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Article

Effect of Vibration Mixing on the Mechanical Properties of Carbon Nanotube-Reinforced Ultra-High-Performance Concrete

by
Li Zhou
1,
Jiangang Yin
2,
Wei Wang
1,
Fucai Liu
3,
Min Xiao
3,
Yibo Yang
4,5,* and
Haibo Cui
3
1
State Grid Hubei Economic Research Institute, Wuhan 430077, China
2
State Grid Hubei Electric Power Co., Ltd., Wuhan 430048, China
3
Guangdong Gaiteqi New Materials Technology Co., Ltd., Qingyuan 511600, China
4
School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China
5
State Key Laboratory of Subtropical Building and Urban Science, South China University of Technology, Guangzhou 510640, China
*
Author to whom correspondence should be addressed.
Buildings 2024, 14(8), 2545; https://doi.org/10.3390/buildings14082545
Submission received: 22 July 2024 / Revised: 15 August 2024 / Accepted: 15 August 2024 / Published: 19 August 2024
(This article belongs to the Section Building Materials, and Repair & Renovation)
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Versions Notes

Abstract

Vibration mixing, characterized by the high-frequency vibrations of the mixing shaft, can enhance the mechanical properties of ultra-high-performance concrete (UHPC). However, the effects of vibration mixing on carbon nanotube (CNT)-reinforced UHPC have not been previously reported. To investigate the impact of vibration mixing on the properties of CNT-reinforced UHPC, a comparative study was conducted using different vibration mixing durations and twin-shaft mixing. The results indicate that for CNT-reinforced UHPC, vibration mixing achieves better flowability, higher wet apparent density, and superior mechanical properties in shorter mixing times compared to twin-shaft mixing, making it a more favorable method. Considering vibration mixing times ranging from 3 to 7 min, the optimal time was found to be 3 min, during which the axial compressive strength increased by 3.3%, the elastic limit tensile strength and tensile strength improved by 14.6% and 15.8%, respectively, and the initial cracking strength and flexural strength increased by 12.6% and 13.4%, respectively, compared to values after 10 min of twin-shaft mixing.

