IMPROVING THE AGING RESISTANCE OF STRAIGHT-RUN BITUMENS BY ADDITION OF PHOSPHORUS-COMPOUNDS

The effect of the addition of small quantities (1 wt%) of phosphoric or polyphosphoric acid and other phosphorus compounds on the physical and chemical characteristics of straight-run (distillation) bitumens was studied. The effect was similar to that induced by a mild blowing process: the peptized material increased, with a shift towards a gel structure, and minor effects on penetration and low-temperature properties were observed. The resistance to ageing measured by the RTFO test was greatly increased, indicating a way of improving the ageing resistance of straight-run bitumens. Besides the lower cost, an advantage of such a process over blowing is the fact that the original bitumen specifications are not dramatically affected; moreover, the low-temperature behaviour is not modified.