Mining Waste in Asphalt Pavements: A Critical Review of Waste Rocks and Tailings Applications

1. Introduction

The mining industry is the backbone of the modern world for supplying essential minerals and metals, generates vast quantities of waste in the form of overburden, tailings, and slag. This mining waste presents a significant global challenge, as it often contains heavy metals and other toxic substances that are dangerous to the environment. The proper and sustainable disposal of this waste is one of the major problems facing the mining industry as these wastes pose severe environmental risks such as soil and water contamination due to the leaching of heavy metals. They are typically disposed of in tailing dams, which pose structural risks and can lead to disastrous environmental and human health impacts, as seen in the 2109 Brumandinho dam disaster in Brazil [1]. The scale of this issue is immense, with mining activities estimated to produce over 100 billion tonnes of waste annually worldwide [2]. In Australia, mining is a major industry and a significant contributor to national waste production. In the 2020–2021 financial year, the Australian mining sector generated 620 million tonnes of waste, a substantial increase from the 502 million tonnes generated in 2018–2019. For this review, the focus is on two major categories of mining waste: waste rock and tailings. Waste rock is the overburden or surrounding rock that must be removed to access the mineral ore, it is generally coarse and heterogeneous with a particle size ranging from large boulders to fine sand and is typically stored in large piles near mining sites [3]. A major environmental concern related to waste rock is the presence of sulphide minerals, which can potentially generate acid mine drainage through weathering [4]. Tailings are the residual material produced after valuable minerals have been extracted from the ore through enrichment processes, resulting in a fine-grained slurry with high water content that can be classified as gravity, flotation, or leach tailings based on the extraction technique [3,4]. Approximately 96% of the processed fine waste ends up in tailings dams, which pose significant risks including water contamination and potential dam failures [5]. The sheer volume of this material with the United States mining operations producing approximately 1 billion tonnes of waste rock annually [3] and an estimated 13 billion tonnes of tailings generated globally each year [6] underscores the urgent need for sustainable management solutions.

At the same time. the global asphalt production is increasing substantially, mainly due to extensive infrastructure development initiatives and rapid urbanization happening worldwide [7]. As urban development continues to expand, the requirement for sustainable, durable and cost-effective pavement materials intensifies, establishing asphalt as the prime choice due to its inherent flexibility, durability and economic benefits [8]. Latest market analysis shows this trend as the recent demand for the asphalt indicating a consistent upward trajectory. For example, the global asphalt market was valued at USD 168.084 billion in 2024 and is projected to reach USD 247.33 billion by 2033, demonstrating a compound annual growth rate (CAGR) of 4.4% [9]. These findings are further supported by other market reports, showing similar growth rates with CAGRs ranging from approximately 4.9% to 5.1% [8,9,10,11]. The continued growth across different market analyses highlights a strong and continuing demand for asphalt, thereby highlighting the critical need to identify and develop alternative sustainable sources of materials for its production. The increasing world population and the continued expansion of urban areas directly contribute to demand for improve and expanded road network. This demand necessitates a large volume of asphalt materials, making the exploration of sustainable alternatives such as waste rock and tailings as increasingly important objective. The flexible pavement heavily relies on natural aggregates, which normally constitute around 90-95% of the total mixture weight [12]. These natural aggregates are finite and non-renewable; additionally, the continuously growing demand for road infrastructure poses a significant threat to their long-term availability. The quantity of aggregates required is substantial; for a single kilometre of bituminous mixture wearing course, the demand can exceed 15,000 tonnes [13]. The depletion of readily available natural aggregates has several consequences, including higher costs and environmental impacts associated with their extraction and processing from quarries. Similarly, asphalt binder, which is a critical component in flexible pavement that binds the aggregates together, is primarily obtained from petroleum, another finite and non-renewable source [12,13]. Petroleum reserves are depleting day by day, raising economic and environmental challenges for the long-term sustainability of traditional asphalt production. Furthermore, asphalt binder is inherently susceptible to ageing due oxidation, exposure to ultraviolet radiation and temperature fluctuations [14]. The finite, non-renewable nature and depletion of aggregates and bitumen, combined with environmental and performance limitations of bitumen compel researchers to investigate and implement alternative and sustainable materials in flexible pavement.

This paper aims to provide a critical review of the existing body of literature available regarding the utilization of waste rock and tailings in asphalt pavement. Specifically, it seeks to address the following key research question: “What are the impacts of incorporating waste rock and tailings as partial or full replacements in flexible pavement on their rheological, mechanical, durability, environmental and economic performance?”.

2. Methodology and Bibliometric Analysis

A systematic literature search has been conducted to identify the relevant research papers relating to utilization of mining waste rock and tailings in the flexible pavement. The research methodology as illustrated in Figure 1, aims to ensure a transparent and reproducible search and selection protocol. They primary databases used are Scopus and Web of Science. Additionally, google scholar was also researched to confirm broader analysis of available literature. The search method used specific keywords related to both mining waste and asphalt to ensure a comprehensive retrieval of existing studies. The primary keywords used include “mining waste”, “bitumen”, “asphalt binder” and “asphalt mixture”. However, to ensure a comprehensive search, synonyms and related terms such as “mine tailings”, “copper tailings”, “iron tailings” and “mine waste” were also identified and considered. Based on the established best practices for effective search Boolean functions “AND” and “OR” were used to capture wide range of relevant literature. A two-stage screening process (title/abstract and full-text) was performed to select articles for the final review. This screening was guided by strict criteria: to be included, studies had to investigate the application of mining waste (tailings or waste rock) as a component in bituminous binders or asphalt mixtures, include empirical data from laboratory or field tests evaluating the material's rheological, mechanical, durability, or environmental performance, be available in English, and have a publication date between January 1, 2010, and April 28, 2025. Conversely, articles were excluded if they focused on non-asphalt applications (e.g., concrete, unbound base layers, soil stabilization), were review or conceptual papers lacking original experimental data, or exclusively characterized mining waste without assessing its performance in asphalt. Following the application of these criteria, a final dataset of 41 articles was selected for detailed analysis.

