A large volume hydrophobic concrete for bridge piers and towers in plateau areas

Abstract

The present invention discloses a large-volume hydrophobic concrete for bridge piers and towers in plateau areas, which comprises the following raw materials by weight: high crack resistance and low heat silicate cement: 250-350 kg / m 3 ; Cement-based hydrophobic material: 50-100 kg / m 3 Rice husk ash: 5-20 kg / m 3 ; Carbon nanotubes: 0.3~1.5kg / m 3 Crushed stone: 1000~1150kg / m 3 ; Artificial sand: 700~850kg / m 3 ; Powdered polycarboxylate water reducer: 0.5~1.5kg / m 3 ; Water: 130~160kg / m 3 The present invention uses high-crack-resistant low-heat Portland cement, cement-based hydrophobic materials, rice husk ash and carbon nanotubes to prepare large-volume hydrophobic concrete, which can reduce concrete shrinkage, improve concrete crack resistance, and enhance the durability of bridge piers and towers in plateau areas.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a large-volume hydrophobic concrete for bridge piers and towers in plateau areas. Background Art

[0002] my country's plateau regions suffer from a harsh climate characterized by large diurnal temperature swings, frequent snowstorms, thin air, and intense sunlight, posing a serious threat to the durability of bridge piers and towers. The plateau's large temperature swings, in the presence of free water, can easily lead to freeze-thaw damage within concrete. Compared to the impact of hydration rate on concrete performance, severe freeze-thaw damage is the primary factor contributing to reduced concrete durability. Concrete contains a large amount of water during mixing, which participates in cement hydration and improves concrete workability. After hardening, the water within the concrete remains in its pores, migrating and exchanging with moisture in the environment. Under conditions of large temperature swings, the free water in the concrete's pores freezes at subfreezing temperatures, generating expansion stresses that increase the concrete's porosity, loosen its structure, and cause aggregate erosion and shedding from the outside in, reducing the concrete's durability.

[0003] To improve the frost resistance and crack resistance of concrete in plateau areas, application number CN202211718909.1 describes a self-healing concrete waterproofing agent for plateau areas. The agent comprises an active component, a reinforcing component, a hydrophobic component, a nano-component, and an expansive component. This waterproofing agent allows concrete to self-heal microcracks caused by environmental factors during service, reducing durability issues caused by these cracks and significantly improving concrete durability. The waterproofing agent is suitable for protecting concrete building materials in the harsh environmental conditions of high-altitude plateau areas. However, the waterproofing agent has low adhesion to the concrete surface, and the waterproofing layer is prone to detachment. In addition to hydrophobic treatment of concrete structures, a large number of studies have been conducted on the overall hydrophobic modification of concrete. For example, by introducing fluoroalkyl silanes into the fresh cement mixture, an overall super-hydrophobic concrete with superior mechanical stability is prepared. The disadvantages of this method are that fluoroalkyl silanes are expensive and environmentally harmful; the introduction of fluoroalkyl silanes can reduce the compressive strength of the concrete. Furthermore, when lipophilic hydrophobic substances are added to cement-based materials, the presence of water makes them difficult to disperse within the cement-based material. This phenomenon leads to uneven hydrophobicity of cement-based materials. Therefore, hydrophobic substances are usually dispersed in aqueous solutions to form emulsions for hydrophobic modification of cement-based materials. However, this method has complicated operation steps and is not suitable for large-scale engineering promotion and application. Summary of the Invention

[0004] The purpose of the present invention is to provide a large-volume hydrophobic concrete for bridge piers and towers in plateau areas. The large-volume hydrophobic concrete is prepared by using crack-resistant low-heat silicate cement, cement-based hydrophobic materials, rice husk ash and carbon nanotubes to improve the durability of the bridge piers and towers in plateau areas.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A large-volume hydrophobic concrete for bridge piers and towers in plateau areas comprises the following raw materials by weight:

[0007] High crack resistance and low heat Portland cement: 250-350 kg / m 3 ;

[0008] Cement-based hydrophobic material: 50-100 kg / m 3 ;

[0009] Rice husk ash: 5-20 kg / m 3 ;

[0010] Carbon nanotubes: 0.3-1.5 kg / m 3 ;

[0011] Crushed stone: 1000~1150kg / m 3 ;

[0012] Machine-made sand: 700-850kg / m 3 ;

[0013] Powdered polycarboxylate water reducer: 0.5~1.5kg / m 3 ;

[0014] Water: 130-160 kg / m 3 .

