Published: April 2016 | Audience: General
Aspects of bitumen performance in chipseals related to the development of a New Zealand performance-based specification for chipseal binders were investigated.
Compatibility with kerosene: Differences due to the base (unmodified) viscosity were far greater than those produced by small differences in kerosene compatibility showing that this requirement is probably unnecessary in the new specification.
Adhesion to aggregate: Acid number and a ‘wetting test’ based on the MSCR test (AASHTO T 350-14) at 25⁰C were suggested for inclusion in the new specification. Such tests provide protection against likely poorly performing bitumens and help ensure batch to batch consistency. The tests would be carried out in conjunction with Vialit plate tests.
Chip retention: Bitumen cohesive energy as a control property for chip retention was investigated. The measured cohesive energy is strongly affected by the viscoelastic properties of the binder. A tensile test at low temperatures is a better alternative with a minimum yield (rupture), stress and strain specified.
At high temperatures tensile tests are impractical and damage through large non-recoverable deformations of the binder below the yield strain must also be controlled for. Instead the MSCR test with a maximum creep compliance and a minimum percent recovery would be used.