Warm Mix Asphalt Technology Research Articles

Comprehensive rheological and mechanistic evaluation of an asphalt binder and mixture modified with warm mix additives.

Though warm mix asphalt (WMA) technology has been introduced for a long time, there is still reluctance in the industry to utilize it in practice. In regions like India, where WMA incorporation into road construction has been limited over the past two decades, building confidence in local binders is imperative for widespread adoption. Thus, the present study appraises the effect of three commonly used WMA additives in India, namely Sasobit®, Evotherm®, and Zycotherm®, with base binder VG-30 on the rheological and mixture performance parameters. Three dosages of each WMA additive were blended with the control binder to give ten binder combinations. Different binder evaluations such as Superpave grading and parameters, frequency sweep testing, multiple stress creep recovery test, and linear amplitude sweep test were conducted for comparative dynamic mechanical analysis. Based on the binder testing results, suitable dosages of WMA additives were established, and mixture testing was carried out using these specific additive dosages. Binder evaluations showed improvement in high-temperature characteristics with Sasobit® and better fatigue performance with Evotherm®, while Zycotherm® did not alter binder properties significantly. The asphalt mixture testing results indicated satisfactory performance with the three additives based on Marshall stability and flow testing. The WMA additives also showed enhancement in moisture susceptibility based on the modified Lottman test with Zycotherm® demonstrating the best performance. Overall, the study underscores promising effects of the three WMA additives across different parameters, signaling their potential for widespread application in real-world scenarios.

A probabilistic investigation of long-term field performance of warm mix asphalt pavements

Warm-mix asphalt (WMA) has been gaining popularity in sustainable road engineering due to its reduced environmental impacts. However, uncertainties remain regarding its long-term pavement performance compared to hot mix asphalt (HMA). Especially, the critical factors influencing the field performance of WMA are yet to be determined. Hence, this study analyzes the long-term field performance of pavement overlaid with WMA, using data from the Specific Pavement Studies 10 (SPS-10) of the long-term pavement performance (LTPP) program. The evaluation includes 58 field sections from nine projects across the United States, encompassing two WMA types (foaming processing and chemical additive) and their corresponding HMA control sections. Performance indicators such as alligator cracking, longitudinal cracking in the wheel path, transverse cracking, rutting, and roughness (measured by the international roughness index, IRI) were considered. Per-state and per-climate region Bayesian multilevel models were built to account for site- and region-level heterogeneity. The study results demonstrated that pavement with WMA performed equally well to the HMA counterparts under similar conditions, indicating that their potential for widespread application in meeting both performance standards and environmental conservation requirements. Also, WMA technologies did not differ in pavement performance, and thus the field performance of WMA was not a dominant factor in deciding WMA technology types. Furthermore, Bayesian multilevel models proved highly effective in performance data varying across construction sites and regions.

Evaluation of warm mix effect in laboratory using a self-developed WMA additive Alube

In response to the problems of high mixing temperatures and energy consumption of polymer-modified asphalt mixtures in road construction, a surfactant-based warm mix additive ‘Alube’ was developed. The warm mix SBS-modified asphalt and its mixture were prepared. Their rheological performance and chemical structure were analysed by the rheological and microscopic tests. The active mixing power (P) of asphalt mixtures were examined by the variable speed mixing (VSM) test. The mixing flowability model was then established to evaluate the warm mix effect. The results indicated that the mixing flowability of asphalt mixtures obeyed the linear Bingham visco-plastic model, and the slope and intercept of the flow straight characterised the mixing viscosity and plastic limit. It is evaluated that 0.7% Alube1 and Evotherm reduced the mixing temperature of SBS-modified asphalt mixture by 14°C and 12°C, respectively. Moreover, Alube1 is suitable for a wide range of applications through warm mix asphalt technology.

Tribology-Based Specifications for Assessing the Production Temperatures of Asphalt Binder

The success of warm mix asphalt (WMA) technology and polymer-modified binders (PMB) depends on the accurate determination of the production temperatures. To date, no standard protocol has been developed to determine the production temperatures of the WMA technology. Recent studies have shown that the production temperature is related to the friction between the aggregate and asphalt binder, which can be explored using tribology. This study attempted to develop a tribology-based approach to evaluate the production temperature of WMA-modified binder and PMB. The ball-on-the-three-plate test was performed using different normal loads (1N, 3N, 5N, and 10N) and sliding speeds (0.05 m/s, 0.1 m/s, and 0.3 m/s). The test results were compared with the equi-viscous (EQ) method. Production temperatures obtained from the EQ method were inappropriate for WMA and PMB. Results of the tribology study showed that the normal load of 1N and 0.3 m/s was found suitable for evaluating the production temperatures. Adding WMA additives resulted in a lower coefficient of friction (CoF), whereas PMB showed higher CoF than viscosity grade binder (V8, which is used for WMA modification). The addition of WMA additive reduced the production temperatures of V8, and reduction was a function of the WMA additive type. Temperature ranges corresponding to the CoF of 0.26 ± 0.021 and 0.33 ± 0.023 were proposed for assessing the mixing and compaction temperatures, respectively.

