| 摘要 |
PROBLEM TO BE SOLVED: To provide a rebound ratio reducing agent and a spraying construction method using the agent which are capable of reducing the rebound ratio upon spraying with the quick-setting concrete and are used when an exposed surface of the ground and mountain such as a tunnel is sprayed with the quick-setting concrete. SOLUTION: This rebound ratio reducing agent contains, for example, polyvinyl alcohol having a 80-90 mol.% degree of saponification and a degree of polymerization of 2,000 or below and a boron compound such as sodium borate. In this spraying construction method, the quick-setting concrete containing cement and a quick-setting material is mixed with the rebound ratio reducing agent. Further the rebound ratio reducing agent is mixed in a position of a spraying nozzle part.
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