A graphene-based cement concrete admixture, its preparation method and application

Abstract

This invention discloses a method for preparing a graphene-based cement concrete admixture, comprising: mixing 1 part by mass of graphene or layered graphite with 40-100 parts by mass of concentrated sulfuric acid; adding 2-8 parts by mass of nitrate and 2-8 parts by mass of strong oxidizing salt at a temperature below 5°C; reacting the mixture to obtain mixture A; pouring mixture A into 150-200 parts by mass of a hydrophilic solvent; mixing and cooling to room temperature; adding 1-3 parts by mass of an organic compound containing peroxy groups; adding 1-4 parts by mass of manganese salt as a catalyst; stirring and reacting; after the reaction is complete, allowing the mixture to stand to obtain a precipitate; washing and drying the precipitate to obtain the graphene-based cement concrete admixture. This invention also discloses the graphene-based cement concrete admixture obtained by the above preparation method. This concrete admixture preparation method is simple, easily dispersed, and can improve the density, strength, and durability of cement concrete, while reducing the production cost of concrete and significantly increasing the lifespan of concrete structures.

Description

Technical Field

[0001] This invention relates to the field of building materials, specifically to a graphene-based cement concrete admixture, its preparation method, and its application. Background Technology

[0002] Cement concrete is the most commonly used building material, characterized by good plasticity, high strength, and low cost. It is widely used in infrastructure construction such as buildings, airports, highways, bridges, and tunnels. However, concrete is a porous material with a high internal porosity. This high porosity limits its strength and makes it susceptible to erosion by water, ions, and other media, thus reducing its durability. Currently, reducing concrete porosity generally requires complex material proportions and elaborate processes, including the introduction of substances such as ultrafine silica fume. This not only increases construction difficulty but also significantly increases the cost of concrete.

[0003] Graphene-based materials are lightweight, have high tensile strength, and high specific surface area. When incorporated into cement-based materials, they can induce cement hydration, making the hydration product—calcium silicate hydrate gel—more compact and reducing its porosity, thereby increasing strength and improving material durability.

[0004] Patent document CN108975781B discloses a concrete admixture, which is composed of the following raw materials by weight: 25-40 parts of redispersible latex powder, 20-30 parts of water-reducing agent, 5-12 parts of hydroxypropyl methylcellulose, 10-20 parts of epoxy resin, and 2-10 parts of graphene oxide-glass fiber-pyridine ionic liquid composite material. This concrete admixture can effectively enhance the bonding force between cement paste and aggregate, improve the strength and permeability coefficient of concrete, and extend the service life of concrete.

[0005] Patent document CN115403295A discloses a green carbon-reducing concrete admixture, green carbon-reducing concrete, and its preparation method. This invention uses a double-admixture water-reducing agent and an expansion agent as the main ingredients, supplemented with graphene oxide, an air-entraining agent, and natural fibers. When applied to concrete, this admixture significantly improves the concrete's freeze-thaw resistance and enhances its toughness while fully ensuring its mechanical properties.

[0006] Although extensive research has been conducted on graphene-based concrete admixtures, current graphene-based concrete admixtures generally tend to agglomerate due to their high surface energy, making them difficult to disperse in water and often requiring prolonged ultrasonic treatment. In actual production, they present high construction difficulties and demanding usage conditions. Furthermore, their high cost and low cost-effectiveness have hindered their large-scale application in construction. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing graphene-based cement concrete admixtures. This method is simple, low-cost, and suitable for large-scale production.

[0008] A method for preparing a graphene-based cement concrete admixture includes the following steps:

[0009] Step 1: By mass, mix 1 part graphene or layered graphite with 40-100 parts concentrated sulfuric acid, add 2-8 parts nitrate and 2-8 parts strong oxidizing salt at below 5°C, and react after mixing to obtain mixture A.

[0010] Step 2: Pour the mixture A obtained in Step 1 into 150-200 parts of hydrophilic solvent, mix and cool to room temperature, then add 1-3 parts of organic matter containing peroxy groups and 1-4 parts of manganese salt as a catalyst, stir to carry out the reaction, and after the reaction is completed, let the mixture stand to obtain the precipitate, wash and dry it to obtain the graphene-based cement concrete admixture.

