Durability of shotcrete rehabilitation treatments of B.C. Hydro dams

• Main Author: Heere, Roland
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/3566

This thesis is about shotcrete as a repair material for concrete dams situated in the moderate climate of south western British Columbia. Work on the thesis started in summer 1993. The experimental part was finished by summer 1994. The project was done in cooperation with British Columbia Hydro and Powertech Labs Inc. A literature analysis focused on shotcrete materials and application techniques for repair purposes. Some literature was found describing long-time performance of shotcrete repairs. State of the art in shotcrete repairs includes mixes containing silica fume and steel fibers. Both the wet-mix and the dry-mix processes are capable of producing durable shotcrete. Latex is controversial as an admixture for shotcrete. Where shotcrete repairs have failed, that was frequently due to frost damage in the substrate or insufficient substrate surface preparation. BC Hydro has six dams repaired with shotcrete. Four of these dams (Stave Blind Slough,- Ruskin, Buntzen and Jordan River Diversion Dams) were examined closely. The original concrete of these dams was of marginal quality and susceptible to freeze-thaw. Repair shotcrete was resistant to local environmental situations, although shrinkage cracking and reflective cracking were observed. Shotcrete on horizontal surfaces and in concave corners had deteriorated. Most shotcrete did not achieve the specific surface and void spacings recommended in the literature for freeze-thaw resistance. Among the recommendations for repair work are: • Use 100 mm thick silica fume shotcrete with steel fibers on vertical surfaces • Use 250 mm steel fiber shotcrete on substrate concrete that will remain water saturated • Avoid shotcrete on horizontal surfaces.