Performance Evaluation of Low Density Polyethylene (LDPE) Modified Rap Containing Asphalt Concrete Mixtures

Abstract

The use of recycled materials and waste in road pavements is increasingly regarded not only as a good choice in terms of sustainability, but also as an appealing option in terms of delivering improved performance in terms of service longevity 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 because they are considered non- biodegradable materials. Furthermore, roads are always in the process of rehabilitation and a lot of road waste is also produced and this waste is called reclaimed asphalt pavement (RAP). As a result, there is an urgent need to discover beneficial uses for this 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 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. Specific to our conditions, the study's objectives focus on performance evaluation of RAP containing LDPE modified asphalt concrete mixes. LDPE was added in different proportions from 2.5% to 7.5% by weight of bitumen by the increment of 2.5 and RAP proportion was kept constant as 30% 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 Tensile Strength Ratio (TSR), Resilient Modulus and Indirect Tensile Fatigue Tests. Results have indicated that LDPE can be conveniently used in bitumen as a modifier and have improved asphalt mixes. It has been observed that LDPE dosage of 5% works best in the presence of 30% RAP. Higher percentage of LDPE results in stiffer bitumen which may lead to premature fatigue cracking. It has been observed that by addition of RAP and LDPE, improves stiffness, fatigue resistance and moisture susceptibility. Moisture susceptibility is increased by 11.54% of modified mixes. Moreover, inclusion of LDPE also improves stiffness of asphalt mixes up to 1.5 times of conventional mixes with 30% RAP and 5% LDPE. Furthermore, fatigue life of asphalt mixes has been doubled. Overall, the asphalt mixes with 30% RAP modified with 5% LDPE has best results.