CN113816695A - Carbon nanotube modified concrete and preparation method and application thereof - Google Patents
Carbon nanotube modified concrete and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 148
- 239000004567 concrete Substances 0.000 title claims abstract description 144
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 139
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 139
- 238000002360 preparation method Methods 0.000 title abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 42
- 239000004568 cement Substances 0.000 claims abstract description 23
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 19
- 239000002048 multi walled nanotube Substances 0.000 claims abstract description 5
- 239000004576 sand Substances 0.000 claims abstract description 4
- 238000002156 mixing Methods 0.000 claims description 19
- 239000006185 dispersion Substances 0.000 claims description 11
- 229910052799 carbon Inorganic materials 0.000 claims description 10
- 239000002994 raw material Substances 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 239000004575 stone Substances 0.000 claims description 5
- 239000011398 Portland cement Substances 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 3
- 229920005646 polycarboxylate Polymers 0.000 claims description 2
- 230000001681 protective effect Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000011068 loading method Methods 0.000 abstract description 10
- 230000009471 action Effects 0.000 abstract description 9
- 239000000463 material Substances 0.000 abstract description 5
- 238000012360 testing method Methods 0.000 description 33
- 230000000694 effects Effects 0.000 description 22
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
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- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 239000002086 nanomaterial Substances 0.000 description 4
- 230000003014 reinforcing effect Effects 0.000 description 4
- 230000035945 sensitivity Effects 0.000 description 4
- 229910000019 calcium carbonate Inorganic materials 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000012669 compression test Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
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- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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Abstract
The invention relates to carbon nanotube modified concrete and a preparation method and application thereof, wherein the carbon nanotube modified concrete comprises cement, fine aggregate, coarse aggregate, a water reducing agent, water and carbon nanotubes, the carbon nanotubes are multi-walled carbon nanotubes, and the fine aggregate is river sand with the fineness modulus of 2.8. The carbon nano tube can improve the typical brittleness characteristic of a concrete material, and the finally obtained carbon nano tube modified concrete has excellent impact resistance, higher toughness and deformation resistance, can solve the serious safety problem of the concrete structure exposed under the impact loading condition to a certain extent, and can effectively prolong the service life of the engineering structure which is easy to suffer from the impact load action.
Description
Technical Field
The disclosure relates to the technical field of civil engineering, in particular to carbon nanotube modified concrete and a preparation method and application thereof.
Background
The addition of nanomaterials to concrete to make nano-concrete has been identified and practiced as a solution to improve the tensile strength, flexural strength and ductility of concrete. The nano material with nano specific effect and physical and mechanical properties can fully exert the reinforcing effect in different levels and stress stages of concrete, and obviously improve the toughness and the shock resistance of the concrete.
Among them, nano silica and nano calcium carbonate are the most common types of nano materials. The nano-silica has higher surface activity, and the nano-calcium carbonate can improve the workability of concrete and can improve the mechanical property and the durability of the concrete when being doped into the concrete. However, nano silica and nano calcium carbonate are easily agglomerated to reduce the reinforcing effect on concrete, and the later strength reduction of concrete is also a disadvantage, and thus the durability of the concrete structure is seriously reduced when it is applied to the concrete structure.
Accordingly, it is desired to provide a nanomaterial reinforced concrete capable of improving the strength, impact resistance, and the like of the concrete.
Disclosure of Invention
In order to solve the technical problems or at least partially solve the technical problems, the present disclosure provides a carbon nanotube modified concrete, and a preparation method and application thereof.
In a first aspect, the present disclosure provides a carbon nanotube modified concrete, which is composed of cement, fine aggregate, coarse aggregate, a water reducing agent, water and carbon nanotubes as raw materials, wherein the carbon nanotubes are multiwalled carbon nanotubes, and the fine aggregate is river sand with a fineness modulus of 2.8.
