Characterization of Low Density Polyethylene (LDPE) Modified Rap Asphaltic Concrete Mixtures

Abstract

The use of recycled materials and waste in road pavements is increasingly regarded not only as a preferred choice to enhance sustainability, but also as an appealing option in improving performance and longevity in service life of pavements. This is particularly true when it comes to recycled plastics and reclaimed asphalt from existing pavement structures. Majority of thin plastic bags are made of low density polymer ethylene (LDPE), which is frequently used for packing, protection, and a variety of other purposes. However, huge volumes of waste plastic bags pose an environmental hazard being non-biodegradable materials. Furthermore, roads are always in the process of rehabilitation producing waste in the form of reclaimed asphalt pavement (RAP). As a result, there is an urgent need to discover beneficial uses for these rising volumes of trash. Past research indicates the use of LDPE improves asphalt concrete properties, however combined effect of utilizing RAP with varying percentage of modifier has not been fully explored. The purpose of this research is to examine the possibility for enhancing the characteristics of asphalt mixtures using RAP as aggregate replacement and LDPE as a kind of polymer in asphalt. Specific to our conditions, the study's objectives focus on Characterization of LDPE modified RAP asphaltic mixtures. LDPE was added in three different proportions (2.5%,5% & 7.5%) by weight of bitumen and two RAP proportions were kept constant at 30% and 50% by weight of aggregate. By adding RAP, bitumen content was reduced from 4.5% to 4.2%. Resultant modified and conventional asphalt mixes were subjected to Dynamic Modulus, Resilient Modulus and Indirect Tensile strength (IDT) performance tests. Experimental results have indicated that LDPE can be conveniently used in bitumen as a modifier and have improved its softening point and penetration grade. It has been observed that LDPE dosage of 5% works best in the presence of 30% RAP. Whereas higher percentage of RAP (50%) results in stiffer bitumen which may lead to premature fatigue cracking. It has been observed that by addition of RAP and LDPE, improves mixtures stiffness, and moisture susceptibility. Moisture susceptibility is reduced by 10%, stiffness improves up to 1.5 times with 30% RAP and 5% LDPE. Overall, the asphalt mixes with 30% RAP modified with 5% LDPE has resulted in optimal combination in this study.