Cracking problems for high strength silica fume concrete used in the dam of Shihlin hydropower project

摘要

Although silica-fume concrete has higher compressive strength to resist abrasion-erosion damage to hydraulic structures, it also has higher potential for cracking than conventional concrete. Due to very low water-cement ratio of the silica-fume concrete, the early-age cracks will be occurred resulting from volume changes caused primarily by autogenous shrinkage and plastic shrinkage when the restraint is provided. Since autogenous shrinkage can not be eliminated in the silica-fume concrete of the case study, some improvements made during construction will help minimize the cracking problems especially for drying and plastic shrinkage cracks. These include that placements can be made with smaller blocks, finishing on silica-fume concrete should be performed in the minimal possible time, initial water curing should begin immediately after finishing is completed, thermal protection should be enforced under cold weather conditions, and subsequent curing should be continued for a long period of time . Although some cracks still appear in early ages of the silica-fume concrete, autogenous healing may occur if the concrete is kept wet-cured. Since the cracking problems being experienced on this project are very similar to those occurred at Kinzua Dam, abrasion resistance will not be affected by cracks because the bond and anchorage of the silica-fume concrete is ensured.