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• Waste cooking and engine oils (WCO, WEO) were investigated as bitumen rejuvenators. • Optimum percentages of the waste oils were 3.5% for the WCO and 5.5% for the WEO. • Rejuvenated bitumen showed less tendency to short-term aging based on DSR results. • Rejuvenated bitumen by both WCO and WEO had a performance grade of PG 64-28. • Rejuvenated 100% RAP mixes cope with Egyptian limits for stability, flow, and ITS. For sustainable pavement construction, this research paper aims to investigate the feasibility of using Waste Cooking Oil (WCO) and Waste Engine Oil (WEO) as rejuvenators on the rheological properties of aged bitumen extracted from Reclaimed Asphalt Pavement (RAP). The aged bitumen was extracted from milled RAP recruited from an old pavement. The rheological characteristics of the rejuvenated bitumen were determined by penetration, softening point, Brookfield viscosity, Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR) tests. In addition, the chemical composition of virgin (control), aged and rejuvenated bitumen by WCO, and WEO was investigated using Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray (EDX). The quality of the rejuvenated bitumen was also evaluated by the Scanning Electron Microscopy (SEM) imaging technique. Based on penetration and softening point testing results, the optimum percentages of the waste oils were found to range from 3.5 to 4.0% for the WCO and from 5.5 to 6.0% for the WEO. The aged bitumen properties were significantly improved by rejuvenators as evidenced by the chemical analysis (FTIR and SEM/EDX) along with the ratio of asphaltenes to maltenes. Furthermore, the surface morphology was renovated as well as the fundamental physical properties of the rejuvenated aged bitumen. Additionally, the rejuvenated bitumen showed less tendency to short-term aging as confirmed by the DSR results. BBR results of rejuvenated aged bitumen samples exhibited comparable performance to those of the control samples at different low temperatures having a performance grade of PG 64-28. Moreover, rejuvenated 100% RAP mixes were found to cope with Egyptian requirements for heavy traffic as binder courses and medium traffic as wearing courses in terms of Marshall stability and flow. Finally, Indirect Tensile Strength (ITS) results were within the specification limits. [ABSTRACT FROM AUTHOR]

This paper mainly aims at investigating the effect of using multi-wall carbon nanotubes (MWCNTs) as an additive on the rheological properties of asphalt. Pristine (P-MWCNTs) were mixed at 120 °C with control asphalt at contents of 0.5%, 1.0%, 2.0% and 3.0% by asphalt weight. The empirical and rheological properties (using the Superpave testing) of the control and modified asphalts were evaluated at different aging conditions. The rheological properties of the modified asphalts were found to improve with increasing the percentage of P-MWCNTs. The high failure temperature and rutting resistance of both unaged and rolling thin film oven aged (RTFO) modified asphalts increased with increasing P-MWCNTs percentage and became suitable for the Egyptian climatic conditions as required by the Superpave binder characterization. At a given temperature, the fatigue cracking resistance and low temperature cracking resistance decreased with increasing P-MWCNTs percentage. [ABSTRACT FROM AUTHOR]

Highlights: [•] NCHRP1-37A yielded better E * values compared to NCHRP 1-40D model at all binder characterization input levels. [•] NCHRP1-37A E * model with Level 3 binder characterization produced the most accurate and the least biased estimates. [•] Because of the hot desert climate in KSA, care should be taken when using such models for E * predictions. [Copyright &y& Elsevier]

• 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]

Highlights • New resilient modulus master surface approach was developed. • The approach characterizes both granular pavement materials and subgrade soils. • The approach considers the effect of stress state and moisture content levels. • The proposed master surface-2018 model produces accurate predictions. Abstract Resilient modulus is a fundamental material property used for pavement materials characterization. A new methodology for predicting the resilient modulus of unbound/stabilized pavement materials and subgrade soils is developed based on a master surface function at a reference water content. The resilient modulus measurements at different levels of water content are shifted horizontally with respect to the octahedral shear stress, and bulk normal stress; simultaneously. A total of 2754 resilient modulus laboratory measurements, obtained from literature, for five granular base materials, four subgrade soils, one recycled crushed concrete material, and three cement-treated stabilized fine materials are used to evaluate the proposed Master Surface model for the resilient modulus prediction as a function of the stress state, and water content. The proposed predictive methodology is compared to well-known models from literature. The comparison of the investigated models exhibits that the Master Surface model has the most precise and unbiased predictions after numerically optimizing the resilient modulus data. [ABSTRACT FROM AUTHOR]

• Recycled Plastic Waste (RPW) improved virgin (VA) & sulfur extended asphalt (SEA). • RPW made VA&SEA stiffer/elastic thus better resistance to rutting/fatigue cracking. • Addition of RPW to VA&SEA slowed the oxidation reactions of the binder. • Addition of RPW to VA&SEA made binder more suitable for wider range of temperature. • The modification effect of RPW on asphalt included chemical and physical processes. This study examines the effect of two different recycled plastic waste (RPW) which are high and low-density polyethylene (RHDPE and RLDPE) on the rheological/viscoelastic characteristics and aging performance of virgin asphalt and sulfur extended asphalt (SEA). Four dosages of the RPW additives representing 2%, 4%, 6%, and 8% by weight of the asphalt binder were investigated. The rheological characteristics of the RPW modified binders (virgin and SEA) are characterized at original and short-term aging conditions through the Rotational Viscometer (RV) and dynamic shear rheometer (DSR) tests. Fatigue performance is also characterized at the long-term aging condition. Also, high-temperature performance, dynamic storage stability (DSS), multiple stress creep and recovery (MSCR) are studied. Testing results show that RPWs lead to improved rutting and fatigue performance. Adding RPW to the virgin and SEA binders slows the binder oxidation reactions during the short-term aging. The Aging Index (AI) is found to be dependent on the asphalt rheological properties, amount/type of RPW, binder type, and temperature. RHDPE leads to an unstable modified virgin asphalt. Less than 4% RHDPE or 8% RLDPE with virgin asphalt show good DSS in terms of degradation and separation. The RPW with SEA meets the requirement of time degradation and separation set by the Federal Highway Administration (FHWA). The temperature susceptibility of asphalt binder decreases dramatically with the RPW modification making the asphalt binder more suitable for use at a wider range of temperatures. [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]