Effect of Waste Plastic on Moisture Damage Resistance of Warm Mix Asphalt Mixtures

The present study aims to investigate the effect of low-density polyethylene (LDPE) waste plastic coupled with warm mix asphalt additive (WMA) on moisture susceptibility of bituminous mixes. Bituminous concrete-II gradation (i.e., BC-II) was selected for preparing the mix. Viscosity grade binder (VG-30) and basalt aggregate were used for the study. Initially, a wet process was adopted, i.e., waste plastic collected domestically was shredded and added to bitumen with 7.5, 10.0, and 12.5% dosage of plastic by weight of bitumen to prepare a set of plastic modified bitumen. Secondly, bitumen was modified with 6% WMA additive, i.e., zeolite which was further treated with 7.5, 10.0, and 12.5% dosage of waste plastic by weight of bitumen to prepare another set of waste plastic-WMA modified bitumen. Using the prepared binder sample, bituminous mixes were designed following Marshall method of mix design. The moisture susceptibility of the prepared mixes, namely control mix, waste plastic modified mix, and plastic-WMA modified mixes were tested using Indirect Tensile Strength (ITS) and Boiling water tests. Results revealed that plastic modified mixes were found to have higher resistance to moisture damage compared with control mix. It was found that tensile strength ratio (TSR) based on ITS test has highest value of 90.42% for 10% plastic modified bituminous mixes compared with control mix (TSR = 84.99%) indicating improved resistance to moisture damage. In addition, 10% plastic modified bituminous mixes showed 99% coating of bitumen retained after boiling water test. It was also interesting to note that incorporation of zeolite did not improve the performance of the mix against moisture damage. Hence, based on the findings of the present study, it may be concluded that the addition of 10% plastic may be used to improve the moisture susceptibility of bituminous mixes.