[0011] Graphene or layered graphene is dispersed in concentrated sulfuric acid. The sulfuric acid molecules, along with ionized hydrogen sulfate and sulfate ions, partially penetrate between the graphene sheets. Adding nitrates accelerates the exfoliation process between the graphene sheets, creating conditions for subsequent oxidation by strong oxidizing salts. After oxidation by the strong oxidizing agent, the large π bonds in the conjugated aromatic domains are extensively disrupted, generating numerous active double bonds. These active double bonds react with peroxy groups in the corresponding organic compounds under the catalysis of manganese salts to form epoxy groups or oxygen-containing polycyclic structures. The abundance of epoxy groups or oxygen-containing polycyclic structures increases the repulsive forces between graphene sheets and enhances their affinity for the solvent phase during dissolution, thus preventing aggregation and ultimately optimizing the application process and improving performance.

[0012] Preferably, the graphene comprises monolayer graphene or oligolayer graphene.

[0013] Preferably, the nitrate includes sodium nitrate, potassium nitrate, or calcium nitrate.

[0014] Preferably, the strong oxidizing salt includes ferrate or permanganate.

[0015] Preferably, the ferrate is sodium ferrate.

[0016] Preferably, the permanganate is potassium permanganate.

[0017] Preferably, in step one, the reaction temperature is 30–50°C and the reaction time is 2–6 hours.

[0018] Preferably, in step two, the organic compound containing a peroxy group includes di-tert-butyl peroxide, peracetic acid, benzoyl peroxide, artemisinin and its derivatives.

[0019] Preferably, in step two, the manganese salt includes manganese sulfate, manganese chloride, manganate, permanganate, or manganese dioxide.

[0020] Preferably, in step two, the reaction time is 30 to 120 minutes.

[0021] The present invention also provides a graphene-based cement concrete admixture prepared by the aforementioned preparation method. This admixture is easily dispersed and can improve the density, strength, and durability of cement concrete.

[0022] The present invention also provides a concrete comprising the aforementioned graphene-based cementitious concrete admixture. This concrete exhibits high density, strength, and durability, and has low production costs, making it suitable for large-scale production and application.

[0023] Preferably, the graphene-based cement concrete admixture accounts for 0.01 to 0.05% of the concrete mass.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] (1) The graphene-based cement concrete admixture of the present invention has low surface energy, is not easy to agglomerate, and has a simple preparation process and low cost, making it suitable for large-scale production.

[0026] (2) The graphene-based cement concrete admixture prepared by the present invention can significantly improve the density, strength and durability of concrete, while reducing the production cost of concrete, improving the cost-effectiveness of graphene-based concrete admixture, which is conducive to its large-scale promotion and greatly improves the service life of concrete structures. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this invention, but not all embodiments.

[0028] Example 1: High-strength and high-durability admixture for graphene-based cement concrete

[0029] By mass, 1 part of sheet graphene and 60 parts of concentrated sulfuric acid were mixed evenly by stirring. Then, 5 parts of sodium nitrate and 5 parts of sodium ferrate were added in an ice-water bath. After being mixed evenly, the mixture was reacted at 40°C for 5 hours to obtain mixture A.

[0030] Slowly pour the mixture A obtained in the above steps into 100 parts of distilled water, mix thoroughly and cool to room temperature, then add 1 part of di-tert-butyl peroxide and 2 parts of manganese sulfate as a catalyst, stir thoroughly, and after the di-tert-butyl peroxide and graphene compound have fully reacted, let the mixture stand.

[0031] After the mixture is allowed to stand, the resulting precipitate is washed and dried to obtain a graphene-based cement concrete admixture.

[0032] Example 2: High-strength and high-durability admixture for graphene-based cement concrete

[0033] The difference between this embodiment and Example 1 lies only in the type and proportion of raw materials. By mass, 1 part of sheet graphene and 70 parts of concentrated sulfuric acid are mixed evenly by stirring. Then, 4 parts of sodium nitrate and 4 parts of sodium ferrate are added in an ice-water bath environment. After being mixed evenly, the mixture is reacted at 40°C for 5 hours to obtain mixture A.

[0034] Slowly pour the mixture A obtained in the above steps into 100 parts of distilled water, mix thoroughly and cool to room temperature, then add 1 part of benzoyl peroxide and 2 parts of manganese sulfate as a catalyst, stir thoroughly, and after artemisinin or its derivatives have fully reacted with the graphene compound, let the mixture stand.

[0035] After the mixture is allowed to stand, the resulting precipitate is washed and dried to obtain a graphene-based cement concrete admixture.

