ACI Certification Practice Exam

What must a field technician measure when creating a test cylinder from concrete used in construction?

1. The temperature of the concrete

2. The slump of the concrete

3. The weight of the aggregate

4. The color of the concrete

The correct answer is: The slump of the concrete

When creating a test cylinder from concrete used in construction, the slump of the concrete is a critical measurement. The slump test is performed to assess the consistency, workability, and overall quality of the fresh concrete mix. This involves forming a cone-shaped mold filled with the concrete sample, then removing the mold to observe how much the concrete settles or "slumps." A proper slump is essential because it provides insight into the water-cement ratio and the mixing process effectiveness, as well as indicating how easy or difficult the concrete will be to place. A mixture with too low a slump can lead to difficulties in compaction and finishing, while too high a slump can indicate excessive water, which could compromise the strength and durability of the cured concrete. While factors like the temperature of the concrete and the weight of the aggregate can influence the performance of the final product, they are not direct measures taken during the cylinder preparation. The color of the concrete plays little to no role in determining the mix's characteristics or performance in structural applications. Therefore, the focus on measuring the slump during the creation of test cylinders is paramount for quality assurance in concrete construction.