Warm-Mix Asphalt Containing Reclaimed Asphalt Pavement: A Case Study in Switzerland

Among the technologies proposed for achieving carbon neutralization in asphalt road pavements, warm-mix asphalt (WMA) has garnered increasing attention in recent years. While WMA holds the potential for various environmental and technical benefits, a comprehensive understanding of its implementation, technology selection, and additives is essential for successful application. This study presents a case where a bio-based chemical additive was employed to produce WMA containing 50% reclaimed asphalt pavement (RAP) for a surface course in Bern, Switzerland. To minimize additional variables during testing and analysis, no other additive or rejuvenator was introduced into the mixtures. The testing plan encompassed laboratory tests on samples collected during material placement and recompacted at varying temperatures in the laboratory, as well as cores extracted from the job site. As anticipated, the presence of the chemical WMA additive did not alter the rheological properties of the reference bitumen. Although in the mixture-scale tests, the WMA mixture exhibited comparable properties to the control hot-mix asphalt (HMA), it is not expected that the small dosage of the chemical additive functions the same grade after reheating and compaction. Nevertheless, the cores extracted from the job site proved the efficiency of the applied WMA technology. In addition, consistent with existing literature, the cracking tolerance (CT) index values of 62 for HMA and 114 and 104.9 for WMA mixtures indicated that the latter is less susceptible to cracking. Consequently, this characteristic could contribute to the enhanced durability of asphalt pavements.

A COMPREHENSIVE REVIEW OF THE USE OF NEUTRAL CARBON AND BIO-OIL WASTES ON WARM MIX ASPHALT CONCRETE

Waste materials can be used to produce cement concrete, asphalt concrete, block concrete, and other construction materials. This has been known for more than 30 years in the field of civil engineering. To allay ecological concerns, several nations are currently researching the reprocessing of neutral carbon and bio-oil wastes (NC&BoWs). These wastes are sustainable, but because of their large volume of landfill disposal, which has detrimental effects on the ecosystem and its inhabitants, they are starting to become quite worried for the ecosystem. Therefore, this study provides a comprehensive review of the use of NC&BoWs on warm mix asphalt (WMA) concrete to lessen our worries about the environment. Numerous investigations have been conducted to enhance various WMA technologies. These three technologies such as foaming, chemical, and organic enhance the structural behavior of WMA concrete and lower the viscosity of the asphalt binder. A bibliometric analysis shows that only 26 out of the 168 articles related to this study were published by Scopus between 2012 and 2023. Full-length articles accounted for 100.0% of Scopus publications, and it seems that not a single review article was accepted and published by Scopus. Based on the subject area, the fields of engineering, materials sciences, and physics and astronomy published 50.0%, 43.5%, and 6.5% of the Scopus articles, respectively. Consequently, the findings suggested that further reviews are necessary to verify NC&BoWs' ongoing efficacy in WMA concrete

Investigation of rheological properties and modification mechanism of SBS-modified asphalt with different warm mix additives

ABSTRACT The application of warm mix asphalt (WMA) technology in polymer-modified asphalt becomes increasingly widespread, but it lacks thorough investigation on the interaction mechanism between warm mix additives and polymers. Accordingly, two new warm mix additives, an organic viscosity-reducing modifier (A) and a surfactant-based modifier (C), were selected to prepare the warm mix SBS-modified asphalt. The basic properties, viscosity-temperature characteristics, ageing resistance and rheological properties of modified asphalt were tested. At last, the modification mechanism was elucidated through a series of microscopic tests. The results indicated that A could more effectively enhance the construction workability of SBS-modified asphalt, while C had little effect on its basic properties. Both new modifiers, especially A, reduced the high-temperature property of asphalt, with partial recovery after short-term ageing. The microstructure test results indicated that the two modifiers were physically modified with SBS-modified asphalt. Both additives improved the dispersion uniformity of SBS particles in asphalt, and the microscopic morphology parameters obtained from quantitative analysis reflect the macroscopic properties of asphalt. Moreover, the light components and rubber powder of A improved the flexibility of asphalt, and C enhanced its low-temperature performance, which demonstrated that these two modifiers were more suitable for asphalt pavements in cold regions.

