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

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  1. For a normal-weight aggregate used in structural concrete, which specific gravity range is most typical?

    Answer: 2.4 – 2.9

    Most natural aggregates (granite, limestone, gravel) have specific gravities between 2.4 and 2.9, reflecting the density of common rock-forming minerals.

  2. Which specific gravity value should be used when converting aggregate volume to mass for concrete mix proportioning?

    Answer: Bulk SSD specific gravity

    Bulk SSD specific gravity is used for mix design volume calculations because it reflects the total volume the aggregate occupies, including permeable pores filled with water.

  3. An aggregate sample dries from field-moist to constant mass. The initial mass was 3,200 g and the oven-dry mass is 3,050 g. What is the total moisture content?

    Answer: 4.92%

    Moisture content = (3200 − 3050) / 3050 × 100 = 150 / 3050 × 100 ≈ 4.92% per ASTM C566.

  4. When soaking coarse aggregate for 24 ± 4 hours before specific gravity testing per ASTM C127, the purpose is to:

    Answer: Allow all permeable pores to fill with water

    The 24-hour soak ensures all permeable pores are saturated, establishing the fully water-saturated condition needed to compute absorption accurately.

  5. How does a high absorption value (e.g., >3%) in a coarse aggregate affect concrete durability in freeze-thaw environments?

    Answer: Increases freeze-thaw damage risk due to ice expansion in pores

    High absorption means more water-filled pores that can freeze, expand, and cause internal cracking, degrading freeze-thaw durability.

  6. A technician calculates bulk specific gravity as 2.62 and apparent specific gravity as 2.70 for the same sample. The difference is due to:

    Answer: The volume of permeable pores included in bulk but excluded from apparent

    Bulk Gs includes permeable pore volume in the denominator, making it lower; apparent Gs excludes those pores, using only solid impermeable volume.

  7. Per ASTM C566, to what temperature must aggregate be dried to determine total moisture content?

    Answer: 110 ± 5°C

    ASTM C566 specifies drying aggregate to constant mass at 110 ± 5°C, the standard oven-dry temperature for construction materials.