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浙江大学学报(工学版)
浙江大学学报(工学版)  2022, Vol. 56 Issue (11): 2280-2289    DOI: 10.3785/j.issn.1008-973X.2022.11.019
土木工程     
高温后碳纳米管混凝土力学性能及细观结构变化
田威1(),高芳芳2,*(),贺礼1
1. 长安大学 建筑工程学院，陕西 西安 710061
2. 兰州理工大学 土木工程学院，甘肃 兰州 710050
Variation of mechanical property and meso structure of MWCNTs concrete exposed to high temperature
Wei TIAN1(),Fang-fang GAO2,*(),Li HE1
1. School of Civil Engineering, Chang’an University, Xi’an 710061, China
2. School of Civil Engineering, Lanzhou University of Technology, Lanzhou 710050, China
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摘要：

为了探究多壁碳纳米管（MWCNTs）对高温后混凝土力学性能和细微观结构的作用机制，采用单轴压缩、计算机断层扫描（X-ray?CT）和电镜扫描（SEM）对高温后MWCNTs增强混凝土的抗压强度、孔径、孔隙率、微观形貌及水化产物的变化趋势进行试验研究. 结果表明，高温后MWCNTs增强混凝土强度损失比普通混凝土降低了11.15%~27.60%；MWCNTs的填充和桥接作用可以阻碍并延缓混凝土内部裂缝的扩展，并对600 ℃以下混凝土内部孔隙网络的形成具有有利影响. 分析冷却方式对混凝土性能的影响发现，浸水冷却引发强烈的热冲效应导致混凝土的性能急速下降，短时间的喷淋冷却有利于高温后混凝土性能的恢复，混凝土试样在空气中自然冷却的损伤程度介于上述两者之间.
关键词： 多壁碳纳米管混凝土;  抗压强度;  细观结构;  高温;  X-ray CT    
Abstract:

The action mechanism of multi walled carbon nanotubes (MWCNTs) on the mechanical properties and meso structure of concrete exposed to high temperature was explored. The compressive strength was studied by the uniaxial compression test. The pore characteristics were detected by computer tomography (X-ray CT) technology. The micro morphology and hydration products were observed by scanning electron microscope (SEM). The results showed that the strength loss of MWCNTs in high temperature compared with ordinary plain concrete reinforced concrete decreased by 11.15%—27.60%. The filling and bridging effect of MWCNTs hindered and delayed the expansion of internal cracks in concrete. MWCNTs had a certain beneficial effect on the formation of internal pore network of the concrete below 600 ℃. The influence of cooling mode on the performance of concrete was also considered. The quench cooling caused a strong thermal shock effect, which led to the rapid decline of performance of concrete. The spray cooling was beneficial to the recovery of properties of concrete exposed to high temperature in a short time. The damage degree of the concrete specimen cooled naturally in air was between the above two.
Key words: MWCNTs concrete    compressive strength    meso structure    high temperature    X-ray CT
收稿日期: 2021-11-18 出版日期: 2022-12-02
CLC:  TU 525.9  
基金资助: 国家自然科学基金资助项目（51379015，51579013）；长安大学优秀博士学位论文培育项目（300102281723）
通讯作者: 高芳芳     E-mail: tianwei@chd.edu.cn;429757009@qq.com
作者简介: 田威（1981—），男，教授，从事岩土材料细观力学分析研究. orcid.org/0000-0001-6480-4321. E-mail： tianwei@chd.edu.cn
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引用本文:

田威,高芳芳,贺礼. 高温后碳纳米管混凝土力学性能及细观结构变化[J]. 浙江大学学报(工学版), 2022, 56(11): 2280-2289.

Wei TIAN,Fang-fang GAO,Li HE. Variation of mechanical property and meso structure of MWCNTs concrete exposed to high temperature. Journal of ZheJiang University (Engineering Science), 2022, 56(11): 2280-2289.

链接本文:

https://www.zjujournals.com/eng/CN/10.3785/j.issn.1008-973X.2022.11.019    或    https://www.zjujournals.com/eng/CN/Y2022/V56/I11/2280

混凝土分组 ρ/（kg·m?3） S/mm fc/MPa
水泥 粗骨料 细骨料 水 减水剂 碳纳米管 分散剂
PC 350 1150 646 157 1.75 ? ? 122 62.45
MC 350 1150 646 157 2.80 0.28 0.56 164 66.86
表 1  混凝土配比
图 1  混凝土试样制备
第1组 冷却方式 第2组 冷却方式
PC-N 自然冷却 MC-N 自然冷却
PC-S 喷淋冷却 MC-S 喷淋冷却
PC-Q 浸水冷却 MC-Q 浸水冷却
表 2  混凝土试样分组
图 2  试验设备及试验流程图
图 3  高温-冷却后混凝土试样表观特征
图 4  高温-冷却后混凝土的残余抗压强度
图 5  高温后MWCNTs混凝土和普通混凝土的微观形貌对比
图 6  多壁碳纳米管（MWCNTs）混凝土的热重曲线
图 7  温度对MWCNTs混凝土水化产物C-S-H的影响
图 8  高温后MWCNTs混凝土的残余抗压强度与水化硅酸钙凝胶（C-S-H）质量损失率之间的关系
图 9  混凝土CT图像处理过程
图 10  高温-冷却后混凝土试样轴向CT扫描断面灰度图
图 11  MWCNTs对混凝土高温-冷却性能的强化机理
图 12  混凝土孔隙率沿其CT扫描方向的分布
图 13  高温-冷却后MWCNTs混凝土孔隙率与抗压强度之间的关系
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