GROUT INJECTION METHOD

PROBLEM TO BE SOLVED: To provide a grout injection method whereby a grout in a nonflowable plastic state is injected by transporting a flowable viscous liquid mainly comprising cement and a montmorillonite clay mineral and a soluble aluminum salt soln. under pressure individually with separate pumps and mixing the liquid and the soln. near at an injection port. SOLUTION: Cement is added to a suspension of a montmorillonite clay mineral (typically, bentonite) to give a flowable viscous liquid. An acidic aluminum salt (e.g. aluminum sulfate) soln. is used as the soluble aluminum salt soln. By this method a small amt. of an aluminum salt can modify a grout to a plastic state without mixing a large amt. of air even when an ordinary amt. of cement is used; bleeding, material separation, and dilution and outflow by water are prevented; unnecessary running away to a remote place is prevented; and, thus, aimed hollows can be filled without fail and limited injection is enabled.