A descriptive and bibliometric analysis was subsequently conducted using the Bibliometrix R-package [15]. This analysis provides insights into publication trends, the geographical distribution of research, and the key journals and collaborative networks driving the field. The annual publication output reveals a growing academic interest in the utilization of mining waste in asphalt pavements, particularly over the last decade. As shown in Figure 2, the number of publications has followed a distinct upward trend. This increased research focus can be attributed to the growing emphasis on the circular economy and the pursuit of sustainable development goals within the construction industry. The analysis indicates that research activity has entered an exponential growth phase in recent years, peaking in 2024 with 9 publications, followed by a strong showing in 2022 with 7 publications. This recent surge underscores the topic's increasing relevance and the ongoing efforts by the scientific community to find viable, evidence-based solutions for mining waste.

To understand the global research landscape, an analysis of the geographical distribution of publications was performed based on the affiliations of the contributing authors. Figure 3 provides a world map illustrating the countries with the highest research output in this domain. The analysis of author affiliations reveals that a few countries lead the research effort. China is the most significant contributor, with its institutions affiliated with 40 publications in the dataset. This is followed by substantial contributions from Brazil (11), Malaysia (8), India (7), and Australia (6). Note that the sum of frequencies exceeds the total number of articles (41) because single publications can have co-authors from multiple countries. The dominant role of these nations likely reflects their large-scale mining industries, which generate significant quantities of waste and create a strong impetus for research into value-added recycling solutions. The wide geographical spread highlights the global nature of the challenge posed by mining waste and the universal interest in developing sustainable construction materials.

The intellectual structure of a research field can be mapped by analysing its primary publication venues and the collaborative networks between institutions. Figure 4 identifies the most impactful journals based on publication volume. The Construction and Building Materials journal, is the premier venue for this research, having published 8 articles during the examined period of time. It focuses mostly on the properties and applications of construction materials, which makes it an ideal outlet. The second most prominent is the Journal of Cleaner Production (4 articles), which signals the strong sustainability driver underpinning this research area. Other key outlets like the Journal of Materials in Civil Engineering (3 articles) and the International Journal of Pavement Engineering (2 articles) confirm that this topic is of high interest to the core civil and pavement engineering communities.

To provide a highly detailed view of the field’s structure, a three-field Sankey diagram was generated (Figure 5). This diagram visualizes the flow of knowledge between three key bibliometric dimensions: research institutions (left field: AU_UN), their respective countries (middle field: AU_CO), and the publication sources (right field: SO). The height of each dimension is proportional to the frequency of occurrence, while the width of the connecting flows illustrates the strength of the relationship. The diagram reveals a leading research ecosystem centred in China (frequency = 47), where a powerful knowledge flow originates from a cluster of highly productive institutions like Changan University (frequency = 47) and Shijiazhuang Tiedao University (frequency = 13). This flow is then predominantly channelled through the "China" node and converges on the journal Construction and Building Materials, indicating a highly active and centralized national research program. Furthermore, the diagram highlights secondary research hubs, with significant, though smaller, flows from institutions in Brazil (frequency = 19), Malaysia (frequency = 8), India (frequency = 12) and Australia (frequency = 6), which are channelled into other top-tier journals. By mapping institutional output to specific publication venues, the diagram effectively outlines the intellectual structure and key distribution channels within the field, providing a clear picture of the global research environment.

3. Utilization of Mining Waste in Flexible Pavement

Incorporating mining waste into the road construction industry offers a highly promising and sustainable approach to addressing environmental challenges while simultaneously enhancing pavement performance. The utilization of mining by-products not only helps reduce the environmental impact associated with the disposal of such waste but also promotes resource efficiency by repurposing materials that would otherwise contribute to land degradation and pollution. Numerous previous studies have demonstrated that integrating various types of mining waste into flexible pavement mixtures can significantly improve key engineering properties. For example, research has reported notable improvements in rutting resistance, which enhances the pavement’s ability to withstand permanent deformation under heavy traffic loads [16,17]. Additionally, the inclusion of mining waste has been shown to increase cracking resistance, thereby extending the lifespan of the pavement by minimizing surface distress and fatigue cracking [18]. Fatigue resistance itself, a critical factor for pavement durability under repeated loading, is also enhanced through this practice [19]. Furthermore, mining waste incorporation improves moisture susceptibility, reducing the potential for water-induced damage that can weaken pavement structures [20]. Studies also highlight increases in stiffness, which contributes to load distribution efficiency and structural integrity, ensuring long-term serviceability and reduced maintenance needs [21,22,23]. Collectively, these findings suggest that mining waste can play a vital role in developing more sustainable, resilient, and cost-effective road infrastructures. Several types of mining waste have been used in the previous studies to improve the properties of the flexible pavement, including Iron tailing [23,24,25,26,27,28,29,30,31,32,33], Copper tailings [34,35,36,37,38,39,40], Phosphate mine waste rocks [41], Tungsten mine tailings [42], Aluminum tailing slurry (ATS) [43], Quartzite waste [22], Nickel & Cobalt tailings [21] Iron ore overburden (IOO) [44], Manganese ore tailings [45], and Taconite [46].

3.1. Mining-Waste Types, Characteristics & Roles

Different types of mining wastes have been evaluated for use in flexible pavements, each with distinctive characteristics affecting their application. Byproducts of mineral extraction and processing vary significantly in their physical and chemical properties. Understanding these properties is critical to evaluate their suitability in asphalt pavement, as a coarse or fine aggregates, mineral fillers, or binder modifiers. Table 1 summarizes the main characteristics and typical uses of key mining waste types.

