The amount of solid plastic waste generated from material packages like plastic bottle and similar utilities within the kingdom of Saudi Arabia has skyrocketed. This is as a result of the increased level of industrial packaging due to rapid industrialisation and fast urbanisation in the country. The associated cost of managing these solid wastes has also multiplied as the task become difficult and enormous. The effect of polypropylene, high- and low-density polyethylene (PP, HDPE and LDPE)-recycled plastic wastes (RPW) on the viscoelastic performance of the local asphalt binder has been investigated. The recycled plastics were obtained by shredding and grounding the RPW to a desirable size for easier blending with the asphalt binder. All the RPWs result in an improved rutting performance. The RPW-modified asphalts upper PG limit increase by at least one level for each 2% increase in the RPW content, in most cases. An increase of 55, 19 and 9% in resilient modulus (M_R) was observed for PP-, HDPE- and LDPE-produced asphalt concrete (AC), respectively. Correlation between the M_R of the AC and non-recoverable creep compliance (J_nr) of the asphalt binder was established. The obtained viscoelastic properties of the RPW-modified binder was utilised to model a typical pavement section using AASHTO mechanistic empirical pavement design guide (ME-PDG) software. The predicted distresses of the modelled pavement shows significant rutting and fatigue performance improvement for pavement produced with the RPW. Elastomeric type of polymer is required to supplement these RPW to enable them meet the AASHTO TP 70 elastic recovery requirement.

Huge amounts of generated non-degradable plastic wastes constitute a major global environmental nuisance. The combined annual municipal solid waste (MSW) generation of Saudi Arabian Kingdom (KSA) exceeds 14,000,000 tonnes, with an average per capita of 1.4 kg/day. Plastic wastes constitute up to 10% of these MSW. The local asphalt can only perform satisfactorily without polymer modification in an environment with a maximum pavement temperature below 64°C. But the 7-day maximum pavement temperature ranges between 64°C and 76°C within the Kingdom. Dynamic storage stability, high-temperature performance, non-recoverable creep compliance (J_nr), and strain recovering tendency of recycled high- and low-density polyethylene (RHDPE and RLDPE), and recycled polypropylene-(RPP) modified asphalt binders in combination with styrene–butadiene–styrene (SBS) and polybilt (PB) were presented in this study. Improved high-temperature performance was observed. Even though the recycled plastic waste-modified binders lack sufficient strain recovering ability, RLDPE and RHDPE could be utilised along with an elastomeric SBS to achieve a higher recovery and strain resistance, than that which could be achieved if the same amount of SBS alone is used. RPP content above 2% will lead to an unstable modified asphalt binder. The RHDPE content below 4% and the RLDPE content below 6% whether containing either SBS or PB have shown good storage stability trait under mild agitation, in terms of both time degradation and separation.

Plastic waste (PW) has long been identified among the direct and indirect primary sources of environmental pollution. Currently, global PW generation is more than 300 million tons annually and is increasing at a rate of 4% per year. Recycling has been recognized as a key technique, among others, for addressing the environmental hazards associated with PW. Prior studies on the modification of asphalt concrete (AC) using PW have been mostly about asphalt binder modification or mineral aggregate substitution for better AC properties. Several studies have focused on stone mastic asphalt concrete (SMA) or isolating recycled polyethylene terephthalate (RPET) as an aggregate substitute. In this study, a combined form of recycled plastic waste (RPW) was used as a mineral aggregate supplement in a dense-graded hot mix asphalt (HMA) AC made with RPW-modified asphalt binder. The term hybrid RPW-AC is used to refer to the HMA AC in this study. The viscoelastic performance of ACs containing combined RPW aggregates were compared with those containing RPET-only aggregates. Dynamic modulus ($|{\mathit{E}}^{*}|$ ) tests, flow number (FN) tests, and rutting resistance tests using an asphalt pavement analyzer (APA) were utilized to evaluate the performance of the hybrid RPW asphalt concrete mixes and were compared to fresh, RPET, and crumb rubber AC. The results showed that combined RPW as an aggregate supplement has advantages over the use of RPET-only aggregates. The hybrid RPW-AC showed superior performance compared to the reference mixtures.