EXTERNAL DAMAGE SELF-REPAIR WATER-BARRIER SHEET

PURPOSE:To rapidly accomplish a self-repair in an occurrence of a defective part, such as a hole, caused by some factor or other in a water-barrier sheet by laminating a water-absorbent, water-swelling sheet on a polymeric roofing. CONSTITUTION:A water-barrier sheet consists of a polymeric roofing 1 and a water-swelling sheet 2 made of a hydrophilic polymer having hydrophilic group in a side chain of the polymer and laminated on one surface of the roofing 1. The water-barrier sheet is formed by laminating the sheet 2 having a water absorptivity 50-1000 times larger than its own weight on the roofing 1. In this manner, even in an occurrence of a defective part, such as a hole, in the polymeric roofing layer, the layer of the water-swelling sheet 2 swells with a water content in waste liquid leaking from a waste, ground water, and rainwater to close the defective part, such as a hole. As a result, a self-repair can be accomplished. The water absorptivity of the sheet 2 is determined to be 50-1000 times larger than its own weight by reason that a rapid self-repair cannot be accomplished by a sheet of a water absorptivity as low as less than 50 times and a mechanical strength is sharply lowered after water absorption in a sheet 2 of a water absorptivity more than 1000 times.