1. Introduction

As a novel cement-based material, ultra-high-performance concrete (UHPC), exhibits high strength, superior toughness, and excellent durability [1,2,3], making it a highly promising material with extensive application prospects. Consequently, it has garnered significant attention from researchers worldwide [4,5]. Carbon nanotubes (CNTs), an advanced nanomaterial, possess exceptional properties, including a large specific surface area, high mechanical strength, and excellent electrical and thermal conductivities [6,7,8,9]. CNTs are a form of carbon allotrope, characterized by their coaxial cylindrical structure composed of hexagonal graphene sheets rolled into tubes. Depending on the number of graphene layers, CNTs can be categorized into single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) [10]. CNTs have a high aspect ratio, with diameters ranging from a few nanometers to tens of nanometers and lengths varying from hundreds of nanometers to tens or even hundreds of micrometers, depending on the graphene layers and production methods [11,12,13]. The unique structure of CNTs endows them with exceptional mechanical properties. Research indicates that the Young’s modulus and tensile strength of CNTs are approximately 1 TPa and 1163 GPa, respectively, which are about 5 times and 2000 times higher than those of steel [14].
In the field of cement-based composite materials, studies have shown that CNTs can be incorporated as one-dimensional nanomaterials or co-mixed with millimeter-scale steel fibers to significantly improve the microstructure and mechanical properties of these composites [13,15]. For example, Cheng et al. [16] conducted experiments on compressive and flexural strengths by incorporating different amounts of CNTs with a 2% volume fraction of steel fibers. The results indicated that the optimal mechanical performance of CNT-reinforced UHPC was achieved with a CNT content of 0.1%. Similarly, Zhang et al. [17] tested the axial tensile and compressive stress–strain curves of UHPC by adding nanoscale CNTs, micron-scale calcium carbonate whiskers, and millimeter-scale steel fibers. Their findings revealed that the macro-scale steel fibers primarily influenced the initial cracking strength and strain of UHPC specimens, while the addition of calcium carbonate whiskers and CNTs significantly enhanced the strain-hardening capacity of UHPC.
UHPC typically features a low water-to-cement ratio and generally includes silica fume, high-range water reducers, and fibers, which impose high demands on the production process and thus limit its widespread application [18,19]. Traditional forced mixing methods have shortcomings such as relatively long mixing times, incomplete homogeneous mixing of material particles, and lower degrees of cement hydration, leading to the micro-aggregation of cementitious particles. In contrast, the vibration mixing process effectively combines macroscopic convective movements with microscopic diffusive movements, achieving a more uniform microscopic mixture of concrete and significantly improving its microstructural properties [20].
Research by Li et al. [21] demonstrated that UHPC specimens subjected to vibration mixing exhibited superior compressive and flexural performances compared to those mixed by conventional methods, under both 28-day standard curing and hot-water curing conditions. Similarly, He et al. [22] compared the workability and mechanical properties of UHPC produced with and without vibration mixing. The results indicated that vibration mixing enhanced the workability by 16.2%, while the compressive and flexural strengths increased by 12.7% and 8.4%, respectively. Luo et al. [23] prepared lightweight high-strength steel fiber concrete using vibration mixing and compared it to conventional forced mixing methods. They found that with a steel fiber content of 0.5%, the flexural strength of specimens prepared by vibration mixing was 24% higher than that of specimens prepared by conventional mixing. When the steel fiber content was increased to 1.0%, the specimens exhibited deflection hardening, with the initial flexural toughness ratio rising from 0.33 to 0.52.
Additionally, the strong van der Waals forces between carbon atoms in CNTs, combined with their high aspect ratio, lead them to easily entangle and form loosely structured, fragile agglomerates. The agglomeration of CNTs would reduce their enhancement effect on UHPC. Therefore, achieving the uniform and effective dispersion of CNTs is of significant importance [24]. The high-frequency vibrational energy input during vibration mixing not only promotes the uniform mixing of macroscopic materials but also holds potential to overcome the strong van der Waals forces between carbon atoms in CNTs, which may be able to effectively disperse CNTs within UHPC.
Currently, there are limited studies on the impact of vibration mixing on the workability and mechanical properties of ultra-high performance concrete. Furthermore, studies specifically focusing on CNT-reinforced UHPC are absent. The novelty of this study is highlighted by its effort to reveal the effects of vibration mixing versus traditional twin-shaft forced mixing on the properties of CNT-reinforced UHPC with the same mix proportion. Three different vibration mixing durations ranging from 3 to 7 min were set to study the impact of vibration mixing on the fresh and mechanical properties of CNT-reinforced UHPC, and the underlying mechanisms were analyzed.

2. Materials and Methods

2.1. Materials

The UHPC premix was supplied by Guangdong Gaiteqi New Materials Technology Co., Ltd., Fogang County, China, and included cementitious materials, fine aggregates, and steel fibers. The water reducer used was a polycarboxylate superplasticizer with a solid content of 22.5%. The defoamer, also provided by Guangdong Gaiteqi New Materials Technology Co., Ltd., was in powder form. The CNT slurry was supplied by Jiangsu Tiannai Technology Co., Ltd., Zhenjiang, China, containing 3.0% CNTs and having a solid content of 4.2%. The appearance of the slurry is shown in Figure 1, microscopic images in Figure 2, and particle size distribution in Figure 3. Tap water was used as the mixing water.