The performance of the concrete can be optimized by doping the multi-walled carbon nanotubes in the concrete; due to the nanometer size effect, the carbon nano tube can fill partial gel pores and capillary pores in the cement matrix, thereby playing the roles of reducing the concrete defect and improving the concrete strength and improving the mechanical property of the concrete; meanwhile, the mineral admixture (fine aggregate) is added to improve the bonding strength of the carbon nano tube and the concrete matrix and reduce the influence of an interface transition region on the performance of the concrete, so that the obtained carbon nano tube modified concrete has excellent impact resistance.
When the crack in the concrete matrix is expanded under the action of a load, the carbon nano tube embedded in the concrete matrix can play a role in crack bridging, limit the expansion of the crack, improve the strength of the concrete, improve the typical brittleness characteristic of a concrete material, greatly improve the deformation resistance and the impact resistance of the concrete, solve the serious safety problem of the concrete structure exposed under the condition of impact loading to a certain extent, and effectively prolong the service life of the engineering structure subjected to the action of impact load.
As a preferred embodiment of the present disclosure, the addition amount of the carbon nanotubes is 0.2 to 0.4%, preferably 0.4%, by weight of the cement.
In the present disclosure, when the addition amount of the carbon nanotubes is 0.4% by weight of the cement, the dispersion effect of the carbon nanotubes in the concrete is the best, the reinforcing effect is the best, and the final modified concrete has excellent impact resistance. If the addition amount of the carbon nanotubes is small, the reinforcing effect is poor, and if the addition amount of the carbon nanotubes is too large, the impact resistance of the concrete is reduced because the carbon nanotubes are aggregated in the concrete and the dispersibility is poor.
As a preferred technical scheme of the present disclosure, the carbon nanotube modified concrete comprises the following raw materials in parts by weight: 366 parts by weight of cement, 680-685 parts by weight of fine aggregate, 1160-1165 parts by weight of coarse aggregate, 3-4 parts by weight of water reducing agent, 160-163 parts by weight of water and 0.7-2 parts by weight of carbon nano tube.
As a specific embodiment of the present disclosure, the carbon nanotube modified concrete comprises the following raw materials in parts by weight: 366 parts by weight of cement, 683 parts by weight of fine aggregate, 1162.9 parts by weight of coarse aggregate, 3.66 parts by weight of water reducing agent, 161 parts by weight of water and 0.732 parts by weight of carbon nano tube.
As a specific embodiment of the present disclosure, the carbon nanotube modified concrete comprises the following raw materials in parts by weight: 366 parts by weight of cement, 683 parts by weight of fine aggregate, 1162.9 parts by weight of coarse aggregate, 3.66 parts by weight of water reducing agent, 161 parts by weight of water and 1.464 parts by weight of carbon nano tube.
As a specific embodiment of the present disclosure, the carbon nanotubes have a purity of > 95 wt% and an inner diameter3-5nm, 8-15nm in outer diameter, 3-12 μm in length, and density > 2.1g/cm3Preferably, the density is 2.15g/cm3。
As a specific embodiment of the present disclosure, the cement is portland cement.
As a specific embodiment of the present disclosure, the coarse aggregate is crushed stone, and the maximum particle size of the crushed stone is 16 mm.
As a specific embodiment of the present disclosure, the water reducing agent is a polycarboxylate water reducing agent.
In a second aspect, the present invention provides a method for preparing a carbon nanotube-modified concrete according to the first aspect, the method comprising the steps of:
(1) mixing the carbon nano tube with the formula amount and part of water and performing ultrasonic dispersion;
(2) mixing the cement, the fine aggregate and the coarse aggregate according to the formula amount, and then adding water with half of the total water consumption for mixing;
(3) mixing the water reducing agent with the rest water according to the formula amount;
(4) and (3) mixing the carbon nano tube dispersion liquid obtained in the step (1) with the mixture obtained in the step (2), adding the mixed liquid obtained in the step (3), and continuously mixing to obtain the carbon nano tube modified concrete.
In a third aspect, the invention provides the use of the carbon nanotube modified concrete of the first aspect in an airport runway, an ocean engineering structure, a seismic area protective structure, or an engineering structure with blasting effect.
