Hot Mix Asphalt Research Articles

Thermal response of an asphalt solar collector: Numerical and experimental validation

This study conducts a numerical analysis and experimental validation of the thermal performance of an asphalt solar collector. Both parallel and serpentine copper tubes with a total length of 3000 mm were embedded in the middle of a 1000 × 600 × 80 mm hot mix asphalt model. The sides and bottom of the test sections were insulated to prevent heat loss to the surrounding environment. Using four values of water mass flow rate and three values of artificial solar radiation, the thermal performance of the system was examined. A mass flow inlet of 0.0038–0.035 kg/s is specified for the water inside the embedded tubes, while 600, 800, and 1000 W/m2 solar radiation is applied on the upper section of the asphalt mix during this study. The thermal response was simulated using the COMSOL Multiphysics 5.6.0.280 heat transfer module. Using a reference asphalt solar collector, the desired parameter effects were investigated independently. The experimental results showed that the efficiencies of the asphalt solar collector with serpentine bare tubes and parallel bare tubes are 53.56 % and 52.85 %, respectively. The numerical simulation reveals that there is no significant thermal effect in the area under the embedded tubes when compared to the area above the tubes that are exposed to solar radiation from above. The average error found between the numerical and experimental results for the water temperature difference inside the embedded tubes of the asphalt solar collector ranged between 6 % and 14 %. This good agreement indicated that the computational fluid dynamics model is reliable and capable of simulating the thermal response of an asphalt solar collector.

Investigating the Impact of Polymer and Portland Cement on the Crack Resistance of Half-Warm Bituminous Emulsion Mixtures

Cold mix asphalt (CMA) is emerging as an environmentally friendly alternative to traditional hot mix asphalt (HMA). It offers advantages such as lower costs, reduced energy demands, decreased environmental impacts, and improved safety aspects. Among the various types of CMA, the cold bitumen emulsion mixture (CBEM) stands out. The CBEM involves diluting bitumen through emulsification, resulting in lower bitumen viscosity. However, this process has certain drawbacks, including extended setting (curing) times, lower early strength, increased porosity, and susceptibility to moisture. This study focuses on enhancing CBEM properties through the utilization of low-energy heat techniques, such as microwave technology, and the incorporation of a polymeric additive, specifically acrylic. These innovations led to the development of a novel paving technology known as a half-warm bitumen emulsion mixture (HWBEM). The research was conducted in two phases. First, the study assessed the impact of low-energy heating on the CBEM. Subsequently, it explored the combined effects of low-energy heating and the addition of an acrylic polymer. CBEM samples containing ordinary Portland cement (OPC) as an active filler were utilized in the sample manufacturing process. The effectiveness of these techniques in enhancing crack resistance was evaluated by analysing the results of the indirect tensile strength test. Notably, CBEM samples containing an amount of 2.5% of acrylic polymer and OPC exhibited the highest resistance to cracking. Furthermore, significant improvements were observed in their volumetric and mechanical properties, comparable to those of HMA.

Determination of the Social Contribution of Sustainable Asphalt Mixes

The social contribution that infrastructure components contribute to a territory tends to be underestimated. Indeed, few studies referring to asphalt pavements take social impact into account in their evaluation. This study proposes and evaluates a method to estimate the social contribution of innovative asphalt mixes used in a test section in Chile. For this, a multi-criteria structure, the Delphi method, was used to validate the evaluation structure, and the Bayesian theory and a Noise-OR model to evaluate the social contribution of asphalt mixes. Thus, for the life cycle of extraction, production, and construction, a set of indicators and social criteria determine a cause-effect decision-making model. Six types of asphalt mixes were evaluated: hot mix asphalt (HMA), warm mix asphalt (WMA) with natural zeolite from Chile, WMA with exported chemical additive, and their variants with and without recycled asphalt pavement (RAP). The results demonstrate that the WMAs with RAP achieve a more significant social contribution, emphasizing its contribution to the landscape, development and innovation, socioeconomic development, and health.

