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Bond behavior and degradation mechanisms of Multi-functional Fabric Reinforced Cementitious Matrix (MFRCM) composites used for ICCP-SS
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| Title: | Bond behavior and degradation mechanisms of Multi-functional Fabric Reinforced Cementitious Matrix (MFRCM) composites used for ICCP-SS |
| Other Titles: | ICCP-SS工法に用いる多機能型繊維補強セメント系複合材料(MFRCM)の付着挙動と劣化メカニズム |
| Authors: | Zhu, Miaochang Browse this author |
| Keywords: | Anodic polarization | | Bond behavior | | Bond slip relationship | | Carbon fabric | | Cementitious matrix | | Degradation mechanisms | | ICCP-SS | | Matrix impregnation | | MFRCM composites |
| Issue Date: | 25-Sep-2020 |
| Publisher: | Hokkaido University |
| Abstract: | A sustainable repair method, which is called ICCP-SS (impressed current cathodic protection
and structural strengthening), has been proposed for deficient reinforced concrete structures
caused by corrosion of steel in concrete. In the implementation of the proposed method, a
material that plays a dual functional role as structural reinforcement and impressed current
anode should be used and applied on concrete substrate. A multifunctional fabric reinforced
cementitious matrix (MFRCM) composite in which carbon fabric is incorporated is employed
as such a functional material. While the MFRCM composite works in an ICCP-SS system the
embedded carbon fabric is subjected to not only anodic polarization that is related to
electrochemistry but also the stress transferred from the surrounding matrix. Thus, there is a
need to investigate the bond behavior and degradation of carbon fabric embedded in the matrix
under anodic polarization, which helps gain an in-depth understanding of the global behavior
of MFRCM composites and the effectiveness and efficiency of the ICCP-SS method.
Systematic research work was carried out, with a major aim at clarifying the bond behavior at
the interface between carbon fabric and cementitious matrix within MFRCM composites under
anodic polarization. In the beginning, the bond behavior of carbon yarn embedded in a range
of cementitious matrices was investigated. The bond slip relationship was determined for the
carbon yarn embedded in various matrices. The results show that the carbon yarns embedded
in various matrices feature a similar bond behavior that can be represented by a trilinear bond
slip relationship. Once the tensile strength is attained, fracture of the embedded carbon yarn can
take place. An approach was derived to calculate the critical embedment length based on the
bond slip relationship. Afterwards, the effect of matrix impregnation on the bond behavior
between carbon fabric and matrix was studied. The outer (impregnated) part and inner
(unimpregnated) part can be distinguished within a single carbon yarn due to limited matrix
impregnation. The percentage of the impregnated part was estimated as 30% of the whole
carbon yarn based on the image process and analysis results. Besides, the respective bond slip
relationship for the outer (matrix-outer part) and inner (outer part-inner part) interface was
determined based on the pullout test results. By carrying out finite element modeling that
incorporates the evaluated bond slip relationships, a good agreement can be achieved between
numerical and experimental results. Besides, the stress transfer at the outer and inner interfaces
and the contribution of the outer and inner parts to carrying the applied force as well as the
effects of key parameters on the pullout behavior were also discussed based on numerical
simulation.
With introducing anodic polarization, MFRCM composites were investigated concerning the
electrochemical performance, the mechanisms of degradation and the bond behavior between
carbon fabric and matrix. Stabilized electrochemical performance can be maintained for
MFRCM composites polarized up to 125 mA/m2, while an exponential growth of cell voltage
can be seen for larger current densities. Using SEM, EDS, FTIR and XPS, the polarization
induced changes in the chemical composition and morphology of carbon fabric and the
surrounding matrix were analyzed. The results reveal that the carbon fabric in the matrix
showed a clear sign of deterioration featured by multiple transverse cracks on the carbon
filaments and significant changes in the surface functional groups. The changes in the
morphology of carbon fabric within MFRCM composites were also discussed. Finally, the
effect of anodic polarization on the bond behavior between carbon fabric and matrix was
examined. The respective bond slip relationship for the outer and inner interface was
determined based on test results obtained from anodically polarized MFRCM composites. The
results show that anodic polarization compromises the bond behavior for both interfaces,
depending on the extent of anodic polarization. With increasing the extent of anodic
polarization, both the local bond strength and the residual bond stress decrease for the outer
interface, while the local bond strength is reduced for the inner interface. |
| Conffering University: | 北海道大学 |
| Degree Report Number: | 甲第14239号 |
| Degree Level: | 博士 |
| Degree Discipline: | 工学 |
| Examination Committee Members: | (主査) 准教授 松本 浩嗣, 教授 松本 高志, 教授 杉山 隆文, 特任教授 横田 弘, 教授 上田 多門(深圳大学), 教授 Zhu Ji-Hua(深圳大学) |
| Degree Affiliation: | 工学院（北方圏環境政策工学専攻） |
| Type: | theses (doctoral) |
| URI: | http://hdl.handle.net/2115/79415 |
| Appears in Collections: | 学位論文 (Theses) > 博士 （工学）
課程博士 (Doctorate by way of Advanced Course) > 工学院(Graduate School of Engineering)
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