Occurs due to loss of lower molecular weight volatiles. This loss rate depends on the concentrations, temperature, and environment.
As bitumen age they incorperate oxygen at reactive sites .
benzyclic carbonic groups
Hetero atoms in Unaged bitumen may be polar or nonpolar
Oxidation may be catalyzed by components in the bitumen and by some metal compounds in the aggregates.
The level of carbonyl or sulphoxide groups is not affected
This mechanism is free radical and is initiated by peroxide formation
The predominant materials formed in oxidation are oxygen polar functionalities
AGING CONCEPTS The amphoterics are the most reactive in terms of reactivity are capable of forming interlinked structures because they have more than one reactive site ( Fig). Mono functional materials with one oxidizable site, can act as chain terminators, limiting the degree of associations. The amphoterics have a large effect on the viscosity of the bitumen; the monofunctional polar molecules do not. .
EFFECT OF DIFFERENT TYPES OF AGEING ON BITUMEN PERFORMANCE
EFFECT OF THERMAL AND ULTRAVIOLET AGING
The study was done by Tan Yi-Qiu1, Wang Jia-Ni1
Three types of base bitumen from different sources with the same penetration grade are taken as A ,B ,C.
EFFECT OF STORAGE ON PROPERTIES
The study was done by Emery and Collonell
COMPARISONOF UV AND THERMAL AGING ON PHYSICAL PROPERTIES ON BITUMEN After UV and Thermal aging penetration and ductility value decreased while softening point is increased
Degradation rates of physical indices of aged bitumen Figure shows the changes to physical indices of bitumen A and B caused by aging. 1 A is more UV radiation sensitive. Its penetration decreased by 42%.ductlity decreased by 77.6% and the softening points increased by 22.6%,showing poor anti –UV ability. 2 B is not very sensitive to UV but is more thermally sensitive .as only small changes caused by UV radiation but greater changes in ductility and softening points caused by thermal aging can be seen . 3 Variations in the physical indices indicate than bitumen has different sensitivities due to Thermal and UV aging.
EFFECT OF THERMAL AND ULTRAVIOLET AGING variation of penetration and viscosity on different samples with storage