Fine Aggregates: In some shotcrete applications, especially those requiring a smoother finish or where the shotcrete needs to pass through smaller nozzle openings, fine aggregates such as sand or fine crushed stone are used. The maximum aggregate size in such cases may be around 3/8 inch (9.5 mm) or smaller.
Coarser Aggregates: For structural shotcrete applications that require higher strength and durability, coarser aggregates can be used. The maximum aggregate size for these mix designs may range from 3/8 inch (9.5 mm) to 3/4 inch (19 mm) or even larger.
Reinforcement Considerations: When shotcrete is used in structural applications and includes steel fibers or mesh reinforcement, the maximum aggregate size is often selected based on the compatibility with the reinforcement. Larger aggregates may be used to ensure that the shotcrete adequately encapsulates and surrounds the reinforcement.
Application Method: The choice of wet-mix or dry-mix shotcrete can also influence the maximum aggregate size. Dry-mix shotcrete (gunite) may accommodate larger aggregates more easily, while wet-mix shotcrete can work well with a range of aggregate sizes.
Project Specifications: The maximum aggregate size for shotcrete should align with the project specifications and engineering requirements. Engineers and concrete specialists design the shotcrete mix to meet the specific needs of each project.
It's important to note that shotcrete mix designs are highly customizable to meet the desired performance characteristics, including strength, durability, and workability. The selection of aggregate sizes, as well as other components of the mix, is part of the mix design process and should be determined based on the project's objectives and the recommendations of qualified professionals.