Performance-related methods for the characterization of cold mix patching materials used in asphalt pavements maintenance

Cold mix patching materials (CMPMs) are commonly used as an alternative to hot mix asphalt (HMA) for repairing road pavement potholes, especially in cold and wet seasons. Currently, the acceptance criteria and expectations for the mechanical strength and durability of CMPMs are often compared or related to those adopted for traditional HMA pavements without considering the specific performance characteristics of CMPMs required to ensure their effectiveness. In response to this, the authors proposed innovative solutions derived from pre-existing methodologies to evaluate CMPMs. Several parameters, indicative of CMPMs' structural and functional performance, were measured to optimize the mix design and systematize the quality assurance/quality control (QA/QC) process at various service life stages and under different boundary conditions. Besides the standard Marshall stability and indirect tensile strength (ITS), which were chosen as references, Hubbard-Field and indentation stability tests were reintroduced, suggesting modified procedures specifically tailored to CMPM stability evaluation. Similarly, brush, Leutner, and locking point test methods were customized for analyzing the raveling potential, bonding properties, and workability of the patching materials. The research outcome showed that Hubbard-Field and indentation stability tests provided more accurate stability assessments, even for materials unsuitable for testing using Marshall stability and ITS methods. Modified brush and Leutner tests effectively replicated real-world conditions, enhancing the relevance of laboratory findings to practical applications. Furthermore, the locking point method enabled mixture workability classification. These findings contribute to a better understanding of CMPM performance and can inform more targeted and effective road repair strategies.

State-of-the-Art Review on Utilization of Fly Ash in Pavement Structures

The use of fly ash in construction has been on the rise, yet its application in pavement construction remains relatively underexplored. This study addresses this gap by critically reviewing 70 years of research on fly ash usage in pavement engineering, offering valuable recommendations. Class 'C' fly ash is employed for soil stabilization, while class 'F' is used in concrete. In both flexible (asphalt) and rigid (concrete) pavements, fly ash primarily functions as a filler material. Fine ash, owing to its fineness, enhances asphalt concrete by reducing void ratios and water sensitivity, as well as easing subgrade compaction while increasing compressive strength. Incorporating fly ash into Hot Mix Asphalt (HMA) enhances resistance to cracking and oxidative ageing. Adding fly ash (up to 25%) significantly boosts soil failure stress and strain values by 106% and 50%, respectively, while a combination of 8% lime and 18% fly ash yields maximum shear strength. A modest amount of lime (1-2%) mixed with 10% fly ash achieves a maximum dry density of 1.98 gm/cm3 at an optimal water content of 12.62%. Additional testing by researchers corroborates and validates the findings of this literature review.

Performance Evaluation of Steel Slag on Hot Mix Asphalt Mixture

Researchers have been actively exploring alternative substances to modify asphalt mixtures and improve their qualities. While asphalt has been the traditional binder used in road construction due to its excellent adhesive and waterproofing properties. In this investigation, an assessment is conducted in a laboratory environment to evaluate the effectiveness of incorporating recycled steel slag as an addition in hot mix asphalt. The utilization of the Superpave mix design methodology was employed in this study to modify fine steel slag with a particle size of 300 m. Various percentages of steel slag modifier, namely 5%, 10%, 15%, and 20% of the total weight of the fine aggregate, were incorporated. The outcomes of this investigation revealed that the mixtures containing steel slag exhibited superior performance compared to those without any slag addition, serving as the control sample (0% (slag. The inclusion of steel slag in the asphalt mixes has demonstrated a significant enhancement in stability while concurrently reducing the levels of permanent deformation. The outcomes derived from the study indicate that asphalt mixtures containing steel slag additives at varying proportions (5%, 10%, 15%, and 20% by weight of the fine aggregates) exhibited superior performance in terms of the indirect tensile modulus test, static creep test, and dynamic creep test when compared to the control sample. Notably, the results highlight that the incorporation of 15% steel slag yielded the most favorable overall performance values among the tested asphalt mixes.

Analysing Witczak 1-37A, Witczak 1-40D and Modified Hirsch Models for asphalt dynamic modulus prediction using global sensitivity analysis

ABSTRACT The dynamic modulus (∣E*∣) of hot-mix asphalt mixes is one of the most time-consuming and labour-intensive material metrics to evaluate in the laboratory. This study introduces a novel paradigm for assessing the ∣E*∣'s most influential elements by employing widely accepted literature models. Witczak 1-37A, Witczak 1-40D, and Modified Hirsch Models are selected for analysing the asphalt dynamic modulus. First, a thorough laboratory database of Arizona State University is used to account for all major input factors, such as mixture gradation, binder qualities, volumetric properties, and testing conditions parameters, during models' validation. Second, each model's performance is evaluated using standard measures to build confidence levels in the subsequent analysis stage. Finally, with the aid of Latin Hypercube Simulation, a comprehensive global sensitivity analysis (GSA) is performed. Three unique GSA approaches are used; namely, elementary effects, variance-based, and PAWN methods, to highlight the effect of each input variable on the magnitude of ∣E*∣. Different GSA tools are strongly recommended since there is no analytical tool for validating the findings with the complex formulations of the selected mathematical models. The GSA demonstrates that the voids ratio in total mix, binder shear modulus, viscosity, phase angle, and binder quantity are the most significant factors.

