Novel nano synergistic interaction high-strength self-sensing cement-based material

Abstract

The invention discloses a novel nano synergistic interaction high-strength self-sensing cement-based material which is prepared from components such as a cement-based cementing material, aggregate, water, a water reducing agent, multi-walled carbon nanotubes, nano titanium dioxide and nano montmorillonite in a synergistic manner according to a specific proportion. Wherein after the multi-walled carbon nanotubes are subjected to surface modification and pre-dispersion treatment, a high-sensitivity three-dimensional conductive network can be formed in a cement matrix; pores of a cement hydration product are filled with nano titanium dioxide, so that the compactness and durability of the material are remarkably enhanced, and the conductivity is enhanced; the nano-montmorillonite is dispersed in a matrix in a lamellar structure, and micro-crack propagation is inhibited and the overall toughness is improved through a bridging effect.

Description

Technical Field

[0001] This invention belongs to the field of novel multifunctional materials, and mainly relates to a novel high-strength self-sensing cement-based material with nano-synergistic enhancement. Background Technology

[0002] As a core component of modern infrastructure, the structural safety assessment of traditional cement-based materials has long relied on periodic visual inspections and localized non-destructive testing techniques. These traditional methods are not only costly in terms of manpower and resources, but also, due to their discreteness and lag, struggle to capture the initiation and continuous evolution of early micro-damage within the structure. This fails to meet the urgent need for real-time, online, and intelligent structural health monitoring and early warning systems in modern large-scale engineering projects. To overcome this limitation and endow concrete materials with inherent "sensing" capabilities, enabling them to transform internal stress, strain, and damage states into measurable physical signals, has become a significant research direction in the field of civil engineering materials over the past two decades.

[0003] In early explorations, researchers primarily aimed to impart conductivity and self-sensing capabilities to cement-based composites by incorporating macroscopically conductive phases, such as steel fibers and carbon fibers. While this method achieved the effect of resistance varying with stress to some extent, its inherent technical limitations restricted practical applications. To form a continuous conductive path, the fiber content typically needs to reach a high level, which often leads to a significant decrease in the workability of fresh concrete and may adversely affect key mechanical properties of hardened concrete, such as compressive strength and elastic modulus. Macroscopic fibers mainly form conductive networks through physical overlap, resulting in low sensitivity to micro-strain and early micro-cracks. The electrical signals exhibit high noise and poor repeatability. During long-term service in corrosive environments such as humidity and salt spray, steel fibers are prone to corrosion, and the interface between carbon fibers and the matrix is ​​easily degraded, leading to decreased stability of the conductive network, severe drift in the sensing signal, and difficulty in ensuring reliable monitoring throughout the entire life cycle.

[0004] To alleviate the limitations of macroscopic conductive phases, carbon-based nanomaterials, represented by carbon nanotubes and graphene, have attracted much attention due to their unique electrical and mechanical properties. Numerous studies both domestically and internationally have shown that carbon nanotubes can form highly efficient percolation conductive networks in cement matrices at low dosages, exhibiting extremely high sensitivity to minute strains and damage, demonstrating promising theoretical prospects. However, carbon nanotubes have a huge specific surface area and extremely high surface energy, making them prone to agglomeration in strongly alkaline cement paste environments. While surface acidification and silane coupling agent modification can improve dispersibility to some extent, maintaining the structural integrity and functional stability of the nanoconductive network under the coupled effects of complex dynamic hydration processes and long-term diverse service environments remains a core technical obstacle hindering its practical application in engineering.

[0005] To overcome the bottlenecks in the application of single nanomaterials, the strategy of multi-component nanocomposite modification has emerged. Co-doping nano-titanium dioxide with carbon nanotubes aims to improve material durability while enhancing conductivity through the micro-filling effect of titanium dioxide. Current research largely focuses on the simple physical mixing of binary systems, lacking systematic design and regulation of the deep synergistic mechanisms between multi-component nanomaterials. While nano-titanium dioxide can optimize some pore structures, its effect on improving the dispersion of carbon nanotubes is limited, and its contribution to improving the material's toughness and crack resistance is insufficient. Under the complex stress-environment coupling effects in practical engineering, its self-sensing function often exhibits problems such as signal attenuation, baseline drift, and weak anti-interference ability, indicating a significant gap from highly reliable and long-life engineering applications.

