CCIL Asphalt Extraction and Recovery Testing

Question 1

What is the primary objective of the quantitative extraction test on an asphalt paving mixture?

Accepted Answer

To separate and determine the asphalt binder content by mass percentage of the total mix

Answer

Quantitative extraction (AASHTO T 164 / ASTM D2172) separates the asphalt cement from the aggregate using a solvent (such as trichloroethylene or methylene chloride) or an ignition method, and determines the binder content as a percentage of the total mix mass. This result is compared against the job mix formula (JMF) to verify mix compliance.

Question 2

In the centrifuge extraction method (AASHTO T 164 Method A), what role does the solvent play?

Accepted Answer

It dissolves the asphalt binder so it can be separated from the aggregate by centrifugal force

Answer

In the centrifuge method, a chemical solvent (historically trichloroethylene; increasingly replaced with safer alternatives) dissolves the asphalt binder from the mix. The solution is then centrifuged to separate the binder-laden liquid from the aggregate, with repeated washing cycles to ensure complete binder removal. The binder content is determined by mass difference.

Question 3

When using the ignition oven method (AASHTO T 308) to determine asphalt binder content, what correction factor must be applied?

Accepted Answer

A calibration correction factor (CF) specific to the mix being tested, determined from trial burns

Answer

The ignition oven burns off the asphalt binder at high temperature (~538°C), but some aggregate mass loss also occurs during burning. A calibration correction factor (CF) — determined by burning samples of known binder content using the actual aggregates from the project — must be applied to the measured binder content to account for this aggregate mass loss and obtain an accurate result.

Question 4

After solvent extraction, why is it important to recover the extracted asphalt binder (rather than discard the solvent-binder solution)?

Accepted Answer

To perform further tests on the binder properties, such as penetration or viscosity, for compliance verification

Answer

Binder recovery (AASHTO T 319 / ASTM D5404 using a rotary evaporator, or ASTM D1856 Abson method) removes the solvent from the extracted binder solution to yield a concentrated binder sample. This recovered binder can then be tested for penetration, viscosity, or PG properties to verify that the binder used in the field mix meets specifications — a critical quality control check.

Question 5

During aggregate washing after centrifuge extraction, what is the purpose of multiple solvent wash cycles?

Accepted Answer

To ensure complete removal of residual binder from aggregate surfaces, improving accuracy of the binder content result

Answer

Multiple wash cycles are performed because a single centrifuge cycle does not remove all binder from aggregate surfaces, particularly from porous or angular aggregates. Each successive wash with fresh solvent dissolves more residual binder. Incomplete washing leads to underestimation of the actual binder content, as some binder remains on the aggregate and is weighed as aggregate mass.

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL - Canadian Council of Independent Laboratories Practice Test

CCIL Asphalt Extraction and Recovery Testing