The utilization of reclaimed asphalt pavement (RAP) in flexible pavement construction and rehabilitation has gained significant traction, driven by the need to conserve limited natural resources. This study explores the effectiveness of bio-based oils derived from harvested crops as rejuvenators in asphalt mixtures containing 50% RAP. Comprehensive assessments were conducted, including penetration, softening point, viscosity and ductility tests, to determine the optimal rejuvenator dosage. Additionally, evaluations of rolling thin film oven (RTFO) aging, retained penetration and ductility, equivalent softening and breaking points, plasticity temperature range, stiffness modulus, complex modulus, and phase angle were performed. Fourier-transform infrared (FTIR) spectroscopy, Marshall immersion, and moisture susceptibility tests further validated the rejuvenator's efficacy in improving asphalt properties. The incorporation of 1.8% bio-oil significantly reduced the viscosity of the mixtures, enhancing workability. The rejuvenator effectively compensated for the loss of light components in aged binders, restoring the maximum and minimum temperature performance to levels comparable to virgin asphalt (VA). Mechanical testing revealed that bio-oil mitigated the aging effects of RAP asphalt, and the rejuvenated mixtures showed considerable improvements over both VA and non-rejuvenated RAP mixtures, where the rejuvenated specimens achieved 90.8 and 89.4% of retained strength index (RSI) values for 24- and 48-h immersion periods, respectively comparing with 88.9 and 86% post-immersion of VA for similar durations. These findings underscore the potential of bio-oil as a sustainable and eco-friendly solution for rejuvenating aged asphalts, paving the way for more sustainable asphalt production practices.

This research addresses the significant challenge posed by early water damage in highway asphalt pavement, a critical concern affecting pavement service performance. To counteract this issue, the utilization of anti-stripping agents in asphalt is explored as a highly effective technical intervention. In this investigation, a carefully selected amine-free additive was employed to modify the asphalt binder. A comprehensive array of physical and rheological tests, covering aspects such as storage stability, penetration, softening point, ductility, elastic recovery, rolling thin-film oven, retained penetration, the ductility of residue, and rotational viscometer assessments, were conducted to examine the multifaceted impact of the anti-stripping agent on the asphalt binder. Additionally, we assessed the asphalt mixture’s sensitivity to moisture through Marshall stability tests after conditioning for 40 min and 24 h, followed by an enhanced immersion test and moisture susceptibility measurement. The results reveal a nuanced interplay of chemical and physical mechanisms influencing the behavior of the asphalt binder. Notably, the incorporation of an anti-stripping agent at a concentration of 0.25–0.5% (by weight of asphalt binder) led to a substantial improvement in the tensile strength ratio (TSR) to 94.9%, a noteworthy enhancement compared to the 80.6% observed with virgin asphalt mixture. Furthermore, the retained stability index (RSI) exhibited a remarkable increase to 98.1%, surpassing the 87.6% recorded for virgin asphalt. This study not only provides crucial insights into the intricate dynamics of asphalt binder performance but also emphasizes the pivotal role of anti-stripping agents in augmenting the structural integrity and resilience of asphalt pavement.

In this work, the mechanical properties and deformation behavior of Hot Mix Asphalt (HMA) reinforced with Glass Fiber (GF) are analyzed. The focus was mainly on determining the effects of different GF content on the behavior/ stability/ stiffness/ permanent deformation of asphalt concrete in wearing courses. The experimental protocol was based on asphalt Al-Daurah cement (40/50 penetration grade) and crushed aggregates obtained from Kavin Company (Zakho, Duhok), with a nominal maximum aggregate size (NMAS) of 12.5 mm, as per ASTM D3515. The study was carried out in two stages. The Optimum Asphalt Content (O.A.C.) was determined to be 5.1% using Marshall mix techniques. In phase two, 5 mixtures were made together with the dry mixing method, adding (GF) at 0% (Control), 0.3%, 0.5%, 0.7%, and 0.9% by weight of the mix. Experimental results showed improved structural integrity of the asphalt when glass fibers were applied. The Marshall Stability was at its maximum at 0.5 % GF (12.5 kN), 25 % higher than the control mixture. Additionally, the Kim Test was used to probe the high-temperature effect, and the Deformation Strength (SD) level increased by ≈ 50% at the same dosage (2.706 MPa > 4.048 MPa). The maximum Marshall Stiffness was 3.8 kN/mm at 0.5% GF, indicating superior shear resistance. Yet, fiber levels above 0.5% lead to decreased performance due to fiber agglomeration and poor workability. The Optimum Glass Fiber Content (O.GF.C.) is 0.5% GF for improving both the durability and rutting resistance of flexible pavements in hot weather.

The service life of a road pavement reduces as it ages and loses quality due to exposure to various traffic loads and environmental conditions. This study investigates the possibility of reusing aged asphalt in pavement by mixing Waste Engine Oil (WEO) and Vacuum Residue (VR) to create a hybrid rejuvenator. Four types of binders, namely, virgin asphalt, aged asphalt, blended aged and virgin asphalt, and rejuvenated hybrid (WEO-VR) with aged and virgin asphalt, were evaluated using rheological and water immersion tests. The results show that WEO-VR greatly enhanced the properties of old asphalt in the presence of water based on rheological parameters. The behaviour of the rejuvenated asphalt mixture was close to that of the virgin asphalt mixture in the stripping resistance tests. Thus, 6.5 % of the total mix's WEO-VR may be used to regenerate old asphalt, paving the way for more environmentally friendly and sustainably manufactured asphalt.