Compared with the prior art, the technical scheme provided by the embodiment of the disclosure has the following advantages:
the carbon nano tube can improve the typical brittleness characteristic of a concrete material, and the finally obtained carbon nano tube modified concrete has excellent impact resistance, higher toughness and deformation resistance, can solve the serious safety problem of the concrete structure exposed under the impact loading condition to a certain extent, and can effectively prolong the service life of the engineering structure which is easy to suffer from the impact load action.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure.
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present disclosure, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
FIG. 1 is a graph of static compressive strength of carbon nanotube modified concrete provided in examples and comparative examples of the present disclosure;
FIG. 2 is a graph of the dynamic compressive strength of carbon nanotube modified concrete as a function of strain rate provided in examples and comparative examples of the present disclosure;
FIG. 3 is a graph showing the variation of the dynamic growth factor of carbon nanotube-modified concrete according to the strain rate in examples and comparative examples of the present disclosure;
FIG. 4 is a graph showing the change of dynamic energy consumption with strain rate of carbon nanotube modified concrete according to examples and comparative examples of the present disclosure;
fig. 5 is a first graph of a first dispersion profile of carbon nanotubes in concrete modified by carbon nanotubes according to example 2 of the present disclosure;
fig. 6 is a second graph illustrating a distribution morphology of carbon nanotubes in concrete in the carbon nanotube-modified concrete provided in example 2 of the present disclosure;
fig. 7 is a graph of the dispersion morphology of carbon nanotubes in concrete in the carbon nanotube-modified concrete provided in comparative example 2 of the present disclosure.
Detailed Description
In order that the above objects, features and advantages of the present disclosure may be more clearly understood, aspects of the present disclosure will be further described below. It should be noted that the embodiments and features of the embodiments of the present disclosure may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure, but the present disclosure may be practiced in other ways than those described herein; it is to be understood that the embodiments disclosed in the specification are only a few embodiments of the present disclosure, and not all embodiments.
Example 1
The embodiment provides carbon nanotube modified concrete (CNTC-0.2), which comprises the following components in parts by weight:
366kg/m3683kg/m cement3Fine aggregate, 1162.9kg/m3Coarse aggregate, 3.66kg/m3Water reducing agent, 161kg/m3Water and 0.732kg/m3Carbon nanotubes.
Wherein the cement is P.O 42.5R-grade ordinary portland cement, the fine aggregate is river sand with fineness modulus of 2.8, the coarse aggregate is broken stone with maximum particle size of 16mm, the water reducing agent is a polycarboxylic acid high-performance water reducing agent with water reducing rate of 30%, and the purity of the multi-walled carbon nano-tube is high>95%, inner diameter of 3-5nm, outer diameter of 8-15nm, length of 3-12 μm, and density of 2.15g/cm3。
The preparation method comprises the following steps:
(1) mixing the carbon nano tube with a small amount of water in a beaker, and performing ultrasonic dispersion for 3min at the dispersion energy of 2.5KJ per gram of the carbon nano tube;
(2) mixing and dry-stirring cement, coarse aggregate and fine aggregate for 2min, and then adding water with half of the total water consumption for mixing and stirring for 2 min;
(3) mixing the water reducing agent with the rest water according to the formula amount;
(4) and (3) adding the carbon nano tube dispersion liquid obtained in the step (1) into the mixture obtained in the step (2), stirring for 2min, adding the mixed liquid obtained in the step (3), and continuously mixing for 2min to obtain the carbon nano tube modified concrete.
Example 2
This example provides a carbon nanotube modified concrete (CNTC-0.4).
The only difference from example 1 is that in this example, the amount of carbon nanotubes added is 1.464kg/m3。
Comparative example 1
This comparative example provides a concrete (PC).
The only difference from example 1 is that in this comparative example, no carbon nanotubes were added.
Comparative example 2
This comparative example provides a carbon nanotube modified concrete (CNTC-0.6).
The only difference from example 1 is that in this comparative example, the amount of carbon nanotubes added was 2.196kg/m3。
And (3) performance testing:
the carbon nanotube modified concrete provided in the examples and comparative examples was prepared as follows to obtain test pieces, and static compression tests and dynamic compression tests were performed to observe the distribution of carbon nanotubes in the concrete.
