Dissertation
MECHANICAL AND LONG-TERM CHARACTERIZATION OF SHOTCRETE-CONCRETE INTERFACE BONDS
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004642
Handle:
https://hdl.handle.net/2376/125071
Abstract
Shotcrete is gaining popularity with vertical and overhead construction where conventional formworks and repairs are difficult to make, costly, and often short-lived. However, if the interface bond qualities between shotcrete and concrete are not adequately formed when the substrate concrete surface lacks cleanliness and soundness, this method could also potentially reduce the life expectancy of structures. In addition, long-term freeze-thaw weathering in northern states also weakens the shotcrete-concrete interface bonds, leading to debonding and rebar corrosion. Therefore, it is essential to characterize the shotcrete-concrete interface bonds to evaluate the performance of composite concrete structures. To this end, the shotcrete-concrete interface bond is evaluated under shear and tension for four substrate surface preparation techniques: chipped (C), pressure-washed (PW), sandblasted (SB), and as-cast (AC). A new mode-II fracture-based test is designed and developed to examine the resistance to potential crack initiation and propagation. Results are correlated with the topography of the substrate surface. A parametric study is conducted using combined concrete damage plasticity and a cohesive zone model on ABAQUS to identify failure mechanisms at the bond interface. The long-term freeze-thaw durability of shotcrete-concrete bonds is assessed, and a probabilistic damage model based on a Weibull distribution is introduced to predict the service life of such interfaces.
It is advised to use various test techniques to assess shotcrete-concrete interface bonds, as different surface preparation methods perform better under certain loading conditions. Nevertheless, the highest surface bond strength and mode-II fracture energy were reported by C. The proposed mode-II fracture-based test offers a viable alternative for bond characterization leading to results with similar variations as shear bond tests. In direct tension tests, profiles with estimated surface texture depths greater than 0.294 mm demonstrated strong bonding. C demonstrated the highest resistance to frost damage, followed by PW and SB, which exhibited comparable degradation. After 300 freeze-thaw cycles, the tensile strength of AC decreased by more than 90%, emphasizing the significance of surface preparation in shotcrete construction. The experimental tests and the finite element analysis showed a strong correlation and verified the existence of adhesive, cohesive, and combined adhesive-cohesive failure modes.
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Details
- Title
- MECHANICAL AND LONG-TERM CHARACTERIZATION OF SHOTCRETE-CONCRETE INTERFACE BONDS
- Creators
- Ayumi Kalpana ManawaduAyumi Kalpana Manawadu
- Contributors
- Haifang Wen (Advisor)Pizhong Qiao (Committee Member)Xianming Shi (Committee Member)Sinisa Mesarovic (Committee Member)Lloyd Smith (Committee Member)Vikram Yadama (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 247
- Identifiers
- 99900898933601842
- Language
- English
- Resource Type
- Dissertation