Practice Test Geeks(ATT) ACI Aggregate Testing Technician Practice Test
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Bulk Density, Voids & Organic Impurities Flashcards

7 cards from real ATT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What value of water density is used in the ASTM C29 void content calculation?

    Answer: 62.3 lb/ft³ (998 kg/m³)

    ASTM C29 uses 62.3 lb/ft³ (997.5 kg/m³) as the standard density of water for computing void content.

  2. A coarse aggregate has a bulk density of 1680 kg/m³ and a bulk specific gravity of 2.65. What is its approximate void content? (Water density = 1000 kg/m³)

    Answer: 36.6%

    Void content = (2.65 × 1000 − 1680) / (2.65 × 1000) × 100 = 970 / 2650 × 100 ≈ 36.6%.

  3. If an aggregate fails the ASTM C40 color test, what is the recommended next step per the standard?

    Answer: Perform a mortar strength test per ASTM C87

    A failing color result does not automatically disqualify the aggregate; ASTM C87 mortar strength testing can determine whether organic material actually harms concrete performance.

  4. After rodding each layer in the ASTM C29 bulk density test, how should the aggregate surface be prepared before adding the next layer?

    Answer: Leveled by rolling the tamping rod across the surface

    After rodding each layer, ASTM C29 requires leveling the aggregate surface by rolling the tamping rod across it before adding the next layer.

  5. What length is specified for the tamping rod used in ASTM C29 bulk density testing?

    Answer: 600 mm (24 in)

    ASTM C29 specifies the tamping rod to be approximately 600 mm (24 in) in length with a hemispherical working end.

  6. What effect do excessive organic impurities in fine aggregate have on Portland cement concrete?

    Answer: They retard cement hydration and reduce concrete strength

    Organic impurities such as humic acid interfere with cement hydration, retarding set time and reducing the long-term strength of the concrete.

  7. In the ASTM C40 test, to what level is the fine aggregate sample placed in the 12-oz prescription bottle?

    Answer: The 4-1/2-oz level

    ASTM C40 requires fine aggregate to be added to the 4-1/2-oz (approximately 130 mL) level in the 12-oz glass prescription bottle.