2.2. Mix Proportions and Sample Preparation

The mix proportions for UHPC are shown in Table 1, with a water-to-cement ratio of 0.16, a steel fiber content of 150 kg/m3, and a CNT content of 0.05% by mass of the cementitious materials. The vibration mixing times were set at 3 min, 5 min, and 7 min and were compared with 10 min twin-shaft mixing.
For twin-shaft mixing, the mixer is driven by a motor, which, through belts and a planetary reducer, rotates two main mixing shafts. The rotating blades on these shafts create cross flows within the mixing drum, causing the mixture components to move both radially and laterally over short distances, thus rapidly producing concrete with macroscopic uniformity through the shear displacement of material particles. During twin-shaft mixing, the raw materials were weighed according to the mix proportions, and the pre-mixed dry mix was added to the mixer for 1 min of dry mixing. Then, the pre-mixed water, superplasticizer, defoamer, and CNT slurry were slowly added, and the mixture was wet-mixed for 10 min before discharging.
In vibration mixing, vibrations were applied to the mixing shafts while mixing concrete, causing the cement particles to tremble and breaking up cohesive cement clusters, leading to the rapid and uniform distribution of cement particles. This method increased the movement speed of the mixture, enhancing the number of effective collisions between cement particles. Consequently, the fine particles in the mixing drum were mixed quickly under stress, and the transformation of the mixture’s surface from the solid to liquid phase was accelerated, speeding up cement hydration. Additionally, the vibration effect cleaned the aggregate surface, increasing the bonding strength between cement and aggregates. During the vibration mixing, the raw materials were weighed according to the mix proportions, and the pre-mixed dry mix was added to the mixer for 1 min of dry mixing. Then, the pre-mixed water, superplasticizer, defoamer, and CNT slurry were slowly added, and the mixture was wet-mixed for the specified time before discharging.
After mixing, the UHPC was poured into molds in a single operation, ensuring the mixture flowed from one side to the other and adding more material as needed. The molds were vibrated on a vibrating table for 60 s. After vibrating, the molds were removed, and the excess mixture was scraped off in a single pass using a trowel, moving from one end to the other. The surface was then leveled, and the fresh UHPC was placed into molds within 15 min.
The specimens were demolded after 24 h of indoor curing at a temperature of 20 ± 5 °C and a relative humidity of over 50%. The demolded specimens were placed in a steam-curing chamber, where the temperature was gradually increased to 90 ± 5 °C at a rate of 15 °C/h, maintained at this temperature for 48 h, and then gradually decreased to room temperature at a rate of 12 °C/h. Finally, the specimens were cured under standard conditions (temperature 20 ± 1 °C, relative humidity ≥ 95%) until the 7-day testing.

2.3. Testing Method

The performance tests of the fresh UHPC mixture were conducted according to the standard GB/T 50080-2016 [25]. The axial compressive strength and static compressive elastic modulus tests were conducted in accordance with the standard T/CECS 864-2021 [26]. Specimens measured 100 mm × 100 mm × 300 mm, with a loading rate of 1.2 MPa/s. The axial tensile strength test followed the standard T/CBMF 37-2018 [27], measuring both the elastic limit tensile strength and the tensile strength. The flexural performance test was conducted in accordance with the standard T/CECS 864-2021 [26]. The specimens were 100 mm × 100 mm × 400 mm prisms, with micrometers installed on the side to collect force and displacement values at the mid-span position at a rate of 10 values per second. The loading rate before the initial cracking was set at 0.12 MPa/s, and after the initial cracking, displacement control was used with a loading rate of 0.1 mm/min. The loading was terminated when the displacement reached 2 mm.

2.4. Microscopic Analysis

Following the axial tensile strength tests, one specimen from each group was selected, and approximately 5 mm thin slices were cut from near the ends using a cutting machine. Blocks roughly 10 mm × 10 mm were taken for mercury intrusion porosimetry (MIP) testing, and 2 mm square fragments were extracted from the thin slices for scanning electron microscope (SEM) microstructural analysis by hammering. Immediately after sampling, the specimens were placed into 20 mL plastic bottles filled with an adequate amount of anhydrous ethanol to prevent further hydration. The bottles were tightly sealed and stored in a cool, dry place until further use. The microstructural morphology of the samples was observed using a HITACHI-SU8220 ultra-high-resolution cold field emission scanning electron microscope. The total porosity and pore size distribution of the samples were measured using an AutoPore IV 9510 high-performance fully automatic mercury intrusion porosimeter manufactured by Micromeritics Instrument Corporation, Norcross, GA, USA.

