Low-dosage carbon nanotube high-performance intelligent waste ceramic concrete and preparation process thereof

Abstract

The application discloses low-dosage carbon nanotube high-performance intelligent waste ceramic concrete and a preparation process thereof, utilizes 0.3% low-dosage carbon nanotubes and waste ceramic combination, adopts ultrasonic and high-speed shearing dispersion carbon nanotube process, and the prepared concrete has 28d flexural strength of 16.8MPa, compressive strength of 105.5MPa, 28d fracture energy and compression work of 209.4J / m 2 And 162.0kN·mm, the resistivity change rate under the action of a cyclic load with an amplitude of 10MPa is as high as 16.17%, and stress / strain sensitivity is 1.62% / MPa and 575.9, respectively. Through the design and preparation of the above high-performance concrete material, the green high-performance intelligent concrete can be obtained under low-dosage carbon nanotubes, the electrical, mechanical properties and low-carbon property of the concrete are improved, and a path for efficient and high-value-added resource utilization of waste ceramic is provided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of building materials, and particularly relates to a production technology of high-performance and green intelligent concrete, in particular to a low-dosage carbon nanotube high-performance intelligent waste ceramic concrete and a preparation process thereof. BACKGROUND

[0002] Carbon nanotubes are nanoscale fibers with a tensile strength of 11-63 GPa, a Young's modulus of about 1 TPa, and a fracture strain of up to 280%, which are ideal reinforcing materials. Numerous studies have shown that carbon nanotubes can improve the micro-defects and cracks of cement-based materials at the micro level, thereby improving the mechanical properties of concrete and imparting intelligent properties to concrete. However, high dosages of carbon nanotubes are usually required to obtain intelligent properties of concrete materials. At the same time, high dosages of carbon nanotubes generally reduce the workability, mechanical properties of concrete, and increase the cost of concrete materials due to difficulty in uniform dispersion and high water absorption. Using a suitable dispersion method to improve the dispersion of carbon nanotubes and improve their modification efficiency is an effective way to solve the contradiction between the improvement of the mechanical properties of concrete and the enhancement of intelligent properties of carbon nanotubes.

[0003] The extensive use of concrete requires a large amount of cement and aggregate, which leads to high energy consumption and increases the load on the environment. Using industrial waste to partially or completely replace cement and aggregate is considered a solution that can reduce the environmental impact of cement production and contribute to the sustainable development of green concrete. Waste ceramic aggregate has high hardness and good wear resistance. Finely ground waste ceramic powder has pozzolanic activity and can be used as a new green mineral admixture. Its electrical conductivity is better than that of ordinary aggregate and cement. The use of waste ceramic in concrete can improve its mechanical and electrical properties, reduce the cost of concrete, and improve its low-carbon properties. SUMMARY

[0004] In order to overcome the defects of the prior art, the present application aims to solve the problems of high carbon emissions, low flexural and compressive strength, poor toughness, difficult dispersion of carbon nanotubes, low modification efficiency, and the need for high dosages of carbon nanotubes to obtain self-sensing properties during the preparation of concrete.

[0005] In order to achieve the above-mentioned application purposes, the present application uses a combination of ultrasonic and high-speed shearing to improve the dispersion effect and modification efficiency of carbon nanotubes. The synergistic effect of carbon nanotubes and waste ceramic is used to incorporate low-dosage carbon nanotubes into waste ceramic concrete to obtain green high-performance intelligent concrete with high flexural and compressive strength, fracture toughness, compressive toughness, and pressure-sensitive properties. The use of waste ceramic admixture to replace part of the cement and all the aggregate improves the electrical, mechanical properties, and low-carbon properties of concrete.

[0006] The application discloses a preparation process of low-dosage carbon nanotube high-performance intelligent waste ceramic concrete.