Iron tailings (IT) a common byproduct of iron ore processing, are extensively studied, and typically consist of fine-grained materials rich in silica (SiO₂) and iron oxide (Fe₂O₃). Their particle size often makes them suitable as a mineral filler in asphalt mastic or a partial replacement for fine or coarse aggregate in asphalt mixtures. The angularity of IT particles can enhance inter-particle friction and mixture stability, while their iron oxide content can improve microwave heating efficiency for self-healing applications. However, the often-acidic character due to high SiO₂ content can sometimes cause adhesion concerns with asphalt binder if not appropriately addressed. For instance, Cui et al. [24] noted that IT, mainly quartz, exhibited rich angularity leading to higher interaction with asphalt, despite having lower adhesion energy than limestone. Wei et al. [23] reported that iron ore tailing (IOT) has smaller particles and a larger specific surface area than limestone filler (LF), enhancing asphalt mastic stiffness. However, IOT's higher hydrophilic coefficient and more acidic nature might result in poorer adhesion with asphalt compared to LF. Cao et al. [25] highlighted weak adhesion due to acidic chemical compositions of iron tailings. The presence of iron oxides is particularly beneficial for relevance involving microwave or induction heating, such as pavement de-icing or encouraging self-healing properties in asphalt [26,27].

Copper Tailings (CT) are another frequently explored fine-grained waste, mainly composed of silica, with varying amounts of other metal oxides (e.g., Al₂O₃, Fe₂O₃, CaO) depending on the ore source. CT has been primarily evaluated as a mineral filler in asphalt concrete and mastic [34,35,38]. Its fineness and particle characteristics, such as a rough surface and often higher specific surface area compared to conventional limestone powder, can influence asphalt adsorption and mastic stiffening [38]. This typically results in improved high-temperature performance of the asphalt mixture. Some studies note that the high silica content in CT might negatively affect moisture resistance, a common concern with siliceous materials in asphalt [34,35]. Other mining-related wastes include iron ore overburden, nickel and cobalt tailings, manganese ore tailings, Quartzite waste, Aluminium tailing slurry, Coal Gangue Powder (CGP), Tungsten mine tailings, and taconite. These materials vary widely in their chemical and physical properties, influencing their suitability and role in asphalt mixture.

The data presented in Table 1 clearly demonstrate the considerable variability in the properties of different secondary materials derived from mining waste. This variability underscores the critical need for thorough and specific characterization of each individual batch or source prior to its incorporation into asphalt mixtures. Since mining waste materials can differ widely depending on their origin, mineral composition, and processing methods, assuming uniform behaviour across different sources can lead to inconsistent pavement performance and durability [18,19,20].

A key factor influencing the performance of these materials in asphalt mixtures is their chemical composition, particularly the content of acidic or alkaline oxides. These chemical constituents play a significant role in determining the nature of the interaction between the binder and the waste material. For instance, the presence of certain oxides can affect the adhesion properties of the binder, as well as the overall moisture susceptibility of the pavement. Moisture damage is a common cause of premature pavement failure, so understanding and controlling the chemical characteristics of mining waste is vital to enhancing durability.

In addition to chemical factors, the physical properties of mining waste, such as particle size distribution, particle shape, surface texture, and specific gravity have a direct and profound impact on both the volumetric design and mechanical behaviour of the asphalt mixture. For example, particle size distribution influences the compatibility and density of the mix, while particle shape and texture affect the internal friction and bonding within the pavement structure. Specific gravity, in turn, affects the calculation of volumetric proportions and ultimately the stability and load-bearing capacity of the finished pavement.

The intended role of the mining waste within the asphalt mixture whether as a filler, fine aggregate, or coarse aggregate is typically dictated by these intrinsic physical and chemical characteristics. Proper classification ensures that the waste material is utilized in a manner that maximizes its benefits and minimizes potential drawbacks. Therefore, a comprehensive evaluation that includes both chemical and physical testing is essential for optimizing the use of mining waste in road construction, thereby improving performance, sustainability, and cost-effectiveness.

3.2. Mining Waste Utilisation Methods & Performance Benefits

Mining wastes have been effectively incorporated into flexible pavements either as full or partial aggregate replacements or as mineral fillers, with optimal dosages determined by specific performance requirements. Quartzite waste employed at 100 % replacement yields mixtures of increased stiffness [22], while phosphate mine waste, although technically viable at 100 %, exhibits weak binder–aggregate adhesion and brittleness that limit its optimal content to ≤ 40 % [41]. Iron ore overburden can fully substitute conventional aggregate without compromising mechanical properties or environmental safety ([44]), whereas iron ore waste at 17 and 20 % replacement satisfies medium-traffic criteria [48]. Iron tailings, when used as aggregate up to 100 %, require modifiers such as hydrated lime or silane coupling agents to mitigate low-temperature cracking and moisture sensitivity [25]. As fillers in asphalt mastic, iron tailings replacing 20–100 % of traditional filler enhance microwave heating and self-healing but may weaken high-temperature rheology and fatigue resistance unless coupling agents are added [23,24,27,28]. Copper tailings powder, applied at binder–powder ratios of 0.3–1.2 or replacing up to 100 % of limestone filler, improves rutting resistance, though high substitution levels can degrade low-temperature cracking and moisture performance [34,38].

Table 2 provides a comprehensive summary of previous studies investigating the performance of flexible pavements incorporating various types of mining waste. The table details critical aspects of each study, including the methods of waste utilization, percentage of material replacement, type of asphalt binder used, key performance outcomes, and the identified optimum content levels. This compilation offers valuable insights into how different mining waste materials influence pavement behaviour under diverse conditions. A recurring finding across these studies is the enhancement of high-temperature performance properties particularly rutting resistance and stiffness when mining waste is incorporated into the asphalt mix. This improvement is largely attributed to the rigid and angular nature of many mining by-products, which can increase the structural integrity of the pavement and reduce permanent deformation under heavy traffic loads. In many cases, the inclusion of mining waste acts to reinforce the mix matrix, thereby improving its load-bearing capacity and resistance to shear forces at elevated temperatures.