3. Results and Discussion

3.1. Ultra-High-Performance Concrete (UHPC) Workability

The workability of UHPC mixtures with different mixing durations (ranging from 3 to 7 min) and mixing methods is presented in Figure 4. As shown in Figure 4, compared to twin-shaft mixing, vibration mixing enhanced the spread of CNT-reinforced UHPC, with longer vibration mixing times resulting in greater spread. When the vibration mixing time was 3 min, the spread or workability of the UHPC reached 570 mm, equivalent to that achieved with 10 min of twin-shaft mixing. The vibration mixing for 5 min made the spread or workability 15 mm larger than that in the twin-shaft mixing group. At a vibration mixing time of 7 min, the spread or workability increased by 50 mm compared to that in the twin-shaft mixing group. Additionally, for the 7 min vibration mixing, the time required to reach a spread of 500 mm (T500) was 13 s, which was less than the 17 s required for twin-shaft mixing. This indicates that vibration mixing significantly improves the workability of CNT-reinforced UHPC. In terms of wet apparent density, vibration mixing showed improvements over twin-shaft mixing. Vibration mixing for 3, 5, and 7 min increased the wet apparent density by 40, 20, 30 kg/m3, respectively, with the highest wet apparent density observed in the Z3 group. This improvement is due to the fact that vibration mixing could more effectively reduce the air content in UHPC mixtures than twin-shaft mixing.

3.2. UHPC Axial Compressive Performances

The results of the axial compressive strength and elastic modulus tests are shown in Figure 5. As seen in Figure 5, vibration mixing had a positive impact on the axial compressive strength and elastic modulus of UHPC. When testing the vibration durations ranging from 3 to 7 min, the highest axial compressive strength was observed with 3 min of vibration mixing, which was 3.3% higher than that of the B10 group. An improvement in the axial compressive strength with vibration mixing was also observed by Zheng et al. [28]. This benefit can be attributed to the more uniform dispersion of materials, particularly the CNTs, within the UHPC matrix after employing vibration mixing, which reduces the porosity and makes the mixture compacted. However, the elastic modulus remains relatively unaffected, likely due to the inherent properties of the UHPC matrix and the limited influence of mixing methods on its stiffness.

3.3. UHPC Tensile Performances

The results of the axial tensile tests are shown in Figure 6. As indicated in Figure 6, vibration mixing improved the tensile performance of UHPC, which is in agreement with the observation of Zheng et al. [28]. The shorter vibration mixing times yielded more pronounced enhancements. Comparing among different groups, the most significant improvement was observed in the Z3 group, where the elastic limit tensile strength and tensile strength were 11.0 MPa and 11.7 MPa, respectively, representing increases of 14.6% and 15.8% compared to the B10 group. The improvement in tensile performance with vibration mixing can be attributed to the better dispersion of CNTs and the reduction in micro-defects within the UHPC matrix. The high-frequency vibrations help in breaking up agglomerates of CNTs, ensuring a more uniform distribution. This uniform dispersion enhances the bridging effect of CNTs within the matrix, improving the load transfer and crack resistance, thereby increasing the tensile strength. The excessive mixing time would damage the internal structure, resulting in lower strength. The optimal mixing time would be influenced by the vibration frequency and the CNT dispersion. Lower vibration frequency and poorly dispersed CNTs may result in a longer optimal mixing time.