[0006] This invention discloses a novel high-strength self-sensing cement-based material with synergistic nanotechnology, comprising cement-based cementitious materials, aggregates, water, water-reducing agents, and multi-walled carbon nanotubes, nano-titanium dioxide, and nano-montmorillonite in a specific ratio. The multi-walled carbon nanotubes, after surface modification and pre-dispersion treatment, form a highly sensitive three-dimensional conductive network within the cement matrix. Nano-titanium dioxide fills the pores of cement hydration products, significantly enhancing the material's density, durability, and conductivity. Nano-montmorillonite, dispersed in the matrix in a layered structure, inhibits microcrack propagation and improves overall toughness through a bridging effect. Summary of the Invention

[0007] This invention aims to systematically address the core contradictions existing in the field of self-sensing cement-based materials, including the contradiction between the high nanomaterial content required for conductive network construction and the degradation of matrix mechanical properties, the contradiction between sensing sensitivity and long-term signal stability, and the difficulty in synergistically achieving sensing function and structural durability under complex service environments. Existing technologies either struggle to balance high strength and high sensing sensitivity, or cannot ensure the stability of the conductive network and the reliability of the sensing signal in harsh environments. To overcome these limitations, this invention designs and discloses a novel high-strength self-sensing cement-based material based on the synergistic design of multi-scale nanomaterials. Through carefully selected functional nanocomponents and their precisely quantified synergistic effects, it aims to achieve integrated optimization of sensing, mechanical, and durability properties.

[0008] According to some embodiments of the present invention, a novel high-strength self-sensing cement-based material with nano-synergistic effects comprises silicate cement or other cementitious materials, finely graded coarse and fine aggregates, mixing water, and a high-efficiency polycarboxylate superplasticizer. Its core innovation lies in the introduction of three functional nanomaterials in specific proportions and after special pretreatment: multi-walled carbon nanotubes, nano-titanium dioxide, and nano-montmorillonite. These three components are not simply physically mixed, but rather, through precise proportioning design and optimized composite processes, they exert unique and complementary functions at the micro and nanoscale during cement hydration and hardening, jointly constructing a high-performance composite material system. This synergistic mechanism is key to the multifunctional integration achieved by the present invention.

[0009] According to some embodiments of the present invention, a novel high-strength self-sensing cement-based material with nano-synergistic effects is disclosed. The multi-walled carbon nanotubes are surface-functionalized (e.g., by introducing carboxyl or hydroxyl functional groups using a strong acid oxidation method) and pre-dispersed in a portion of the mixing water to form a homogeneous and stable suspension slurry with the aid of ultrasonic treatment and surfactants. The dosage is controlled within a critical range of 0.05% to 0.3% of the total mass of the cementitious material, aiming to form a complete permeable conductive network within the matrix with the lowest effective dosage. The carbon nanotubes treated in this way effectively avoid agglomeration in strongly alkaline cement slurry. After uniform dispersion, they overlap to form a three-dimensional conductive pathway that is highly sensitive to stress, strain, and microcracks, serving as the "nerve unit" for achieving the material's highly sensitive self-sensing function.

[0010] According to some embodiments of the present invention, a novel high-strength self-sensing cement-based material with nano-synergistic enhancement is disclosed, wherein the nano-titanium dioxide is preferably anatase type, with an average particle size between 20 and 50 nm, and an adsorption amount of 0.5% to 3.0% of the total mass of the cementitious material. Its main functions are microstructure enhancement and auxiliary stabilization: on the one hand, the nanoscale titanium dioxide particles can effectively fill the gel pores and transition zone pores between cement hydration products, significantly refining the pore size distribution and improving the density, compressive strength, and impermeability of the matrix; on the other hand, its high chemical stability and surface properties help improve the interface, providing a more stable physical support environment for the carbon nanotube network, and to a certain extent assisting charge transport, jointly enhancing the stability of the conductive network during long-term service.

