Conductive cement-based materials based on modified aggregate-supported graphene and their preparation method
By modifying aggregates and loading them with graphene, combined with a small amount of carbon fiber, the problems of uneven dispersion and high cost of graphene in cement-based materials are solved, achieving improved conductivity and reduced cost, making it suitable for large-scale applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN UNIV OF TECH
- Filing Date
- 2024-01-10
- Publication Date
- 2026-07-31
AI Technical Summary
In existing technologies, graphene is unevenly dispersed in cement-based materials, resulting in poor electrical conductivity. Furthermore, the demand for graphene is large and its cost is high, making large-scale application difficult.
Conductive cement-based materials were prepared by surface modification of aggregates, loading graphene dispersion onto the modified aggregates, and adding a very small amount of carbon fiber.
It improves the dispersibility and conductivity of graphene in cement-based materials, reduces the amount of graphene used, simplifies the process, lowers costs, and is suitable for large-scale production.
Smart Images
Figure CN117923841B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of conductive cement-based materials technology, specifically to a conductive cement-based material based on modified aggregate loaded with graphene and its preparation method. Background Technology
[0002] Ordinary concrete has high resistivity and is a poor conductor of electricity. Adding a certain amount of conductive phase to ordinary concrete can improve its conductivity, thus creating conductive concrete. Graphene is often used as one of the conductive phases added to cement concrete materials, possessing excellent electrical and mechanical properties. Current research mostly involves directly adding graphene to cement-based materials, which easily leads to uneven dispersion and fails to fully utilize its excellent conductivity. Alternatively, some researchers have used chemical vapor deposition to deposit graphene on the surface of cement-based materials. However, the demand for graphene is large, the process is complex, and the cost is high, making it unsuitable for large-scale production and utilization. Summary of the Invention
[0003] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a conductive cement-based material based on modified aggregate loaded with graphene and its preparation method, thereby solving the technical problems of uneven graphene dispersion, poor conductivity, large graphene demand, and high cost in existing conductive cement-based materials.
[0004] In a first aspect, the present invention provides a method for preparing a conductive cement-based material based on modified aggregate-supported graphene, comprising the following steps:
[0005] Surface modification treatment of aggregate: The aggregate is added to a mixed solution of silane coupling agent and first solvent, followed by a first stirring reaction. After the reaction is completed, the aggregate is filtered, washed, and dried to obtain the surface-modified aggregate.
[0006] Graphene dispersion treatment: Graphene is dispersed in a second solvent to obtain a graphene dispersion.
[0007] Graphene-loaded modified aggregate: The surface-modified aggregate is added to the graphene dispersion, followed by a second stirring reaction. After the reaction is completed, the aggregate is filtered and dried to obtain graphene-loaded aggregate.
[0008] Preparation of conductive cement-based materials: Carbon fiber and graphene-loaded aggregates are added to cement, water is added and mixed evenly, and then the mixture is poured, pre-cured, demolded and cured a second time to obtain conductive cement-based materials.
[0009] The mass ratio of the surface-modified aggregate to graphene is 100:(0.15-0.4); the amount of carbon fiber used is 0.1wt%-0.3wt% of the total amount of graphene-loaded aggregate and cement in the conductive cement-based material.
[0010] In a second aspect, the present invention provides a conductive cement-based material based on modified aggregate loaded with graphene, which is obtained by the preparation method of the conductive cement-based material based on modified aggregate loaded with graphene provided in the first aspect of the present invention.
[0011] Compared with the prior art, the beneficial effects of the present invention include:
[0012] This invention improves the dispersibility of nano-graphene in cement-based materials by firmly dispersing and loading it onto surface-modified aggregates, without affecting the excellent properties of graphene itself. This allows the electrical and mechanical properties of nano-graphene in cement-based composite materials to be fully utilized. Simultaneously, by adding a very small amount of carbon fiber to connect the graphene-loaded aggregates, the resistivity of the cement-based materials can be significantly reduced. The small amount of graphene loaded on the modified aggregate surface, in conjunction with the small amount of carbon fiber, significantly improves the conductivity of the cement-based materials and enhances the micromechanical properties of the aggregate-hydration product interface. This invention features a simple process, low cost, and excellent loading effect, making it suitable for large-scale application. Attached Figure Description
[0013] Figure 1 This is a SEM image of the surface morphology of the aggregate used in Embodiment 1 of the present invention before surface modification treatment;
[0014] Figure 2 This is a SEM image of the surface morphology of the aggregate used in Embodiment 1 of the present invention after surface modification treatment;
[0015] Figure 3 This is a SEM image of the surface morphology of the aggregate used in Comparative Example 2 of this invention, which was directly loaded with graphene without surface modification treatment.