[0015] Furthermore, the high crack resistance and low heat Portland cement consists of 95 wt% of high crack resistance and low heat Portland cement clinker and 5 wt% of gypsum.

[0016] Furthermore, the clinker rate values of the high-cracking-resistant, low-heat Portland cement clinker are: lime saturation coefficient: 0.80-0.88; silicon rate: 2.50-2.70; aluminum rate: 0.70-0.75.

[0017] Furthermore, in the high crack resistance and low heat Portland cement clinker, the C4AF content is greater than 17%, the C3A content is less than 5%, and the MgO content ranges from 2 to 5%.

[0018] Furthermore, the specific surface area of the high crack resistance low heat Portland cement is 300-350m 2 / kg.

[0019] Furthermore, the cement-based hydrophobic material is prepared by grinding 60-80wt% of high-cracking-resistant low-heat silicate cement clinker, 10-20wt% of limestone, 10-20wt% of high-titanium slag, and 1-1.5wt% of stearic acid; preferably, the grinding speed is 100-150r / min, and the grinding time is 30-45min.

[0020] Furthermore, in the cement-based hydrophobic material, the content of particles with a particle size of ≤3 μm is 6-9%, the content of particles with a size of 3-32 μm is 73-78%, the content of particles with a size of 32-65 μm is 12-20%, and the content of particles with a size of ≥65 μm is less than 1%.

[0021] Furthermore, the cement-based hydrophobic material has a 45 μm sieve residue of 8 to 10%, a characteristic particle size of 19±0.2 μm, and a uniformity coefficient of 0.93 to 0.95.

[0022] The particle gradation curve of the cement-based hydrophobic material is close to the Fuller curve.

[0023] Furthermore, the rice husk ash is prepared by placing the rice husk in a high-temperature furnace at 500-700° C. and calcining it for 1-3 minutes to obtain particles containing 10-20% carbon residue.

[0024] The rice husk ash is rich in active silicon dioxide.

[0025] Furthermore, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 8 to 15 nm and a length of 30 to 50 nm.

[0026] The carbon nanotubes have good infrared light absorption and hydrophobic properties.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) By controlling the content of C4AF and C3A in high-crack-resistant, low-heat Portland cement, concrete shrinkage can be reduced. C4AF has the lowest brittleness coefficient and volume shrinkage rate. In high-crack-resistant, low-heat Portland cement, increasing its content to above 17% can effectively reduce concrete shrinkage. In addition, since C3A has a high shrinkage deformation rate, controlling its content to below 5% can reduce concrete shrinkage and improve concrete crack resistance.

[0029] (2) Stearic acid and high crack resistance low heat Portland cement clinker, limestone and high titanium slag are ground together to form a cement-based hydrophobic material, so that stearic acid can be evenly distributed on the surface of the material. When the concrete is stirred, the cement-based hydrophobic material is evenly distributed, thereby improving the hydrophobicity of the concrete, and solving the problem of uneven distribution of hydrophobic agents in concrete in the prior art. In addition, due to the addition of hydrophobic materials, the concrete fluidity will inevitably deteriorate. For this reason, the present invention utilizes high crack resistance low heat Portland cement clinker, high titanium slag, and limestone with different grindability to prepare a hydrophobic material with a particle gradation close to the ideal distribution. Through the gradation advantage, the water demand is reduced and the mechanical properties of the concrete are improved.

[0030] (3) Cement-based hydrophobic materials are filled in order according to particle size. Large particles support each other to form a skeleton, and fine particles are filled in the gaps in the skeleton of large particles. They are intertwined with each other and play a role in rolling lubrication for large particles. On the one hand, the density of cement slurry can be improved. On the other hand, the amount of water used in slurry preparation can be reduced, thereby improving the stability and structural strength of cement slurry and reducing the drying shrinkage value.

