Massachusetts Unrestricted Construction Supervisor License Practice Test

What is the maximum size aggregate that can be used in shotcrete?

1. 1/2 inch

2. 3/4 inch

3. 1 inch

4. 1 1/2 inch

The correct answer is: 3/4 inch

The maximum size aggregate that can be used in shotcrete is determined by the requirements for achieving proper bonding and workability during application. Aggregate size is a critical factor in shotcrete because larger aggregates can affect the flow and adherence of the mixture when it is projected onto surfaces. Using a maximum size of 3/4 inch for the aggregate allows for a good balance between structural integrity and ease of application. This size supports the necessary workability, ensuring that the shotcrete can be effectively sprayed onto vertical or overhead surfaces without segregation or excessive rebound, which can occur with larger aggregates. In contrast, larger aggregate sizes, such as 1 inch or 1 1/2 inch, may compromise the quality of the application by making the mixture difficult to spray, leading to inconsistency and issues with the final finish. Therefore, the choice of 3/4 inch aggregate aligns with industry standards for shotcrete applications, ultimately enhancing the performance and durability of the structure being created.