Functional cement mortar composite material and preparation method thereof

Abstract

The invention discloses a functional cement mortar composite material and a preparation method thereof, and belongs to the field of building materials. The preparation method comprises the following steps: preparing reduced graphene oxide from L-ascorbic acid and graphene oxide, mixing a polycarboxylate superplasticizer (PC) with the reduced graphene oxide to prepare a uniformly dispersed PC-reduced graphene oxide suspension, and finally compounding the PC-reduced graphene oxide suspension, Portland cement and river sand to form the cement mortar composite material. The reduced graphene oxide cement mortar composite material prepared by the invention can effectively improve the functionality of cement mortar, including electrical conductivity, pressure sensitivity and electrothermal property.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and more particularly to a functional cement mortar composite material and a preparation method thereof. Background Art

[0002] Cement mortar is currently the most widely used building material in the world and an essential component of concrete construction. However, with the advancement of science and the development of society, demands for cement mortar have expanded beyond strength to include greater functionality, such as electrical conductivity, thermoelectricity, pressure sensitivity, and Joule heating. To further enhance the functionality of cement mortar, researchers have experimented with incorporating various functional materials into it. Therefore, the search for fillers that can effectively modify the properties of cement mortar, in order to enhance its functionality, has become a current research priority.

[0003] Reduced graphene oxide is a graphene derivative produced by oxidizing and then reducing graphene. As a carbon conductive material, graphene has excellent electrical conductivity, but its high hydrophobicity and chemical inertness prevent it from truly bonding with cement and exerting its excellent properties. The oxidized graphene surface is rich in oxygen-containing functional groups. The presence of these oxygen-containing functional groups transforms the graphene from hydrophobic to hydrophilic and allows it to participate in the cement hydration process, achieving better bonding with the cement base. However, the presence of these oxygen-containing functional groups also breaks the large π bonds between the graphene sheets. Reduced graphene oxide restores some of the large π bonds to improve conductivity while still being water-soluble, allowing for better bonding with the cement base. The excellent conductivity and water solubility of reduced graphene oxide offer the potential for improving the functionality of cement mortar materials. Summary of the Invention

[0004] In view of this, the technical solution of the present invention uses L-ascorbic acid as a reducing agent to reduce graphene oxide to prepare reduced graphene oxide and adds it to cement mortar to prepare functional cement mortar. The cement mortar prepared by this method has good electrical conductivity, pressure-sensitive properties and electrical-to-heat conversion properties.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a functional cement mortar composite material comprises the following steps:

[0007] (1) dispersing graphene oxide in deionized water, then adding L-ascorbic acid, ultrasonicating, and allowing to react. After the reaction is completed, filtering and washing to obtain reduced graphene oxide;

[0008] (2) dispersing a polycarboxylate water reducer in deionized water at a concentration of 0.5% by weight of cement, and then adding the reduced graphene oxide prepared in step (1) and uniformly mixing to obtain a PC-reduced graphene oxide suspension;

[0009] (3) Compounding the PC-reduced graphene oxide suspension obtained in step (2) with silicate cement and river sand to form a functional cement mortar composite material.

[0010] Preferably, the method for preparing graphene oxide comprises the following steps:

[0011] 1 g of graphite powder was mixed with 23 ml of 98% concentrated H2SO4 and 3 g of KMnO4 was added. The mixture was reacted in an ice bath for 3 to 4 hours, and then ultrasonically treated at 100 W power for 8 to 12 hours. Deionized water was then added to dilute the mixture and the reaction was continued. After the reaction was completed, 10 ml of 30% H2O2 was added, and the mixture was centrifuged at 10,000 r / min for 5 to 10 minutes and then washed to obtain graphene oxide.

[0012] When diluting, first add 46 ml of deionized water and continue the reaction for 15 minutes, then add 120 ml of deionized water at 75-90°C for dilution.

[0013] Preferably, in step (1), the mass ratio of L-ascorbic acid to graphene oxide is 2:1, and the concentration of graphene oxide in deionized water is 1 g / L.

[0014] Preferably, in step (1), the ultrasonic treatment time is 30 to 60 minutes at a power of 100W, and the reaction is allowed to stand for 1 to 24 hours.

[0015] Preferably, in step (1), deionized water is used for washing until the washing liquid becomes neutral.

[0016] Preferably, in step (2), the mass ratio of the polycarboxylate water-reducing agent to the reduced graphene oxide is 2.5:2.

[0017] Preferably, the uniform mixing in step (2) is carried out by magnetic stirring at 240 rpm and ultrasonic mixing, specifically, magnetic stirring is first performed for 5 to 10 minutes, and then the mixture is ultrasonically treated at a power of 100 W for 10 to 20 minutes.