[0031] (4) Due to incomplete combustion of rice husks, the rice husk ash contains amorphous carbon powder, which can refine the pores of concrete, reduce the wettability of cement paste, and improve the hydrophobicity of concrete.

[0032] (5) Since cement-based hydrophobic materials, rice husk ash, and carbon nanotubes are all internally incorporated into concrete, if the concrete cracks, the fracture surface still has uniform hydrophobicity, and moisture will not penetrate into the interior of the concrete through the cracks.

[0033] (6) Multi-walled carbon nanotubes have the ability to absorb infrared light. In winter, the carbon nanotubes inside the concrete absorb infrared rays and convert them into heat, which can increase the temperature inside the concrete and thus improve the concrete's frost resistance. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] As a preferred embodiment of the present invention, this embodiment provides a large-volume hydrophobic concrete for bridge piers and towers in plateau areas, comprising the following raw materials by weight:

[0037] High crack resistance and low heat silicate cement: 250kg / m3 ;

[0038] Cement-based hydrophobic material: 100kg / m 3 ;

[0039] Rice husk ash: 5kg / m 3 ;

[0040] Carbon nanotubes: 1.5kg / m 3 ;

[0041] Crushed stone: 1150kg / m 3 ;

[0042] Machine-made sand: 733kg / m 3 ;

[0043] Powdered polycarboxylate water reducer: 0.5kg / m 3 ;

[0044] Water: 160kg / m 3 .

[0045] In this embodiment, the high crack resistance and low heat Portland cement is composed of 95 wt % of high crack resistance and low heat Portland cement clinker and 5 wt % of gypsum.

[0046] Furthermore, the clinker rate values of the high crack resistance and low heat silicate cement clinker are: lime saturation coefficient: 0.80; silicon rate: 2.70; aluminum rate: 0.73.

[0047] Furthermore, in the high crack resistance low heat Portland cement clinker: the C4AF content is 18%, the C3A content is 1.5%, and the MgO content ranges from 5%.

[0048] Furthermore, the specific surface area of high crack resistance low heat Portland cement is 320m 2 / kg.

[0049] In this embodiment, the cement-based hydrophobic material is prepared by grinding 60wt% of high-cracking-resistant low-heat silicate cement clinker, 20wt% of limestone, 20wt% of high-titanium slag, and 1.5wt% of stearic acid in a ball mill at a speed of 150r / min for 30 minutes.

[0050] Furthermore, in the cement-based hydrophobic material, the content of particles with a particle size of ≤3 μm is 9%, the content of particles with a size of 3 to 32 μm is 73%, and the content of particles with a size of 32 to 65 μm is 18%.

[0051] Furthermore, the 45 μm sieve residue of the cement-based hydrophobic material is 9.2%, the characteristic particle size is 18.8 μm, and the uniformity coefficient is 0.93.

[0052] In this embodiment, the rice husk ash is prepared by calcining the rice husk in a high-temperature furnace at 500° C. for 3 minutes to obtain particles containing 10% carbon residue.

[0053] In this embodiment, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 8 nm and a length of 50 nm.

[0054] Example 2

[0055] As a preferred embodiment of the present invention, this embodiment provides a large-volume hydrophobic concrete for bridge piers and towers in plateau areas, comprising the following raw materials by weight:

[0056] High crack resistance and low heat silicate cement: 350kg / m 3 ;

[0057] Cement-based hydrophobic material: 50kg / m 3 ;

[0058] Rice husk ash: 20kg / m 3 ;

[0059] Carbon nanotubes: 0.5kg / m 3 ;

[0060] Crushed stone: 1150kg / m 3 ;

[0061] Machine-made sand: 700kg / m 3 ;

[0062] Powdered polycarboxylate water reducer: 1.5kg / m 3 ;

[0063] Water: 130kg / m 3 .