[0016] Figure 4 This is a low-magnification SEM image of the surface morphology of the aggregate loaded with graphene after surface modification treatment used in Example 1 of this invention.
[0017] Figure 5 This is a high-magnification SEM image of the surface morphology of the aggregate used in Example 1 of this invention after surface modification treatment and graphene loading. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0019] To address the following problems in existing technologies: such as the uneven dispersion of graphene, which prevents it from fully utilizing its excellent conductivity and interfacial reinforcement properties; or the need for complex processes such as chemical vapor deposition; or the existing conductive cement-based materials, which directly incorporate carbon fibers and graphene into the cement matrix in a certain proportion, are not only difficult to disperse but also costly, requiring a high graphene content to achieve the desired conductivity, and excessive conductive phase content can have adverse effects on the mechanical properties of cement concrete; and current research rarely focuses on the conductivity of aggregates, while making ordinary aggregates into conductive aggregates and adding them to cement-based materials has enormous research potential and is conducive to large-scale promotion and utilization, this invention is established.
[0020] In a first aspect, the present invention provides a method for preparing a conductive cement-based material based on modified aggregate-supported graphene, comprising the following steps:
[0021] S1. Surface modification treatment of aggregate: The aggregate is added to a mixed solution of silane coupling agent and first solvent, followed by a first stirring reaction. After the reaction is completed, the aggregate is filtered, washed, and dried to obtain the surface-modified aggregate.
[0022] S2. Graphene dispersion treatment: Graphene is dispersed in a second solvent to obtain a graphene dispersion.
[0023] S3. Modified aggregate loaded with graphene: The surface-modified aggregate is added to the graphene dispersion, followed by a second stirring reaction. After the reaction is completed, the aggregate is filtered and dried to obtain the graphene-loaded aggregate.
[0024] S4. Preparation of conductive cement-based materials: Carbon fiber and graphene-loaded aggregates are added to cement, water is added and mixed evenly, and then the mixture is poured, pre-cured, demolded and cured a second time to obtain conductive cement-based materials.
[0025] Because the mechanical strength of the transition zone between ordinary aggregates and cement is weak, and the dispersion of graphene directly added to cement-based materials is very difficult, resulting in unsatisfactory conductivity, this invention adopts a method of loading graphene onto the surface of modified aggregates to increase the surface roughness of the aggregates, enhance the physical and chemical bonding strength between the aggregates and graphene, solve the graphene dispersion problem, improve the conductivity of the aggregates, and facilitate the preparation of conductive smart cement-based materials. At the same time, the excellent mechanical properties and interfacial reinforcement properties of graphene are utilized to enhance the bonding strength of the transition zone between aggregates and cement after mixing, thereby improving the mechanical properties.
[0026] Furthermore, this invention, based on loading a very small amount of graphene onto the surface of modified aggregates, incorporates a small amount of carbon fiber into cement-based materials. Graphene, as a nanoscale superfiber, can enrich the nanoscale conductive network when loaded onto the aggregate surface. The conductive aggregates loaded with graphene are connected by a small amount of carbon fiber. The very small amount of graphene loaded onto the surface of modified aggregates, together with a very small amount of carbon fiber, can not only greatly reduce the resistivity of cement-based materials, giving them significant conductivity, but also enhance the mechanical properties of the interfacial transition zone between aggregates and cement matrix. This is of great significance for improving the durability of conductive concrete.
[0027] In this embodiment, in step S1, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550). The silane coupling agent can connect functional groups such as amino groups to the surface of the aggregate, thereby increasing its surface activity and enhancing the bonding strength of graphene to the aggregate surface.
[0028] In this embodiment, in step S1, the first solvent is anhydrous ethanol.
[0029] In this embodiment, in step S1, the volume ratio of the silane coupling agent to the first solvent is 1:(5-20), and more specifically 1:9. A volume ratio that is too high or too low will affect the loading effect of graphene on the aggregate surface, potentially causing problems such as graphene detachment and failure in subsequent applications.