3.4. UHPC Flexural Performances

The results of the flexural performance tests are presented in Figure 7 and Figure 8. The energy absorption and ductility index are shown in Table 2. The ductility index is the ratio of the energy absorption capacity to the energy absorption at yield. Vibration mixing enhanced both the initial cracking strength and flexural strength of UHPC. The enhancements in the flexural performance gradually increased with the vibration time, which is consistent with the results presented by Liu et al. [29]. Compared to that in the twin-shaft-mixed B10 group, the initial cracking strengths of the UHPC vibration mixed for 3, 5, and 7 min increased by 12.6%, 19.1%, and 26.1%, respectively. Correspondingly, the flexural strength increased by 13.4%, 5.6%, and 18.5%, respectively. The load–displacement curves for UHPC during bending tests had similar trends across different mixing methods. However, the envelopes of the curves for the vibration-mixed specimens were larger than those of the twin-shaft-mixed specimens, indicating better ductility in the vibration-mixed samples. This improved ductility can also be observed by the higher ductility index and energy absorption in Table 2. Notably, the specimens mixed for 3 min (Z3) and 7 min (Z7) showed superior performance. The improved flexural performance and ductility with vibration mixing can be attributed to the enhanced dispersion of CNTs and the more uniform distribution of fibers within the UHPC matrix. This results in better crack bridging and energy absorption capabilities, leading to higher flexural strengths and improved ductility.

3.5. Mechanism Analysis

The preceding studies have demonstrated that vibration mixing can enhance the mechanical properties of CNT-reinforced UHPC. This enhancement can improve the safety and durability of the UHPC structures, extend the service life of the structures, and reduce the usage of the UHPC to achieve the same load capacities, which hold significance in structural engineering practices. The enhancing mechanisms may be attributed to three main reasons, as follows.
  • The intense vibrations in vibration mixing help expel trapped air from the UHPC mixture, resulting in an increased wet apparent density and improved mechanical properties.
  • Although CNTs are prepared as a well-dispersed slurry before use, their dispersion within UHPC is challenging with twin-shaft mixing due to its lower mixing frequency. Vibration mixing, with its high-frequency vibrations, promotes a more uniform distribution of CNTs within the UHPC matrix than twin-shaft mixing, thereby enhancing its mechanical properties. Zheng et al. [30] also reported a similar benefit of vibration mixing on improving the distribution of steel fibers within UHPC.
  • During bending or tensile loading, once the matrix cracks, the tensile stress is transferred to the steel fibers. As the load increases, the fibers are gradually pulled out, eventually leading to specimen failure. Vibration mixing improves the dispersion of CNTs, enhancing the mechanical properties of the paste and the transition zone. This improvement increases the bond strength between the matrix and the steel fibers, making fiber pull-out more difficult and thus improving the tensile and flexural performance of UHPC.
Based on the above analysis, further SEM and MIP analyses were conducted on the Z3 and B10 groups to investigate the mechanisms of strength enhancement in CNT-reinforced UHPC due to vibration mixing. Figure 9 shows the SEM images of UHPC prepared with different mixing methods. From Figure 9, it can be observed that the UHPC structures prepared by both mixing methods are dense, with no visible CNT agglomerations or individual CNTs. Comparatively, the hydration products in the vibration-mixed specimens appear denser.
The results of the MIP tests for individual groups of UHPC are shown in Table 3 and Figure 10. As seen in Table 3 and Figure 10, the average pore diameter and porosity of the vibration-mixed specimens were significantly reduced compared to those of the twin-shaft mixed specimens, by 50.8% and 25.3%, respectively. The ability of vibratory mixing to reduce the porosity has also been evidenced by Zheng et al. [28]. The pore size distribution indicates that the pore structure of the vibration-mixed specimens is optimized, with a marked decrease in the proportion of large pores. The reductions in large pore proportion and overall porosity lead to a denser UHPC structure, which macroscopically manifests as an increase in wet apparent density and an improvement in mechanical properties.
In addition, it is worth noting that the optimal mixing time would be influenced by other factors, including CNT dispersion and vibration frequency. The CNT dispersion with different CNT contents may have different optimal mixing times for vibration mixing. Similarly, a shorter mixing duration may be needed when the vibration frequency decreases. Some further analyses could be performed to reveal the effects of other factors.