[0064] In this embodiment, the high crack resistance and low heat Portland cement is composed of 95 wt % of high crack resistance and low heat Portland cement clinker and 5 wt % of gypsum.

[0065] Furthermore, the clinker rate values of the high crack resistance and low heat silicate cement clinker are: lime saturation coefficient: 0.85; silicon rate: 2.60; aluminum rate: 0.70.

[0066] Furthermore, in the high crack resistance low heat Portland cement clinker: the C4AF content is 19%, the C3A content is 1.0%, and the MgO content ranges from 2.0%.

[0067] Furthermore, the specific surface area of high crack resistance low heat Portland cement is 350m 2 / kg.

[0068] In this embodiment, the cement-based hydrophobic material is prepared by grinding 80 wt% of high-cracking-resistant low-heat silicate cement clinker, 10 wt% of limestone, 10 wt% of high-titanium slag, and 1.0 wt% of stearic acid in a ball mill at a speed of 100 r / min for 45 minutes.

[0069] Furthermore, in the cement-based hydrophobic material, the content of particles with a particle size of ≤3 μm is 6%, the content of particles with a size of 3 to 32 μm is 78%, and the content of particles with a size of 32 to 65 μm is 16%.

[0070] Furthermore, the cement-based hydrophobic material has a 45 μm sieve residue of 9.8%, a characteristic particle size of 19.0 μm, and a uniformity coefficient of 0.95.

[0071] In this embodiment, the rice husk ash is prepared by calcining the rice husk in a high-temperature furnace at 700° C. for 1 minute to obtain particles containing 15% carbon residue.

[0072] In this embodiment, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 15 nm and a length of 30 nm.

[0073] Example 3

[0074] As a preferred embodiment of the present invention, this embodiment provides a large-volume hydrophobic concrete for bridge piers and towers in plateau areas, comprising the following raw materials by weight:

[0075] High crack resistance and low heat silicate cement: 300kg / m 3 ;

[0076] Cement-based hydrophobic material: 75kg / m 3 ;

[0077] Rice husk ash: 13kg / m 3 ;

[0078] Carbon nanotubes: 0.9 kg / m 3 ;

[0079] Crushed stone: 1000kg / m 3 ;

[0080] Machine-made sand: 850kg / m 3 ;

[0081] Powdered polycarboxylate water reducer: 1.0kg / m 3 ;

[0082] Water: 150kg / m 3 .

[0083] In this embodiment, the high crack resistance and low heat Portland cement is composed of 95 wt % of high crack resistance and low heat Portland cement clinker and 5 wt % of gypsum.

[0084] Furthermore, the clinker rate values of the high crack resistance and low heat silicate cement clinker are: lime saturation coefficient: 0.88; silicon rate: 2.50; aluminum rate: 0.75.

[0085] Furthermore, in the high crack resistance low heat Portland cement clinker: the C4AF content is 19%, the C3A content is 1.9%, and the MgO content ranges from 3.5%.

[0086] Furthermore, the specific surface area of high crack resistance low heat Portland cement is 330m 2 / kg.

[0087] In this embodiment, the cement-based hydrophobic material is prepared by grinding 70 wt% of high-cracking-resistant low-heat silicate cement clinker, 15 wt% of limestone, 15 wt% of high-titanium slag, and 1.2 wt% of stearic acid in a ball mill at a speed of 125 r / min for 45 minutes.

[0088] Furthermore, in the cement-based hydrophobic material, the content of particles with a particle size of ≤3 μm is 8%, the content of particles with a size of 3-32 μm is 76%, the content of particles with a size of 32-65 μm is 15%, and the content of particles with a size of ≥65 μm is less than 1%.

[0089] Furthermore, the cement-based hydrophobic material has a 45 μm sieve residue of 9.0%, a characteristic particle size of 18.9 μm, and a uniformity coefficient of 0.95.

[0090] In this embodiment, the rice husk ash is prepared by calcining the rice husk in a high-temperature furnace at 500° C. for 2 minutes to obtain particles containing 20% carbon residue.

[0091] In this embodiment, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10 nm and a length of 40 nm.