[0007] ①According to the designed mixing ratio, various raw materials are weighed;

[0008] ②Water, a polycarboxylic acid high-efficiency water reducing agent and carbon nanotubes are mixed, and after appropriate oscillation, the mixed solution is subjected to ultrasonic treatment and high-speed shearing dispersion emulsification treatment for 8-12 min; the ultrasonic power is set to 60%, and the mixed solution is controlled in temperature by an ice water bath, so that the carbon nanotube mixed solution is well dispersed;

[0009] ③Cement and waste ceramic powder are uniformly poured into a concrete mixer and dry stirred for 120 s, and then the carbon nanotube mixed solution subjected to ultrasonic dispersion and cooled to room temperature is poured into the mixer, and the stirring is continued for 120 s;

[0010] ④The ceramic aggregate is uniformly poured into the mixer and stirred for 15 min, so that a concrete mixture with good fluidity is obtained;

[0011] ⑤The mixture is poured into a mold, placed on a vibrating table, vibrated until the surface is covered with slurry, then the surface of the test piece is smoothed with a spatula, and the surface is covered with a fresh-keeping film to prevent water evaporation;

[0012] ⑥The mold is removed after being cured in a standard environment for 24 h, and the removed test piece is cured in water at 20±1 DEG C.

[0013] Further, the raw materials and the mixing ratio in step ① comprise: cement, 75% of the mass of cementitious materials; ceramic powder, 25% of the mass of cementitious materials; ceramic aggregate, 1 times of the mass of cementitious materials; polycarboxylic acid water reducing agent, 2.5% of the mass of cementitious materials; carbon nanotubes, 0.3% of the mass of cementitious materials; and water-cement ratio, 0.18.

[0014] Further, the water reducing agent is preferably a polycarboxylic acid high-efficiency water reducing agent.

[0015] Further, the cement is preferably ordinary Portland cement.

[0016] Further, the ceramic aggregate is obtained by crushing and screening waste ceramic tiles, has a fineness modulus of 1.98 and an apparent density of 2400-2500 kg / m 3 .

[0017] Further, the ceramic powder is obtained by grinding the waste ceramic aggregate, has a particle size of 0-1 mm and a specific surface area of 1000-1100 m 2 / kg.

[0018] A low-dosage carbon nanotube high-performance intelligent waste ceramic concrete prepared by the above process.

[0019] The application of the above low-doped carbon nanotube high-performance intelligent waste ceramic concrete in green intelligent buildings and as sensors in structural health monitoring.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] ①The combination of ultrasonic and high-speed shearing promotes the dispersion of carbon nanotubes and improves the modification efficiency of carbon nanotubes. In the case of low doping, carbon nanotubes can endow cement-based materials with higher self-sensing performance on the basis of high mechanical performance.

[0022] ②The use of waste ceramic powder to replace part of the cement and the use of waste ceramic as aggregate can optimize the performance and structure of the concrete, promote the formation of a widely distributed reinforcing network of carbon nanotubes in the cement-based material, and improve the electrical and self-sensing performance of the matrix; and play a synergistic modification role.

[0023] ③The incorporation of waste ceramic powder can partially replace cement, and the replacement of natural sand with waste ceramic aggregate can reduce the accumulation and environmental pollution of waste ceramic; through the design of high-performance concrete materials, green intelligent high-performance concrete can be obtained, which not only has good economic efficiency, but also meets the requirements of green low-carbon, energy saving and emission reduction. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The column chart of the flexural strength of the concrete test piece prepared for the example;

[0025] Figure 2 The column chart of the compressive strength of the concrete test piece prepared for the example;

[0026] Figure 3 The sensing performance of the concrete test piece prepared for the example: (a) stress and resistance change rate change curve; (b) strain and resistance change rate change curve. DETAILED DESCRIPTION

[0027] The application will be further described below in conjunction with specific examples, but in no way limit the application. To avoid repetition, in the following examples, the raw materials are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified. The detection of the flexural and compressive strength of the concrete test piece is in accordance with GB / T17671-2021 "Cement Mortar Strength Test Method (ISO Method)", and the detection of the fracture toughness and compressive toughness of the concrete test piece is in accordance with CECS13-2009 "Fiber Concrete Test Method Standard".