[0030] This invention does not limit the type and particle size of aggregates, and those skilled in the art can select them according to actual conditions. For example, the type of aggregate can be siliceous sand, and the particle size range of the aggregate can be 0.075mm-2.36mm, etc.
[0031] In this embodiment, in step S1, the ratio of aggregate to the mixed solution of silane coupling agent and first solvent is 1g:(1-3)mL, and more specifically 1g:2mL.
[0032] In this embodiment, in step S1, the first stirring reaction is carried out at room temperature, and the stirring time is more than 12 hours, and further 12-24 hours.
[0033] In this embodiment, in step S1, the washing method is water washing, and the number of washing cycles is 3-5 times.
[0034] In this embodiment, in step S2, the second solvent is water.
[0035] In this embodiment, in step S2, the ratio of graphene to the second solvent is (0.075-0.2)g:100mL, and more specifically (0.1-0.15)g:100mL.
[0036] In this embodiment, in step S2, the dispersion method is ultrasonic dispersion, and the dispersion time is 30-60 minutes.
[0037] In this embodiment, in step S3, the mass ratio of the surface-modified aggregate to graphene is 100:(0.15-0.4), preferably 100:(0.2-0.3). If the amount of graphene is too small, it will not be conducive to the loading of graphene on its surface, and may cause insufficient loading; if the amount of graphene is too large, it may cause unnecessary waste of graphene and increase costs.
[0038] In this embodiment, in step S3, the second stirring reaction is carried out at room temperature for a stirring time of at least 12 hours, or more specifically, 12-24 hours. Both excessively high and low temperatures affect the loading effect. Graphene exhibits thermal contraction and expansion; too low a temperature results in slow molecular thermal motion and an unsatisfactory loading effect, while too high a temperature increases the cost of loading graphene and makes the operation more cumbersome. Considering both cost and ease of implementation, this experiment uses room temperature to load graphene onto the aggregate surface, which is simple to operate and more conducive to large-scale promotion and utilization.
[0039] This invention does not limit the amount of aggregate used in conductive cement-based materials, and those skilled in the art can select it according to the actual situation. In some specific embodiments of this invention, the mass ratio of graphene-loaded aggregate to cement is (1-3):1, and more specifically 7:3.
[0040] In this embodiment, in step S4, the amount of carbon fiber used is 0.1wt%-0.3wt% of the total amount of graphene-loaded aggregate and cement in the conductive cement-based material, preferably 0.15wt%-0.2wt%. If the amount of carbon fiber is too high, it will be difficult to disperse, resulting in a decrease in conductivity and negatively affecting the mechanical properties of the cement-based material; if the amount of carbon fiber is too low, it will be difficult to form a complete conductive network, which will also lead to a decrease in conductivity.
[0041] In this embodiment, in step S4, the amount of water used is 10wt%-20wt% of the total amount of graphene-loaded aggregate and cement in the conductive cement-based material.
[0042] This invention does not limit the type and grade of cement, and those skilled in the art can select according to the actual situation. For example, the cement can be PI 42.5, etc.
[0043] This invention does not limit the drying method, and those skilled in the art can choose according to the actual situation. For example, the drying temperature is 40-100℃, and the drying time is 1-24h.
[0044] This invention does not limit the conditions for pre-curing and secondary curing, and those skilled in the art can choose according to the actual situation. For example, the conditions for pre-curing can be: curing at room temperature for 12-24 hours; the conditions for secondary curing can be: curing in a spray curing room, room temperature, relative humidity ≥95%, curing for 7-28 days.
[0045] In a second aspect, the present invention provides a conductive cement-based material based on modified aggregate loaded with graphene, which is obtained by the preparation method of the conductive cement-based material based on modified aggregate loaded with graphene provided in the first aspect of the present invention.
[0046] Example 1
[0047] (1) Surface modification treatment of aggregate: 70g of silica sand aggregate with a particle size of 0.075mm-2.36mm was added to a container containing 140mL of a mixed solution of silane coupling agent (KH550) and anhydrous ethanol (volume ratio 1:9). The container containing the silica sand aggregate and the silane coupling agent solution was then placed at room temperature and stirred for 24h to ensure full contact between the aggregate and the silane coupling agent solution, thereby enhancing the surface modification effect. After the reaction was completed, the modified aggregate was washed 3-5 times with deionized water by filtration, and finally dried in a 40℃ oven for 24h to obtain the surface-modified aggregate.
