SUITABILITY OF MODIFIED BINDERS FOR SUSTAINABLE FLEXIBLE PAVEMENT CONSTRUCTION IN CONTEXT OF BANGLADESH

Abstract

60/70 bitumen is used as the main binder in pavement construction of Bangladesh which experiences numerous types of defects require frequent maintenance and are extremely vulnerable to traffic loading, moisture damage and temperature changes. Hence, an effort has been made to enhance the bitumen quality by adding modifiers with the neat bitumen. And also, bituminous concrete mixes have been evaluated for some performance parameters to justify the bitumen quality. On the other hand, vehicles are increasing approximately 0.5 million per year in Bangladesh with the increase of life standard, country development, economic zones, population and road network which produce a significant amount (150,000 tons) of non-biodegradable waste tires. It may be advantageous for the environment and the economy by using this waste material as a bitumen modifier, producing Crumb Rubber Modified Bitumen (CRMB). Polymer Modified Bitumen (PMB) is used in many countries over the world due to its enhanced properties, so it has also been considered to verify the suitability over neat binder and CRMB. The research includes laboratory investigation of binders (60/70, PMB & CRMB) properties and found CRMB has more enhanced. Marshall mix design approach has been used to determine the Marshall properties and Optimum Bitumen Content (OBC). The OBC’s of bituminous mixes prepared by neat 60/70 bitumen, PMB, and CRMB were found to be 5.05%, 5.10% and 5.30% respectively. The retained stability of 60/70 bitumen, PMB, and CRMB mixtures were found to be 79.0%, 92.6% and 95.0% respectively. Based on Indirect Tensile Strength (IDT) test, the Tensile Strength Ratio (TSR) values for the respective mixtures were found to be 84.0%, 94.4% and 93.2%. Again, based on moisture induced damage test, the TSR values were found to be 83.1%, 90.1% and 93.0% for the respective bituminous mixes. The modified bitumen showed higher softening point, higher elastic recovery, lower temperature susceptibility and lower stripping value. Moreover, higher resistance to moisture induced damage and retained stability were observed for the modified bituminous mixes. Finally, it can be concluded that, the performance of modified binders are better than that of neat 60/70 bitumen as they are less susceptible to temperature and moisture, causing less maintenance and rehabilitation costs over the pavement's lifespan. Since the CRMB performed best out of the two modified bitumen, it can be considered as a sustainable alternative for durable and effective road development in Bangladesh.