Abstract:
The global concern over plastic waste arises from its detrimental impact on agriculture, marine life and human health. Despite its slow degradation, plastic use continues to rise. Conversely, discarding steel slag in open environments threatens biodiversity and undermines land fertility. Prior research indicates the potential use of these materials for pavement. However, steel slag, despite its advantages, requires more bitumen due to its numerous pores.In this study, steel slag was coated with PET(Polyethylene Terephthalate) by dry mixing process and incorporated into asphalt concrete.
A series of AC mixes were prepared independently through coating process utilizing varying amount of steel slag (10%, 20%, 30% by weight of aggregate) and PET (0%, 5%, 10%, 15%, 20% by wight of binder), including a virgin mix devoid of these added materials.All the 16 sets and 240 specimensunderwent Marshall tests (medium traffic) and Indirect Tensile Strength (ITS) test in both unconditioned (dry) and conditioned (wet) state besides some routine property tests of individual constituents.
Steel slag is found acceptable up to 30% usage based on ACV and AIV. Flash and fire points of PET are well above the temperature of AC mix preparation.Increasing PET content leads to higher OTBC(optimum total binder content) but lower OBC(optimum bitumen content) for a specific slag percentage.Due to its pores, slag consumes more binder, leading to the increase of both OTBC and OBC along with stabilityvalue with rising slag content for a specific PET percentage. Both dry and wet ITS values for different combinations surpass those of the virgin AC mix. As anticipated, unconditioned specimens exhibit higher strength compared to their conditioned counterparts.S30_P20 (30% slag coated with 20% PET) and S20_P5 show the highest ITS for unconditioned specimens, indicating strong resistance to fatigue, temperature cracking, and rutting.S20_P10 and S30_P15 have the highest TSR values of 0.96 and 0.92, making them the most moisture-resistant combinations among all.The cost trend decreases as slag and PET content increases, resulting in upward savings compared to the virgin AC mix. With a 9.4% decrease in material costs, S30_P15 offers substantial savings, exceeding BDT 4 lakh per kilometer when compared to the virgin AC mix.After the observations, S30_P15 is recommended over all the combinations for its high stability, ITS and TSR value along with 9.4% savings in material cost.