Gypsum composition for dry-curing coating material, gypsum-based coating material, and construction method for gypsum-based coating material

A gypsum-based coating material comprising:

• hemihydrate gypsum having a mean particle diameter in a range of 50 μm or less;
• calcium carbonate having a mean particle diameter in a range of 50 μm or less;
• a setting retarder;
• and
• water,
• wherein the gypsum-based coating material forms a coating film through drying the coating material,
• the gypsum-based coating material has a content of the calcium carbonate in a range from 10 to 400 parts by mass and a content of the setting retarder in a range of 0.1 parts by mass or more each relative to 100 parts by mass of the hemihydrate gypsum,
• the hemihydrate gypsum comprises at least one material selected from the group consisting of α-hemihydrate gypsum, β-hemihydrate gypsum, and III-anhydrous gypsum, and
• initial setting time of a hydration reaction that occurs when water is added to a combination of the hemihydrate gypsum, the calcium carbonate, and the setting retarder so as to form the gypsum-based coating material is in a range of 24 hours or longer,
• wherein the initial setting time of the hydration reaction is measured according to JIS A 6904, except that normal consistency in the JIS A 6904 is set at a penetration depth of 20±2 mm, and
• the initial setting time of the hydration reaction corresponds to an initial setting in the JIS A 6904.