The method for preparing the test piece comprises the following steps:
pouring the uniformly mixed mixture into a prepared die with the size of 100mm multiplied by 100mm, vibrating and compacting by a vibrating table, placing the die in a standard curing room (the temperature is 20 +/-2 ℃, and the relative humidity is more than 95 percent) for 24 hours, then removing the die from the test piece, and continuously placing the test piece into the curing room for curing for 15 days when the age is reached; cylindrical test pieces with the size of phi 50 multiplied by 50mm required by the dynamic split pulling experiment are prepared through core drilling, cutting and polishing, and the test pieces are continuously placed into a curing room to be cured to the age of 28 days.
(1) Static compressive strength
Testing the static compressive strength of the carbon nanotube modified concrete by using a universal material testing machine; before testing, coating thin layers of lubricating oil on two ends of a test piece to eliminate frictional resistance between the test piece and a loading pressure plate; during testing, the test piece is placed on the lower loading platen, and then the upper loading platen is slowly moved. When the upper loading pressure plate is contacted with the test piece, the test piece is loaded to 10 percent of the compressive strength of the test piece at the loading rate of 0.1MPa/s and then unloaded to 0 percent, after the steps are repeated for three times, the test piece can be tightly contacted with the loading pressure plate, and then the strain rate is 0.1mm/min (the strain rate is 3.33 multiplied by 10)-5s-1) The loading rate is loaded until the test piece is damaged, the strength of the test piece is automatically acquired by the system, and the result is shown in figure 1.
Fig. 1 is a graph showing the static compressive strength of the carbon nanotube-modified concrete provided in examples and comparative examples, and as shown in fig. 1, when the doping amount of the carbon nanotube is 0.2 to 0.4 wt%, the static compressive strength of the concrete increases with the increase of the doping amount of the carbon nanotube and is higher, and when the doping amount of the carbon nanotube is 0.6 wt%, the static compressive strength of the concrete is significantly reduced.
(2) Dynamic compressive strength
Testing the impact resistance of the carbon nanotube modified concrete by adopting a Hopkinson pressure bar device; by applying high-pressure nitrogen, the punch impacts the incident rod and forms incident waves, when the incident waves are transmitted to an interface between the test piece and the incident rod, due to impedance mismatching of the two, a part of the incident waves are reflected back to the incident rod to form reflected waves, and the rest of the incident waves penetrate through the test piece and enter the transmission rod to form transmitted waves; incident waves and reflected waves can be collected by strain gauges pasted on an incident rod, and transmitted waves are collected by strain gauges pasted on a transmitted rod; the dynamic stress and strain rate of the carbon nanotube modified concrete can be calculated by the following formula (I) and formula (II):
in the formula: sigma (t),
Respectively is the axial stress and the strain rate of the carbon nano tube modified concrete test piece; epsiloni(t)、εr(t)、εt(t) incident, reflected and transmitted strain pulses, respectively; a. theb、AsThe cross sectional areas of the Hopkinson pressure bar and the carbon nano tube modified concrete test piece are respectively; ebThe modulus of elasticity of the compression bar; cbThe longitudinal wave velocity in the compression bar; lsThe length of the carbon nanotube modified concrete sample.
Fig. 2 is a graph showing the change of the dynamic compressive strength of the carbon nanotube modified concrete with the strain rate according to the examples and the comparative examples, and it can be seen from fig. 2 that the dynamic compressive strength of the carbon nanotube modified concrete increases nonlinearly with the strain rate, and when the strain rates are similar, the change rule of the dynamic compressive strength and the static compressive strength of the carbon nanotube modified concrete with the doping amount of the carbon nanotube is consistent. When the doping amount of the carbon nano tube is less than or equal to 0.4 wt%, the dynamic compressive strength of the carbon nano tube modified concrete is increased along with the increase of the doping amount of the carbon nano tube, and when the doping amount of the carbon nano tube is 0.6 wt%, the dynamic compressive strength of the carbon nano tube modified concrete is lower. The carbon nano tubes can enhance the compressive strength of concrete through a pore filling effect and a crack bridging effect, but when the doping amount of the carbon nano tubes is too large, the dispersion uniformity of the carbon nano tubes is reduced, and more air bubbles are easily introduced in the mixing process of the mixture, so that the internal defects of the concrete are increased, and the dynamic compressive strength of the concrete is reduced.