[0048] (2) Graphene dispersion treatment: 0.14g of graphene was added to 140mL of deionized water and ultrasonically dispersed for 30min to obtain graphene dispersion.
[0049] (3) Graphene-loaded modified aggregate: 70g of surface-modified aggregate was added to 140mL of graphene dispersion, wherein the mass of graphene in the suspension was 0.14g. The mixture was stirred at room temperature for 24h. After the process was completed, it was filtered and placed in a 40℃ forced-air drying oven for 24h to obtain graphene-loaded aggregate.
[0050] (4) Preparation of conductive cement-based material: 70g of graphene-loaded aggregate was added to 30g of PI 42.5 cement and mixed for 10min. Then 0.15g of carbon fiber was added and finally 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0051] The resistivity of the conductive cement-based composite sample after 28 days of curing was tested using the two-electrode method with the test voltage fixed at 20V. The resistivity was found to be 0.346Ω·m, indicating excellent conductivity.
[0052] Example 2
[0053] (1) Surface modification treatment of aggregate: 70g of silica sand aggregate with a particle size of 0.075mm-2.36mm was added to a container containing 140mL of a mixed solution of silane coupling agent (KH550) and anhydrous ethanol (volume ratio 1:9). The container containing the silica sand aggregate and the silane coupling agent solution was then placed at room temperature and stirred for 24h to ensure full contact between the aggregate and the silane coupling agent solution, thereby enhancing the surface modification effect. After the reaction was completed, the modified aggregate was washed 3-5 times with deionized water by filtration, and finally dried in a 40℃ oven for 24h to obtain the surface-modified aggregate.
[0054] (2) Graphene dispersion treatment: 0.14g of graphene was added to 140mL of deionized water and ultrasonically dispersed for 30min to obtain graphene dispersion.
[0055] (3) Graphene-loaded modified aggregate: 70g of surface-modified aggregate was added to 140mL of graphene dispersion, wherein the mass of graphene in the suspension was 0.14g. The mixture was stirred at room temperature for 24h. After the process was completed, it was filtered and placed in a 40℃ forced-air drying oven for 24h to obtain graphene-loaded aggregate.
[0056] (4) Preparation of conductive cement-based material: 70g of graphene-loaded aggregate was added to 30g of PI 42.5 cement and mixed for 10min. Then 0.3g of carbon fiber was added and finally 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0057] The resistivity of a conductive cement-based composite sample cured for 28 days was tested using the two-electrode method with a fixed test voltage of 20V, and the resistivity was found to be 0.638Ω·m.
[0058] Example 3
[0059] (1) Surface modification treatment of aggregate: 70g of silica sand aggregate with a particle size of 0.075mm-2.36mm was added to a container containing 140mL of a mixed solution of silane coupling agent (KH550) and anhydrous ethanol (volume ratio 1:9). The container containing the silica sand aggregate and the silane coupling agent solution was then placed at room temperature and stirred for 24h to ensure full contact between the aggregate and the silane coupling agent solution, thereby enhancing the surface modification effect. After the reaction was completed, the modified aggregate was washed 3-5 times with deionized water by filtration, and finally dried in a 40℃ oven for 24h to obtain the surface-modified aggregate.
[0060] (2) Graphene dispersion treatment: 0.14g of graphene was added to 140mL of deionized water and ultrasonically dispersed for 30min to obtain graphene dispersion.
[0061] (3) Graphene-loaded modified aggregate: 70g of surface-modified aggregate was added to 140mL of graphene dispersion, wherein the mass of graphene in the suspension was 0.14g. The mixture was stirred at room temperature for 24h. After the process was completed, it was filtered and placed in a 40℃ forced-air drying oven for 24h to obtain graphene-loaded aggregate.
[0062] (4) Preparation of conductive cement-based material: 70g of graphene-loaded aggregate was added to 30g of PI 42.5 cement and mixed for 10min. Then 0.06g of carbon fiber was added and 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0063] The resistivity of the conductive cement-based composite sample after 28 days of curing was tested using the two-electrode method with the test voltage fixed at 20V, and the resistivity was found to be 16.5Ω·m.
