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 o r polyphosphoric acid and other phosphorus compounds on the physical a nd chemical characteristics of straight-run (distillation) bitumens wa s studied. The effect was similar to that induced by a mild blowing pr ocess: the peptized material increased, with a shift towards a gel str ucture, and minor effects on penetration and low-temperature propertie s were observed. The resistance to ageing measured by the RTFO test wa s greatly increased, indicating a way of improving the ageing resistan ce of straight-run bitumens. Besides the lower cost, an advantage of s uch a process over blowing is the fact that the original bitumen speci fications are not dramatically affected; moreover, the low-temperature behaviour is not modified.