Part 4 of this standard specifies the test method for the adhesion of water-cracking repair materials to wet concrete surfaces in underground concrete structures. During the repair of underground structures, wet concrete surfaces are often a critical environment for the bonding of repair materials to substrates. The standard describes in detail the test procedures and equipment requirements. By evaluating the adhesion of repair materials to wet concrete surfaces, it is possible to ensure that they can effectively seal cracking and prevent water leakage in actual use.