Abstract:
Polymer modification of bitumen has increasingly become the norm in designing optimally
performing pavements. Pavements with polymer modification exhibits greater resistance to
permanent deformation and thermal cracking, and decreased fatigue damage and temperature
susceptibility. Polymer Modified bitumen (PMB) are effectively used in many countries over
last three decades to construct pavements with superior performance and extended service
life. This research was aimed at identifying the need to implement PMB in Sri Lanka, and
also developing a testing procedure for PMB based on currently available empirical test
methods.
Five unmodified binders used in Sri Lanka was subjected to a series of laboratory testing in
order to study their temperature susceptibility, high and low temperature behavior and
moisture damage. The results were compared with the existing pavement conditions and it
was understood that their performance is limited in above mentioned aspects. To understand
the performance of PMB, a case study was done using two PE modified bitumen samples
and two SBS modified bitumen samples. They were subjected to a series of laboratory tests
which confirmed that the both types of PMB are suitable to overcome the limitations
exhibited by unmodified binders.
The necessity of having a proper testing procedure for PMB is discussed and a specification
was proposed considering the available testing facilities in Sri Lankan Laboratories. The test
methods were selected considering the adequate control of binder properties during
application and usage. Penetration test is included to control the intermediate temperature
properties and for the identification of binder grades. Softening point test controls the high
temperature properties while viscosity test controls the mixing and compaction temperatures.
Elastic recovery test and solubility test were employed in order to identify the amount of
polymer in PMB. Storage stability test determines the separation tendency of polymer from
bitumen. Flash point limits are set for the application safety. Thus all the essential
parameters of bitumen are controlled by the proposed specification. The requirement limits
are set considering different PMB specifications of several other countries, past research
outcomes and laboratory test results.
The proposed specification which is based on empirical test methods facilitates an adequate
quality control of Polymer Modified Bitumen and it would be a useful guideline for
implementation of PMB for HMA in Sri Lanka