[0011] According to some embodiments of the present invention, a novel high-strength self-sensing cement-based material with nano-synergistic effects is disclosed, wherein the nano-montmorillonite is calcium-based nano-montmorillonite, which is a white powder and has not undergone additional processing before use. Its dosage ranges from 0.5% to 2.5% of the total mass of the cementitious material. The montmorillonite sheets can be well exfoliated and dispersed in a hydrated environment, and its core function lies in toughening and optimization: the nanosheets, as physical barrier agents, can effectively hinder the propagation of microcracks, consuming a large amount of energy through crack deflection, bridging, and sheet pull-out mechanisms, thereby significantly improving the fracture toughness and crack resistance of the composite material; simultaneously, its unique sheet structure can also promote further spatial dispersion of carbon nanotubes during stirring, optimizing the homogeneity of the conductive network.

[0012] According to some embodiments of the present invention, a novel high-strength self-sensing cementitious material with synergistic nanotechnology is disclosed, wherein the incorporation of the three nanocomponents follows a specific addition sequence and composite process. It is generally recommended to first mix a pre-dispersed carbon nanotube slurry with a fully hydrated and dispersed nano-montmorillonite suspension to form a primary functional slurry, which is then co-stirred with dry materials and a liquid phase containing a water-reducing agent and nano-titanium dioxide. This process aims to maximize the utilization of the physicochemical properties of each component, ensure the uniform distribution of nanomaterials in macroscopic concrete, and promote effective synergy at the microscale, ultimately achieving an overall improvement in material performance.

[0013] According to some embodiments of the present invention, a novel high-strength self-sensing cement-based material with nano-synergistic enhancement is characterized by the following features compared with the prior art: (1) The present invention constructs a stable conductive network with low doping based on carbon nanotubes and nano-titanium dioxide, realizing conductivity and strain sensing performance, and providing an electrical signal source for monitoring.

[0014] (2) This invention significantly improves the compressive strength and fracture toughness of the material through the synergistic enhancement of nano-titanium dioxide and nano-montmorillonite, overcoming the bottleneck of insufficient strength of traditional conductive concrete. Attached Figure Description

[0015] Figure 1 is a schematic diagram of the principle of a novel high-strength self-sensing cement-based material with nano-synergistic enhancement in an embodiment of the present invention.

[0016] Part number in the figure: 1- A concrete sample of a novel high-strength self-sensing cement-based material with synergistic nano-effects, 1-1 nano-titanium dioxide, 1-2 nano-montmorillonite, 1-3 carbon nanotubes.

[0017] Figure 2 is a magnified schematic diagram of nano-titanium dioxide in an electron microscope of a novel high-strength self-sensing cement-based material with nano-synergistic effect in an embodiment of the present invention.

[0018] Figure 3 is a schematic diagram of nano-montmorillonite in an electron microscope of a novel high-strength self-sensing cement-based material with nano-synergistic enhancement in an embodiment of the present invention.

[0019] Figure 4 is a magnified schematic diagram of carbon nanotubes in an electron microscope of a novel high-strength self-sensing cement-based material with nano-synergistic enhancement in an embodiment of the present invention. Detailed Implementation

[0020] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings: Combination Figure 1 The present invention discloses a novel high-strength self-sensing cement-based material with nano-synergistic enhancement, characterized in that: after optimization and adjustment, the proportions of each component in the material are as follows, and the raw materials are in the following mass parts: 100 parts of ordinary silicate cement; 170 parts of medium sand with a fineness modulus of 2.6; 275 parts of crushed stone with a particle size of 5-20mm; 40 parts of mixing water; 0.6 parts of polycarboxylate-based high-performance water-reducing agent; and functional nano-components including 0.1 parts of pre-dispersed multi-walled carbon nanotubes, 1.5 parts of nano-titanium dioxide powder, and 1.2 parts of nano-montmorillonite powder. In the preparation process, nano-montmorillonite is first pre-hydrated to form a stable suspension, and then combined with pre-dispersed multi-walled carbon nanotube slurry. Subsequently, nano-titanium dioxide is mixed with water-reducing agent and residual water to form a slurry, and then thoroughly stirred with the aforementioned nano-composite slurry. Finally, this functional composite slurry is stirred together with dry-mixed cement and aggregate for 4-6 minutes until completely homogeneous. After molding, compaction, and curing under standard conditions for 28 days, a specimen with high strength, high toughness, and self-sensing properties is obtained.