4. Conclusions

This study investigated the effects of vibration mixing on the workability and mechanical properties of CNT-reinforced UHPC, comparing it with traditional twin-shaft mixing. The following conclusions can be drawn.
  • Vibration mixing is shown to be a more effective method for CNT-reinforced UHPC, offering better flowability, higher wet apparent density, and superior mechanical properties compared to twin-shaft mixing, even with shorter mixing times.
  • For the best balances of axial compressive strength, tensile strength, and flexural performance, a vibration mixing time of 3 min is optimal, considering the vibration mixing times ranging from 3 to 7 min.
  • The significant improvement in the mechanical performance of UHPC with vibration mixing is attributed to two main factors: (a) the intense vibrations help expel air from the UHPC mixture, leading to an increased wet apparent density, reduced porosity, and a lower number of large pores in the hardened UHPC, thereby enhancing its mechanical properties; (b) vibration mixing promotes the uniform dispersion of CNTs, which improves the matrix strength and the transition zone, thereby increasing the bond strength between the matrix and steel fibers and enhancing the overall strength.
For future research, the long-term durability of CNT-reinforced UHPC prepared with vibration mixing can be investigated under various environmental conditions. The effect of other factors impacting vibration mixing, such as the status of CNT dispersion and vibration frequency, can be studied in the future as well. Additionally, exploring the scalability of vibration mixing for large-scale production and practical construction applications is crucial.

Author Contributions

Conceptualization, L.Z. and J.Y.; methodology, W.W.; validation, F.L., Y.Y. and H.C.; formal analysis, M.X.; investigation, L.Z.; resources, W.W; data curation, L.Z.; writing—original draft preparation, L.Z.; writing—review and editing, Y.Y.; visualization, J.Y.; supervision, Y.Y.; project administration, Y.Y.; funding acquisition, L.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the State Grid Corporation of China, grant number 5200-202322138A-1-1-ZN.

Data Availability Statement

Data are available based on the request.

Conflicts of Interest

Author Jiangang Yin was employed by the company State Grid Hubei Electric Power Co., Ltd. Authors Fucai Liu, Min Xiao and Haibo Cui were employed by the company Guangdong Gaiteqi New Materials Technology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from State Grid Corporation of China. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.

