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

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  1. In the ASTM C29 bulk density test, what quantity is subtracted from the combined mass of container plus aggregate to determine the mass of aggregate alone?

    Answer: The mass of the empty measure

    Bulk density = (mass of container + aggregate − mass of empty container) ÷ volume of container.

  2. Higher void content in a coarse aggregate sample most likely indicates that the particles are:

    Answer: Angular, irregular, or poorly graded

    Angular and irregular particles pack less efficiently, leaving more void space between particles and resulting in higher void content.

  3. What must be accurately known before bulk density can be calculated from an ASTM C29 test?

    Answer: The calibrated volume of the measure

    Bulk density is calculated as mass divided by volume, so the calibrated volume of the measure must be accurately determined.

  4. To what level is the NaOH solution added in the ASTM C40 prescription bottle after placing the aggregate?

    Answer: The 7-oz level

    After placing aggregate to the 4-1/2-oz mark, the 3% NaOH solution is added until the total liquid level reaches the 7-oz (approximately 200 mL) mark.

  5. What is the primary practical use of bulk density (unit weight) data obtained from ASTM C29?

    Answer: To convert between volume and mass for concrete mix design batching

    Bulk density is used primarily in mix designs to convert volume measurements to mass (weight) for batching aggregate quantities in concrete production.

  6. Which scenario would most likely produce the HIGHEST bulk density value in an ASTM C29 test?

    Answer: Well-graded aggregate tested by the rodding method

    Well-graded aggregate allows small particles to fill voids between larger ones, and rodding further reduces air voids, together producing the highest bulk density.

  7. In the ASTM C40 organic impurities test, the bottle is stoppered and shaken after adding NaOH. What is the correct action immediately after shaking?

    Answer: Allow the sample to stand undisturbed for 24 hours before color comparison

    After shaking, the bottle is allowed to stand undisturbed for 24 hours so organic compounds fully leach into the NaOH solution before the color comparison is made.