Suitability of warm mix asphalt (WMA) technologies based on performance and energy consumption

Studying the effects of material variability on the performance of warm mix asphalt (WMA) is important to understand the benefits of reduced production temperatures. This study compares the performance of five different WMA mixtures prepared with two varying base binders and two different aggregate sources. The rutting, fatigue, and moisture sensitivity of asphalt mixtures were evaluated using cyclic compression test, indirect tensile cracking test, and modified Lottman test, respectively. Additionally, a theoretical analysis was used to compare the energy consumption during the production process. The results indicated that the performance of WMA is a function of the type of the base binder, aggregate source, and the type of WMA technology. Nonetheless, all the WMA mixtures contributed to higher energy savings in comparison to hot mix asphalt (HMA). Based on the ranking framework used in this study, the use of Rediset is recommended to achieve adequate performance and lower energy consumption.

Innovative geopolymer-based cold asphalt emulsion mixture as eco-friendly material

In recent years, there has been a growing interest in cold asphalt emulsion mixture (CAEM) due to its numerous advantages, including reduced CO2 emissions, energy savings, and improved safety during construction and application. However, CAEM has often been considered inferior to hot mix asphalt (HMA) in terms of performance. To address this issue and achieve desirable performance characteristics, researchers have been exploring the modification of CAEM using high-cost additives like ordinary Portland cement. In this study, the focus was on investigating the effects of utilizing waste alkaline Ca(OH)2 solution, ground granulated blast-furnace slag (GGBFS), and calcium carbide residue (CCR) as modifiers to enhance the properties of CAEM. The aim was to develop an innovative geopolymer geopolymer-based cold asphalt emulsion mixture (GCAE). The results of the study revealed that the use of waste alkaline Ca(OH)2 solution led to an increase in early hydration, which was confirmed through scanning electron microscopy. Furthermore, the experimental findings demonstrated that waste alkaline Ca(OH)2 solution significantly contributed to the rapid development of early-age strength in GCAE. As a result, GCAE showed great potential for utilization in pavement applications, particularly for roads subjected to harsh service conditions involving moisture and temperature. By exploring these alternative modifiers, the study highlights a promising avenue for enhancing the performance of CAEM and potentially reducing the reliance on expensive additives like ordinary Portland cement. The development of GCAE has the potential to offer improved performance and durability in pavement applications, thus contributing to sustainable and efficient road infrastructure.

Effects of a two-phase mixing process on warm-mix asphalt by factorial analysis

Warm-mix asphalt (WMA) was produced using a two-phase mixing process without additives, with bitumen–emulsion-coated aggregates and with bitumen at different mixing temperatures (MTs). The asphalt samples were prepared with 8% ground granulated blast-furnace slag fillers determined from hot-mix asphalt (HMA) analysis, with different bitumen-to-emulsion ratios and different MTs. Using the factorial design technique, the effects of the selected factors on Marshall performance parameters were investigated using interaction plots and main effect plots. The analysis from contour plots revealed that WMA prepared at 120°C with a bitumen-to-emulsion ratio of 80:20 performed best, with indirect tensile strength, tensile strength ratio, retained stability, rutting tests and ravelling loss values all meeting the standard code limits. Compared with HMA, the chosen WMA had a 37% lower ravelling loss.