[0064] Example 4
[0065] (1) Surface modification treatment of aggregate: 70g of silica sand aggregate with a particle size of 0.075mm-2.36mm was added to a container containing 140mL of a mixed solution of silane coupling agent (KH550) and anhydrous ethanol (volume ratio 1:9). The container containing the silica sand aggregate and the silane coupling agent solution was then placed at room temperature and stirred for 24h to ensure full contact between the aggregate and the silane coupling agent solution, thereby enhancing the surface modification effect. After the reaction was completed, the modified aggregate was washed 3-5 times with deionized water by filtration, and finally dried in a 40℃ oven for 24h to obtain the surface-modified aggregate.
[0066] (2) Graphene dispersion treatment: 0.07 g of graphene was added to 140 mL of deionized water and ultrasonically dispersed for 30 min to obtain graphene dispersion.
[0067] (3) Graphene-loaded modified aggregate: 70g of surface-modified aggregate was added to 140mL of graphene dispersion, wherein the mass of graphene in the suspension was 0.07g. The mixture was stirred at room temperature for 24h. After the process was completed, it was filtered and placed in a 40℃ forced-air drying oven for 24h to obtain graphene-loaded aggregate.
[0068] (4) Preparation of conductive cement-based material: 70g of graphene-loaded aggregate was added to 30g of PI 42.5 cement and mixed for 10min. Then 0.15g of carbon fiber was added and finally 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0069] The resistivity of the conductive cement-based composite sample after 28 days of curing was tested using the two-electrode method with the test voltage fixed at 20V, and the resistivity was found to be 3.58Ω·m.
[0070] Example 5
[0071] (1) Surface modification treatment of aggregate: 70g of silica sand aggregate with a particle size of 0.075mm-2.36mm was added to a container containing 140mL of a mixed solution of silane coupling agent (KH550) and anhydrous ethanol (volume ratio 1:9). The container containing the silica sand aggregate and the silane coupling agent solution was then placed at room temperature and stirred for 24h to ensure full contact between the aggregate and the silane coupling agent solution, thereby enhancing the surface modification effect. After the reaction was completed, the modified aggregate was washed 3-5 times with deionized water by filtration, and finally dried in a 40℃ oven for 24h to obtain the surface-modified aggregate.
[0072] (2) Graphene dispersion treatment: 0.28g of graphene was added to 140mL of deionized water and ultrasonically dispersed for 30min to obtain graphene dispersion.
[0073] (3) Graphene-loaded modified aggregate: 70g of surface-modified aggregate was added to 140mL of graphene dispersion, wherein the mass of graphene in the suspension was 0.28g. The mixture was stirred at room temperature for 24h. After the process was completed, it was filtered and placed in a 40℃ forced-air drying oven for 24h to obtain graphene-loaded aggregate.
[0074] (4) Preparation of conductive cement-based material: 70g of graphene-loaded aggregate was added to 30g of PI 42.5 cement and mixed for 10min. Then 0.15g of carbon fiber was added and finally 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0075] The resistivity of the conductive cement-based composite sample after 28 days of curing was tested using the two-electrode method with the test voltage fixed at 20V, and the resistivity was found to be 0.379Ω·m.
[0076] Comparative Example 1
[0077] Aggregate and graphene direct mixing treatment: 70g of silica sand with a particle size of 0.075mm-2.36mm and 0.14g of graphene were directly added to 30g of PI 42.5 cement and mixed for 10min. Then 0.15g of carbon fiber was added, and finally 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated to compact it, and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0078] The resistivity of the conductive cement-based composite sample after 28 days of curing was tested using the two-electrode method with the test voltage fixed at 20V, and the resistivity was found to be 91.27Ω·m.
[0079] Comparative Example 2
[0080] (1) Graphene dispersion treatment: 0.14g of graphene was added to 140mL of deionized water and ultrasonically dispersed for 30min to obtain graphene dispersion.
[0081] (2) Unmodified aggregate loaded with graphene: 70g of silica sand with a particle size of 0.075mm-2.36mm was added to 140mL of graphene dispersion, wherein the mass of graphene in the suspension was 0.14g. The mixture was stirred at room temperature for 24h. After the process was completed, it was filtered and placed in a 40℃ forced-air drying oven for 24h to obtain aggregate loaded with graphene.
