ACI Concrete Field Testing Technician - Grade I Practice Exam

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What is the maximum size aggregate for which the slump test is applicable?

1.0 in. [25 mm]
1.5 in. [37.5 mm]
2.0 in. [50 mm]
2.5 in. [62.5 mm]

The correct answer is: 1.5 in. [37.5 mm]

The slump test is a crucial method for determining the consistency and workability of fresh concrete. The maximum size of aggregate that can be used while still allowing for an accurate slump test is typically limited to 1.5 inches (37.5 mm). When aggregate larger than this is used, it can introduce variability and inconsistencies in the measurement, as larger particles may not move freely or may affect the overall flow of the concrete mix. Using aggregate that exceeds this maximum size can lead to unreliable slump measurements, as the presence of larger aggregate can interfere with the integrity of the slump cone during the test. Consequently, the standard practices set forth by ASTM C143 (the standard test method for slump of hydraulic cement concrete) specifically state that the maximum size aggregate should not exceed 1.5 inches. Hence, this makes 1.5 inches the maximum size aggregate for which the slump test is applicable.