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BITUMEN AGEING AND HYDRATED LIME

The doctoral thesis consists of a literature review and four papers describing experimental studies of the influence of hydrated lime on bitumen ageing. The literature review describes contemporary knowledge of bitumen with respect to chemistry, rheology and modification. The relations between chemical composition and mechanical behavior are discussed. In a section treating rheology, a distinction is made between fundamental mechanical properties, related to constitutive equations, and empirical properties solely related to the test methods used. Mechanisms of bitumen ageing are described, with stress on oxidation, which is generally accepted as the most important one. Different factors affecting ageing are discussed as well as additives for inhibition of bitumen ageing: anti-oxidants, hydrated lime and polymers. Optimistic expectations have existed since the beginning of the 1970s, that hydrated lime, beside being a useful antistripping agent, also might work as an inhibitor of bitumen hardening. These expectations appeared to be supported by results of several laboratory investigations. In studies presented in these thesis, laboratory ageing of bitumen was performed by standardised methods that are generally accepted to resemble real life conditions during production and service. The results show, that under such conditions, the anti-ageing capacity of hydrated lime is fairly modest. However, it was also shown, that using more severe ageing conditions hydrated lime can bring a striking reduction in ageing index. There are several pathways of bitumen oxidation, and one of them is catalysation. Different metal containing compounds naturally occurring in bitumen, in particular various vanadium complexes, are supposed to catalyse bitumen ageing. One mechanism of hydrated lime that has been suggested, is inhibition of catalyst induced oxidation. Indications in favour of this proposition was provided by an ageing study, in which various amounts of a vanadium containing catalyst was added to bitumen. The mechanical properties of bitumen are highly dependent on molecular polarity, and since hydrated lime is a surface active material, it is reasonable to expect that hydrated lime has a significant impact on molecular configurations and structure of bitumen. Accordingly it appeared possible that hydrated lime affects low temperature physical hardening and low temperature mechanical properties, such as capacity of dissipation of stored deformation energy. A study was performed, using a bending beam rheometer (BBR) for comparative tests of samples that were either neat, containing hydrated lime or calcium carbonate filler. However, no significant influence of the fillers was found on the low temperature physical hardening. (A)

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  • Corporate Authors:

    KUNGLIGA TEKNISKA HOEGSKOLAN, INSTITUTIONEN FOER INFRASTRUKTUR OCH PLANERING

    STOCKHOLM,   Sweden  SE-100 44
  • Authors:
    • JOHANSSON, L S
  • Publication Date: 1998

Language

  • English

Media Info

  • Features: References;
  • Pagination: 13p + a p.
  • Serial:
    • TRITA-IP FR
    • Issue Number: 98-38
    • Publisher: KUNGLIGA TEKNISKA HOEGSKOLAN, INSTITUTIONEN FOER INFRASTRUKTUR OCH PLANERING
    • ISSN: 1104-683X

Subject/Index Terms

Filing Info

  • Accession Number: 00822218
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • Files: ITRD, ATRI
  • Created Date: Jan 7 2002 12:00AM