Practice Test Geeks(ATT) ACI Aggregate Testing Technician Practice Test
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Unit Weight & Voids Testing Flashcards

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Read the first 7 Unit Weight & Voids Testing flashcards as text

  1. For the unit weight test, ASTM C29 requires that the tamping rod be a round, straight steel rod of what diameter?

    Answer: 5/8 inch (16 mm)

    ASTM C29 specifies a tamping rod with a diameter of 5/8 inch (16 mm) and hemispherical tip for rodding.

  2. A unit weight test produces a bulk unit weight of 98 lb/ft³ for a crushed stone with bulk specific gravity (OD) of 2.68. What is the approximate void content?

    Answer: 41%

    Voids = [1 − (98 / (2.68 × 62.4))] × 100 = [1 − 0.586] × 100 ≈ 41%, indicating significant interparticle void space.

  3. Why is the jigging compaction method preferred over rodding for aggregate that is too coarse to be effectively rodded?

    Answer: Jigging delivers compaction energy through the walls of the measure rather than through individual particle contacts

    Jigging transmits compaction energy through the measure walls, which is more effective for large particles that a rod cannot adequately penetrate.

  4. Which of the following best describes 'loose unit weight' as opposed to 'rodded unit weight'?

    Answer: Unit weight of aggregate filled into the measure without compaction

    Loose unit weight is determined by filling the measure using the shoveling procedure without any rodding or jigging compaction.

  5. What effect does increasing the nominal maximum aggregate size have on the required measure volume for ASTM C29 testing?

    Answer: Larger NMAS requires a larger measure

    ASTM C29 requires increasingly larger measures as aggregate nominal maximum size increases to ensure a statistically representative sample.

  6. After determining the unit weight of aggregate, the technician wants to report void content but only has the bulk specific gravity on an SSD basis. What adjustment is needed?

    Answer: Convert SSD bulk specific gravity to OD bulk specific gravity by accounting for absorption

    ASTM C29 uses bulk dry (OD) specific gravity in the voids formula; the SSD value must be converted using the absorption to obtain the OD value.

  7. Under ASTM C29, how is the unit weight measure recalibrated when the results from two successive calibration trials differ by more than 0.1%?

    Answer: Discard both results and run at least two additional trials until consistency is achieved

    If successive calibration trials differ by more than 0.1%, additional determinations are made until two consecutive results agree within 0.1%, and those two are averaged.