The relationship between the dynamic compressive strength and the strain rate of the carbon nanotube modified concrete can be expressed by the following formula (III):
σ＝alog(θ)+b (III)
wherein sigma is the dynamic compressive strength of the carbon nanotube modified concrete, MPa; a. b is a correlation coefficient, and the units are respectively MPa.s and MPa; theta is the strain rate, s-1。
A comparison of the fitting results of formula (III) with the test results is shown in FIG. 2, and the fitting results of the relevant parameters are shown in Table 1.
TABLE 1
| Parameter(s) | CNTC-0.2 | CNTC-0.4 | CNTC-0.6 | PC |
| a | 34.88 | 40.096 | 19.839 | 29.81 |
| b | 8.0842 | 7.305 | 13.847 | 8.7295 |
| R2 | 0.9985 | 0.9915 | 0.9954 | 0.9953 |
As can be seen from FIG. 2 and Table 1, the consistency of the calculation result of formula (III) and the test result is better, which shows that formula (III) can effectively represent the change rule of the dynamic compressive strength of the carbon nanotube modified concrete along with the strain rate. The crack bridging effect of the carbon nano tube is beneficial to improving the shock resistance of the concrete, thereby improving the strain rate sensitivity of the dynamic tensile strength of the concrete. As can be seen from Table 1, the strain rate sensitivity of CNTC-0.4 is most pronounced.
(3) Dynamic growth factor
The strain rate effect of the dynamic compressive strength of cement-based materials can generally be characterized by a dynamic growth factor, which is the ratio of the dynamic compressive strength to the static compressive strength of the cement-based material.
FIG. 3 is a graph showing the variation of the dynamic growth factor of carbon nanotube-modified concrete according to the strain rate in examples and comparative examples; as can be seen from fig. 3, the dynamic growth factor of the carbon nanotube modified concrete increases nonlinearly with the strain rate, and under the condition of appropriate carbon nanotube doping amount and similar strain rate, increases with the increase of the carbon nanotube doping amount, which indicates that the strain rate effect of the dynamic compressive strength of the carbon nanotube modified concrete gradually increases, and when the carbon nanotube doping amount is too large, the dynamic growth factor significantly decreases, which indicates that the strain rate effect of the dynamic compressive strength of the carbon nanotube modified concrete significantly decreases.
The strain rate effect of the dynamic compressive strength of the carbon nanotube modified concrete can be attributed to the crack propagation effect and the lateral inertia effect. The crack propagation effect means that the propagation rate of cracks is limited, and the stress wave input rate is obviously increased along with the increase of the strain rate, so that the energy input by external force can be dissipated by the concrete only by generating more cracks, and the stress required by crack generation is greater than that required by crack propagation, thereby increasing the dynamic compressive strength of the concrete. The transverse inertia effect means that the lateral deformation of the concrete is limited due to the inertia effect, so that a test piece is approximately in a confining pressure state, the dynamic compressive strength of the concrete is increased, the crack bridging effect of the carbon nano tubes is used for inhibiting crack expansion, the crack expansion effect and the transverse inertia effect of the concrete are increased, and the strain rate effect of the dynamic compressive strength of the concrete is improved.
The relationship between the dynamic growth factor and the strain rate of the carbon nanotube modified concrete can be characterized by the formula (IV):
DIF＝mlog(θ)+n (IV)
the comparison between the fitting result of the formula (IV) and the test result is shown in FIG. 3, and it can be seen from FIG. 3 that the consistency between the calculation result of the formula (IV) and the test result is better, which shows that the formula (IV) can effectively represent the change rule of the growth factor of the dynamic compressive strength of the carbon nanotube modified concrete along with the strain rate.
The results of the fit of the relevant parameters are shown in table 2.
