ACI Concrete Strength Testing Technician Practice Test

Which of the following must be checked after the load is applied but before reaching the specimen strength?

1. The pad thickness

2. The overall diameter of the cylinder

3. The axis of the cylinder's vertical alignment

4. The retention ring's integrity

The correct answer is: The axis of the cylinder's vertical alignment

The axis of the cylinder's vertical alignment must be checked after the load is applied but before reaching the specimen strength because maintaining proper vertical alignment is crucial for ensuring that the load is evenly distributed across the specimen. Misalignment can lead to eccentric loading, which may artificially influence the strength results and potentially lead to a failure that does not accurately reflect the strength of the concrete. Aligning the specimen ensures that the forces acting on it are as intended, allowing for reliable and valid test results. Other choices refer to important aspects of the testing procedure but do not specifically address the critical nature of vertical alignment at the moment after the load is applied. For instance, pad thickness is important for reducing stress concentrations but is typically verified before loading. The overall diameter of the cylinder is necessary for calculating concrete strength but is also confirmed prior to testing. The retention ring's integrity is associated with ensuring that the specimen doesn’t shift during the test, but again, it is checked as part of preparation. The aspect of vertical alignment directly affects the immediate application of load and the reliability of the strength data obtained during the test process.