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  26. T/CECS 864-2021; Standard for Test Method of Ultra-High Performance Concrete. Shanghai Research Institute of Building Science Co., Ltd.: Shanghai, China, 2021. Available online: https://www.gongbiaoku.com/book/3dt21846axm (accessed on 15 March 2024).
  27. T/CBMF 37-2018; Fundamental Characteristics and Test Methods of Ultra-High Performance Concrete. China Building Materials Federation: Beijing, China, 2018. Available online: https://www.ccpa.com.cn/site/content/4185.html (accessed on 15 March 2024).
  28. Zheng, Y.; Zhou, Y.; Huang, X.; Min, Y.; Luo, H.; Chen, Y.; Li, W. Study on performance improvement of ultra-high performance concrete by vibration mixing. Constr. Build. Mater. 2022, 327, 126823. [Google Scholar] [CrossRef]
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Figure 1. Appearance of the carbon nanotube (CNT) slurry.
Figure 1. Appearance of the carbon nanotube (CNT) slurry.
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Figure 2. Microscale morphology of the CNTs.
Figure 2. Microscale morphology of the CNTs.
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Figure 3. Particle size distributions of the CNTs.
Figure 3. Particle size distributions of the CNTs.
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Figure 4. Performances of fresh ultra-high-performance concrete (UHPC): (a) spread; (b) time to reach 500 mm spread; (c) wet apparent density.
Figure 4. Performances of fresh ultra-high-performance concrete (UHPC): (a) spread; (b) time to reach 500 mm spread; (c) wet apparent density.
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Figure 5. Axial compressive performances of UHPC: (a) axial compressive strength; (b) elastic modulus.
Figure 5. Axial compressive performances of UHPC: (a) axial compressive strength; (b) elastic modulus.
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Figure 6. Tensile performance of UHPC: (a) elastic limit tensile strength; (b) tensile strength.
Figure 6. Tensile performance of UHPC: (a) elastic limit tensile strength; (b) tensile strength.
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Figure 7. Flexural performances of UHPC: (a) initial cracking strength; (b) flexural strength.
Figure 7. Flexural performances of UHPC: (a) initial cracking strength; (b) flexural strength.
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Figure 8. Load–displacement curves of UHPC under flexural loading.
Figure 8. Load–displacement curves of UHPC under flexural loading.
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Figure 9. Scanning electron microscope morphologies of the UHPC with: (a) vibration mixing Z3; (b) twin-shaft mixing B10.
Figure 9. Scanning electron microscope morphologies of the UHPC with: (a) vibration mixing Z3; (b) twin-shaft mixing B10.
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Figure 10. Pore size distributions of UHPC.
Figure 10. Pore size distributions of UHPC.
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Table 1. Mix proportions for ultra-high-performance concrete (UHPC).
Table 1. Mix proportions for ultra-high-performance concrete (UHPC).
IDMixing MethodMixing TimeUHPC Premix
(kg/m3)		Water
Reducer (kg/m3)		Defoamer
(kg/m3)		Water
(kg/m3)		CNT Slurry
(kg/m3)
Z3Vibration Mixing3 min2239.5380.4118.23517.5
Z5Vibration Mixing5 min2239.5380.4118.23517.5
Z7Vibration Mixing7 min2239.5380.4118.23517.5
B10Twin-Shaft Mixing10 min2239.5380.4118.23517.5
Table 2. Energy absorption and ductility index of UHPC under flexural loading.
Table 2. Energy absorption and ductility index of UHPC under flexural loading.
IDEnergy Absorption Capacity (kN·mm)Energy Absorption at Yield (kN·mm)Ductility Index
Z3187.853.5952.33
Z5167.753.7844.38
Z7191.913.2059.97
B10157.663.4345.97
Table 3. Mercury intrusion porosimetry results of UHPC.
Table 3. Mercury intrusion porosimetry results of UHPC.
IDTotal Pore Volume (mL/g)Average Pore Diameter (nm)Porosity (%)Pore Size Distribution (%)
<10 nm10–100 nm100–1000 nm>1000 nm
Z30.041787.969.140.600.050.358.14
B100.0632178.7112.240.330.640.4010.87
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MDPI and ACS Style

Zhou, L.; Yin, J.; Wang, W.; Liu, F.; Xiao, M.; Yang, Y.; Cui, H. Effect of Vibration Mixing on the Mechanical Properties of Carbon Nanotube-Reinforced Ultra-High-Performance Concrete. Buildings 2024, 14, 2545. https://doi.org/10.3390/buildings14082545

AMA Style

Zhou L, Yin J, Wang W, Liu F, Xiao M, Yang Y, Cui H. Effect of Vibration Mixing on the Mechanical Properties of Carbon Nanotube-Reinforced Ultra-High-Performance Concrete. Buildings. 2024; 14(8):2545. https://doi.org/10.3390/buildings14082545

Chicago/Turabian Style

Zhou, Li, Jiangang Yin, Wei Wang, Fucai Liu, Min Xiao, Yibo Yang, and Haibo Cui. 2024. "Effect of Vibration Mixing on the Mechanical Properties of Carbon Nanotube-Reinforced Ultra-High-Performance Concrete" Buildings 14, no. 8: 2545. https://doi.org/10.3390/buildings14082545

APA Style

Zhou, L., Yin, J., Wang, W., Liu, F., Xiao, M., Yang, Y., & Cui, H. (2024). Effect of Vibration Mixing on the Mechanical Properties of Carbon Nanotube-Reinforced Ultra-High-Performance Concrete. Buildings, 14(8), 2545. https://doi.org/10.3390/buildings14082545

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