TABLE 2
| Parameter(s) | CNTC-0.2 | CNTC-0.4 | CNTC-0.6 | PC |
| m | 0.8992 | 1.0118 | 0.6326 | 0.8457 |
| n | 0.2084 | 0.1834 | 0.4416 | 0.2476 |
| R2 | 0.9985 | 0.9915 | 0.9954 | 0.9953 |
As can be seen from Table 2, the addition of 0.2 to 0.4 wt% of carbon nanotubes improves the strain rate sensitivity of the concrete dynamic growth factor.
(4) Dynamic energy consumption
According to the principle of an SHPB test, the energy dissipated by the carbon nanotube modified concrete sample in the impact load action process can be calculated by incident wave energy, reflected wave energy and transmitted wave energy, and the calculation formula is shown as formula (V):
in the formula, WdEnergy dissipated by the carbon nanotube modified concrete test piece, J; epsiloni(t)、εr(t)、εt(t) incident, reflected and transmitted strain pulses, respectively; a. theb、EbThe cross sectional area and the elastic modulus of the compression bar are respectively; cbIs the longitudinal wave velocity in the strut.
Fig. 4 is a graph showing the change of dynamic energy consumption with strain rate of carbon nanotube modified concrete provided in examples and comparative examples. As can be seen from fig. 4, the dynamic energy consumption of the carbon nanotube modified concrete also increases nonlinearly with the strain rate, and when the strain rate is similar, the dynamic energy consumption of the concrete increases with the increase of the strain rate under the condition of the carbon nanotube with proper doping amount; when the doping amount of the carbon nano tube is too large, the dynamic energy consumption of the carbon nano tube modified concrete is reduced, but the dynamic energy consumption is still larger than that of the reference group concrete; this is mainly due to the fact that although the amount of carbon nanotubes is too large, the dynamic energy consumption of concrete is still increased by the bridging effect of some effective carbon nanotubes or the energy consumption of pulling out under the load.
The dynamic energy consumption and the strain rate of the carbon nano tube modified concrete satisfy the relationship shown in the formula (VI):
Wd＝pln(θ)+q (VI)
in the formula, Wd is the dynamic energy consumption of the carbon nanotube modified concrete; p and q are correlation coefficients, and the units are J.s and J respectively; theta is the strain rate, s-1。
The comparison of the fitting result of the formula (VI) and the test result is shown in FIG. 4, and it can be seen from FIG. 4 that the consistency of the calculation result of the formula (VI) and the test result is good, which indicates that the established formula (VI) can effectively represent the relationship between the dynamic energy consumption and the strain rate of the carbon nanotube modified concrete.
The results of the fit of the relevant parameters are shown in table 3.
TABLE 3
| Parameter(s) | CNTC-0.2 | CNTC-0.4 | CNTC-0.6 | PC |
| p | 57.662 | 66.021 | 45.388 | 29.498 |
| q | -30.307 | -28.908 | -21.078 | -2.5001 |
| R2 | 0.9998 | 0.9889 | 0.9972 | 0.9819 |
As can be seen from Table 3, the incorporation of carbon nanotubes also improved the strain rate sensitivity of the concrete for dynamic energy consumption.
(5) Carbon nanotube dispersion
5-6 are graphs of the dispersion profile of carbon nanotubes in concrete in 0.4% of the carbon nanotube modified concrete provided in example 2 of the present disclosure; as can be seen from fig. 5, due to the nano-size effect, the carbon nanotubes may fill a part of gel pores and capillary pores in the cement matrix, thereby playing a role in reducing concrete defects and improving concrete strength; as can be seen from fig. 6, the carbon nanotubes are similar to nanofibers, and when the carbon nanotubes expand under the action of crack load in the concrete matrix, the carbon nanotubes embedded in the concrete matrix can play a role in bridging cracks to limit the expansion of the cracks, thereby further improving the strength of the concrete; therefore, as can be seen from fig. 5 and 6, the addition of the carbon nanotubes improves not only the static compressive strength of the concrete but also the dynamic compressive strength of the concrete.
