Effects of Particle-Size Distribution in Dry Process Shotcrete

Dry-mix shotcrete has been successfully used for many years in construction and repair. Its unique pneumatic application yields an in-place material with low workability and relatively high stiffness well adapted to vertical and overhead applications without formwork. For some time, reduction of rebound--particles not adhering to the surface during shooting--has received attention due to its important effects on costs and in-place properties. The aim of this project is to study the effects of the particle-size distribution of the granular phase in dry-mix shotcrete. The results presented confirm the validity of what is known as ACI Gradation No. 2 for shotcrete recommended by ACI Committee 506, Shotcreting. Moreover, a fundamental approach involving optimal packing density offers a simple and interesting explanation of the observed behavior and a basis for future work.