[0028] The raw material mixing ratio is shown in Table 1. Test piece 1 of the example is a raw material mixing ratio of a low-dosage carbon nanotube high-performance intelligent waste ceramic concrete mixed with 0.3 wt.% multi-walled carbon nanotubes, and three test pieces with the same raw material mixing ratio, i.e., test pieces 1-1, 1-2 and 1-3, are prepared.

[0029] Table 1 Raw material mixing ratio of the example

[0030]

[0031] The compressive strength, flexural strength, fracture toughness and compression toughness of the low-dosage carbon nanotube waste ceramic high-performance concrete are tested at 7d and 28d ages by using an electronic universal testing machine, wherein the loading rate of the compressive strength and the compression toughness is 1.2mm / min, and the loading rate of the flexural strength and the fracture toughness test is 0.1mm / min. At 28d age, the self-sensing performance of the low-dosage carbon nanotube waste ceramic high-performance concrete is tested by using an alternating current meter, a strain acquisition instrument and an electronic universal testing machine. The test conditions of the self-sensing performance under cyclic loading are as follows: the loading amplitude is 10MPa, the loading rate is 0.4mm / min, and the cyclic loading times is 7.

[0032] Example

[0033] The preparation process of the low-dosage carbon nanotube high-performance intelligent waste ceramic concrete comprises the following steps:

[0034] ①The various raw materials are weighed according to the designed mixing ratio; the water reducing agent is Point-S polycarboxylic acid high-efficiency water reducing agent; the cement is ordinary Portland cement P·O 52.5; the ceramic aggregate is obtained by crushing and sieving the waste ceramic tiles from a local ceramic tile processing factory, the fineness modulus is 1.98, and the apparent density is 2435kg / m 3 ; the ceramic powder is obtained by grinding the waste ceramic aggregate, the particle size is 0-1mm, and the specific surface area is 1071m 2 / kg.

[0035] ②The water, the polycarboxylic acid high-efficiency water reducing agent and the carbon nanotubes are poured into a beaker, and after appropriate oscillation, the mixture in the beaker is treated by an ultrasonic processor and a high-speed shearing dispersion emulsifier for 10min, the ultrasonic power is set to 60%, and the dispersion liquid is controlled by an ice water bath, so as to obtain a well-dispersed carbon nanotube mixture;

[0036] ③The cement and the waste ceramic powder are uniformly poured into a concrete mixer and stirred for 120s, then the carbon nanotube mixture cooled to room temperature after ultrasonic dispersion is poured into the mixer, and the stirring is continued for 120s;

[0037] ④ Pour the waste ceramic fine aggregate evenly into the mixer and mix for 15 minutes until a concrete mixture with good fluidity is obtained;

[0038] ⑤ Pour the mixture into a mold (40mm×40mm×160mm), place it on a vibrating table, vibrate until slurry appears on the surface, then smooth the surface of the specimen with a trowel and cover the surface with plastic wrap to prevent moisture evaporation;

[0039] ⑥ After curing the mold in a standard environment for 24 hours, demold the specimen. Place the demolded specimen in water at 20±1℃ for curing. Perform performance tests at the corresponding age.

[0040] The test results of various properties of the concrete in the examples are as follows: Figures 1-3 As shown in Table 2. From Figure 1 It can be seen that when the carbon nanotube content is 0.3%, the average 7-day and 28-day flexural strengths of the waste ceramic high-performance concrete are 17.0 MPa and 16.8 MPa, respectively (calculated from the average values ​​of three specimens with the same mix proportion, Specimens 1-1, 1-2, and 1-3). Figure 2 It can be seen that the average 7-day and 28-day compressive strengths of the waste ceramic high-performance concrete with 0.3% carbon nanotubes can reach 94.4 MPa and 105.5 MPa, respectively. Table 2 shows that the average 7-day and 28-day fracture energies of the waste ceramic high-performance concrete with 0.3% carbon nanotubes are 160.5 J / m². 2 and 177.3 J / m 2 The average compressive energy at 7 days and 28 days were 114.8 kN·mm and 150.8 kN·mm, respectively. These mechanical property test results indicate that a combination of low-dosage carbon nanotubes and waste ceramics can produce green, high-performance concrete with high flexural and compressive strength, fracture toughness, and compressive toughness.

