ATT Specific Gravity & Absorption 2

Question 1

What does the term 'apparent specific gravity' represent for aggregates?

Accepted Answer

Ratio of aggregate mass to the mass of an equal volume of water, excluding permeable pores

Answer

Apparent specific gravity excludes permeable pore space, using only the impermeable solid volume.

Question 2

In AASHTO T 85, what is the required soaking period for coarse aggregate before testing specific gravity?

Accepted Answer

24 ± 4 hours

Answer

AASHTO T 85 requires coarse aggregate to soak in water for 24 ± 4 hours before testing.

Question 3

When determining fine aggregate specific gravity by ASTM C128, the pycnometer is filled with water to what level after adding the aggregate?

Accepted Answer

The calibration mark on the neck

Answer

The pycnometer is filled to its calibration mark to ensure a known, reproducible water volume.

Question 4

An aggregate has a bulk SSD specific gravity of 2.62 and a bulk oven-dry specific gravity of 2.58. Which statement is correct?

Accepted Answer

The aggregate absorbs water, since SSD > OD specific gravity

Answer

When SSD specific gravity exceeds OD specific gravity, the permeable pores hold absorbed water, which is typical for absorptive aggregates.

Question 5

For fine aggregate, what instrument is typically used to determine when SSD condition is achieved in ASTM C128?

Accepted Answer

Metal cone and tamping rod

Answer

ASTM C128 uses the cone test — the fine aggregate slumps when surface moisture is gone, indicating SSD condition.

(ATT) ACI Aggregate Testing Technician Practice Test