ACI Concrete Field Testing Technician - Grade I Practice Exam

For wet-sieving a concrete sample larger than the maximum aggregate size, which sieve should be used?

1. 3/4 in. (19 mm) sieve

2. 1 in. (25 mm) sieve

3. 1 1/2 in. (37.5 mm) sieve

4. 2 in. (50 mm) sieve

The correct answer is: 1 1/2 in. (37.5 mm) sieve

The optimal choice for wet-sieving a concrete sample larger than the maximum aggregate size is the 1 1/2 in. (37.5 mm) sieve. The reason this sieve is appropriate is that, when dealing with aggregates, it is crucial to retain as much of the larger particles as possible while allowing finer materials to pass through. In this scenario, wet sieving is employed to separate the fine aggregates from the coarse aggregates while minimizing the potential for clumping or segregating the concrete mixture. Using a sieve that is too small could lead to the retention of larger aggregates that should otherwise pass through or could obscure finer aggregates, affecting the accuracy of the test. The 1 1/2 in. sieve strikes a balance by being large enough to capture the majority of larger particles in the concrete sample while still allowing finer materials to be washed out and separated effectively from the sample, leading to a more accurate assessment of the aggregate's composition in the concrete mix. Selecting a different size such as a smaller sieve would not effectively retain the intended aggregates, whereas a larger sieve would not allow for proper segregation of finer materials, thereby affecting results.