[0082] (3) Preparation of conductive cement-based material: 70g of graphene-loaded aggregate was added to 30g of PI 42.5 cement and mixed for 10min. Then 0.15g of carbon fiber was added and finally 12g of deionized water was added and mixed for 10min. The mixture was poured into a 20*20*100mm steel mold, vibrated and then electrode plates were inserted with a spacing of 80mm between the two electrode plates. The steel mold was then wrapped tightly with plastic wrap and cured at room temperature for 24h. After curing, the mold was demolded and placed in a spray curing room (room temperature, relative humidity ≥95%) for 28 days to obtain conductive cement-based material.
[0083] The resistivity of the conductive cement-based composite sample after 28 days of curing was tested using the two-electrode method with the test voltage fixed at 20V, and the resistivity was found to be 46.5Ω·m.
[0084] Please see Figure 1-5 , Figure 1 This is a SEM image of the surface morphology of the aggregate used in Embodiment 1 of the present invention before surface modification treatment. Figure 1 It can be seen that the surface of the aggregate was smooth before modification treatment; Figure 2 This is a SEM image of the surface morphology of the aggregate used in Embodiment 1 of the present invention after surface modification treatment. Figure 2 It can be seen that the surface of the aggregate becomes rough after the modification treatment; Figure 3 This is a SEM image of the surface morphology of the aggregate used in Comparative Example 2 of this invention, which was directly loaded with graphene without surface modification treatment. Figure 3 It can be seen that the loading effect is poor when graphene is directly loaded onto aggregates without surface modification treatment; Figure 4-5 This is a SEM image of the surface morphology of the aggregate loaded with graphene after surface modification treatment used in Example 1 of the present invention. The aggregate loaded with graphene after surface modification treatment has a good loading effect, indicating that the method of the present invention can effectively load graphene on the surface of aggregate.
[0085] Meanwhile, to make the effects of this application more intuitive, the component dosage and resistivity results of the above embodiments and comparative examples are summarized in Table 1.
[0086] Table 1. Component dosage and resistivity results of embodiments and comparative examples of the present invention.
[0087]
[0088]
[0089] As shown in Table 1, this invention, by using aggregate modified with a silane coupling agent and loading a small amount of graphene, along with a small amount of carbon fiber, to incorporate into cement-based materials, achieves a conductivity improvement of several orders of magnitude compared to ordinary cement-based materials. At the same graphene content, the modified aggregate exhibits a higher degree of graphene loading and better conductivity compared to unmodified aggregate. Furthermore, the study found that the optimal graphene loading is 0.2 wt% of the modified aggregate mass, and the optimal carbon fiber content is 0.15 wt% of the total mass of aggregate and cement in the modified aggregate-loaded conductive cement-based material, resulting in a significant improvement in the conductivity of the cement mortar compared to the control group.
[0090] Compared to Example 1, Example 2 uses carbon fiber accounting for 0.3 wt% of the total mass of aggregate and cement in the conductive cement-based material. The resistivity of the resulting conductive cement-based material is slightly increased compared to Example 1, indicating that excessive carbon fiber content may have a negative impact on the conductivity of the cement-based composite material. This may be related to the hydrophobicity of the carbon fiber itself and the agglomeration of the carbon fiber.
[0091] Compared to Example 1, Example 3 uses carbon fiber accounting for 0.06 wt% of the total mass of aggregate and cement in the conductive cement-based material. The conductivity of the prepared conductive cement-based material decreased, indicating that when the carbon fiber content is too low, an effective conductive network cannot be formed inside the cement-based composite material.
[0092] Compared to Example 1, Example 4 used 0.1 wt% graphene as a percentage of the modified aggregate mass, and the conductivity of the prepared conductive cement-based material decreased, indicating that when the graphene loading is low, a graphene coating layer cannot be fully formed on the aggregate surface.
[0093] Compared to Example 1, Example 5 uses graphene at 0.4 wt% of the modified aggregate mass. The conductivity of the prepared conductive cement-based material is similar to that of Example 1. Although the conductivity is comparable, the higher graphene content increases the preparation cost.
[0094] Compared to Examples 1-5, Comparative Example 1 directly added carbon fibers and graphene to cement, and the conductivity was far inferior to that of Examples 1-5. This indicates that by directly incorporating carbon fibers and graphene, they tend to agglomerate in the cement matrix and cannot form a complete conductive network. When the amount used is small, the conductivity is poor.