[0036] Example 3: High-strength and high-durability admixture for graphene-based cement concrete

[0037] The difference between this embodiment and Example 1 lies only in the type and proportion of raw materials. By mass, 1 part of sheet graphene and 80 parts of concentrated sulfuric acid are mixed evenly by stirring. Then, 4 parts of sodium nitrate and 5 parts of sodium ferrate are added in an ice-water bath environment. After being mixed evenly, the mixture is reacted at 40°C for 5 hours to obtain mixture A.

[0038] Slowly pour the mixture A obtained in the above steps into 100 parts of distilled water, mix thoroughly and cool to room temperature, then add 2 parts of peracetic acid and 2 parts of manganese dioxide as a catalyst, stir thoroughly, and after artemisinin or its derivatives have fully reacted with the graphene compound, let the mixture stand.

[0039] After the mixture is allowed to stand, the resulting precipitate is washed and dried to obtain a graphene-based cement concrete admixture.

[0040] Example 4: High-strength and high-durability admixture for graphene-based cement concrete

[0041] The difference between this embodiment and Example 1 lies only in the type and proportion of raw materials. By mass, 1 part of sheet graphene and 70 parts of concentrated sulfuric acid are mixed evenly by stirring. Then, 4 parts of sodium nitrate and 3 parts of sodium ferrate are added in an ice-water bath environment. After being mixed evenly, the mixture is reacted at 40°C for 5 hours to obtain mixture A.

[0042] Slowly pour the mixture A obtained in the above steps into 100 parts of distilled water, mix thoroughly and cool to room temperature, then add 3 parts of peracetic acid and 2 parts of potassium manganate as a catalyst, stir thoroughly, and after artemisinin or its derivatives have fully reacted with the graphene compound, let the mixture stand.

[0043] After the mixture is allowed to stand, the resulting precipitate is washed and dried to obtain a graphene-based cement concrete admixture.

[0044] Comparative Example 1: Graphene Concrete Admixture

[0045] The monolayer graphene was directly supplied by the manufacturer (manufacturer: Nanjing Jicang Nanotechnology Co., Ltd., product name: porous graphene, grade: JCPSG-300-5).

[0046] Comparative Example 2: Graphene Oxide Concrete Admixture

[0047] Graphene oxide is supplied directly by the manufacturer (manufacturer: Nanjing Jicang Nanotechnology Co., Ltd., product name: high-purity graphene oxide, grade: JCGO-100-1-3).

[0048] The performance of the samples from Examples 1-4, the samples from Comparative Examples 1-2, and the blank sample were tested below.

[0049] Water and cementitious material (ordinary Portland cement P·O 42.5) are mixed at a water-cement ratio of 0.35:1 and a cement-sand ratio of 1:3, and stirred evenly to obtain cement mortar for later use.

[0050] The concrete admixtures obtained in the above embodiments were added to the cement mortar at a mass ratio of 0.03%. The modified cement-based composite material was then poured into a mold. After molding, the mold was removed after 24 hours, and the concrete was placed in a curing room with a temperature of 25°C and a humidity of over 90% for standard curing to obtain concrete test blocks. Meanwhile, cement mortar test blocks without any admixtures were used as blank examples, and the mechanical properties at different ages were tested according to the "Test Method for Strength of Cement Mortar" (GB / T 17671-2021). The results are shown in Table 1.

[0051] Table 1. Results of flexural and compressive strength of the example samples and comparative sample at 7d and 28d.

[0052]

[0053] As shown in Table 1, the 7-day and 28-day compressive and flexural strengths of the sample from the embodiments of the present invention are higher than those of the comparative example and far exceed those of the blank sample.

[0054] Each group of samples underwent freeze-thaw cycle testing to evaluate its durability. The relative dynamic modulus of elasticity and mass loss rate of each group of samples were tested after freeze-thaw cycles, and the results were recorded every 50 freeze-thaw cycles. The residual strength ratio of each group of samples was also tested after 300 freeze-thaw cycles, as shown in Tables 2-4.

[0055] As shown in Tables 2-4, the samples from the embodiments of the present invention exhibited higher durability in freeze-thaw cycles compared to the blank and comparative samples. The blank sample and the sample of Comparative Example 1 showed relative loss of dynamic modulus and mass after 100 freeze-thaw cycles. The sample of Comparative Example 2 showed mass loss after 150 freeze-thaw cycles. However, the samples from the embodiments of the present invention only showed relative loss of dynamic modulus and mass after 200 freeze-thaw cycles. Furthermore, after 200 freeze-thaw cycles, the blank sample and the sample of Comparative Example 1 disintegrated, and the sample of Comparative Example 2 disintegrated after 250 freeze-thaw cycles. The samples from the embodiments of the present invention still exhibited high residual strength after 300 freeze-thaw cycles, and their durability was extended by nearly 100% compared to the blank sample.