Improved parameter acquisition of generalized Maxwell model in asphalt mixtures by continuous relaxation spectrum

The generalized Maxwell (GM) model is widely used to describe the viscoelastic behavior and predict performance of asphalt mixtures. However, the existing methods may not provide satisfactory accuracy because relaxation spectral distribution features are not considered. In this study, the methods (area equalization (AE) and peak equalization (PE) method) consider the distribution characteristics of the relaxation spectrum were proposed to obtain the Prony series parameters of the GM model. Two typical asphalt mixtures, HMA (hot mix asphalt mixture) and WMA (warm mix asphalt mixture), were used as case studies. The Prony series parameters of the GM model obtained by the proposed methods and existing methods (traditional fitting (TF) method and Limit equalization (LE) method) were discussed and analyzed. The derived Prony series parameters were also employed in finite element (FE) simulations to inversely predict dynamic modulus, and the simulated results were then compared with the experimental results. The results indicate that the spring stiffnesses of Maxwell elements in the Prony series parameters obtained by different methods have different distribution features. For the TF method, the Maxwell element with larger relaxation time has smaller spring stiffness. In the LE and PE method, the spring stiffness of the Maxwell element first increases and then decreases as the relaxation time increases. The spring stiffness is the same for the different Maxwell elements in the AE method. More importantly, the number of branches of the GM model is increased from 6 to 12, the relative error of the predicted dynamic modulus of HMA by the PE, AE, LE and TF method is reduced from 29.8% to 4.8%, from 49.9% to 25.9%, from 61.4% to 32.7%, from 159.1% to 133.9% respectively. The PE method has the best accuracy in FE analysis, even with a smaller number of branches of the GM model. The similar conclusion can also be summarized in the dynamic modulus prediction of WMA. Therefore, the PE method that considers the rate of change of the relaxation spectrum is preferentially recommended to obtain the Prony series parameters of the GM model.

Adaptive construction approach for virtual samples of hot mix asphalt based on 3-D structural characterization of laboratory compact specimens

Marshall and Superpave gyratory compactor (SGC) methods are widely applied in pavement engineering. Laboratory samples derived from the two methods have great difference in aggregate structure, which should be adequately characterized and considered to generate virtual samples of Marshall and Superpave mixture. To characterize the aggregate structure in realistic samples of asphalt mixture, six laboratory-compacted samples, three Marshall and three SGC, are prepared under SMA-13 gradation and then three-dimensionally (3-D) reconstructed. Next, the statistical indicators of the aggregate structure are extracted, analyzed, and characterized to develop an algorithm for adaptive construction of virtual samples conforming to the structural characteristics of realistic samples. Four virtual samples, two Marshall and two SGC, are generated to verify the control effect of the proposed approach on the aggregate structure to simulate the internal structure of realistic samples. Results indicate that virtual samples capture close structural characteristics with laboratory samples of Marshall and SGC, which validates the effectiveness of the proposed approach.

Effects of Fly Ash Geopolymer Hot Mix Asphalt Additive on the Rheological Properties of Unaged and Short-Term Aged Asphalt Binder

Asphalt pavement has the advantages of driving comfort and convenient maintenance, which has been widely applied to highway construction. However, due to the continuously increased traffic volume, it is recognized that asphalt binder and mixtures with enhanced characteristics are needed to guarantee the durability of the functional performance of transportation infrastructures. This study was carried to evaluate the effect of fly ash geopolymer additive on the rheological properties of unaged and short-term aged asphalt binder. In the respect, asphalt binder 80/100 and 60/70 penetration grade with 0, 3, 5, 7, 9 and 11% fly ash geopolymer by weight of asphalt binder were prepared. The results indicated that the addition of FAG significantly increases the stiffness (G*) and decreases the phase angle (δ) for both unaged and short-term aged modified asphalt binder compared to the control asphalt binder. This can be proved that presence of FAG significantly improved rutting parameter i.e G*/sin δ compared to control in which capable to resist rutting at higher temperature. In terms of failure temperature, highest failure temperature of 9% FAG modified asphalt binder indicated that the binder is less susceptible to be rutting at high pavement temperature for both unaged and short-term aged, respectively. Overall research conclusions are that 9% of FAG is proposed as the minimal content to be used as an additive in asphalt binder for further mixture evaluations.

Mechanical performance of cup lump rubber modified asphalt mixtures incorporating polyphosphoric acid

