A process for assembling pipe segments, comprising the steps of: a) providing a first length of insulated pipe and a second length of insulated pipe, each having at least one bare end which is free of insulation; b) joining a bare end of the first length of insulated pipe to a bare end of the second length of insulated pipe to form a joint which resides in a gap between the insulation of the first and second lengths of insulated pipe and c) introducing a curable polyurethane forming reaction mixture into the gap and curing the reaction mixture to form a cured polyurethane elastomer in the gap between the insulation of the first and second lengths of insulated pipe, said elastomer covering the joint and adhering to the insulation on each side of the gap, wherein the reaction mixture comprises at least one polyether polyol having a hydroxyl equivalent weight of at least 1000, 1 to 20 parts by weight of 1,4-butanediol per 100 parts by weight of the polyether polyol(s), an aromatic polyisocyanate in amount to provide an isocyanate index of 80 to 130 and a zinc carboxylate catalyst, and further wherein the reaction mixture further contains an epoxy resin in an amount up to 20 parts by weight per 100 parts by weight of the polyether polyol(s), the reaction mixture contains no more than 5% by weight based on the weight of epoxy resin, of a catalyst for the reaction of an epoxy group with an isocyanate group to form an oxazolidinone and no more than 5% by weight based on the weight of the epoxy resin, of an amine curing agent or sulfide curing agent, and the cured elastomer contains epoxy groups from the epoxy resin. a) providing a first length of insulated pipe and a second length of insulated pipe, each having at least one bare end which is free of insulation; b) joining a bare end of the first length of insulated pipe to a bare end of the second length of insulated pipe to form a joint which resides in a gap between the insulation of the first and second lengths of insulated pipe and c) introducing a curable polyurethane forming reaction mixture into the gap and curing the reaction mixture to form a cured polyurethane elastomer in the gap between the insulation of the first and second lengths of insulated pipe, said elastomer covering the joint and adhering to the insulation on each side of the gap, wherein the reaction mixture comprises at least one polyether polyol having a hydroxyl equivalent weight of at least 1000, 1 to 20 parts by weight of 1,4-butanediol per 100 parts by weight of the polyether polyol(s), an aromatic polyisocyanate in amount to provide an isocyanate index of 80 to 130 and a zinc carboxylate catalyst, and further wherein the reaction mixture further contains an epoxy resin in an amount up to 20 parts by weight per 100 parts by weight of the polyether polyol(s), the reaction mixture contains no more than 5% by weight based on the weight of epoxy resin, of a catalyst for the reaction of an epoxy group with an isocyanate group to form an oxazolidinone and no more than 5% by weight based on the weight of the epoxy resin, of an amine curing agent or sulfide curing agent, and the cured elastomer contains epoxy groups from the epoxy resin.