[0041] Depend on Figure 3 It can be seen that, under cyclic loading, the resistivity change rate of high-performance concrete containing 0.3% carbon nanotube waste ceramics changes synchronously with the stress / strain changes, reaching 16.17%, and the stress / strain sensitivity reaches 1.62% / MPa and 575.9, respectively. The above self-sensing performance test results indicate that the combination of low-dosage carbon nanotubes and waste ceramics can yield green high-performance concrete with intelligent properties. In summary, green high-performance intelligent concrete can be obtained through the above design of concrete materials.

[0042] Table 2. Fracture energy and compressive energy of the specimens in the examples.

[0043]

[0044] For any skilled person familiar with the art, many possible variations and modifications of the technical solutions of the present application can be made using the technical content disclosed above without departing from the scope of the technical solutions of the present application, or modified as equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solutions of the present application shall still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A low-dosage carbon nanotube high-performance intelligent waste ceramic concrete, characterized in that, The 7d and 28d fracture energy average of the waste ceramic high-performance concrete mixed with 0.3% carbon nanotubes are 160.5 J / m 2 and 177.3 J / m 2 respectively, and the 7d and 28d compression work average are 114.8 kN·mm and 150.8 kN·mm respectively; under cyclic loading, the resistivity change rate of the waste ceramic high-performance concrete mixed with 0.3% carbon nanotubes changes synchronously with the change of stress / strain, the resistivity change rate reaches 16.17%, and the stress / strain sensitivity reaches 1.62% / MPa and 575.9 respectively; The preparation process of the low-dosage carbon nanotube high-performance intelligent waste ceramic concrete comprises the following steps: ①According to the designed mixing ratio, various raw materials are weighed; The raw materials and their mixing ratio include: cement, 75% of the mass of cementitious materials; ceramic powder, 25% of the mass of cementitious materials; ceramic aggregate, 1 times of the mass of cementitious materials; polycarboxylic acid water reducing agent, 2.5% of the mass of cementitious materials; carbon nanotubes, 0.3% of the mass of cementitious materials; The water-binder ratio is 0.18; The ceramic aggregate is obtained by crushing and screening waste ceramic tiles, has a fineness modulus of 1.98 and an apparent density of 2400-2500 kg / m 3 ; The ceramic powder is ground from waste ceramic aggregate, with a particle size of 0-1 mm and a specific surface area of 1000-1100 m 2 / kg; The water reducing agent is a polycarboxylic acid superplasticizer, and the cement is ordinary Portland cement; ②Mix water, polycarboxylic acid superplasticizer and carbon nanotubes, and treat the mixed solution with ultrasonic wave and high-speed shearing dispersion emulsification for 8-12 min, and control the temperature of the mixed solution with ice water bath; ③Add cement and ceramic powder into a concrete mixer and dry stir for 120 s, then pour the mixed solution in step ② which is cooled to room temperature after ultrasonic dispersion into the mixer, and continue to stir for 120 s; ④Pour the ceramic aggregate into the mixer evenly and stir for 15 min to obtain a mixture; ⑤Pour the mixture into a mold, vibrate to the surface to make the slurry, and cover the surface with plastic wrap; ⑥After curing in the standard environment for 24 h, demold the mold, and place the demolded test piece in water at 20±1℃ for curing; and obtain the low-dosage carbon nanotube high-performance intelligent waste ceramic concrete.

2. Application of the low-dosage carbon nanotube high-performance intelligent waste ceramic concrete in green intelligent buildings and as a sensor in structural health monitoring.

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