CCIL Hot Mix Asphalt Field Density Testing 4

Question 1

When performing a nuclear gauge density test on HMA, the gauge must be placed at least how far from any vertical obstruction or edge of pavement?

Accepted Answer

300 mm (12 in)

Answer

Nuclear gauges must be placed at least 300 mm (12 in) from vertical obstructions to avoid backscatter interference that would give false readings.

Question 2

In the context of HMA density acceptance, what does the term 'lot' typically refer to?

Accepted Answer

A defined quantity of pavement used as a statistical unit for acceptance

Answer

A lot is a defined quantity of pavement material (often by area, tonnage, or linear distance) used as the statistical basis for acceptance decisions.

Question 3

Which of the following conditions would most likely cause a nuclear density gauge to read LOWER than the actual density of HMA?

Accepted Answer

Air gap between the gauge and the pavement surface

Answer

An air gap between the gauge and the pavement surface allows gamma rays to scatter in air rather than the material, resulting in a falsely low density reading.

Question 4

When using the core-and-weigh method to determine field density of HMA, which measurement is taken to calculate air void content?

Accepted Answer

The bulk specific gravity of the core and the theoretical maximum specific gravity of the mix

Answer

Air void content is calculated as the percentage difference between theoretical maximum specific gravity (Gmm) and the bulk specific gravity (Gmb) of the compacted core.

Question 5

A technician notices the roller pattern used during HMA compaction did not achieve the required density. What is the FIRST corrective action that should be taken?

Accepted Answer

Increase the number of roller passes on the still-workable mat

Answer

If the mat is still within the workable temperature range, additional roller passes should be applied immediately to achieve the required density before the mix cools.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL Hot Mix Asphalt Field Density Testing 4