Sustainable Pavement Construction in Sensitive Environments: Low-Energy Asphalt with Local Waste Materials and Geomaterials

Low-energy asphalt techniques, such as warm mix asphalt (WMA), combined with the rational consumption of geomaterials and waste recycling would promote more sustainable and energy-efficient asphalt pavements. In volcanic environments, a significant proportion of aggregate production is discarded due to its extreme porosity, and used tires generate a main environmental issue as well. While recycled rubber powder from tire waste can enhance the mechanical behavior of asphalt, it also raises its viscosity. Therefore, joining rubberized asphalt containing local waste geomaterials with WMA technologies is crucial to reduce the manufacturing temperatures and emissions and to produce more eco-efficient pavements. For this purpose, the most relevant technological characteristics of rubberized warm mix asphalt with residual aggregates from highly vesiculated volcanic rocks are tested in the laboratory and contrasted with conventional mixtures. The outcomes demonstrate not only the feasibility of the production of such mixtures in line with the current specifications, but also show a significant improvement in the resistance to moisture and to plastic deformations, and an improvement in the stiffness modulus. The eco-efficiency indicators conclude that the energy consumption and emissions are reduced by 9%, enabling the reuse of waste materials by more than 95%.

Characterization of aged bitumen recovered from in-situ polymer-modified HMA and WMA using advanced technologies

The growing attention of public opinion towards the environment has prompted, in the last decades, to find eco-sustainable and economic alternatives to the traditional productions of hot-mix asphalt (HMA). Under these auspices, the use of warm mix asphalt (WMA) technology applied to mixtures containing reclaimed asphalt (RA) has grown, also due to the well-proven advantages in terms of plant odor emissions and improved working conditions. In addition, it is now known that the mechanical performance of WMAs is completely comparable, even superior in some cases, to that of HMAs. However, to date, there is no comparison in terms of long-term performance of bitumens used in full-scale pavements laid with the two different technologies. Therefore, the aim of this research is to evaluate the oxidative and rheological state of four bitumens recovered from different layers of a full-scale pavement prepared with WMA and HMA technologies and set up a methodology tool set for investigating the physicochemical properties of bitumens. An in-depth laboratory investigation, carried out through physicochemical and rheological tests, has shown that the bitumens used in WMA mixtures are characterized by less oxidation than HMA ones (which are characterized by longer relaxation and glass transition times) and the Styrene-Butadiene-Styrene (SBS) polymers inside them are less degraded and still contribute positively to the rheological response even after five years in service, demonstrating the ability of the chemical additive to act as possible “sacrificial agent”, safeguarding the rheological characteristics of polymer modified bitumens (PMBs).

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.

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.

Influence of Warm Mix Asphalt Additives on the Physical Characteristics of Crumb Rubber Asphalt Binders

This investigation is centered around the application of warm mix asphalt (WMA) technologies to address workability concerns linked to rubberized asphalt binders. The primary aim of incorporating crumb rubber (CR) and WMA additives is to establish a robust paving method that fosters energy conservation, efficient waste management, noise reduction, and improved overall performance. The current study aims to comprehensively characterize and differentiate the physical attributes of rubberized asphalt binders by employing three distinct WMA additives: Sasobit, Cecabase RT and Rediset WMX. These additives are introduced into eight unique asphalt binders. Laboratory assessments are carried out to evaluate the workability and physical properties of these binders. The evaluation encompasses penetration, softening point, penetration index, penetration viscosity number, storage stability, ductility, viscosity, and stiffness modulus analyses. The findings indicate that the rubberized asphalt binder enhanced with Sasobit demonstrates the highest levels of both hardness and softening point in comparison to asphalt binders supplemented with alternative WMA additives. The evaluation of storage stability underscores the satisfactory stability across all modified asphalt binders. Both the unmodified and modified binders meet the requirements stipulated by the ductility test; the rubberized asphalt binder modified with Rediset falls short. The rubberized asphalt binder improved with Sasobit displays the most notable enhancement in workability. Furthermore, the blend of crumb rubber and Sasobit binder reveals the highest stiffness modulus values under conditions of intermediate and high temperatures with 1.88 and 0.46 MPa, respectively. In summation, the rubberized asphalt binder incorporating crumb rubber with Sasobit showcases superior improvements in both stiffness and workability compared to counterparts modified with Cecabase RT and Rediset WMX.

