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• SEA modified with rPE is sustainable, economic, and ecofriendly alternative. • rPE made SEA stiffer/elastic thus better resistance to rutting/fatigue cracking. • Addition of rPE to SEA improved elastic and viscous properties. This research evaluates the rheological properties of virgin asphalt and sulfur extended asphalt (SEA) modified with two types of recycled plastic waste (rPW). The investigated plastic wastes are the recycled low-density polyethylene (rLDPE) and recycled high-density polyethylene (rHDPE). It also assesses the environmental and economic benefits of recycling such materials. A total of 16 modified binder samples are produced by adding rLDPE and rHDPE modifiers to virgin asphalt and SEA in four different concentrations of 2%, 4%, 6%, and 8% by weight of asphalt. The basic and rheological properties of the virgin and modified asphalts are explored by conventional tests, and advanced rheological tests at different aging conditions. Finally, cost-effectiveness and environmental analyses are conducted. The environmental benefit analysis is performed by comparing carbon and non-methyl volatile organic compound (NMVOC) emission from the various recycled polyethylene (rPE) with the manufacturing process of the same quantities of virgin LDPE and HDPE when used to modify asphalt. The effect of incorporating sulfur into virgin asphalt on the environment is also determined. Results show that modification yields a higher binder complex shear modulus (G*) and a lower loss tangent (tan δ) at all traffic speeds meaning improved rut resistance behavior under heavy traffic loading and high temperature conditions. About 29% reduction in material cost occurs when rPE-modified SEA is used instead of virgin asphalt. The environmental and economic analyses show that using SEA modified with rPE for road construction is an economic, sustainable, and ecological alternative with better performance compared to virgin asphalt. [ABSTRACT FROM AUTHOR]

• Granular base material was stabilized by geopolymer, calcium carbide residue (CCR) • CCR was activated by a diluted linear alkyl benzene sulfonic acid (LABSA) • Seven solid/liquid (CCR: diluted LABSA) mixes were prepared and investigated. • Geopolymer of (300/1000) ml LABSA with a (80%:20%) achieved best strength (UCS) • Stabilized aggregate by CCR/LABSA gels produced denser and uniform microstructures. Alkali activated industrial waste/by-product geopolymers have recently gained extensive attention from researchers as a replacement for cement in concrete manufacturing. However, little attention has been given to their employment as a stabilizer of unbound granular base/subbase (UGB) materials in road construction. Stabilizing granular base materials with geopolymers is explored in this study. The investigated geopolymer is composed of calcium carbide residue (CCR), a waste product resulting from the manufacturing of acetylene gas, which activated by a linear alkyl benzene sulfonic acid (LABSA). Four proportions of sulfonic acid dilution ratios and seven solid/liquid (CCR/diluted LABSA) mixes were prepared. The unconfined compressive strength (UCS) of the mixtures was determined in the laboratory. The maximum UCS was achieved by blending a diluted LABSA of (300/1000) ml with a geopolymer (solid: liquid) blend proportion of (80%:20%) by the total weight of aggregate. Based on the results, aggregate mixtures of 2.5%, 5%, 7.5%, and 10% of geopolymer blend content were prepared to determine the maximum UCS value corresponded to the optimum geopolymer mixing ratio. This optimum geopolymer ratio was recommended at 7.5%, which was then exposed to different curing times and environmental conditions to explore the variation in UCS as well as the elastic modulus (E). In addition, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) measurements revealed that the stabilized aggregate contained geopolymer gels generally produced microstructures that are more uniform and denser than the untreated aggregate structure. A blend of CCR and LABSA can be used as a feasible and sustainable eco-friendly alternative as a stabilizing agent for UGB in pavement engineering applications. [ABSTRACT FROM AUTHOR]