To provide a quick-drying water-based resin composition for constructing a thick film, from which a thick film can be constructed on a treating surface of a concrete structure or the like, which can be dried within 12 hours after being applied, and whose applied coating film has excellent durability, for example, water resistance, acid resistance and alkali resistance, and to provide a surface treatment method using the same.

The invention relates to a water-based resin composition for constructing a thick film containing a water-based synthetic resin emulsion (A) and an organic filler (B) and having a nonvolatile content of 65 to 80 mass%. A solid content ratio of the emulsion to the filler is 7/3 to 3/7. An average particle size of the organic filler is 0.5 mm or less.