Recycled Concrete Aggregates (RCA)-based asphalt mixtures: A performance-related evaluation with sustainability-criteria verification

This investigation aims to explore the feasibility of using Recycled Concrete Aggregate (RCA) as a partial replacement for Natural Aggregates (NAs) in the production of Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA). As WMA technology, Iterlow T (a chemical additive) was selected. For both types of asphalt mixtures, the RCA dosages of 0, 15, 30 and 45% by weight of coarse aggregates were considered. Notably, four different RCA sources were assessed, and the alkali-silica reaction and attached mortar quantity were analyzed for each one. In order to examine the effect of the coarse RCA on the performance-related properties of the asphalt mixtures, a test protocol was conducted. This protocol comprised four tests, i.e., stiffness modulus, moisture susceptibility, rutting resistance, and fatigue life. Additionality, a sustainability-criteria verification was performed employing the Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) methodologies. Respectively, the LCA and LCCA estimate each alternative's environmental impacts and production costs. Consequently, the main finding obtained were: (i) as the coarse RCA content increases, asphalt mixtures exhibit a reduction in their mechanical performance; (ii) the performance-related properties of the HMAs and WMAs with a 15% RCA dosage are acceptable, but more elevated amounts generate highly noticeable deterioration; and (iii) 15% of coarse RCA minimizes the environmental burdens and maximizes the cost-effectiveness of the asphalt mixtures fabrication. Thus, the main contribution to the literature that achieves this research is to perform a comprehensive multi-criteria examination on the potential of the RCA as a recycled material to minimize the depletion of non-renewable resources.

Performance evaluation of WMA mixtures with RAP

Nowadays, asphalt industries are seeking for new methodologies in order to minimize global warming and emission of greenhouse gases. One of the solutions found out was the use of warm mix asphalt (WMA) technology which allows reduction in asphalt mixing, working and compaction temperature. WMA reduces the desired temperature in comparison with hot mix asphalt by 20–40°C. In addition to this issue, the lack of superior quality natural aggregate resources everywhere around the world, it is essential to use the available natural resources efficiently along with the available construction and demolition waste such as recycled asphalt pavement (RAP) if possible, without compromising in the performance of the mixtures. In this study, reclaimed asphalt pavement was used as partial replacement for conventional aggregates and binder. The RAP contents of 0%, 25% and 50% were considered. Zycotherm was used as warm mix additive which improves the pavement moisture resistance by serving as an anti-stripping agent. The mixtures were prepared with HMA @ 130°C, HMA @ 160°C, WMA @ 130°C and all these three mixtures with partial replacement with RAP. The RAP material with 0, 25 and 50% replacement was adopted for both HMA and WMA for DBM grade 2 course. Zycotherm was added by 0.1% by weight of binder in both HMA and WMA mixes. The prepared test specimens were tested for Marshall and indirect tensile strength (ITS) test. The test results indicated that the WMA blend prepared using 0.1% by the weight of binder content showed good results compared to the hot mix asphalt @ 130°C. The indirect tensile strength ratio (TSR) of mixes containing RAP is found to be higher when compared to the mixes without RAP indicating lower moisture susceptibility of the mixtures. This study demonstrated the possible use of RAP in WMA mixes with better performance than HMA.

Study on Use of Various Type of Warm Mix Asphalt (WMA) Additive’s in Asphalt Binder

Abstract: Recent years have seen a substantial increase in interest in warm mix asphalt (WMA) technology as a sustainable substitute for traditional hot mix asphalt (HMA) production. There are many benefits to adding warm mix asphalt additives to the asphalt binder, including less energy use, lower emissions, better workability, and longer pavement life. According to studies, the rheological and mechanical characteristics of the asphalt binder are significantly impacted by the use of warm mix asphalt additives. These additions often reduced the viscosity of the binder, improved workability, and increased rutting resistance. Additionally, the use of particular warm mix asphalt additives showed improved fatigue resistance and moisture resistance, making them ideal candidates forlong-lasting and sustainable paving

High and intermediate temperature performance of warm asphalt rubber containing conventional warm mix additives and novel chemical surfactant