[0092] Comparative Example 1

[0093] The concrete of this comparative example includes the following raw materials by weight:

[0094] Ordinary low-heat Portland cement: 250kg / m 3 ;

[0095] First-grade fly ash: 105kg / m 3 ;

[0096] Crushed stone: 1150kg / m 3 ;

[0097] Machine-made sand: 733kg / m 3 ;

[0098] Powdered polycarboxylate water reducer: 0.5kg / m 3;

[0099] Water: 160kg / m 3 .

[0100] In this comparative example, the ordinary low-heat Portland cement consists of 95 wt % of ordinary low-heat Portland cement clinker and 5 wt % of gypsum.

[0101] Furthermore, the clinker rate values of ordinary low-heat Portland cement clinker are: lime saturation coefficient: 0.78; silicon rate: 2.80; aluminum rate: 0.90.

[0102] Furthermore, in ordinary low-heat Portland cement clinker: the C4AF content is 13.9%, the C3A content is 3.8%, and the MgO content is 1.0%.

[0103] Furthermore, the specific surface area of ordinary low-heat Portland cement is 343m 2 / kg.

[0104] Comparative Example 2

[0105] The concrete of this comparative example includes the following raw materials by weight:

[0106] Ordinary low-heat Portland cement: 350kg / m 3 ;

[0107] First-grade fly ash: 70kg / m 3 ;

[0108] Crushed stone: 1150kg / m 3 ;

[0109] Machine-made sand: 700kg / m 3 ;

[0110] Powdered polycarboxylate water reducer: 1.5kg / m 3 ;

[0111] Water: 130kg / m 3 .

[0112] In this comparative example, the ordinary low-heat Portland cement consists of 95 wt % of ordinary low-heat Portland cement clinker and 5 wt % of gypsum.

[0113] Furthermore, the clinker rate values of ordinary low-heat Portland cement clinker are: lime saturation coefficient: 0.78; silicon rate: 2.80; aluminum rate: 0.90.

[0114] Furthermore, in ordinary low-heat Portland cement clinker: the C4AF content is 13.9%, the C3A content is 3.8%, and the MgO content is 1.0%.

[0115] Furthermore, the specific surface area of ordinary low-heat Portland cement is 343m 2 / kg.

[0116] Comparative Example 3

[0117] The concrete of this comparative example includes the following raw materials by weight:

[0118] Ordinary low-heat Portland cement: 300kg / m 3 ;

[0119] First-grade fly ash: 89kg / m 3 ;

[0120] Crushed stone: 1000kg / m 3 ;

[0121] Machine-made sand: 850kg / m 3 ;

[0122] Powdered polycarboxylate water reducer: 1.0kg / m 3 ;

[0123] Water: 150kg / m 3 .

[0124] In this comparative example, the ordinary low-heat Portland cement consists of 95 wt % of ordinary low-heat Portland cement clinker and 5 wt % of gypsum.

[0125] Furthermore, the clinker rate values of ordinary low-heat Portland cement clinker are: lime saturation coefficient: 0.78; silicon rate: 2.80; aluminum rate: 0.90.

[0126] Furthermore, in ordinary low-heat Portland cement clinker: the C4AF content is 13.9%, the C3A content is 3.8%, and the MgO content is 1.0%.

[0127] Furthermore, the specific surface area of ordinary low-heat Portland cement is 343m 2 / kg.

[0128] The concrete prepared in Examples 1 to 3 and the concrete prepared in Comparative Examples 1 to 3 were tested for basic physical and mechanical properties, hydrophobicity, and frost resistance. The test results are shown in Tables 1 and 2.

[0129] Table 1 Basic physical and mechanical properties of concrete

[0130]

[0131] As shown in Table 1, the large-volume hydrophobic concrete prepared using high-crack-resistant, low-heat Portland cement, cement-based hydrophobic materials, rice husk ash, and carbon nanotubes exhibits a slump similar to that of conventional concrete (comparative example), but with a slightly increased air content. Using the same amount of cementitious materials, the 3d and 28d strengths of each example were higher than those of the corresponding comparative example.

