Development of a polymer-modified bitumen specification based on empirical tests – case study for Sri Lanka

Pavements with polymer modification exhibit greater resistance to permanent deformation, less thermal cracking, less fatigue damage and less temperature susceptibility. Implementation of polymer-modified bitumen (PMB) is currently taking place in developing countries and the absence of PMB specification has always been a constraint. This research was aimed at developing a testing procedure for PMB, based on test methods that are currently available 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 identify 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 presence 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 acceptance limits are determined 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 adequate quality control of PMB and it would be a useful guideline for the implementation of PMB for hot mix asphalt in Sri Lanka.