However, the influence of mining waste on other critical pavement properties, such as low-temperature cracking resistance, fatigue performance, and moisture susceptibility, appears to be more variable. These performance aspects are highly sensitive to several interrelated factors, including the mineralogical and chemical composition of the waste, particle size and shape, the dosage used, and the presence or absence of additional modifiers (e.g., polymers, anti-stripping agents, rejuvenators). For instance, some wastes may contribute positively to fatigue resistance by enhancing binder aggregate bonding, while others may cause embrittlement or reduce flexibility, leading to premature cracking under repeated loading or thermal stress. Moisture susceptibility is another area where results diverge. Certain mining wastes, particularly those with high levels of hydrophilic compounds or poor adhesion characteristics, can increase the likelihood of moisture-induced damage such as stripping. Conversely, when appropriately treated or combined with adhesion promoters, these materials can actually improve moisture resistance.

Therefore, while the overall trend points toward the potential benefits of using mining waste in flexible pavement construction especially in terms of high-temperature performance caution must be taken in evaluating and optimizing mix designs for other performance criteria. A case-by-case approach, supported by laboratory testing and performance modelling, is essential to ensure that the selected mining waste type and dosage deliver the desired outcomes without introducing new risks. Additionally, the use of performance-enhancing additives may be necessary in some cases to mitigate adverse effects and fully realize the benefits of mining waste incorporation.

Several knowledge gaps persist in the literature. While many studies focus on the initial mechanical properties, there is often limited investigation into the long-term performance and durability of pavements incorporating these wastes, including aspects like aging effects of the modified binders and mixtures. Calandra et al. [45] noted an anti-aging effect with Manganese ore tailings, but this is not universally studied for all waste types. Environmental impact assessments, particularly comprehensive leaching studies beyond initial TCLP tests, are not consistently reported for all waste types to ensure long-term environmental safety. Limited number of studies provided some leaching data; more extensive research is crucial for confirming long-term environmental safety. Investigations by Guo et al. [34], Shamsi & Zakerinejad [44], Qin et al.[43] , Wei et al. [23] and Lei et al. [38], among others, indicate that asphalt effectively immobilizes heavy metals from incorporated wastes, with leachate concentrations remaining far below regulatory limits. However, these findings rely on short-term laboratory tests. A strong argument for further research is that these methods fail to account for the cumulative effects of real-world, long-term exposure to weathering, freeze-thaw cycles, and varying pH over a pavement's full-service life. Therefore, comprehensive studies simulating these conditions are necessary to definitively assess the long-term leaching risk. Furthermore, while some studies like Guo et al. [34], Li et al. [27], Qin et al. [43], Shamsi & Zakerinejad [44] and Wei et al. [42] provide cost-benefit analyses, more widespread economic feasibility studies considering transportation, processing, and long-term maintenance costs are needed to promote practical adoption. Inconsistencies in optimal dosages and performance outcomes across different studies for similar waste types (e.g., iron tailings) suggest that the specific physical and chemical properties of the waste, which can vary significantly by source, play a critical role and require detailed characterization in each case.

4. Impact of Mining Waste on Asphalt Performance

4.1. Rutting Resistance

Rutting resistance is defined as the ability of a pavement to resist the permanent deformation due to repeated loading at high temperature. Rutting is commonly quantified via Dynamic Shear Rheometer (DSR) rutting factor (|G*|/sin δ), Multiple Stress Creep Recovery (MSCR) parameters (non-recoverable creep compliance Jnr and percent recovery R), dynamic stability (wheel-tracking tests), or cumulative permanent deformation (PDA) under cyclic loads. Across a variety of mining wastes, the combination of angular particle morphology, high specific surface area, and surface roughness generally yields improved rutting performance by stiffening the binder and enhancing aggregate interlock [22,28,34,43]. Various studies have particularly investigated the high temperature rutting resistance of the asphalt mastic by using mining wastes. Wang et al. [47] examined the coal gangue powder (CGP) as a filler in asphalt mastic at different asphalt to filler ratios using MSCR tests at 64°C, they reported that CGP modified mastic demonstrated lower non recoverable creep compliance Jnr than limestone mastics, reaching a PG 70E grade after RTFOT aging. S. Li et al. [28] investigated asphalt mastic in which limestone filler was replaced 20% to 100% by iron tailing (IT), raw IT increased Jnr and reduce recovery, highlighting weaker rutting resistance but the addition of 1.5% silane coupling agent fully resorted Jnr and recovery to levels matching limestone mastics, indicating complete mitigation of IT negative effects. Lei et al. [38], the evaluate copper-tailings-filled asphalt mastics at for ratios from 0.3 to 0.4. They found that replacing limestone filler with copper tailings boosted the complex modulus |G*| by 35–65 %* at identical filler-to-asphalt ratios, and raised |G*|/sin δ, though the relative improvement gradually declined as filler content increased, demonstrating markedly enhanced resistance to permanent deformation due to copper tailing finer particles, larger surface area and rougher texture strengthening the filler–binder network. Finally, Qin et al. [43] explored aluminium tailing slurry (ATS) as a binder modifier, finding that DSR temperature sweeps (40–76 °C) revealed progressive increases in rutting factor (G*/sin δ) with higher ATS dosages, and MSCR tests at 54 °C showed that a 9% ATS dosage reduced Jnr by 26% and 27.3 % while boosting recovery by about 43.3% and 34.5% at 0.1 and 3.2 kPa respectively, confirming significant enhancement in rutting resistance.

