ACI Certification Practice Exam

When preparing for density tests in concrete, what should be done with the sample containing large aggregate?

1. Wet-sieve the sample

2. Dry-sieve the sample

3. Crush the sample completely

4. Ignore the size of the aggregate

The correct answer is: Wet-sieve the sample

When preparing a sample for density tests in concrete that contains large aggregate, wet-sieving the sample is the most appropriate method. This technique involves using water to help separate the fine particles from the larger aggregates. Wet sieving is effective because it reduces the chances of segregation and loss of fine material during the sieving process, ensuring that the sample remains representative of the original concrete mix. This method also minimizes the risk of damaging the larger aggregates, which could occur if dry sieving were used, as the agitation from dry sieving can lead to breakage or dislodgment of particles. Therefore, wet sieving allows for more consistent and accurate measurement of the density of the concrete, accommodating the presence of large aggregate without compromising the integrity of the sample.