PURPOSE: To obtain the concrete or mortar-protective material by incorporating an unsaturated polyester resin and/or vinyl ester resin with each specified amount of molecular sieves and cement.

CONSTITUTION: This concrete or mortar-protective material is obtained by incorporating (A) 100 pts.wt. of an unsaturated polyester resin (e.g polyethylene terephthalate) and/or vinyl ester resin (e.g. an unsaturated polyester with the terminal modified with vinyl group) with (B) 1-50 pts.wt. of molecular sieves (e.g. manufactured by Union Showa Ltd.: molecular sieves 4A) and (C) 5-300 pts.wt. of cement (e.g. Portland cement) and, if necessary, furthermore, (D) 2-300 pts.wt. of aggregate and/or filler (e.g. crushed stone). Incorporation of the water-adsorbing component B can obtain this mortar-protecting material excellent in storage stability.