[0022] Figure 2This is a magnified electron microscope image of nano-titanium dioxide in a novel high-strength self-sensing cement-based material with nano-synergistic effects, as described in this invention. As shown, the nano-titanium dioxide particles are uniformly embedded in the micropores of cement hydration products in a highly dispersed state. Their effective micro-filling effect significantly refines the pore structure of the matrix, not only improving the material's density, mechanical strength, and impermeability, but also providing a more robust physical support environment for the long-term stability of the carbon nanotube conductive network, thus synergistically enhancing overall durability.

[0023] Figure 3 This is a magnified electron microscope image of nano-montmorillonite in a novel high-strength self-sensing cement-based material with nano-synergistic effects, as described in this invention. The image clearly shows nano-montmorillonite uniformly dispersed in a peeled, lamellar morphology. These lamellar layers play a crucial bridging and crack-resistant role in the cement matrix. When microcracks propagate to this point, their paths are deflected, bypassed, or effectively blocked, thereby consuming fracture energy and significantly improving the material's fracture toughness and crack resistance. Simultaneously, this lamellar structure also provides beneficial steric hindrance for the uniform dispersion of carbon nanotubes.

[0024] Figure 4 This is a magnified electron microscope image of carbon nanotubes in a novel high-strength self-sensing cement-based material with nano-synergistic enhancement, as described in this invention. The image shows that the pre-dispersed carbon nanotubes form an overlapping and interwoven three-dimensional conductive network within the matrix. This network is extremely sensitive to stress, strain, and micro-damage; changes in its topology directly cause regular changes in the overall resistance of the material, thus achieving high sensitivity and real-time electrical response to the internal mechanical state of the structure. This is the core mechanism by which the material achieves its self-sensing function. Example

[0025] The mixture consists of 100 parts ordinary silicate cement, 150 parts standard sand, 260 parts 5-16mm granite crushed stone, 35 parts mixing water, and 0.8 parts polycarboxylate-based high-performance water-reducing agent. The functional nanomaterial composition is as follows: 0.08 parts multi-walled carbon nanotubes, 1.0 part anatase nano-titanium dioxide, and 0.8 parts nano-montmorillonite, with carbon nanotubes and titanium dioxide accounting for 0.08% and 1% of the cementitious material mass, respectively. In preparation, nano-montmorillonite is first mixed with 20% of the total mixing water and stirred at low speed for 24 hours to allow for full hydration and expansion. Then, carboxylated multi-walled carbon nanotubes are mixed with an appropriate amount of polycarboxylate water-reducing agent and some mixing water, and ultrasonically treated to form a stable dispersion slurry. The above two slurries are then combined with nano-titanium dioxide powder, the remaining water-reducing agent, and the remaining water and sheared at high speed to prepare a uniform composite functional slurry. Finally, this functional slurry is added together with pre-dry-mixed cement, sand, and stone into a forced mixer and mixed until uniform. After being discharged and molded, specimens are obtained after standard curing. Example

[0026] This embodiment prepares a highly durable self-sensing concrete suitable for long-term monitoring in harsh environments. The raw materials, by weight, are: 100 parts marine silicate cement, 165 parts river sand, 275 parts crushed stone, 38 parts mixing water, and 0.7 parts slow-release polycarboxylate superplasticizer. The functional nanomaterial composition is: 0.12 parts hydroxylated multi-walled carbon nanotubes, 2.0 parts nano-titanium dioxide, and 1.5 parts nano-montmorillonite, with their respective weight percentages in the cementitious material being 0.12%, 2%, and 1.5%. First, the nano-montmorillonite is pre-hydrated and then composited with a pre-dispersed multi-walled carbon nanotube slurry. After mixing nano-titanium dioxide with the superplasticizer and water to form a slurry, it is thoroughly stirred with the aforementioned nanocomposite slurry. Finally, this functional composite slurry is mixed with the pre-dry-mixed cement, admixtures, and aggregates until completely homogeneous. After molding and curing, specimens are obtained. Example

