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(4-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 of1.5 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 R3SiO1/2 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,
• (C) a resinous copolymer predominantly comprising R′3SiO1/2 units and SiO2 units, a molar ratio of R′3SiO1/2 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′ does not contain or contains alkenyl in a total amount of less than 0.0001 mol/g, in an amount of 0 to 400 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), (B), and (C) is in a range of 0.32 to 0.75 when component (C) contains alkenyl,
• (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.