Pavement

This study obtained an indication of the proportion of Australian commercially manufactured polymer modified binders (PMBs) liable to segregate, identifed suitable tests to measure segregation propensity and proposes measures to help prevent or minimise changes in PMB properties during transport and storage. Twelve commercial styrene butadiene styrene (SBS) binders and one polybutadiene (PBD) binder were obtained. The Softening Point of the samples was determined before and after the European storage stability test, which involves oven storage of the PMB at 180 °C for three days. Two of the SBS binders segregated during sample splitting procedures and two segregated during testing. Comparison of the Softening Point of samples before and after storage identified three SBS samples which degraded. Rheological testing indicated that degradation had resulted in a loss in elastic behaviour. It was concluded that segregation and degradation in SBS PMBs were important issues.

To identify problem batches of PMBs it is suggested that consideration be given to investigating the relationship between the results of the European storage stability and the Austroads segregation test. The inclusion of the ease of remixing test, which currently allows failed PMBs to be accepted if they can be remixed in the laboratory, should be reviewed in light of current practices. The specification requirements could be written in such a way that problem batches are rapidly detected and action taken to ensure that subsequent batches are acceptable.