[0027] This embodiment prepares a self-sensing concrete focusing on high toughness and accurate early warning of crack damage. The raw materials, by weight, are: 85 parts ordinary Portland cement, 15 parts slag powder, 170 parts medium sand, 265 parts crushed stone, 42 parts mixing water, and 0.6 parts water-reducing agent. The functional nanomaterial composition is: 0.15 parts multi-walled carbon nanotubes, 0.8 parts nano-titanium dioxide, and 2.2 parts nano-montmorillonite. A step-by-step incorporation process is used in the preparation. First, the slag powder is dry-mixed evenly with cement to form a composite cementitious material. Then, a nano-montmorillonite suspension is initially mixed with the cementitious material, followed by the addition of nano-titanium dioxide and some mixing water. Finally, pre-dispersed carbon nanotube slurry and the remaining components are added and stirred. After molding and curing, a specimen with excellent toughness and damage sensing ability is obtained.

Claims

1. A novel high-strength self-sensing cement-based material with nano-synergistic enhancement, characterized in that, It includes cement-based cementitious materials, aggregates, water, water-reducing agents, and functional nano-components, wherein the functional nano-components include multi-walled carbon nanotubes, nano-titanium dioxide, and nano-montmorillonite.

2. The high-strength self-sensing cement-based material according to claim 1, characterized in that, The multi-walled carbon nanotubes are added at a rate of 0.05% to 0.3% of the total mass of the cementitious material, the nano-titanium dioxide is added at a rate of 0.5% to 3.0% of the total mass of the cementitious material, and the nano-montmorillonite is added at a rate of 0.5% to 2.5% of the total mass of the cementitious material.

3. The high-strength self-sensing cement-based material according to claim 1 or 2, characterized in that, The multi-walled carbon nanotubes are modified by surface carboxylation or hydroxylation and then incorporated into a uniform suspension slurry after being processed by a pre-dispersion process.

4. The high-strength self-sensing cement-based material according to claim 1 or 2, characterized in that, The nano-titanium dioxide is anatase type, with an average particle size between 20-50 nm.

5. The high-strength self-sensing cement-based material according to claim 1 or 2, characterized in that, The nano-montmorillonite is calcium-based nano-montmorillonite, which is a white powder and has not undergone any additional processing before use.

6. A method for preparing a high-strength self-sensing cement-based material as described in any one of claims 1-5, characterized in that, Includes the following steps: The pre-dispersed multi-walled carbon nanotube slurry, nano-montmorillonite suspension, nano-titanium dioxide, and a portion of mixing water and water-reducing agent are mixed to form a uniform functional slurry; then the functional slurry is stirred together with cement, aggregate and other dry components until it is uniformly mixed.

7. The preparation method according to claim 6, characterized in that, The pre-dispersion treatment of the multi-walled carbon nanotubes includes: placing the surface-modified multi-walled carbon nanotubes in an aqueous solution containing a dispersant, and then subjecting them to ultrasonic and high-speed shearing treatment to form a stable and dispersed suspension slurry.

8. A method for monitoring structural health, characterized in that, The high-strength self-sensing cement-based material as described in any one of claims 1-5 is used to construct or repair civil engineering structural components to be monitored, and the internal stress, strain state and damage evolution are sensed in real time by monitoring the changes in resistance or resistivity of the components during service.

9. The structural health monitoring method according to claim 8, characterized in that, By analyzing the time-domain and amplitude characteristics of the resistance or resistivity change signal, the health status of the structure is graded and assessed for early warning. The health status includes the elastic working stage, the plastic development stage, the microcrack initiation stage, and the macrocrack propagation stage.

10. The structural health monitoring method according to claim 8 or 9, characterized in that, The civil engineering structural components include key load-bearing parts of bridges, tunnels, buildings, dams, or utility tunnels.

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