Aternatives to automotive gas oil (AGO) used to flux (soften) bitumen used in chipsealing have been investigated.
AGO is known to rapidly evaporate from the seal, which is both uneconomic and environmentally unsound.
Non-volatile, tall oil pitch (TOP), waste motor oil distillation bottoms (WODB), and a commercial rejuvenating oil (RO) were investigated as alternatives. TOP, WODB and RO were effective as fluxes. Approximately 10 times the concentration of WODB and TOP and three times the concentration of RO were needed to give the fluxing effect of a given AGO concentration. All the alternatives showed no weight loss after storage as 3.0 mm films at 43 degrees C.
The rate of hardening, as measured by the rate of viscosity at 25 degrees C before and after the test, was compared to that of a control 180/200 bitumen. The AGO fluxed binder hardened faster than the control, whereas the alternative fluxes showed a slower rate. The order of hardening was AGO > 180/200 ~ TOP > RO > WODB. The AGO fluxed binder had reached the same viscosity as the control after 3.3 years, ie there was no softening effect apparent. The other fluxed binders had viscosities considerably lower than that of the control.
These findings were confirmed by moduli measurements over the temperature range 5–50 degrees C. Apart from requiring heated tanks, no major alterations are foreseen necessary to sealing practices if any of the alternative fluxes are adopted.
Keywords: Chipsealing, flux, bitumen