Study on the Influence of a New Liquid Accelerator on Shotcrete Performance

Shotcrete is an essential preliminary support means in New Austrian Tunneling Method (NATM) construction and plays a very important role in controlling the stability of surrounding rock. The accelerator is a necessary admixture in shotcrete and its quality can greatly affect shotcrete performance. This paper proposes a new liquid accelerator characterized by short initial and final setting time, small dosage, and good adaptability to cement. Laboratory tests and field tests are conducted to verify the influence of this liquid accelerator on shotcrete performance. Numerical simulation is carried out to study the strength growth of shotcrete with the passage of time and interaction between the strength and stress release of surrounding rock. The results show that the initial and final setting time of this liquid accelerator is with 2 minutes and 4 minutes respectively. Its dosage is only 1.5% to 4% of the cement quantity. Adding this liquid accelerator can effectively improve the early strength and reduce the later strength loss of shotcrete, achieving better supporting effects for surrounding rock. During spraying concrete in actual engineering, it is an ideal liquid accelerator for shotcrete, characterized by little resilience, no slurry shedding, and low dust.