ACID-RESISTANT PROTECTING MEMBER FOR CONCRETE

摘要

PROBLEM TO BE SOLVED: To suppress a reaction of a cement component of a molded product made of a concrete with a soil component and improve the durability of the molded product by mixing a hemihydrate gypsum with an alkaline silica sol and phosphoric acid or its salt and hardening the resultant mixture. SOLUTION: Both of theα- and theβ-types can be used as a hemihydrate gypsum and a commercially available alkaline silica sol can intactly be used. The ratio of the silica sol to the hemihydrate gypsum used is preferably 0.03-0.3 expressed in terms of weight ratio of the silica solid content/hemihydrate gypsum. Phosphoric acid or its salt is added in order to prevent a gelation phenomenon caused by mixing the hemihydrate gypsum with the silica sol and phosphoric acid, etc., or its salts are specifically cited. The amount of the added phosphoric acid or its salt is preferably 0.01-0.3 wt.% based on the total amount of the hemihydrate gypsum and the alkaline silica sol. A water-reducing admixture is preferably further compounded when producing a protecting member. A surfactant such as a ligninsulfonic salt is cited as the water-reducing admixture.