ATT Bulk Density, Voids & Organic Impurities 2

Question 1

In the ASTM C29 rodding method for bulk density, how many times is the tamping rod inserted per layer?

Accepted Answer

25 times

Answer

ASTM C29 requires the rod to be inserted 25 times per layer, distributing the strokes evenly over the surface.

Question 2

What concentration of NaOH solution is used in the ASTM C40 organic impurities test?

Accepted Answer

3% by weight

Answer

ASTM C40 specifies a 3% sodium hydroxide (NaOH) solution by weight for detecting organic impurities in fine aggregate.

Question 3

What does a color darker than the reference standard in the ASTM C40 test indicate?

Accepted Answer

The aggregate may contain injurious organic impurities

Answer

A color darker than Organic Plate No. 3 indicates the fine aggregate may contain harmful organic impurities that could adversely affect concrete.

Question 4

How many approximately equal layers are used when filling the measure by the rodding method in ASTM C29?

Accepted Answer

3 layers

Answer

ASTM C29 requires the measure to be filled in three approximately equal layers, each rodded 25 times.

Question 5

How long must the ASTM C40 test sample stand after adding NaOH before comparing colors?

Accepted Answer

24 hours

Answer

ASTM C40 requires the sample and NaOH solution to stand for 24 hours before performing the color comparison.

(ATT) ACI Aggregate Testing Technician Practice Test