PURPOSE: To obtain the title composition which prevents the occurrence of holes of concrete structure for man-made gathering-place of fish, wave suppression, check of erosion of rivers and the ocean and preserves alkali from elution, containing an emulsion resin, iron (compound), etc.

CONSTITUTION: The objective composition comprising (A) an emulsion resin composed of an acrylic/styrene copolymer, a vinyl acetate/Veova(R) copolymer, urethane (one pack type) or epoxy (one pack type) having ≤15°C lowest film- forming temperature and ≤20% saponification degree, (B) iron and/or an iron compound such as iron sulfate, iron sulfide, iron oxide, iron nitrate, iron hydroxide, iron carbide, iron carbonate or iron nitride and, in the case of the iron compound showing acidity, (C) a hydrating agent such as calcium hydroxide or cement powder caustic soda.