[0018] Preferably, in step (3), the mass ratio of PC-reduced graphene oxide suspension, silicate cement and river sand is 1:2.18:6.7.

[0019] The present invention also provides a functional cement mortar composite material prepared by the method described in the above technical solution. After the materials are mixed, they are placed in a mold and wait for 1 day to be formed. After forming, the mold is removed and cured for 28 days under standard curing conditions.

[0020] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a functional cement mortar composite material and a preparation method thereof, which has the following beneficial effects:

[0021] The green reducing agent L-ascorbic acid used in the present invention is low in price, has no toxic products and does not pollute the environment. The reduction process is mild and can remove oxygen-containing functional groups to restore large π bonds while retaining some functional groups, so that they can be better combined with cement mortar and the functionality of the cement mortar can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of resistivity testing using the four-electrode method. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] The preparation process of graphene oxide used in the following examples is as follows:

[0026] 1 g of graphite powder was mixed with 23 ml of 98% concentrated H2SO4 and 3 g of KMnO4 was added. The mixture was reacted in an ice bath for 3 to 4 hours, and then ultrasonically treated at 100 W power for 8 to 12 hours. Deionized water was then added to dilute the mixture and the reaction was continued. After the reaction was completed, 10 ml of 30% H2O2 was added, and the mixture was centrifuged at 10,000 r / min for 5 to 10 minutes and then washed to obtain graphene oxide.

[0027] The particle size distribution of river sand is shown in Table 1:

[0028] Table 1 River sand particle size distribution

[0029]

[0030] Example 1

[0031] (1) 2 g of L-ascorbic acid and 1 g of graphene oxide were added to 1 L of deionized water, the mixed solution was ultrasonically treated for 30 min, allowed to react for 1 h, filtered, and rinsed with deionized water until the washing liquid was neutral to obtain reduced graphene oxide;

[0032] (2) using 2.5 g of polycarboxylic acid water reducer to mix with 2 g of reduced graphene oxide prepared in step (1), first magnetically stirring for 8 min, and then ultrasonically treating the mixture for 20 min to prepare a uniformly dispersed PC-reduced graphene oxide suspension;

[0033] (3) The PC-reduced graphene oxide suspension, silicate cement and river sand were stirred and mixed according to the mass of 227.63 g, 495 g and 1485 g respectively, and the mixture was formed after 1 day and cured for 28 days.

[0034] Example 2

[0035] (1) Add 2 g of L-ascorbic acid and 1 g of graphene oxide to 1 L of deionized water, ultrasonically treat the mixed solution for 30 min, let it stand for 12 h, filter it, and rinse it with deionized water until the washing liquid is neutral to obtain reduced graphene oxide;

[0036] (2) using 2.5 g of polycarboxylic acid water reducer to mix with 2 g of reduced graphene oxide prepared in step (1), first magnetically stirring for 10 min, and then ultrasonically treating the mixture for 10 min to prepare a uniformly dispersed PC-reduced graphene oxide suspension;

[0037] (3) The PC-reduced graphene oxide suspension, silicate cement and river sand were stirred and mixed according to the mass of 227.63 g, 495 g and 1485 g respectively, and the mixture was formed after 1 day and cured for 28 days.

[0038] Example 3

[0039] (1) 2 g of L-ascorbic acid and 1 g of graphene oxide were added to 1 L of deionized water, the mixed solution was ultrasonically treated for 30 min, allowed to react for 24 h, filtered, and rinsed with deionized water until the washing liquid was neutral to obtain reduced graphene oxide;

[0040] (2) using 2.5 g of polycarboxylate water reducer to mix with 2 g of reduced graphene oxide prepared in step (1), first magnetically stirring for 5 min, and then ultrasonically treating the mixture for 20 min to prepare a uniformly dispersed PC-reduced graphene oxide suspension;

[0041] (3) The PC-reduced graphene oxide suspension, silicate cement and river sand were stirred and mixed according to the mass of 227.63 g, 495 g and 1485 g respectively, and the mixture was formed after 1 day and cured for 28 days.

[0042] Comparative Example 1

[0043] The difference from Example 1 is that no PC-reduced graphene oxide is added.

[0044] Experimental example

[0045] The reduced graphene oxide cement mortar composite materials prepared in Examples 1 to 3 of the present invention and the ordinary cement mortar material (GBT 17671-2021 cement mortar strength test method (ISO method)) were tested for resistivity using the four-electrode method (such as Figure 1 As shown), pressure sensitivity test and electric-to-thermal performance test.

[0046] Before testing, the specimens were placed in a forced air drying oven for 24 h to eliminate the influence of free water inside the composite material on the results.