In asphalt mixtures, recycled mining wastes likewise yield notable improvements in rutting performance, as shown in Table 3. Guo et al. [34] developed self-sensing asphalt concretes by substituting limestone filler with up to 50% copper tailings (CT) and adding 0.3% conductive carbon fibre (CF); wheel-tracking tests at 60 °C demonstrated dynamic stability exceeding 4500 passes/mm surpassing control mixtures and meeting high-temperature criteria while maintaining moisture susceptibility and low-temperature performance. Mendonça et al. [22] assessed dense-graded mixtures using isotropic (IAM) and foliated (FAM) quartzite wastes as aggregates, MeDiNa simulations predicted rut depths below 6 mm under 1 × 10⁶ and 5 × 10⁶ ESALs which is well under the 20 mm maximum permissible deformation, demonstrating satisfactory rutting resistance. Xue et al. [26] explored microwave maintenance technology with iron tailings as aggregate, where high-temperature dynamic stability tests on specimens prepared with 4.75–13.2 mm iron tailings showed raised high-temperature dynamic stability by 16.6% than basalt mixture and that microwave maintenance uniformly heated the surface above 126 °C within 2 min.

Table 3 presents a detailed overview of the rutting performance observed in flexible pavements modified with various types of mining waste. Rutting, a form of permanent deformation typically occurring under high temperatures and repeated loading, is a major distress mechanism that affects pavement service life and user safety. The studies summarized in the table 3 evaluate how the inclusion of mining waste used as filler, fine aggregate, or coarse aggregate impacts the resistance of asphalt mixtures to rutting. A consistent finding across the reviewed studies is the enhancement of rutting resistance when mining waste is incorporated into the asphalt mix, particularly at optimal replacement levels. This improvement is often attributed to the angular shape, rough texture, and high hardness of many mining by-products, which increase internal friction and interlocking within the mix matrix. In addition, some mining wastes contribute to the stiffening of the asphalt binder or matrix, further reducing the susceptibility of the mix to deformation under heavy traffic loads.

For instance, the use of copper slag and iron tailings s both rich in hard minerals and with angular particle shapes demonstrated significant improvements in dynamic stability and wheel tracking test results. Similarly, iron ore tailings when finely ground and properly blended, acted as performance-enhancing fillers that improved the rigidity and rutting resistance of asphalt mixtures. In several cases, the studies identified an optimum replacement percentage (typically ranging from 10% to 30% by weight of aggregate or filler) beyond which performance gains plateaued or began to decline due to issues such as brittleness or poor workability. Overall, the evidence presented in Table 3 highlights the potential of mining waste to enhance the high-temperature performance of asphalt pavements. However, achieving optimal rutting resistance requires careful consideration of material characteristics, mix design parameters, and field performance testing to ensure the structural and functional integrity of the pavement over time.

4.2. Fatigue Resistance

Fatigue cracking is a principal distress type in asphalt pavements under repetitive traffic loading. Fatigue resistance is typically investigated at the binder level using time sweep, Linear Amplitude Sweep (LAS) and at the mixture level using indirect-tensile (IDT) fatigue tests or mechanistic empirical simulations (e.g., MeDiNa). Mining wastes such as iron tailings (IT), copper tailing, and other mining waste have been evaluated for their effect on both mastic and mixture fatigue life, with results highlighting that when properly dosed and treated, these by-products can meet or even enhance the fatigue performance [24,28,29,45].

At the mastic level, Cui et al. [24] examined the use of iron tailings (IT) as partial replacements for limestone filler in asphalt mastic. Using Dynamic Shear Rheometer based Linear Amplitude Sweep (LAS) tests at 20 °C under strains of 2.5 %, 5 %, and 7.5 %, they found that the finest IT delivered an Nf@5 % of ≈ 1.09×10⁷ cycles, closely approaching the 1.34×10⁷ cycles achieved by limestone mastics. Gray correlation analysis revealed that both interfacial adhesion energy and interaction ability of asphalt with mineral filler (each correlating ≈ 0.58 with fatigue life) jointly govern mastic durability, suggesting that tailoring IT surface chemistry and morphology is essential for optimizing fatigue resistance. Building on this, S. Li et al. [28] investigated mastics with 20–100 % iron-tailings filler replacing limestone, both unmodified and treated with 1.5 % silane coupling agent (SCA). In unmodified mastics, fatigue life Nf dropped by about 7.1 % at 2.5 % strain and 15.5 % at 5.0 % strain compared to limestone controls, whereas SCA treatment not only restored Nf to near control levels and for the 80 % IT mastic even improved it by enhancing the binder filler adhesion. Wang et al. [47] compared coal gangue powder (CGP), limestone, and cement fillers in emulsified mastics, CGP mastics shows lower fatigue resistance than limestone controls, unaged CGP mastics at powder-to-binder (P/B) ratios of 0.9, 1.2, and 1.5 showed fatigue-life drops of 50.8 %, 21.1 %, and 8.2 % at 2.5 % strain, respectively, and after RTFOT aging at 5 % strain, fatigue life fell by 47.7 % (P/B = 0.6) and 40.4 % (P/B = 1.5). Calandra et al. [45] found that incorporating up to 10 % w/w Mn tailings into bitumen increase the fatigue parameter (G*·sin δ) as compared to the control binder which indicate lower fatigue resistance.

Table 4 shows the fatigue properties of several studies. At the mixture level, de Moraes et al. [29] replaced fine aggregate with iron ore tailing with different percentage (7.5%, 10%, and 12.5%) in hot-mix asphalt, they found that all IT modified mixtures produced strong Wöhler (S–N) curves with R² > 0.80. At low stress amplitudes, the 7.5 % and 10 % IoT mixes outperformed the control in cycles to failure, while at higher stresses the control and 12.5 % IT mixes were superior. Overall, the 12.5 % IoT blend exhibited the longest fatigue life across all stress levels, reflecting its greater stiffness and resistance to cyclic damage. Mendonça et al. [22] evaluated mixtures fully substituting aggregate with isotropic or foliated quartzite waste. Foliated-quartzite mixture (FAM) consistently endured more load cycles to failure than the isotropic-quartzite mixture (IAM), with both achieving R2 > 0.8. Furthermore, Brazilian mechanistic empirical pavement simulations using MeDiNa predicted that both mixtures would keep fatigue crack area below 30 % and rutting under 20 mm for up to 5×10⁶ equivalent axle loads, indicating they meet design criteria for medium-heavy traffic. Guimarães et al. [48] examined the utilization of iron ore waste as a fine aggregate replacement at 17% and 20% replacement, the results shows that 20 % iron-ore processing waste (Mixture 2) slightly reduced fatigue life and its S–N slope was steeper and it dropped to Fatigue Class 0 while the mixture with 17 % waste plus 8 % sand (Mixture 3) not only matched the control’s Fatigue Class 1 but exhibited marginally higher fatigue life constant values. In other words, up to 17 % mining waste can be used without harming and may even modestly improve fatigue resistance, whereas a full 20 % replacement leads to a modest decline.