Natural rubber (NR) producing countries face rubber production and price fluctuations. NR production's high cost and low market price have produced an extensive demand for alternative applications of NR. This paper examined the influence of cup lump rubber (CLR) and polyphosphoric acid (PPA) on the mechanical performance of asphalt mixtures. The five modified blends were selected for the hot mix asphalt (HMA) performance analysis. The results revealed that the CLR increasing content in the bitumen ultimately increases the optimum bitumen content (OBC) for the asphalt mixture. There is a significant difference in the base mixture OBC (5.19 %) compared to the cup lump rubber-modified bitumens (CLRMBs). The CLRMB6 + 0.5PPA asphalt mixture OBC was 5.32 %, which is higher among all the mixtures. The rutting findings demonstrated that the control mixture exhibited the highest strain of 1.71 %, followed by CLRMB6 with 1.43 %, CLRMB3 + 0.5PPA with 1.1 %, CLRMB9 with 0.7 %, and CLRMB6 + 0.5PPA with the lowest strain of 0.47 %. The creep stiffness modulus of all mixtures met the minimum requirement of ≥75 MPa. The results implied that the CLR and the PPA displayed incredible potential to improve the asphalt mixture's resilient modulus (MR). The CLRMB9 resilient modulus increased significantly by 22 % compared to the control mixture. The CLRMB6 + 0.5PPA has a higher MR of 5210 MPa than the other modified mixtures and the control mixture with 3521 Ma. Thus, the study's findings suggest that the CLR, in conjunction with the 0.5PPA exhibits a decisive effect on the asphalt mixture performance and could be beneficial as a sustainable material in the pavement industry.

Evaluation of Rutting, Fatigue, and Moisture Resistance of Low-Energy Asphalt Mixtures Modified by Crumb Rubber

Low-energy asphalt (LEA) mixture, as an alternative to hot mix asphalt (HMA) due to its lower mixing temperature, has advantages such as reducing energy consumption and environmental pollutants. LEA has poor performance characteristics due to the presence of water in its manufacturing process and low mixing temperature. All the studies about LEA have been focused only on investigating the performance of this asphalt mixture, and the effect of additives in its modification is one of the research gaps in this field. Therefore, the use of crumb rubber (CR) and determining its optimal percentage in modifying the performance characteristics of LEA is considered an innovation of this research. In this research, the performance characteristics of LEA modified by 10%, 15%, and 20% CR were evaluated. In order to examine the rutting behavior, moisture sensitivity and fatigue resistance, dynamic creep, indirect tensile strength (ITS), and four-point bending beam tests were applied, respectively. The results of creep curves and flow numbers (FNs) indicated that modifying LEA by 15% increased the rutting resistance by 1.92 and 2.3 times, respectively, compared to the HMA specimen at the stress level of 207 and 310 kPa. Moreover, the evaluation of the creep strain slope revealed that modifying LEA significantly reduced stress sensitivity. ITS test showed an increase in tensile strength ratio by 22% in the specimen with 10% CR compared to the unmodified specimen. In the evaluation of fatigue resistance, while LEA containing 10% CR had almost similar results to the HMA specimen, other specimens represented a shorter fatigue life, so that with the increase in CR percentage, the fatigue life decreased. Determination of fatigue life by energy ratio and Rowe and Bouldin criteria showed similar results. Finally, by determining the plateau value (PV) in the ratio of the dissipated energy change method, the lowest PV was assigned to the 10% CR-modified LEA and HMA specimens, respectively.

Laboratory evaluation of oak ash waste for use in hot mix asphalt modification

In this study, the effect of Oak Ash (OA), a biomass waste, on the mechanical properties of hot mix asphalt (HMA) was investigated and its usability in road engineering was evaluated. For this purpose, firstly, various physical and chemical properties of B70/100 penetration class pure asphalt, OA and crushed limestone aggregate were determined. Then, the optimum asphalt content (OAC) of the mixture was determined according to the Marshall mix design method using aggregate and pure asphalt. Based on this determined content, pure and OA added (1%, 2%, 4% and 6% by weight of asphalt) modified hot mix specimens were prepared. Pure and OA added modified mixture specimens were subjected to Marshall stability, indirect tensile strength (ITS), moisture damage, indirect tensile stiffness modulus (ITSM), static-dynamic creep and calorie tests. According to the results obtained, it has been determined that the OA additive has an improving effect on all mechanical properties of the mixtures, especially on the permanent deformation resistance at high temperatures. It is considered that the use of this additive at a rate of 2% in the hot mixture can increase the resistance of the pavement against deterioration and reduce the maintenance and repair costs of the road.