Fig. 7 is a graph of a dispersion morphology of carbon nanotubes in concrete in 0.6% carbon nanotube modified concrete provided by comparative example 2 of the present disclosure, and as can be seen from fig. 7, when the doping amount of the carbon nanotubes is too large, the carbon nanotubes are difficult to be uniformly dispersed in the concrete, and defects inside the concrete are easily increased; in addition, in the process of mixing the mixture, excessive carbon nanotubes which are not uniformly dispersed are easy to introduce air bubbles, so that the internal defects of the concrete are further increased, and the mechanical property of the concrete is further reduced; however, part of the carbon nanotubes effectively dispersed and bonded with the concrete matrix can still play the role of pore filling and crack bridging, and the carbon nanotubes are broken or pulled out in the crack propagation process to destroy and dissipate more energy, so that the dynamic energy consumption of the CNTC-0.6 is still larger than that of PC.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The foregoing are merely exemplary embodiments of the present disclosure, which enable those skilled in the art to understand or practice the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. The carbon nanotube modified concrete is characterized in that raw materials of the carbon nanotube modified concrete comprise cement, fine aggregate, coarse aggregate, a water reducing agent, water and carbon nanotubes, wherein the carbon nanotubes are multiwalled carbon nanotubes, and the fine aggregate is river sand with a fineness modulus of 2.8.
2. The carbon nanotube-modified concrete according to claim 1, wherein the carbon nanotubes are added in an amount of 0.2 to 0.4%, preferably 0.4%, by weight based on the weight of the cement.
3. The carbon nanotube modified concrete according to claim 1 or 2, wherein the carbon nanotube modified concrete comprises the following raw materials in parts by weight: 366 parts by weight of cement, 680-685 parts by weight of fine aggregate, 1160-1165 parts by weight of coarse aggregate, 3-4 parts by weight of water reducing agent, 160-163 parts by weight of water and 0.7-2 parts by weight of carbon nano tube.
4. The carbon nanotube modified concrete according to claim 3, wherein the carbon nanotube modified concrete comprises the following raw materials in parts by weight: 366 parts by weight of cement, 683 parts by weight of fine aggregate, 1162.9 parts by weight of coarse aggregate, 3.66 parts by weight of water reducing agent, 161 parts by weight of water and 0.732 parts by weight of carbon nano tube.
5. The carbon nanotube modified concrete according to claim 3, wherein the carbon nanotube modified concrete comprises the following raw materials in parts by weight: 366 parts by weight of cement, 683 parts by weight of fine aggregate, 1162.9 parts by weight of coarse aggregate, 3.66 parts by weight of water reducing agent, 161 parts by weight of water and 1.464 parts by weight of carbon nano tube.
6. The carbon nanotube-modified concrete according to any one of claims 1 to 5, wherein the carbon nanotubes have a purity of > 95 wt%, an inner diameter of 3 to 5nm, an outer diameter of 8 to 15nm, a length of 3 to 12 μm, and a density of > 2.1g/cm3。
7. The carbon nanotube-modified concrete according to any one of claims 1 to 6, wherein the cement is ordinary portland cement;
and/or the coarse aggregate is crushed stone, and the maximum particle size of the crushed stone is 16 mm;
and/or the water reducing agent is a polycarboxylate water reducing agent.
8. The method for producing carbon nanotube-modified concrete according to any one of claims 1 to 7, characterized by comprising the steps of:
(1) mixing the carbon nano tube with the formula amount and part of water and performing ultrasonic dispersion;
(2) mixing the cement, the fine aggregate and the coarse aggregate according to the formula amount, and then adding water with half of the total water consumption for mixing;
(3) mixing the water reducing agent with the rest water according to the formula amount;
(4) and (3) mixing the carbon nano tube dispersion liquid obtained in the step (1) with the mixture obtained in the step (2), adding the mixed liquid obtained in the step (3), and continuously mixing to obtain the carbon nano tube modified concrete.
9. Use of the carbon nanotube modified concrete of any one of claims 1-7 in an airport runway, an oceanographic engineering structure, or a seismic area protective structure.
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Application publication date: 20211221 |