PURPOSE: To improve the adhesive strength of a thermosetting-resin protective film to a cement-based base material by forming an intermediate film of the composition contg. specified urethanic unsaturated prepolymer and a dicyclopentadiene derivative on the base material.

CONSTITUTION: A polyisocyanate compd. (e.g. diphenylmethane diisocyanate) is allowed to react with an ethylenic unsaturated monomer (e.g. 2-hydroxyethyl methacrylate) having a hydroxyl group to produce an unsaturated prepolymer. The prepolymer is then mixed with a dicyclopentadiene derivative shown by the formula (R1 is a 2-12C alkylene glycol residue or 4-12C oxaalkylene glycol residue, and R2 is H or methyl). The obtained composition is applied on a cement-based base material and cured, then a thermosetting resin composition (e.g. unsaturated polyester resin composition) is applied and/or laminated on the cured material along with a reinforcing material and cured, hence the base material is protected, and excellent durability, etc., are imparted.