Lab Testing Procedures Flashcards

The Modified Proctor compaction test (AASHTO T 180) differs from the Standard Proctor primarily in its:

Answer: Number of soil layers and hammer energy

AASHTO T 180 uses 5 layers and a 10-lb hammer dropped 18 inches, resulting in about 4.5 times the compaction energy of the Standard Proctor.

When testing aggregate for flat and elongated particles per ASTM D 4791, a particle is considered elongated if its longest dimension exceeds its shortest dimension by a ratio of:

Answer: 3:1

ASTM D 4791 defines elongated particles as those with a length-to-thickness ratio exceeding 3:1 at the specified ratio being tested.

Which equipment is used to measure the air content of freshly mixed concrete by the pressure method per AASHTO T 152?

Answer: Air entrainment meter (Type B pressure meter)

The Type B pressure meter (air meter) applies a known pressure to the concrete sample and measures the volume change to calculate air content.

A soil sample has a wet mass of 450 g and a dry mass of 380 g. What is the moisture content?

Answer: 18.4%

Moisture content = (wet mass − dry mass) / dry mass × 100 = (450 − 380) / 380 × 100 = 18.4%.

During a Marshall stability test on compacted asphalt specimens, the loading rate specified by AASHTO T 245 is:

Answer: 2 in/min

AASHTO T 245 requires a constant deformation rate of 2 inches per minute (50 mm/min) when determining Marshall stability and flow.

The plasticity index (PI) of a soil is calculated as:

Answer: Liquid limit minus plastic limit

PI = LL − PL; it represents the range of moisture content over which a soil behaves plastically.

When performing the Los Angeles Abrasion test (AASHTO T 96) on coarse aggregate, the abrasive charge used is:

Answer: Steel balls

The Los Angeles machine uses a specified number of steel balls as the abrasive charge that impact and grind the aggregate during rotation.