[0095] Compared to Examples 1-5, Comparative Example 2 involved loading unmodified aggregate with graphene and then adding it to cement along with carbon fibers. The conductivity was also far inferior to that of Examples 1-5, indicating that when aggregate is loaded with graphene directly without surface modification, the graphene may detach and peel off, affecting the conductivity.
[0096] In summary, this invention loads graphene onto the surface of aggregates using a simple room-temperature stirring method. The aggregates themselves are not conductive, but after being loaded with nano-graphene, they exhibit excellent conductivity, achieving a breakthrough from zero to one. At the same time, by loading graphene onto the aggregates, the conductivity and surface roughness of the aggregates are greatly improved. When added to the cement matrix, the interfacial bonding strength between the aggregates and the cement matrix is enhanced. After loading a very small amount of graphene, the conductivity effect is significantly improved compared to ordinary aggregates when added to cement-based materials.
[0097] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for the preparation of a graphene loaded electrically conductive cementitious material based on modified aggregates, characterized by, Includes the following steps: Surface modification treatment of aggregate: The aggregate is added to a mixed solution of silane coupling agent and first solvent, followed by a first stirring reaction. After the reaction is completed, the aggregate is filtered, washed, and dried to obtain the surface-modified aggregate. Graphene dispersion treatment: Graphene is dispersed in a second solvent to obtain a graphene dispersion. Graphene-loaded modified aggregate: The surface-modified aggregate is added to the graphene dispersion, followed by a second stirring reaction. After the reaction is completed, the aggregate is filtered and dried to obtain graphene-loaded aggregate. Preparation of conductive cement-based materials: Carbon fiber and graphene-loaded aggregates are added to cement, water is added and mixed evenly, and then the mixture is poured, pre-cured, demolded and cured a second time to obtain conductive cement-based materials. Wherein, the silane coupling agent is γ-aminopropyltriethoxysilane; the first solvent is anhydrous ethanol; the volume ratio of the silane coupling agent to the first solvent is 1:(5-20); the volume ratio of the aggregate to the mixed solution of the silane coupling agent and the first solvent is 1g:(1-3)mL; the mass ratio of the surface-modified aggregate to graphene is 100:(0.15-0.4); and the amount of carbon fiber is 0.1wt%-0.3wt% of the total amount of graphene-loaded aggregate and cement in the conductive cement-based material.
2. The method for preparing conductive cement-based materials based on modified aggregate supported on graphene according to claim 1, characterized in that, The second solvent is water; the ratio of graphene to the second solvent is (0.075-0.2) g: 100 mL; the dispersion method is ultrasonic dispersion, and the dispersion time is 30-60 min.
3. The method for preparing conductive cement-based materials based on modified aggregate supported on graphene according to claim 1, characterized in that, The mass ratio of the surface-modified aggregate to graphene is 100:(0.2-0.3).
4. The method for preparing conductive cement-based materials based on modified aggregate supported on graphene according to claim 1, characterized in that, The first and second stirring reactions were carried out at room temperature for a stirring time of more than 12 hours.
5. The method for preparing conductive cement-based materials based on modified aggregate supported on graphene according to claim 1, characterized in that, The amount of carbon fiber used is 0.15wt%-0.2wt% of the total amount of graphene-loaded aggregate and cement in the conductive cement-based material.
6. The method for preparing conductive cement-based materials based on modified aggregate supported on graphene according to claim 1, characterized in that, In the preparation steps of the conductive cement-based material, the mass ratio of the graphene-loaded aggregate to the cement is (1-3):1; the amount of water used is 10wt%-20wt% of the total amount of the graphene-loaded aggregate and cement used in the conductive cement-based material.
7. The method for preparing conductive cement-based materials based on modified aggregate supported on graphene according to claim 1, characterized in that, The pre-curing conditions are: room temperature curing for 12-24 hours; the secondary curing conditions are: spray curing room, room temperature, relative humidity ≥95%, curing for 7-28 days.
8. A conductive cement-based material based on modified aggregate supported on graphene, characterized in that, The conductive cementitious material based on modified aggregate loaded with graphene is obtained by the preparation method of the conductive cementitious material based on modified aggregate loaded with graphene as described in any one of claims 1-7.