不同形态回收碳纤维混凝土弯曲性能及微观结构

江佳正; 曹忠露; 赵轩; 杨鼎宜; 苏忠纯

不同形态回收碳纤维混凝土弯曲性能及微观结构

江佳正^{1, 2},
曹忠露^{1, 2, 3, ,},
赵轩¹,
杨鼎宜⁴,
苏忠纯^{1, 2}

1.
中交天津港湾工程研究院有限公司, 天津 300222
2.
中交第一航务工程局有限公司, 天津 300461
3.
港口岩土工程技术交通行业重点实验室, 天津 300222
4.
扬州大学建筑科学与工程学院, 扬州 225127

基金项目: 中交一航局揭榜挂帅项目(2022-YHJBGS-02)；中交一航局科技研发项目(2022-7-19)；交通运输行业重点科技项目清单(2022-MS1-065)；中交集团青年创新项目(2023-ZJKJ-QNCX04)

详细信息

通讯作者:
曹忠露，博士，正高级工程师，硕士生导师，研究方向为高性能混凝土材料与结构耐久性　E-mail: caozhonglu@126.com

中图分类号: TU528.58
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- 文章访问数: 54
- HTML全文浏览量: 48
- 被引次数: 0
出版历程
- 收稿日期: 2024-05-07
- 修回日期: 2024-05-28
- 录用日期: 2024-06-19
- 网络出版日期: 2024-06-29

Flexural properties and microstructure of recycled carbon fiber concrete with different morphologies

JIANG Jiazheng^{1, 2},
CAO Zhonglu^{1, 2, 3
, ,},
ZHAO Xuan¹,
YANG Dingyi⁴,
SU Zhongchun^{1, 2}

1.
Tianjin Port Engineering Institute Co., Ltd. of CCCC First Harbor Engineering Co., Ltd., Tianjin 300222, China
2.
CCCC First Harbor Engineering Co., Ltd., Tianjin 300461, China
3.
Key Laboratory of Port Geotechnical Engineering, Ministry of Communications, Tianjin 300222, China
4.
College of Civil Science and Engineering, Yangzhou University, Yangzhou 225127, China

Funds: Unveiling and Leading Projects of CCCC First Harbor Engineering Co., Ltd. (2022-YHJBGS-02); Technology Research and Development Projects of Project of CCCC First Harbor Engineering Co., Ltd. (2022-7-19); Key Technology Projects in the Transportation Industry (2022-MS1-065); Youth Innovation Project of CCCC (2023-ZJKJ-QNCX04)

摘要

摘要: 将回收碳纤维(RCF)掺入混凝土制备绿色环保材料是实现碳纤维增强复合材料固废回收利用的有效方式。为探究RCF对混凝土材料弯曲性能的影响，将三种RCF按不同掺量与长度掺入混凝土中，通过四点弯曲试验，分析了回收碳纤维混凝土(RCFC)破坏形态、荷载-挠度曲线和弯曲强度的变化规律；提出了新的初裂点确定方法并进行了弯曲韧性评价，结合SEM从微观层面解释内在原因；基于MIP测得的孔隙率提出了新的弯曲强度预测公式。结果表明：RCF可改善试件破坏形式，提升RCFC弯曲强度和韧性，弯曲强度最高提升38.67%，弯曲韧性指标I₂₀最高提升70.14%；不同形态的RCFC试件弯曲强度、弯曲韧性指数、等效弯曲强度及弯曲韧性比的影响规律并不相同，这主要和RCF表观形貌有关，从弯曲韧性角度来看掺入1.5%长度12mm的RCF-A时性能最佳。本文研究结论和提出的计算方法可为RCFC的性能提升及推广应用提供参考。
- 回收碳纤维 /
- 弯曲韧性 /
- 微观结构 /
- 孔隙率 /
- 弯曲强度预测
Abstract: Green materials can be prepared by incorporating recycled carbon fibers (RCF) into concrete, which is an effective way to realize the recycling of carbon fiber reinforced composite solid waste. In order to investigate the effect of RCF on the flexural properties of concrete, RCF from three different manufacturers were incorporated into concrete at different contents and lengths. Four-point bending tests were carried out to analyze the failure modes, load-deflection curves and flexural strength of recycled carbon fiber reinforced concrete (RCFC). A new method for determining the initial cracking point was proposed, and the flexural toughness was evaluated. The intrinsic causes were explained at the microscopic level in combination with SEM. A new bending strength prediction formula was proposed based on the porosity measured by MIP. The results show that RCF can improve the failure mode and improve the flexural strength and toughness, with a maximum increase of 38.67% in flexural strength and 70.14% in flexural toughness index I₂₀. The effects of different forms of RCFC specimens on the flexural strength, flexural toughness index, equivalent flexural strength and flexural toughness ratio are not the same, which is mainly related to the apparent morphology of RCF. From the perspective of flexural toughness, the best performance is achieved when 1.5 wt% RCF-A with a length of 12 mm is incorporated. The research conclusions and calculation methods can provide reference for the performance enhancement and application of RCFC.
- recycled carbon fibers /
- flexural toughness /
- microstructure /
- porosity /
- flexural strength prediction