Collectively, all these studies as shown in Table 4 are covering binder-level to mixture level demonstrate that mining wastes, if properly processed, dosed, and surface-treated, can maintain or even enhance fatigue resistance in asphalt mastics and mixtures. Critical parameters include filler/aggregate content, particle size and morphology, interfacial adhesion (boosted by coupling agents), and optimal powder-to-binder ratios. By carefully engineering these variables, sustainable incorporation of mining by-products into asphalt pavements can be achieved without compromising fatigue life.

4.3. Moisture Susceptibility

Moisture susceptibility is one of the fundamental distress mechanisms in asphalt pavements, caused by weakening of the adhesive bond between binder and aggregate under water exposure. It is typically investigated by Marshall stability ratio (MSR) from water immersion Marshall tests, the freeze–thaw splitting tensile strength ratio (TSR), or indirect tensile strength ratio after conditioning. A minimum MSR or TSR of 80 % (or 70 -75 % for some specifications) is typically required for satisfactory moisture resistance [25,33,34].

Table 5 shows the moisture susceptibility of mining waste in previous studies. Lei et al. [38] investigated bond strength (after waste immersion) of copper-tailings in the asphalt mastic. The traditional limestone filler was replaced with copper tailing at a filler to asphalt ratios of 0.3,0.6,0.9, and 1.2. They observed that copper-tailing mastics displays decline in bond-strength under water compared to limestone mastics but still exhibits limited reduction in moisture stability. Copper tailings in asphalt mastic shows acceptable moisture durability, particularly at lower filler content (F/A ≈ 0.6) because higher tailings contents increase the moisture damage. Guo et al. [34] found that replacing limestone filler with 50 % copper tailings (CT) in asphalt mixture, produced MSR values exceeding 80 % and freeze–thaw TSR above 85 %, meeting specification requirements. However, CT substitution dosage of 75 % and 100 % fell below this standard threshold, demonstrating lower moisture resistance at high CT contents. Xue et al. [26] evaluated SMA-13 mixtures replacing basalt aggregate with iron tailings of various particle size, water-immersion MSR ranged from 88.54 % to 92.83 % (basalt control = 94.78 %), and freeze–thaw TSR from 80.65 % to 84.55 % (control = 87.69 %), all above typical 80 % thresholds. All iron tailings showed satisfactory performance and meet the standard requirement against moisture resistance and can be used as aggregate replacement in the asphalt pavement, despite having modest reduced performance compared to basalt (control). Mendonça et al. [22] evaluated asphalt mixtures using isotropic (IAM) and foliated (FAM) quartzite waste aggregates, both IAM and FAM exceeded minimum tensile strength requirements after freeze–thaw conditioning, demonstrating that quartzite waste does not affect the moisture susceptibility. Ullah et al. [33] similarly highlight that conductive asphalt concretes incorporating iron tailings as 25% replacement to natural aggregate. All tailing mixtures with carbon fibre (CF) up to 0.6 % easily surpass the 75 % TSR requirement, indicating satisfactory moisture susceptibility. while at 0.8 % CF, moisture resistance collapses, with TSR value of 26% far below specification.

5. Environmental Impacts of Mining-Waste Use in Flexible Pavements

The growing interest in using the mining waste as alternative materials in asphalt pavement come from two critical points, addressing the increasing challenges of huge mining waste and reducing the dependence on rapidly decreasing conventional construction resources. Although, the engineering feasibility and performance benefits of utilizing waste materials such as iron tailing, copper tailing, aluminium slurry, iron ore overburden and others into asphalt are thoroughly evaluated. However, a detailed analysis of their environmental impact is uppermost important. Environmental assessment is critical to validate that these innovative methods outcome genuinely sustainable solutions, lower the potential ecological damage, for instance the release of toxic substances or increased carbon footprint, and aligning with circular economy principles [34,38,44].

5.1. Leaching & Toxicity Potential

A substantial environmental concern correlated with the incorporation of mining wastes in construction industry is the potential for leaching of heavy metals and other toxic substances into the surrounding soil and groundwater. Therefore, many of the evaluated studies placed a strong importance on assessing this risk. The most common method used for this evaluation was the Toxicity Characteristic Leaching Procedure (TCLP), as employed by Guo et al. [34] for copper tailings (CT) in self-sensing asphalt , Shamsi & Zakerinejad [44] for iron ore overburden (IOO) in HMA, Qin et al. [43] for aluminum tailing slurry (ATS) modified asphalt, Oluwasola et al. [54] for EAF steel slag and copper mine tailings mixes, and Wei et al. [23] for iron ore tailing (IOT) filler in asphalt mastic. Lei et al. [38] also used TCLP for copper tailings powder (CTP) in asphalt mastic, expand it with acid digestion tests on the raw CTP to comprehend baseline hazardous content.

