High-flowability and low- strength concrete for backfill

PURPOSE: A high-flowable low-strength concrete composition for ground displacement is provided to obtain high mobility and workability by high air content and to have low strength by low binder content. CONSTITUTION: A high-flowable low-strength concrete composition for ground displacement comprises water, binding material, fine aggregate, thick aggregate and water reducing agent. The unit quantity is 185-205kg/m^3, and the water-binder ratio is 90-105%. The thick aggregate has a maximum size of 25mm and has a fine aggregate percentage of 52.5-57.5%. The binding material is composed of one kind of cement and a blending material. The blending material is one or more which are selected from fly ash and blast furnace slag micro powder. 5-12% of air volume is mixed and the slump is 150mm or greater. The binding material comprises 15-42 wt% of type I cement, 28-40 wt% of ground granulated blast-furnace slag, 20-55 wt% of fly ash. The amount of the water reducing agent is 0.5-0.7 wt% compared to the binding material.