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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.

Read the first 7 Strength Testing Technician flashcards as text

  1. What is the specified rate of load application when testing concrete cylinders for compressive strength per ASTM C39?

    Answer: 35 ± 7 psi/s (0.25 ± 0.05 MPa/s)

    ASTM C39 specifies a constant loading rate of 35 ± 7 psi/s (0.25 ± 0.05 MPa/s) applied continuously and without shock throughout the test.

  2. Per ASTM C39, the bearing surfaces of cylinders must not depart from a plane by more than:

    Answer: 0.002 inch (0.050 mm)

    ASTM C39 requires bearing surfaces to be plane within 0.002 inch (0.050 mm), which is why capping or end grinding is typically required.

  3. Per ASTM C39, the diameter of a test cylinder used to calculate compressive strength must be the average of two measurements taken at:

    Answer: Right angles to each other at or near mid-height

    ASTM C39 requires diameter to be determined from two measurements at right angles to each other taken at or near mid-height of the specimen.

  4. According to ASTM C39, what age tolerance is permitted when testing concrete cylinders specified for a 28-day strength result?

    Answer: ± 20 hours

    ASTM C39 allows 28-day specimens to be tested within ± 20 hours of the specified test age.

  5. A cylinder measures 5.90 inches long and 3.00 inches in diameter, giving an L/D ratio of approximately 1.97. Which statement best describes how to handle this specimen per ASTM C39?

    Answer: Test and report the result with no correction since L/D is between 1.75 and 2.10

    ASTM C39 correction factors apply only when L/D is below 1.75; an L/D of 1.97 falls within the acceptable range and needs no correction.

  6. Which fracture pattern described in ASTM C39 is characterized by a well-formed cone on one end with no significant cracking through the capping material?

    Answer: Type 1 cone fracture

    A Type 1 fracture in ASTM C39 shows a well-formed cone on one or both ends with no cracks running through the caps, indicating good end conditions.

  7. When a test result is the average of two companion cylinders and one shows damage due to an improper cap (not a concrete deficiency), what should be done per ASTM C39?

    Answer: Discard the defective cylinder and report the companion result alone

    If a cylinder fails due to an obvious fabrication or capping defect, its result is discarded and the strength is reported from the valid companion cylinder.