The pollutants of major concern among these studies were heavy metals such as Chromium (Cr), Cadmium (Cd), Lead (Pb), Copper (Cu), Zinc (Zn), Barium (Ba), Nickel (Ni), and Cobalt (Co) [23,34,38,43,44,54]. The results from these leaching tests were constantly positive, demonstrating that the asphalt binder plays a critical role in capturing and immobilizing these potentially hazardous substances. For example, Guo et al. [34] found that heavy metal leaching from CT-asphalt concrete were "far below the strict regulatory limit value as class I groundwater." Shamsi & Zakerinejad [44] stated that although raw IOO may have leachable pollutants, the HMA integrating IOO demonstrated substantially lower concentrations, well within safe limits, indicating bitumen assists in solidification/stabilization. Similarly, Qin et al. [43] reported that ATS-modified asphalt had a “very low pollution risk”. Oluwasola et al. [54] also concluded that for mixture with EAF steel slag and copper mine tailings, the concentrations of identified heavy metals in TCLP test did not go over standard limits. Wei et al. [23] and Lei et al. [38] reported similar findings for IOT and CTP in asphalt mastics, respectively, with metal concentrations being “far below the limitations in the specification”, proving a low contamination risk. Lei et al. [38] further noted that even under higher temperature (70°C) leaching tests, most metal concentrations remained low, emphasizing the effective immobilization by the asphalt. Table 6 summarizes the heavy metal leaching findings from the papers that conducted relevant tests. The concentrations are generally for the final asphalt product (mixture or mastic) where available, as this is most relevant to in-service environmental impact.

A comprehensive review of studies [21,23,32,39,54,59] that employed leaching tests indicates that mining wastes, when incorporated into asphalt mixtures or asphalt mastic, generally pose a low environmental risk in terms of leachability. This low leaching potential is primarily attributed to the effective encapsulation of the waste particles by the bitumen binder. Bitumen acts as a hydrophobic and impermeable matrix, which significantly restricts the mobility of potentially hazardous elements such as heavy metals commonly found in certain types of mining waste. The physical and chemical interaction between the binder and the waste materials helps immobilize contaminants, preventing their release into the surrounding environment, particularly under typical in-service conditions. Multiple studies as shown in Table 6 have demonstrated that even under simulated aggressive environmental scenarios, such as prolonged exposure to water or acidic solutions, the release of harmful substances remains well below regulatory limits. This suggests that asphalt mixtures can serve as an effective containment medium for certain classes of industrial and mining by-products. Moreover, the encapsulation mechanism not only supports environmental safety but also aligns with the principles of sustainable construction and circular economy by enabling the reuse of waste materials in infrastructure applications. However, it is important to note that the leaching behaviour can vary depending on the specific chemical composition of the mining waste, the particle size, and the degree of dispersion within the asphalt matrix. Therefore, site specific and material-specific leaching assessments remain essential prior to large scale application to ensure long-term environmental compliance.

In summary, the findings from leaching studies support the environmental suitability of using mining waste in asphalt pavements. When properly processed and incorporated, these materials offer a safe and effective means of recycling industrial by-products, contributing to both environmental protection and resource efficiency.

5.2. Greenhouse-Gas Emissions

One of the critical factors to determine the environmental sustainability of the mining waste in the flexible pavement is investigation of greenhouse gas (GHG) emissions. The emissions of GHG emission can be reduced by decreasing energy consumption during processing and transporting of alternative materials compared to virgin ones, and preventing emissions related with disposal by diverting waste from landfills. Among the reviewed literature, Choudhary et al. investigate the direct evaluation of Global warming potential (GWP) for asphalt mixture using several types of fillers, including copper tailing (CT). They found out that the utilization of CT as filler could result in 6% reduction in GWP for the wearing course of the flexible pavement as compared to a virgin mixture with stone dust. This reduction was due to lower GWP linked with production/availability of CT and reduced requirements for conventional aggregate [37].

Various papers indirectly highlight that utilizing mining waste into asphalt can decrease the GHG emissions. For example, enhanced microwave dicing of IOO modified HMA [44] and resources saving by use of IT [23,24,25,28], CT [34,37,38], other mining waste [43], indicate lower energy requirements for quarrying, crushing, and transport. However, none of these studies investigated the GHG reduction via LCA or direct emissions measurements. Where GWP evaluated [37], it depends on the material quantity calculations and generic emissions factors. Overall, the literature lacks GHG emission evaluation during production stage for waste modified asphalt, variations in waste processing, transport distances, and replaced virgin materials. Future research should undertake comparative LCAs to thoroughly calculate the environmental advantages of mining-waste substitution.

The collective outcomes from the reviewed literature strongly support the environmental benefits of employing a various mining waste in flexible pavements, mostly through significant resource conservation and effective waste diversion [23,24,25,28]. A reliable conclusion across multiple studies using TCLP tests is the effective immobilization of potentially hazardous heavy metals by the asphalt binder, resulting in leachates that generally meet environmental quality standards [23,34,38,43,44,54]. However, a considerable knowledge gap exists in the direct quantification of greenhouse gas emissions. Furthermore, comprehensive Life-Cycle Assessments (LCAs) covering a wide array of impact categories and system boundaries are especially not reported in the literature, hindering a truly holistic environmental evaluation with conventional materials. Future research should prioritize conducting detailed LCAs for various mining-waste-modified asphalts and develop standardized protocols for GHG emission accounting to vigorously validate and promote these materials as sustainable alternatives in pavement engineering.

6. Economic Impacts of Mining-Waste Use in Flexible Pavements

Evaluating the economic impact of utilizing mining waste into flexible pavements is critical for defining the overall viability and encouraging sustainable practices in road construction industry. Beyond core aim of waste valorisation and decreasing the dependence on conventional materials, the economic analysis provides critical information for decision makers, including government institutions, private organizations, and investors. These evaluations quantify direct cost savings from material substitution, investigate potential long term financial benefits using lifecycle cost analyses (LCCA), and consider wider economic effects such as local job creation and decreasing landfill pressure [23,44]. Justifying these economic factors is vital to overcome initial resistance, justify new technology investments, and ensure mining-waste-modified asphalt is both eco-friendly and cost-effective [25,28].

