PURPOSE:To control contstantly the setting time of grout by a method wherein liquid A is prepared by adding water to Portland cement, liquid B is prepared by adding water and specified setting-retardant to a mixt. of calcium aluminate mineral and gypsum, the liquid A is mixed with the liquid B, and the mixt. is injected into the ground. CONSTITUTION:Liquid A is prepared by adding water to Portland cement. Liquid B is prepared by suspending a mixt. of calcium aluminate mineral and gypsum into an aq. soln. of a setting-retardant consisting of at least one alkaline material selected from (a) bicarbonates, such as sodium bicarbonate or potassium bicarbonate, and (b) sodium carbonate, potassium carbonate, disodium phosphate, or trisodium phosphate. The liquid A and the liquid B are fed separately to each grout pump. While the liquid A is mixed with the liquid B within a Y-type pipe connected to each discharge port of each pump, the mixt. is injected into the ground.
