PURPOSE: To prevent bulging by a method wherein an exhauster is connected to a deaerator for substrate respiration, the surface of a concrete layer is coated with a primer, the exhauster is driven, air is exhausted and the upper section of a primer layer is coated with a waterproof material.

CONSTITUTION: An expansion joint or the opening section of an air-permeable groove mounted or formed to a substrate concrete layer 30 is covered with a sealing material to form a cavity 40, and a plurality of deaerators 10, 20 for backing respiration are installed so as to be communicated with the cavity 40. An exhauster 60 is connected to the deaerators 10, 20, the surface of the concrete layer is coated with a primer, the exhauster 60 is driven and air is exhausted, and moisture contained in the concrete layer 30 is vaporized and sucked and dried forcibly. The upper section of a primer coated layer is coated with a film waterproof material to form a waterproof layer 50, the exhauster 60 is removed and the deaerators 10, 20 are used successively as deaerators for substrate respiration. Accordingly, the bulging phenomenon of the waterproof layer 50 by steam can be prevented.