ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the minimum thickness for a glass or acrylic strike-off plate in the slump test?

1. 1/4 in. [6 mm]

2. 1/2 in. [12 mm]

3. 3/4 in. [19 mm]

4. 1 in. [25 mm]

The correct answer is: 1/2 in. [12 mm]

The minimum thickness for a glass or acrylic strike-off plate in the slump test is specified as 1/2 inch (12 mm) to ensure durability and stability during the testing process. A thicker plate is necessary to prevent warping or bending, which could lead to inaccurate measurement of the concrete’s slump. This thickness also provides a flat surface to effectively level off the concrete mixture, allowing for consistent test results. The 1/2 inch specification strikes a balance between being sturdy enough to handle the weight of the concrete without deforming while being manageable in terms of weight for field testing. When evaluating the other thickness options, while thicker plates may offer additional stability, they exceed the minimum requirement, which does not provide advantages for the specific purpose of conducting the slump test. Hence, the 1/2 inch thickness remains the standard in maintaining test accuracy and practical usability in the field.