ACI Concrete Field Testing Technician - Grade I Practice Exam

The correct choice regarding the maximum particle size of aggregate that can be used in a 6 by 12 inch (150 mm by 300 mm) cylinder mold is based on the principle that the largest aggregate particle should not exceed one-third of the diameter of the cylinder.

In this case, the diameter of the cylinder mold is 6 inches (or 150 mm), and one-third of this dimension is 2 inches (50 mm). This means that aggregates must be smaller than or equal to this size to ensure proper concrete compaction and consistent testing results. Larger aggregate sizes could hinder proper filling of the mold, result in voids, or affect the structural properties of the concrete.

Therefore, using aggregates larger than 2 inches could compromise the integrity of the testing process and the accuracy of the strength results derived from the cylinders. The other options suggest particle sizes greater than this threshold, which would not comply with the best practices outlined in concrete testing procedures.