ACI Certification Practice Exam

What must be done when concrete contains aggregate larger than permitted for a specific test method?

1. It must be crushed

2. It must be dry sieved

3. It must be wet sieved

4. It can remain unaltered

The correct answer is: It must be wet sieved

When concrete contains aggregate larger than what is allowed for a specific test method, wet sieving is the proper procedure to ensure that the aggregate size complies with the requirements. Wet sieving involves passing the material through a sieve while it is saturated with water, which helps to prevent the finer particles from clogging the sieve openings. This method is particularly effective for separating aggregates of various sizes without losing material due to dust or other fine particles. Wet sieving is crucial for achieving accurate results in tests where aggregate size can significantly impact the concrete’s properties or the test outcomes. This practice ensures that the sample used for testing accurately represents the aggregate size distribution required for the specified method, maintaining the integrity and reliability of the test results. In contrast, simply crushing the aggregate may not yield an accurate representation of the original material's size distribution and can alter its properties. Dry sieving, while a common method for certain tests, may not adequately separate all the particles if finer materials are present, so it is less effective in this context. Leaving the concrete unaltered can lead to discrepancies in test results and does not comply with required testing standards.