Quantitative evaluation on the energy saving and emission reduction characteristics of warm mix asphalt mixtures

In response to global environmental protection policies, and the imperatives of achieving carbon peaking and carbon neutrality goals, warm mix asphalt (WMA) technology garnered increasing prominence in the field of pavement engineering. This study conducted a quantitative assessment of the energy-saving and emission-reduction characteristics of WMA mixtures throughout their lifecycle, encompassing the production and construction phases. To achieve this, 70# asphalt, SBS modified asphalt, Alube@, and ACMP@ WMA mixtures were selected, and their optimal mixing temperatures were determined through the rigorous variable speed mixing test. We formulated calculation models for energy consumption and carbon emissions at each stage, and incorporated a self-developed variable temperature emission test to measure the CO2 emissions resulting from asphalt heating volatilization. The findings revealed that the two warm mix additives effectively lowered the mixing temperature of 70# asphalt mixture by 25–26 °C. Comparatively, it was estimated that WMA mixtures exhibited reductions in energy consumption ranging from 16.5 % to 23.0 %, 11.3 % to 36.5 %, and 15.4 % to 47.4 % during the raw material heating, mixing, and compaction processes, respectively, when compared with the two hot mix asphalt (HMA) counterparts. Moreover, the noteworthy reductions in carbon emissions stemming from fuel combustion and asphalt heating volatilization were observed for the WMA mixtures. On-site measurements further corroborated that the WMA mixtures clearly manifested pronounced energy-saving and emission-reduction effects during the production and spreading phases. In conclusion, WMA is an environmentally friendly technology with promising prospects for widespread applications.

Evaluation of porous asphalt mixtures stabilized by human scalp hair

Porous asphalt (PA) is an open-graded hot mixed asphalt that presents improved surface drainage during rainfall, improving road safety in wet weather and preventing rainfall water from receding in closed areas. The main challenge facing PA paving is binder draindown during mix transportation and placement due to the confluence of low fillers cases, open-graded aggregate gradation, and high asphalt contents. Mineral fibers such as slag wool (SW), despite their negative effects on human health and the environment, have been used as stabilizers in PA mixtures to increase binder retention and avoid stability reduction. This study evaluates using human scalp hair (HSH) as an alternative stabilizing fiber to SW in PA mixtures. Using HSH in PA mixtures is a sustainable waste recycling method and an economical solution to enhance the binder retention and stability of PA mixtures. The performance of the PA mixtures that stabilized with SW (control) and HSH was compared with National Asphalt Pavement Association (NAPA) requirements. The fiber length of 1–5 mm was maintained for SW and HSH. The PA standard gradation suggested by NAPA was used to form the stone matrix of the investigated PA mixtures. The Marshall design method was used to obtain the optimum asphalt and stabilizer contents. The performance evaluation tests were performed on SW and HSH mixtures, including loss of stability, moisture sensitivity, draindown, cantabro abrasion and rutting depth. Based on the results of the performance evaluation tests, the PA mixtures stabilized by HSH show a convergent performance compared with those stabilized by SW. The findings indicated that HSH can be considered an adequate stabilizer for PA mixtures instead of SW fibers.

Pemanfaatan Limbah Gypsum Sebagai Subtitusi Filler Dalam Campuran Aspal Panas Dengan Metode Perendaman Berulang

This research was made using gypsum waste which is expected to improve the quality of asphalt concrete to the characteristics and meet the technical requirements to be used as road pavement materials. This study aims to analyze the characteristics of hot mix asphalt (AC-WC) using oil asphalt with variations of gypsum waste in repeated immersion. This study uses an experimental method, namely an experiment to get results, thus it will be seen the utilization of gypsum waste in asphalt concrete construction with variations in gypsum waste levels of 10%, 15%, and 20%. The results showed that the use of gypsum waste will affect the characteristics of the asphalt mixture

Material and mix design aspects of hot recycled asphalt mixes: A review.

Sustainability in road construction can be achieved by integrating recycled materials in the production of new pavement. One such approach is using reclaimed asphalt pavement materials (RAPM) in hot mix asphalt (HMA). Successful implementation of RAPM in HMA can only be achieved by having good comprehension of the essential material characterisation and design process. The main objective of this review is to summarise the literature and provide a keen understanding of the characterisation of materials involved (RAPM and rejuvenators) and mix design, by giving due consideration to the interaction of virgin and recycled materials. Widely used techniques for extraction and recovery of reclaimed asphalt pavement (RAP) binder have been reviewed. The advantages and disadvantages of different characterisation techniques are identified. The effect of various factors on the volumetrics of the recycled mixes is presented. Insight in to the requirements of a rejuvenator by taking into account the changes in binder after ageing is provided. Aspects that need further exploration to normalise and increase the confidence of RAPM in HMA are also highlighted as the future recommendations.