[0047] The electric-to-thermal performance test involves placing the dried specimen in a refrigerator and refrigerating it to 0°C. Using a DC regulated power supply to power it, a 30V voltage is applied to both ends of the specimen, and the surface temperature change of the specimen is recorded after 15 minutes under the power-on condition.

[0048] The test results are shown in Table 2.

[0049] Table 2 Functional test results of reduced graphene oxide cement mortar composite materials of Examples 1 to 3

[0050] performance Example 1 Example 2 Example 3 Comparative Example 1 Resistivity (Ω·m) 296 127.87 93.56 9996 Varistor voltage change value (v) 0.014 0.021 0.034 0 Temperature change (℃) 6 8 11 3

[0051] As can be seen from Examples 1, 2, and 3, the composite materials produced in this application exhibit significantly improved electrical conductivity, pressure-sensitive properties, and electrothermal heating performance. Furthermore, Example 3 exhibits optimal functionality, concluding that a reasonable reduction reaction time of graphene oxide and L-ascorbic acid can produce a relatively ideal reduced graphene oxide cement mortar composite material product.

[0052] Among current reducing agents, L-ascorbic acid has a mild reduction strength, produces no harmful substances during the reduction process, and is environmentally friendly and non-polluting. For the preparation of reduced graphene oxide, while restoring the large π bonds between carbon atoms in different layers that determine conductivity, it also retains some oxygen-containing functional groups, preserving the chemical properties of reduced graphene oxide and enabling it to bind well with cement mortar. Cement mortar itself has minimal electrical conductivity. Reduced graphene oxide not only has good conductivity, but the oxygen-containing functional groups on its surface and edges reduce the van der Waals forces between its layers, allowing it to be better dispersed in the cement mortar to form a coherent conductive network, effectively improving the conductivity of the cement mortar and, in turn, enhancing other functional properties of the cement mortar, such as pressure sensitivity and electrical-to-thermal conversion.

[0053] The reduced graphene oxide cement mortar composite material prepared in this application can transform the electrical insulation properties of ordinary cement mortar materials, develop the functionality of cement mortar materials, and can be used for indoor heating, health monitoring of concrete structures, crack repair and durability evaluation.

[0054] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a functional cement mortar composite material, characterized in that: The following steps are involved: (1) dispersing graphene oxide in deionized water, then adding L-ascorbic acid, ultrasonicating, and allowing to react. After the reaction is completed, filtering and washing to obtain reduced graphene oxide; (2) dispersing a polycarboxylate water reducer in deionized water at a concentration of 0.5% by weight of cement, and then adding the reduced graphene oxide prepared in step (1) and uniformly mixing to obtain a PC-reduced graphene oxide suspension; (3) Compounding the PC-reduced graphene oxide suspension obtained in step (2) with silicate cement and river sand to form a functional cement mortar composite material.

2. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: The graphene oxide preparation method comprises the following steps: 1 g of graphite powder was mixed with 23 ml of 98% concentrated H2SO4 and 3 g of KMnO4 was added. The mixture was reacted in an ice bath for 3 to 4 hours, and then ultrasonically treated at 100 W power for 8 to 12 hours. Deionized water was then added to dilute the mixture and the reaction was continued. After the reaction was completed, 10 ml of 30% H2O2 was added, and the mixture was centrifuged at 10,000 r / min for 5 to 10 minutes and then washed to obtain graphene oxide. When diluting, first add 46 ml of deionized water and continue the reaction for 15 minutes, then add 120 ml of deionized water at 75-90°C for dilution.

3. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: In step (1), the mass ratio of L-ascorbic acid to graphene oxide is 2:1, and the concentration of graphene oxide in deionized water is 1 g / L.

4. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: In step (1), the ultrasonic treatment time is 30 to 60 minutes at a power of 100W, and the reaction is allowed to stand for 1 to 24 hours.

5. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: In step (1), deionized water is used for washing until the washing liquid becomes neutral.

6. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: In step (2), the mass ratio of the polycarboxylic acid water reducer to the reduced graphene oxide is 2.5:

2.

7. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: In step (2), the uniform mixing is carried out by magnetic stirring at 240 rpm and ultrasonic mixing. Specifically, the mixture is first magnetically stirred for 5 to 10 minutes, and then ultrasonically treated at a power of 100 W for 10 to 20 minutes.

8. The method for preparing a functional cement mortar composite material according to claim 1, characterized in that: In step (3), the mass ratio of PC-reduced graphene oxide suspension, silicate cement and river sand is 1:2.18:6.

7.

9. A functional cement mortar composite material prepared by the method according to any one of claims 1 to 8.

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