The potential for cost savings is a main driver for investigating the consumption of mining waste in asphalt pavements. Several studies have emphasised direct cost saving by replacing conventional materials like limestone filler or conventional aggregates with mining wastes, which are usually available at a lower cost or even free of charge. For example, the use of iron ore tailings (IOT) as a filler can led to considerable economic benefits due to the low cost of IOT[23]. Similarly, aluminum tailing slurry (ATS) as an asphalt modifier provides significant economic benefits [43]. Cui et al. [24] note that iron tailings are significantly cheaper than limestone, approximately one-quarter of the price, which can lead to substantial cost reductions in pavement maintenance and construction. Qin et al. [43] performed a cost-benefit analysis (CBA) for aluminum tailing slurry (ATS) modified asphalt and found that its application is profitable (BCR of 1.19), with benefits coming from the low cost of ATS and savings on other modifiers. Similarly, Wei et al. (2022) conducted a cost analysis for asphalt mastic incorporating iron ore tailing (IOT) and found considerable economic benefits (BCR >1) arising from savings in LF purchase, IOT disposal costs, and transportation if IOT sources are near processing plants. Shamsi & Zakerinejad [44] performed a cost–benefit analysis of hot-mix asphalt using iron-ore overburden (IOO) residues and found that, for large-scale application across Iran, substituting IOO yields a net present-value saving of USD 926.4 million (at a 3.75 % discount rate). In their Goharzamin mine-site case study, 9.5 km of on-site pavement using local IOO residues directly saved approximately USD 960000. Choudhary et al. [37] found that surface courses made with specific waste fillers, such as limestone sludge dust (LD), copper tailing (CT), and glass powder (GP), were more economical than conventional stone dust courses, with CT mixes being up to 5% more economic. The reported cost reductions vary depending on the type of waste, replacement level, and local economic conditions (e.g., transportation costs for waste materials). Some studies focused on the cost of filler replacement in mastics or mixtures, while others assessed the overall pavement construction cost or the cost per ton of asphalt mix. Several studies employ comparative cost analysis based on material prices and transportation distances.

The overall economic feasibility of utilizing mining waste in flexible pavements is generally reported as positive, primarily due to material cost savings and environmental co-benefits. Lifecycle cost analysis (LCCA) and Quantitative ROI or specific payback periods are not commonly detailed, but metrics like NPV and BCR are used. Lei et al. [38] utilized Net Present Value (NPV) and Benefit-Cost Ratio (BCR) for copper tailings powder, finding a BCR greater than 7.4, indicating a highly favourable return over a 10-year period and confirming excellent economic feasibility. Wei et al. [23] and Li et al. [27] both utilized CBA for evaluating iron tailing-based asphalt mixtures. Shamsi & Zakerinejad [44] also employed CBA for IOO pavements, considering a ten-year return period and using Net Present Value (NPV) as an economic parameter. Qin et al. [43] conducted a cost-benefit analysis for ATS-modified asphalt. Lei et al. [38] analysed economic perspectives for copper tailings powder (CTP) in asphalt mastic, also using CBA and NPV.

The studied literature, reinforced by comparative finding in the Table 7, consistently reveals that using mining waste in flexible pavements offers tangible economic benefits, mostly through direct cost savings from material replacement. Trends show transportation costs critically influence these savings. Many studies also highlight environmental benefits that strengthen the positive economic viewpoint by reducing disposal needs. However, a significant knowledge gap remains in widespread LCCA application, most analyses focus on initial costs. The economic impacts of construction practice changes and supply chain variability for these non-traditional materials also require more research [62,63,64]. Future work should prioritize detailed LCCAs, long-term performance studies for accurate maintenance cost prediction, and developing strong supply chains for mining wastes.

7. Conclusions and Future Recommendation

This critical review has systematically synthesized and analysed the current state of research on the utilization of waste rock and tailings in asphalt pavements. The bibliometric analysis mapped the intellectual structure of the field, revealing a recent and rapid growth in research, led by institutions in countries with significant mining activity. The performance analysis demonstrates that a wide range of mining wastes can be successfully incorporated as aggregates and fillers, often enhancing key properties such as high-temperature rutting resistance.

The findings strongly support the practical potential of these materials to serve as a viable and sustainable alternative to finite virgin aggregates and fillers, thereby advancing circular economy principles within the pavement industry. The utilization of this large mining waste not only provides a solution for waste management but also reduces the environmental and economic burden of quarrying natural resources. To transition from laboratory feasibility to standard practice, future research must pivot to address the critical knowledge gaps identified. By systematically resolving these reservations, the pavement engineering community can develop the robust standards and specifications needed to confidently and responsibly integrate mining wastes into the road infrastructure of the future.

Based on the findings of this review, the following recommendations for future research are proposed to address the remaining knowledge gaps:

• Future work must move beyond short-term mechanical properties by conducting long-term field monitoring of trial pavement sections under real traffic and environmental conditions. This should be complemented by laboratory research employing advanced aging simulations, such as multi-stage Pressure Aging Vessel (PAV) protocols and ultraviolet (UV) aging, to accurately predict the evolution of mixture properties and resistance to fatigue and low-temperature cracking over a full-service life.
• A holistic understanding of the environmental and economic implications is required. This necessitates comprehensive Life-Cycle Assessments (LCA) to quantify the cradle-to-grave environmental footprint, including energy consumption and emissions. Concurrently, thorough Life-Cycle Cost Analyses (LCCA) should be performed to model the full economic impact, covering material processing, transport, construction, and long-term maintenance costs, providing asset managers with robust data for decision-making.
• To confirm the long-term efficacy of bitumen in encapsulating heavy metals, research is needed to assess leaching behaviour under dynamic and realistic environmental conditions, such as varying pH levels and repeated freeze-thaw cycles. This will build confidence in the environmental safety of using mining wastes in pavement structures.
• To address the significant variability in mining wastes from different sources, a critical research need is the development of a standardized characterization and classification protocol. This would link the mineralogical, chemical, and physical properties of wastes to their expected performance in asphalt, creating a foundation for reliable specifications. Research should also focus on developing cost-effective beneficiation techniques to homogenize waste materials for consistent performance.