ATT Organic Impurities Assessment 3

Question 1

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

Accepted Answer

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

Answer

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.

Question 2

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

Accepted Answer

85%

Answer

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.

Question 3

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

Accepted Answer

Hydrocarbons such as motor oil

Answer

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.

Question 4

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

Accepted Answer

After 24 hours of standing

Answer

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

Question 5

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

Accepted Answer

The aggregate is free of harmful organic impurities

Answer

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

(ATT) ACI Aggregate Testing Technician Practice Test

(ATT) ACI Aggregate Testing Technician Practice Test

ATT Organic Impurities Assessment 3