This research project investigated the differences in cohesive energies of model chipseal samples prepared from bitumen emulsions, the base binders, and the kerosene cutback base binder.
The aim was to determine if it was possible to construct chipseals by using a lower residual bitumen application rate whilst still retaining adequate performance.
Analysis of the NZTA RAMM (Road Asset and Maintenance Management) database indicated that chipseals are indeed being prepared using emulsions at lower residual bitumen application rates than cutback binders. But also that emulsion seals have neither yet seen sufficiently long service, nor in sufficient numbers, to determine any differences in lifetimes compared with cutback seals.
Laboratory results from Opus Research, Petone 2014 have indicated that cohesive energies of the bitumen layer in single layer chipseals prepared from cutback binders are lower than those prepared from emulsions of the same base binder, which are lower than those prepared from the base binders themselves.
The suggestion, based on the balance of the data, is that viable chipseals may well be possible at lower bitumen application rates when applied as emulsions (provided the emulsified bitumen was not itself cutback).