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Strength Testing Technician Flashcards

7 cards from real ACI Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. When consolidating a 6×12 inch concrete cylinder by rodding per ASTM C31, how many equal layers are required?

    Answer: Three layers

    ASTM C31 requires three equal layers when making 6×12 inch cylindrical specimens consolidated by rodding.

  2. What are the diameter and minimum length specified for the tamping rod used to consolidate standard concrete cylinder specimens per ASTM C31?

    Answer: 5/8-inch diameter, 24 inches long

    ASTM C31 specifies a tamping rod that is 5/8 inch (16 mm) in diameter and at least 24 inches (600 mm) long with a hemispherical tip.

  3. When using an internal vibrator to consolidate concrete cylinder specimens per ASTM C31, the vibrator diameter must not exceed what fraction of the mold diameter?

    Answer: One-fourth

    Per ASTM C31, the vibrator diameter shall not exceed one-fourth (1/4) of the diameter of the mold being filled.

  4. Per ASTM C31, what temperature range must be maintained during initial curing of concrete cylinder specimens in the field?

    Answer: 60–80°F (16–27°C)

    ASTM C31 requires specimens to be maintained between 60°F and 80°F (16°C and 27°C) during the initial curing period.

  5. After the top surface of a freshly cast cylinder is struck off, it must be finished so that it departs from a true plane by no more than:

    Answer: 1/16 inch (1.6 mm)

    The struck-off top surface must be finished level within 1/16 inch (1.6 mm) of a true plane per ASTM C31.

  6. Per ASTM C31, freshly cast concrete specimens must be protected from vibration, shock, and disturbance for a minimum of how long after molding?

    Answer: 24 hours

    Specimens must not be disturbed or transported for the first 24 hours after molding to prevent damage to the fresh concrete microstructure.

  7. When making concrete beam specimens for flexural strength testing per ASTM C31, which consolidation method is permitted when the measured slump is 3 inches (75 mm) or greater?

    Answer: Either rodding or internal vibration

    Per ASTM C31, when slump is 3 inches or more, consolidation may be achieved by either rodding or internal vibration.