[0132] Table 2 Concrete hydrophobicity and frost resistance

[0133]

[0134] As shown in Table 2, the contact angle of a water droplet on the surface of the large-volume hydrophobic concrete (Example) can reach over 130°, indicating super-hydrophobicity; in contrast, the contact angle of a water droplet on the surface of the conventional concrete (Comparative Example) is approximately 45°, indicating hydrophilicity. After immersion for one hour, the hydrophobic concrete prepared in accordance with the present invention has a water absorption rate of only 1.5%, while conventional concrete has a water absorption rate of over 3.5%. After 300 freeze-thaw cycles (quick freezing method), the hydrophobic concrete exhibits a mass loss rate of less than 5%, and a decrease in dynamic elastic modulus of no more than 20%.

[0135] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are intended to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or refinements made to the main design concept and spirit of the present invention that have no substantive significance, provided that the technical problems they solve are still consistent with those of the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields should also be included in the patent protection scope of the present invention.

Claims

1. A large volume hydrophobic concrete for bridge piers and towers in plateau areas, characterized in that: Includes the following weights of raw materials: High crack resistance and low heat Portland cement: 250~350kg / m 3 ; Cement-based hydrophobic material: 50~100 kg / m 3 ; Rice husk ash: 5~20 kg / m 3 ; Carbon nanotubes: 0.3~1.5 kg / m 3 ; Crushed stone: 1000~1150 kg / m 3 ; Machine-made sand: 700~850 kg / m 3 ; Powdered polycarboxylate water reducer: 0.5~1.5 kg / m 3 ; Water: 130~160 kg / m 3 ; The high crack-resistant, low-heat Portland cement is composed of 95 wt% of high crack-resistant, low-heat Portland cement clinker and 5 wt% of gypsum; the high crack-resistant, low-heat Portland cement clinker has a C4AF content greater than 17%, a C3A content less than 5%, and a MgO content ranging from 2 to 5%; The cement-based hydrophobic material is prepared by grinding 60-80 wt% of high crack resistance low heat Portland cement clinker, 10-20 wt% of limestone, 10-20 wt% of high titanium slag, and 1-1.5 wt% of stearic acid. The cement-based hydrophobic material comprises: particles with a diameter of ≤3 μm in a content of 6-9%, particles with a diameter of 3-32 μm in a content of 73-78%, particles with a diameter of 32-65 μm in a content of 12-20%, and particles with a diameter of ≥65 μm in a content of less than 1%; The rice husk ash is particles containing 10-20% carbon residue.

2. The large-volume hydrophobic concrete for bridge piers and towers in plateau areas according to claim 1, characterized in that: The clinker rate values of the high-cracking-resistant low-heat Portland cement clinker are: lime saturation coefficient: 0.80~0.88; silicon rate: 2.50~2.70; aluminum rate: 0.70~0.

75.

3. The large-volume hydrophobic concrete for bridge piers and towers in plateau areas according to claim 1, characterized in that: The specific surface area of the high crack resistance and low heat silicate cement is 300-350 m 2 / kg.

4. The large-volume hydrophobic concrete for bridge piers and towers in plateau areas according to claim 1 is characterized in that: The grinding speed is 100~150r / min, and the grinding time is 30~45min.

5. The large-volume hydrophobic concrete for bridge piers and towers in plateau areas according to claim 1 is characterized in that: The cement-based hydrophobic material has a 45 μm sieve residue of 8-10%, a characteristic particle size of 19±0.2 μm, and a uniformity coefficient of 0.93-0.

95.

6. The large-volume hydrophobic concrete for bridge piers and towers in plateau areas according to claim 1 is characterized in that: The rice husk ash is prepared by placing the rice husk in a high-temperature furnace at 500-700° C. and calcining it for 1-3 minutes to obtain particles containing 10-20% carbon residue.

7. The large-volume hydrophobic concrete for bridge piers and towers in plateau areas according to claim 1 is characterized in that: The carbon nanotubes are multi-walled carbon nanotubes with a diameter of 8-15 nm and a length of 30-50 nm.

Images