Practice Test Geeks(ATT) ACI Aggregate Testing Technician Practice Test
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Specific Gravity & Absorption Flashcards

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Read the first 7 Specific Gravity & Absorption flashcards as text

  1. A coarse aggregate sample has an OD mass of 4,856 g, SSD mass of 4,921 g, and submerged mass of 3,057 g. What is the absorption (%)?

    Answer: 1.34%

    Absorption = ((4921 - 4856) / 4856) × 100 = (65 / 4856) × 100 ≈ 1.34%.

  2. What is the primary reason that aggregates with high absorption values can be problematic in concrete?

    Answer: They may absorb mixing water, effectively lowering the water-cement ratio

    High-absorption aggregates can draw water from the paste, reducing effective w/c ratio and potentially causing workability loss.

  3. In the wire basket method for coarse aggregate (ASTM C127), what is the purpose of the wire basket?

    Answer: To hold the aggregate submerged while its mass is determined in water

    The wire basket is suspended in water on a balance to obtain the submerged (buoyant) mass of the aggregate.

  4. If apparent specific gravity is 2.71 and bulk OD specific gravity is 2.61 for the same aggregate, what can be inferred?

    Answer: The permeable pore volume is significant

    A larger difference between apparent and bulk OD specific gravity indicates a greater permeable pore volume within the particles.

  5. Which aggregate characteristic directly affects the calculation of batch weights in mix design using specific gravity?

    Answer: Volume of aggregate per unit mass (reciprocal of specific gravity)

    Mix design uses specific gravity to convert between aggregate mass and volume, so it directly affects batch weight calculations.

  6. What action is taken if air bubbles are observed in the pycnometer during the fine aggregate specific gravity test?

    Answer: Agitate or roll the pycnometer to dislodge the air bubbles

    ASTM C128 requires agitating or rolling the pycnometer to remove entrapped air, which would otherwise cause low mass readings.

  7. Why is the pycnometer method preferred over the wire basket method for fine aggregates?

    Answer: Fine particles would fall through the openings of a wire basket

    Fine aggregate particles are too small to be retained in a wire basket, so a volumetric pycnometer is used instead.