Thesis Format
Monograph
Degree
Doctor of Philosophy
Program
Civil and Environmental Engineering
Supervisor
ElNaggar, M. Hesham
Abstract
The use of shotcrete in tunneling and underground structures is extensive due to its excellent adhesion, low rebound, and rapid development of strength. Accelerators are key additives in shotcrete, significantly influencing its performance. This research investigates the interaction between various accelerators and cement-based shotcrete mixtures through laboratory experiments and full-scale field spraying trials. The study examines the effects of different accelerator types (silicate-based and alkali-free) and dosages on the mechanical properties, hydration kinetics, and microstructure of shotcrete mixtures. Laboratory tests were conducted on cement pastes to assess flowability, compressive strength development, and hydration behavior using isothermal calorimetry. Full scale field trials involved spraying shotcrete panels and evaluating early-age and long-term compressive strength, as well as analyzing the microstructure through X-ray diffraction and thermogravimetric analysis. The research highlights the significant differences between laboratory-mixed samples and field-sprayed shotcrete, providing insights into the impact of the spraying process on accelerator reactivity, hydration kinetics, and overall shotcrete performance. The findings contribute to a better understanding of shotcrete behavior in real-world applications and offer guidance for optimizing shotcrete mix designs for various construction projects. Furthermore, finite element analyses are conducted to realistically simulate shotcrete behaviour in two important geotechnical applications. The structural performance of shotcrete as a tunnel lining material and for rock support in deep excavation of a manhole is numerically investigated and its important performance characteristics in these applications are identified.
Summary for Lay Audience
Shotcrete is a special type of concrete that is sprayed onto surfaces, commonly used in building tunnels and underground structures. It sticks well, has minimal waste, and hardens quickly. Key to its performance is chemical additives called accelerators, which help it set and harden faster. This research studies how different accelerators affect shotcrete by conducting both lab experiments and real-world field testing. In the lab, this study tested how well the shotcrete flows, how quickly it gains strength, and how it reacts with water. Thus, advanced techniques were used to understand the chemical changes happening inside the shotcrete. In the field trials, shotcrete was sprayed onto panels and its strength was overtime. Also, shotcrete internal structure was analyzed to see how the spraying process affected it. It was found that shotcrete behaves differently when mixed in the lab compared to when it is sprayed in the field. This research helps us understand these differences and provides tips on how to create better shotcrete mixtures for construction projects. It also used engineering computer software to simulate real shotcrete underground projects to explore how shotcrete behaves under different conditions, offering further insights for optimizing its use in various applications.
Recommended Citation
ElSayed, Esraa, "Performance of Shotcrete with Various Accelerators: Laboratory, Field, and Numerical Analyses for Geotechnical Applications" (2025). Electronic Thesis and Dissertation Repository. 10803.
https://ir.lib.uwo.ca/etd/10803