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图 1 回收碳纤维(RCF)外观

Figure 1. Appearance of recycled carbon fibers (RCF)

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图 2 三种RCF的形貌外观

Figure 2. Morphological appearance of three RCFs

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图 3 四点弯曲试件及装置示意图(单位：mm)

Figure 3. Four-point bending specimen and device diagram (Unit: mm)

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图 4 弯曲韧性指数计算示意图

Figure 4. Calculation diagram of toughness index

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图 5 RCF荷载-挠度曲线初裂点计算示意图

Figure 5. Determination diagram of initial crack point of RCF load-deflection curve

M_max—Point of peak load；M_0.2、M_0.5、M_0.8—Point with 20%、50%、80% of peak load; A—Point of initial cracking load

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图 6 NC和回收碳纤维混凝土(RCFC)典型弯曲破坏形态

Figure 6. Typical flexural failure form of NC and recycled carbon fiber reinforced concrete (RCFC)

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图 7 不同RCFC平均荷载-挠度曲线

Figure 7. Average load-deflection curve of different RCFC

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图 8 RCFC弯曲强度

Figure 8. Flexural tensile strength of RCFC

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图 9 RCF掺量和弯曲韧性指数的关系

Figure 9. Relationship between RCF mass content and toughness index of RCFC

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图 10 RCF长度和弯曲韧性指数的关系

Figure 10. Relationship between RCF length and toughness index of RCFC

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图 11 RCFC等效弯曲强度和弯曲韧性比

Figure 11. Equivalent flexural strength and flexural toughness ratio of RCFC

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图 12 RCFC微观形态

Figure 12. Microstructure of RCFC

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图 13 RCF-A试件孔隙率

Figure 13. Porosity of part samples of RCF-A

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表 1 回收碳纤维性能参数

Table 1. Properties of RCFs

Fiber	Length/ mm	Recycling method	Adhesive Yes or No	Diameter/μm	Density/ (g·cm⁻³)	Tensile strength/MPa	Tensile modulus/GPa	Carbon content/%
RCF-A	6/12/18	Direct cutting	Yes	5.83	1.78	3536	230	95.0
RCF-B	6/12/18	Heat treatment	No	7.28	1.80	3474	230	91.3
RCF-C	6/12/18	Direct cutting	Yes	7.28	1.79	2866	230	92.8

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表 2 试件编号及配合比

Table 2. Number and mix proportion of specimens

Sample No.	RCF parameter			Sample No.	RCF parameter
Sample No.	Type	Content/wt%	Length/mm	Sample No.	Type	Content/wt%	Length/mm
NC	—	—	—	RCF-B0.5%-L12	B	0.5	12
RCF-A0.5%-L6	A	0.5	6	RCF-B1.0%-L12	B	1	12
RCF-A0.5%-L12	A	0.5	12	RCF-B1.5%-L12	B	1.5	12
RCF-A0.5%-L18	A	0.5	18	RCF-B1.5%-L6	B	1.5	6
RCF-A1.0%-L6	A	1.0	6	RCF-B1.5%-L18	B	1.5	18
RCF-A1.0%-L12	A	1.0	12	RCF-D0.5%-L12	C	0.5	12
RCF-A1.0%-L18	A	1.0	18	RCF-C1.0%-L12	C	1	12
RCF-A1.5%-L6	A	1.5	6	RCF-C1.5%-L12	C	1.5	12
RCF-A1.5%-L12	A	1.5	12	RCF-C1.5%-L6	C	1.5	6
RCF-A1.5%-L18	A	1.5	18	RCF-C1.5%-L18	C	1.5	18

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表 3 参数拟合结果及RCFC弯曲强度预测情况

Table 3. Parameter fitting results and flexural strength prediction of RCFC

Parameter fitting results
$ k $	$ \alpha \tau $	$ \beta $	$ \gamma $
1.3078	84.7983	0.5816	0.9273
Measured and predicted values of bending strength
No.	Porosity/%	Measured value/MPa	Predicted value /MPa
RCF-A1.5%- L 6	12.67	6.30	6.27
RCF-A1.5%-L12	12.26	6.26	6.32
RCF-A0.5%-L18	10.85	6.92	6.92
RCF-A1.0%-L18	12.38	6.35	6.35
RCF-A1.5%-L18	13.09	6.40	6.37

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