Development of Injectable Water-Stop for Grouting in Underground Concrete Structure Joint

Abstract

Abstract In the case of water leakage at the diaphragm wall concrete panel joint, secondary grouting is usually conducted from outside of the structure after construction, but the remedial treatment requires high costs and time because of the uncertainty of the leakage location. The idea of this study is to incorporate the grouting hose into the conventional water-stop installed at the construction joint, and thus, grouting can be effectively performed. A state of the practice of water-stop, inside which grouting material can be injected, was designed and manufactured. Accordingly, an injection methodology was developed. The original geometry of the commercial water-stop was not changed, and the existing center hole was selectively renovated as an injecting tube. Micro-opening on the tube surface was optimized as a slit shape for discharging grouting material. The injection system and methodology were suitably created to fit to this product. Injection performances were verified with various experiments for pure water, microcement, modified acryl, and polymer urethane. Real-scale vertical injection experiments at 15 m of height proved that the developed water-stop can be applicable for commercial grouting materials within 30 minutes. A workable threshold viscosity of grouting material would be estimated to be 200 cP. Workable injection pressures are recommended after both actual injection tests and numerical analysis; 2–5 bar for materials with low viscousness, such as microcement and modified acryl, and 5–8 bar for high-viscous materials, such as polymer urethane. An injection test at concrete joints successfully demonstrated grouting performance. Long-term waterproofing capability was proved against continuous 5–bar application, representing 50 m of water pressure for a consecutive 15 months.