was filled into a mold, a specimen of 40mm×40mm×160mm was prepared. The specimen was placed on a vibration table and vibrated for 5 minutes. Then it was placed in a curing box at room temperature of 20℃ and humidity greater than 95% for curing. The compressive strength was then measured and cured under standard curing conditions until the specified age.

[0100] Simultaneously, cement specimens without graphene additives were prepared as a blank control. Cement and mixing water were mechanically combined, and cement mortar specimens of 40mm×40mm×160mm were prepared according to standard requirements. After vibration on a vibrating table for 5 minutes, they were placed in a curing chamber at room temperature of 20℃ and humidity greater than 95% for curing. Then, the compressive strength was measured. After curing under standard conditions to the specified age, the control group was used for compressive strength measurement.

[0101] The strength of cement mortar products cured for 3 days, 7 days and 28 days was determined according to GB / T 17671—1999 "Test Method for Strength of Cement Mortar (ISO Method)".

[0102] Figure 6 The experimental results of the graphene-cement composite material prepared in Example 5 and the blank group are as follows: Figure 6 As shown, the compressive strengths of the graphene-cement composite material prepared in Example 5 after curing for 3 days, 7 days and 28 days were 25.5, 34.6 and 54.9 MPa, respectively, which were 21.4%, 23.6% and 27.7% higher than the strength of the cement specimen without graphene additive. Figure 7 The experimental results of the graphene-cement composite material prepared in Example 6 and the blank group are as follows: Figure 7 As shown, the compressive strengths of the graphene-cement composite material prepared in Example 6 after curing for 3 days, 7 days, and 28 days were 25.6, 34.5, and 54.6 MPa, respectively, which were 21.9%, 23.2%, and 26.9% higher than the strength of the cement specimen without graphene additives. Figure 8 The experimental results of the graphene-cement composite material prepared in Example 7 and the blank group are as follows: Figure 8As shown, the compressive strengths of the graphene-cement composite material prepared in Example 7 after curing for 3, 7, and 28 days were 26.5, 34.8, and 55.2 MPa, respectively, representing increases of 26.2%, 24.3%, and 28.4% compared to the cement specimen without graphene additives. Furthermore, the experimental results of the graphene-cement composite materials prepared in Examples 8-10, along with the control group, also showed that the compressive strength of the graphene-cement composite material after curing for 3, 7, and 28 days was more than 20% higher than that of the cement specimen without graphene additives. Therefore, it is evident that incorporating the graphene cement additive prepared in this invention into cement significantly improves the compressive strength of the cement.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention, including combinations of various technical features in any other suitable manner, should also be considered as the content disclosed in the present invention and should be included within the protection scope of the present invention.

Claims

1. A method for preparing a liquid-phase exfoliated graphene cement additive, characterized in that, Includes the following steps: Step S1: Prepare a stripping agent solution using pure water, bile salt anionic surfactant, and nonionic surfactant. Add graphite raw material to the prepared stripping agent solution and mix thoroughly to obtain a graphite pre-stripping dispersion. The bile salt anionic surfactant is one of sodium cholate, sodium deoxycholate, and sodium taurodeoxycholate. The nonionic surfactant is one of polyvinylpyrrolidone, fatty alcohol polyoxyethylene ether, amine oxide, alkyl polyglycoside, and Tween 80. The ratio of the bile salt anionic surfactant to the nonionic surfactant is 1:1 mg / mL. Step S2: The graphite pre-exfoliated dispersion obtained in step S1 is subjected to assisted exfoliation and dispersion by ultrasonic bath in a water bath to obtain a graphene mixed dispersion system. Step S3: Centrifuge the graphene mixed dispersion system obtained in step S2, take the upper layer solution for dialysis, remove unpeeled particles or graphite sheets, and obtain graphene cement additive.

2. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In the stripping agent solution, the concentration of the bile salt anionic surfactant is 1-10 wt%, and the concentration of the nonionic surfactant is 1-10 wt%.

3. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In step S1, the graphite raw material is one or more of the following: natural flake graphite, spherical graphite, expandable graphite, graphite oxide powder, and directional pyrolytic graphite.

4. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In step S1, the concentration of graphite raw material in the prepared stripping agent solution is 0.1-20 wt%.

5. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In step S1, the stirring is magnetic stirring, with a speed of 500-2000 rpm and a stirring time of 0.5-5 hours.

6. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In step S2, the mixture is stirred for 5 minutes every 30 minutes during the ultrasonic process.

7. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In step S2, the ultrasonic frequency range is 20-70kHz, and the ultrasonic time is 0.5-12 hours.

8. The preparation method of the liquid-phase exfoliated graphene cement additive according to claim 1, characterized in that, In step S3, the centrifugation speed is 5000-20000 rpm and the centrifugation time is 5-30 minutes.

9. A graphene cement additive, characterized in that, The graphene cement additive is prepared by the method described in any one of claims 1-8.

10. A method for preparing a graphene-cement composite material, characterized in that, Includes the following steps: Step S1: Prepare a stripping agent solution using pure water, bile salt anionic surfactant, and nonionic surfactant. Add graphite raw material to the prepared stripping agent solution and mix thoroughly to obtain a graphite pre-stripping dispersion. The bile salt anionic surfactant is one of sodium cholate, sodium deoxycholate, and sodium taurodeoxycholate. The nonionic surfactant is one of polyvinylpyrrolidone, fatty alcohol polyoxyethylene ether, amine oxide, alkyl polyglycoside, and Tween 80. The ratio of the bile salt anionic surfactant to the nonionic surfactant is 1:1 mg / mL. Step S2: The graphite pre-exfoliated dispersion obtained in step S1 is subjected to assisted exfoliation and dispersion by ultrasonic bath in a water bath to obtain a graphene mixed dispersion system. Step S3: Centrifuge the graphene mixed dispersion system obtained in step S2, take the upper layer solution for dialysis, remove unpeeled particles or graphite sheets, and obtain graphene cement additive. Step S4: Add the graphene cement additive obtained in step S3 to the cement and mix to obtain a graphene-cement composite material.

11. The method for preparing the graphene-cement composite material according to claim 10, characterized in that, In step S4, the addition ratio of the graphene cement additive is 0.1-30 wt%.

12. A graphene-cement composite material, characterized in that, The graphene-cement composite material is prepared by the method described in any one of claims 10-11.

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