Practice Test Geeks(ATT) ACI Aggregate Testing Technician Practice Test
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Organic Impurities Assessment Flashcards

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  1. What is the purpose of ASTM C87 in relation to organic impurities testing?

    Answer: To compare mortar strength made with suspect aggregate to mortar made with clean aggregate

    ASTM C87 compares the compressive strength of mortar made with the suspect aggregate to mortar made with clean Ottawa sand to assess actual strength impact.

  2. Under ASTM C87, what minimum strength ratio (suspect mortar vs. clean mortar) is typically required for aggregate acceptance?

    Answer: 85%

    ASTM C87 requires the suspect aggregate mortar to achieve at least 95% of the strength of the control mortar made with Ottawa sand for acceptance.

  3. Which of the following organic substances is LEAST likely to be detected by the ASTM C40 colorimetric test?

    Answer: Hydrocarbons such as motor oil

    Hydrocarbons like motor oil do not react with NaOH to produce the characteristic yellow-brown color, making them less detectable by the ASTM C40 method.

  4. When comparing the test solution color to the organic plate in ASTM C40, the comparison is made:

    Answer: After 24 hours of standing

    The color comparison is performed after the mixture has stood undisturbed for 24 hours to allow full extraction of organic compounds.

  5. What does it mean if the supernatant liquid in the ASTM C40 test is colorless?

    Answer: The aggregate is free of harmful organic impurities

    A colorless supernatant indicates no significant organic impurities are present that react with NaOH, so the aggregate is considered acceptable.

  6. In ASTM C40, the reference color standard used for comparison is known as:

    Answer: Organic plate No. 3 (or Gardner color standard No. 11)

    The reference is Organic Plate No. 3, which corresponds to Gardner Standard Color No. 11, used as the maximum acceptable color limit.

  7. Which aggregate type is NOT required to undergo organic impurities testing per ASTM C33?

    Answer: Manufactured sand from crushed limestone

    Manufactured sand produced by crushing stone is generally free of organic matter and is typically exempt from the ASTM C40 organic impurities requirement under ASTM C33.