Appendix B 1 General
The following description refers principally to the preparation of laboratory mixed samples of dense graded asphalt for compaction in a gyratory compactor. Similar procedures also apply to other mix types and to laboratory mixed materials for Marshall compaction, as well as samples taken from asphalt production, with some differences as noted below.
The major difference introduced in conjunction with the design of asphalt mixes using gyratory compaction was the emphasis on controlling oxidation of the binder. Exposure of thin films of binder at high temperature (as occurs during mixing, and storage of mixed material) can lead to comparatively rapid increases in viscosity due to oxidation.
The resilient modulus test is sensitive to binder (viscosity) hardness, whereas Marshall flow and stability are relatively insensitive. The sensitivity of modulus to binder viscosity resulted in the adoption of a conditioning process (Alderson 1994). This standardises the degree of binder oxidation that occurs during asphalt sample preparation.
Manufactured samples taken from asphalt production should be sampled in accordance with AS 2891.1.1.
Procedures for the mixing, quartering and conditioning of samples are described in AS 2891.2.1.