Waterproof sheet and waterproof treatment

A method of waterproof treating an outdoor tank resting on a concrete pedestal, said method comprising

• applying a waterproof sheet comprising a pressure-sensitive adhesive layer across an externally exposed boundary between the tank and the pedestal, with the pressure-sensitive adhesive layer of the waterproof sheet being directly attached to the tank and the pedestal without a primer, and
• applying a silicone sealant along the outer periphery of the pressure-sensitive adhesive layer of the waterproof sheet to form a sealing layer at the outer periphery of the pressure-sensitive adhesive layer,
• wherein the waterproof sheet comprises an elastic silicone rubber base sheet having a thickness of 0.2 to 5 millimeters, said silicone rubber base sheet having a hardness of 10 to 90 on JIS A scale, with
• the pressure-sensitive adhesive layer having a thickness of 0.3 to 3 millimeters disposed on only one surface of said base sheet, the adhesive layer comprising a pressure-sensitive adhesive silicone resin or gel and being formed of a cured product of an addition cure silicone rubber composition comprising
• (A) 20 to 100 parts by weight of an organopolysiloxane containing at least two silicon-bonded alkenyl groups in a molecule, having the average compositional formula (1):
• R1aSiO(1-a)/2 (1)
• wherein each R1 is independently a halogen atom or cyano radical-substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, and a is a positive number of 1.5 to 2.8,
• (B) 0 to 80 parts by weight of a resinous copolymer predominantly comprising R3SiO1/2 units and SiO2 units, a molar ratio of R3SiO/1/2 units to SiO2 units being in a range of 0.5 to 1.5, wherein R is a halogen atom or cyano radical-substituted or unsubstituted monovalent hydrocarbon group, and R contains alkenyl in a total amount of at least 0.0001 mol/g,
• the total amount of components (A) and (B) being 100 parts by weight,
• (D) an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms in a molecule in an amount of 0.5 to 30 parts by weight relative to 100 parts by weight of components (A) and (B) combined, the amount being such that a molar ratio of silicon-bonded hydrogen in component (D) to silicon-bonded alkenyl group in components (A) and (B) is in a range of 0.2 to 1.5, and
• (E) an addition reaction catalyst in an amount which provides 0.5 to 1,000 ppm of platinum group metal based upon the total weight of components (A), (B), and (C), the hardness of the pressure-sensitive adhesive layer being lower than the hardness of the rubber base, and the pressure-sensitive adhesive layer having a bond strength of 0.5 to 10 N/25 mm to glass.