PURPOSE: To provide the titled grout usable in a wide range of gel time from flash setting to slow setting, excellent in workability, by incorporating a water- soluble ferrous salt as a major hardener.

CONSTITUTION: A grout which comprises as a main material sodium silicate (e.g., water glass No.3 with a concn. of 25vol%) as a principal ingredient and water-soluble ferrous salt (e.g., FeSO4) as a main hardener. Said grout is easy to adjust flash and slow setting, and particularly well suited for composite grouting. Example: 25l of water glass and 25l of water are mixed to form 50l of liq. A, and, separately, FeSO4 as a major hardener and NaHSO4 as a stabilizer are used to make 50l of liq. B. When aiming at a gel time of 6sec, 2.5kg of FeSO4 and 3.7kg of NaHSO4 are mixed as liq. B, and when aiming at 2min, 2.0kg of FeSO4 and 2.9kg of NaHSO4 are mixed.