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 sample at SSD condition is placed in an oven and dried. The mass decreases from 503.0 g to 496.5 g. What is the absorption?

    Answer: 1.31%

    Absorption = ((503.0 - 496.5) / 496.5) × 100 = (6.5 / 496.5) × 100 ≈ 1.31%.

  2. What does 'effective absorption' mean in the context of aggregate mix design?

    Answer: The amount of water the aggregate will absorb from the mix beyond its current moisture content

    Effective absorption is the additional water an aggregate will absorb from the mix, calculated as total absorption minus current moisture content.

  3. According to ASTM C127, what is the minimum recommended sample mass for coarse aggregate with a nominal maximum size of 25 mm (1 in.)?

    Answer: 2 kg

    ASTM C127 recommends a minimum sample mass of approximately 2 kg for 25 mm nominal maximum size aggregate.

  4. Which specific gravity value is used in the void content calculation for aggregates (ASTM C29)?

    Answer: Bulk OD specific gravity

    ASTM C29 uses bulk OD specific gravity to calculate the void content of aggregates in the rodded or jigged unit weight test.

  5. During towel-drying of coarse aggregate to reach SSD, how can a technician confirm that SSD has been achieved?

    Answer: The aggregate shows a dull, surface-dry appearance with no free moisture film

    SSD for coarse aggregate is indicated when the particles show a dull, matte surface with no visible free water film.

  6. If two aggregate sources have identical absorption values but different bulk OD specific gravities, what is the practical consequence for concrete mix design?

    Answer: The lower specific gravity aggregate will require a larger volume to achieve the same mass, affecting mix proportions

    Lower specific gravity means less mass per unit volume, so more aggregate volume is needed for the same batch mass, changing mix proportions.

  7. What is the effect on calculated bulk specific gravity if entrapped air bubbles are not removed from the pycnometer during fine aggregate testing?

    Answer: Calculated specific gravity will be higher than actual

    Entrapped air reduces the measured mass of water displaced, making the aggregate appear to displace less water and yielding an artificially high specific gravity.