To remove a sleeve easily after concrete placement by forming the outer peripheral surface of a sleeve which provides an opening (hole) on the opening of a concrete structure, such as beams, walls and slabs with alkaline decomposable polyester resin.
A sleeve 1 (raw hole forming form) consisting of alkaline degradable polyester resin at least on the outer peripheral surface is set up at a set-up position of utility piping for a plumbing system or an air conditioning duct or the like. It is also possible to form the whole sleeve with alkaline degradable polyester-based resin. Alkaline hydrolytic degradable aliphatic series or aromatic polyester is adopted for this polyester resin while they may be replaced with a polymer manufactured with chemical synthesis or microbes. This sleeve 1 is mounted on the form and concrete 5 is placed so that the concrete 5 may be cured and decomposed (eroded) with alkali contained in the concrete in parallel to the concrete curing, thereby forming a clearance 6 between a concrete structure 5 and the form. This construction makes it possible to remove the sleeve 1 with ease.
TANAKA HIDEO
KOBAYASHI SADAO
SUMIYOSHI FUMIO
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