Branch Report:
14th December 2005
Binders for
Asphalt
On the 14th
December Ron Taylor from BP Bitumen UK gave a presentation titled ‘Binders
for Asphalt’ to 27 Members. Ron defined bitumen
and described its source from crude oil
and the variations of crude oil and the affect on the amount of bitumen
obtained from it. He stated that from the 1500 different crude oils
available in the world only approximately 100 were suitable sources for
bitumen. The production of bitumen and the processes involved in the
distilled and the semi-blown production methods and the associated grades
were described, along with the various testing procedures used on the
bitumen such as penetration test and softening point.
The behaviour of the bitumen with regard
to the final asphalt product performance was also discussed and the
reasons why modification is needed such as increased traffic levels,
congestion resulting in slower traffic speeds and the need for longer
lasting products. Ron then described what a polymer was and various type
and the benefits provided by polymers such as reduced temperatures
susceptibility and enhance elasticity or increased viscosity or both. The
degree of modification depends on a number of factors such as polymer type
and concentration, degree of dispersion through the bitumen as well as
bitumen type and chemistry and the bitumen and polymer compatibility.
The process of producing polymer modified
bitumen was detailed and how they can improve the performance of asphalt,
with regard to deformation resistance particularly the problem of rutting,
improve low temperature properties and they can improve fatigue resistance
and cohesion, reducing problems such as fretting and chipping loss. They
can also reduce binder drainage and improve resistance to fuel.
Polymer
modified bitumens are increasingly being used in order to meet the growing
demands for improved asphalt performance brought about by higher traffic
loads/stresses, client demands for better value for money and the public’s
demand for quiet, spray free, smooth running surfaces.