[0056] Table 2. Relative dynamic modulus of freeze-thaw cycles for the example samples and comparative samples.

[0057] sample initial 50 times 100 times 150 times 200 times 250 times 300 times Example 1 100.00％ 100.00％ 100.00％ 100.00％ 99.04％ 91.16％ 88.58％ Example 2 100.00％ 100.00％ 100.00％ 100.00％ 98.26％ 90.79％ 80.34％ Example 3 100.00％ 100.00％ 100.00％ 100.00％ 99.26％ 91.06％ 82.53％ Example 4 100.00％ 100.00％ 100.00％ 100.00％ 98.54％ 90.07％ 83.37％ blank sample 100.00％ 100.00％ 95.11％ 85.52％ 66.13％ Disintegration Disintegration Comparative Example 1 100.00％ 100.00％ 95.36％ 86.67％ 67.39％ Disintegration Disintegration Comparative Example 2 100.00％ 100.00％ 100.00％ 94.27％ 84.90％ 71.53％ Disintegration

[0058] Table 3. Freeze-thaw cycle mass loss rate of the sample in the example and the comparative sample.

[0059] sample initial 50 times 100 times 150 times 200 times 250 times 300 times Example 1 0.00％ 0.00％ 0.00％ 0.01％ 0.11％ 0.28％ 0.64％ Example 2 0.00％ 0.00％ 0.00％ 0.01％ 0.17％ 0.37％ 0.78％ Example 3 0.00％ 0.00％ 0.00％ 0.09％ 0.21％ 0.41％ 1.07％ Example 4 0.00％ 0.00％ 0.00％ 0.07％ 0.18％ 0.36％ 0.88％ blank sample 0.00％ 0.00％ 0.03％ 0.65％ 3.47％ Disintegration Disintegration Comparative Example 1 0.00％ 0.00％ 0.02％ 0.71％ 3.68％ Disintegration Disintegration Comparative Example 2 0.00％ 0.00％ 0.00％ 0.02％ 0.83％ 4.45％ Disintegration

[0060] Table 4. Freeze-thaw cycle mass loss rate of the sample in the example and the comparative sample.

[0061]

[0062] As can be seen from the above, when applied to cement concrete, this invention can significantly improve the strength and durability of concrete materials and extend their service life. Compared with other graphene-based concrete admixtures, this invention exhibits advantages such as low operational difficulty, simple experimental requirements, convenient construction, and high cost-effectiveness. It has strong technical advantages in application scenarios such as areas with high requirements for concrete material durability and high-altitude and cold regions.

Claims

1. A method for preparing a graphene-based cement concrete admixture, characterized in that: Includes the following steps: Step 1: By mass, mix 1 part graphene or layered graphite with 40-100 parts concentrated sulfuric acid, add 2-8 parts nitrate and 2-8 parts strong oxidizing salt at below 5°C, and react after mixing to obtain mixture A. Step 2: Pour the mixture A obtained in Step 1 into 150-200 parts of hydrophilic solvent, mix and cool to room temperature, then add 1-3 parts of organic matter containing peroxy groups and 1-4 parts of manganese salt as a catalyst, stir to carry out the reaction, and after the reaction is completed, let the mixture stand to obtain the precipitate, wash and dry it to obtain the graphene-based cement concrete admixture. The graphene includes monolayer graphene or oligolayer graphene; the strong oxidizing salt includes ferrate or permanganate; the manganese salt includes manganese sulfate, manganese chloride, manganate or permanganate; the organic compound containing peroxy group includes di-tert-butyl peroxide, peracetic acid, benzoyl peroxide, artemisinin and its derivatives. In step one, the mixture is reacted at a temperature of 30-50°C for 2-6 hours. In step two, the reaction is carried out by stirring, and the reaction time is 30~120 minutes.

2. A graphene-based cement concrete admixture, characterized in that: It is prepared using the preparation method described in claim 1.

3. A type of concrete, characterized in that: The admixture comprises the graphene-based cement concrete admixture as described in claim 2, which accounts for 0.01 to 0.05% of the concrete mass.

Images