The asphalt industry has long been challenged with finding sustainable solutions to enhance the performance of asphalt mixtures while mitigating their environmental impact. One promising avenue is the incorporation of waste filler materials into asphalt mixtures. This review explores the feasibility and effectiveness of utilizing waste filler in asphalt mixtures, focusing on its effects on the mechanical characteristics, durability, and sustainability of asphalt pavements. Various waste filler materials, such as rice husk ash, fly ash, and construction and demolition wastes, have been examined in terms of their potential as substitutes for traditional filler materials such as limestone and mineral powders. This review synthesizes literature to assess the impact of waste fillers on the performance of asphalt mixtures, including rutting resistance, fatigue behavior, moisture susceptibility, and aging characteristics. This work begins by examining the interaction of the asphalt fillers to provide clarification. The usage of various waste fillers is then examined. With fewer harmful environmental consequences than traditional cement manufacturing has, waste filler materials improve the strength and durability of asphalt mixtures. This research underscores the promising future of waste filler materials as environmentally friendly and innovative materials. To fully capitalize on their benefits, further research, standardization, and widespread use of waste filler-based products are necessary.

Harnessing the power of phase change materials (PCMs) in asphalt pavements proposes a sustainable solution for addressing temperature-related issues, affording more robust and energy-efficient infrastructure. PCMs hold enormous potential for reforming various industries due to their ability to store and release large amounts of thermal energy, offering noteworthy benefits in energy efficiency, thermal management, and sustainability. The integration of PCMs within pavements presents an increasingly exciting field of research. PCMs have the ability to efficiently manage the changes in and distribution of temperature in asphalt pavements via the release and absorption of latent heat that occurs during the phase shifts of PCMs. Asphalt pavements experience less severe temperatures and a slower rate of temperature fluctuation as a result of this, which in turn reduces the amount of stress caused by temperature. In addition, the function of temperature adjustment that PCMs provide is natural, intelligent, and in line with the direction in which the development of smart pavements is heading in the future. This study aims to explore the impact of organic, inorganic, and mixed organic–inorganic PCMs on diverse surface characteristics of asphalt. In addition, this review addresses current challenges associated with using PCMs in asphalt and explores potential advantages that could facilitate future research in addition to broadening the implementation of PCMs in construction.

The subgrade soil layer is the most essential part of the pavement system. Many pavement failures can be associated with subgrade weak strength and stiffness qualities. Therefore, it is necessary to strengthen this layer before building the other pavement layers. One of the essential methods utilized to enhance the engineering characteristics of this layer is soil stabilization. Stabilization methods are many and varied, but chemical and mechanical stabilization are the most common. This research aims to evaluate the strength of stabilized soils by using a dynamic cone penetration (DCP) test. To achieve this aim, subgrade soil was provided from a roadway project in Kerbala city and stabilized with 2.5 and 5% of Portland cement by weight of the dry soil. Then, the cemented subgrade soil was reinforced with 6 and 12 mm of polypropylene discrete fiber. The fiber was added to the soil with the following contents: 0.5, 1, and 2%. The characteristics of stabilized soils were evaluated by determining three parameters: dynamic cone penetration index (DCPI), in-situ California bearing ratio (CBR), and bearing capacity obtained from the DCP test. The results showed that when Portland cement was increased from 0 to 2.5% and then to 5% by weight of the dry soil, the DCPI value gradually decreased while increasing both CBR and bearing capacity. However, adding 6 and 12 mm fiber contents (0.5, 1, and 2) to the cement–sand mixture containing 2.5 and 5% cement led to increased DCPI and a gradual decrease in CBR and bearing capacity. Also, the results showed that the DCPI for a 12 mm fiber is lower than that for 6 mm fibers, while the CBR and bearing capacity for a 12 mm fiber are greater than those of 6 mm fibers for all ratios. Accordingly, the results of the DCP tests showed that the most significant support for the soil is obtained when the soil is stabilized using 5% cement with 12 mm of fiber by weight of dry soil.

Subgrade soil is a natural formation utilised as a foundation for pavement layers, which means that it must be strong enough to support the pavement system. Subgrades such as loose sand, clay and silt soils thus need to be stabilised in order to improve in-situ performance. Several different geotechnical techniques have been utilised for soil stabilisation, and in this research, experimental work was carried out to examine the use of hydrated lime and waste plastic fibre as sustainable additives to enhance the characteristics of loose subgrade sand. The hydrated lime was added at several different percentages (4, 6, 8, and 10% by dry weight of soil), and the laboratory tests results revealed that adding 8% lime to the soil provided the best strength characteristics. The optimum lime-treated sandy soil was then reinforced by the addition of waste plastic fibre with lengths ranging from 5 to 20 cm added at three percentages (1, 2 and 3% by dry weight of soil). The dynamic behaviours of the reinforced stabilised soil in terms of surface deflection and dynamic modulus were evaluated using a light weight deflectometer test (LWD). The results illustrated that adding 10 cm waste plastic fibre at 3 wt.% content led to an increase in the dynamic modulus of 28.12% and a decrease in the surface deflection of 21.35% as compared to natural subgrade soil.

The long-term performance of asphalt pavements is influenced by the quality of the supporting subgrade, with subgrade required to prevent premature asphalt pave

This research investigates the potential application of employing waste tire crumbs as a partial replacement of subgrades soils for constructing roadway and air