Warm mix asphalt (WMA) technology is widely used to address the workability concerns of rubberized asphalt paving materials. In this study, a novel chemical surfactant – alube– is proposed for the production of warm asphalt rubber (WAR) binders. To assess its suitability, the high and intermediate temperature performances of the resultant alube-WAR binder (AWAR) was compared with those of two conventionally produced WAR binders, namely sasobit-WAR binder (SWAR) and rediset-WAR binder (RWAR). An economic evaluation of the WAR binders was also done in order to assess their cost-competitiveness. For the high-temperature performance study, the high-temperature viscosity, viscosity-temperature susceptibility (VTS), rutting resistance, and stress sensitivity were investigated, while for the intermediate-temperature performance, the fatigue resistance factor was evaluated. Different findings were obtained from the performance and cost investigation. Alube was found to successfully lower the high temperature viscosity of AR binder but not as effective as the two conventional WMA additives. The VTS property of AR binder was only improved by the organic WMA additive (sasobit), while the chemical additives (rediset and alube) showed negative effects. In terms of rutting resistance, AWAR was superior to RWAR and AR, but was outperformed by SWAR. Also, SWAR was the least susceptible to stress changes, while AWAR and RWAR showed comparable performance. Based on the G*sin δ test, the fatigue resistance of the AR binder improved after the incorporation of the chemical additives and deteriorated after sasobit was added, and the performance ranking was determined as RWAR > AWAR > AR > SWAR. Overall, only SWAR had a better high-temperature performance than AWAR, whereas for intermediate temperature performance, only RWAR was better. Furthermore, economic analysis showed that AWAR is the most cost effective of the three WAR binders. The findings of this study indicate that alube has the potential of being utilized as a WMA additive for AR binders and can be utilized in wide range of road projects due to its cost-effectiveness.

Evaluation of Warm Mix Crumb Rubber Modified Asphalt Mixture (WCRMA) on resisting permanent deformation

Crumb rubber (CR) is generated from the recycling of used or discarded car tires and has long been utilized in the paving industry. Crumb rubber can be used in asphalt mixes in two ways: dry process and wet process. However, compared to standard combinations, crumb rubber modified asphalt (CRMA) requires much higher mixing and compaction temperatures. As a potential substitute, using warm mix asphalt (WMA) technology significantly lower hot-mix asphalt (HMA) production and placement temperatures through viscosity reduction. In accordance, the objectives of the study are to produce warm mix crumb rubberized asphalt mixtures (WCRMA) using a dry process and to evaluate WCRMA’s performance in terms of rutting resistance. WCRMA is produced by adding 1, 3, and 5% Sasobit® of the total weight of the binder. The rutting performance of WCRMA was evaluated by Dynamic Creep test. The result showed that the asphalt mixes with the largest percentages of Sasobit® (5%) showed the lowest lowest accumulated strain and permanent deformation. The modified asphalt mixture performed better and had greater rutting resistance due to the replacement of fine aggregate with crumb rubber and the addition of Sasobit® compared to control sample.

Ageing Evaluation of Foamed Polymer Modified Bitumen with Bio-Flux Additive

This paper presents the results of an analysis of the changes in the stiffness of asphalt binders modified with a bio-flux additive and subjected to the processes of foaming and short-term ageing. The purpose of the analyses was to determine changes in the rheological properties of asphalt binder as a result of technological processes characteristic of hot and warm mix asphalt technology. Three asphalt binders with similar penetration but varying degrees of polymer modification were tested: 50/70, 45/80-55 polymer-modified bitumen, and 45/80-80 highly modified bitumen. Tests were carried out on four groups of binders: original binders, foamed binders after 14 days of storage, non-foamed binders after Rolling Thin Film Oven Test (RTFOT) ageing, and foamed binders after 14 days of storage subjected to RTFOT ageing. The master curves of the complex shear modulus G* were analysed, and three indexes of binder stiffening were determined, characterising the investigated effects. The tests showed that some of the stiffening indices significantly depended on the degree of polymer modification and the content of the bio-flux additive. Moreover, it was found that the foaming process in the case of paving-grade bitumen and polymer-modified bitumen did not contribute to the additional stiffening of the binders.

Effect of warm mix asphalt (WMA) technologies on the moisture resistance of asphalt mixtures

Moisture damage has been identified as a major concern for asphalt pavements. This concern becomes more critical when the asphalt mixtures are prepared at lower mixing and compaction temperatures using technologies such as warm mix asphalt (WMA). In this study, the effect of different WMA technologies on the moisture resistance of asphalt mixtures was studied using a variety of experimental investigations including bond strength ratio (BSR), percentage coating, retained Marshall stability (RMS), and tensile strength ratio (TSR). Two aggregate sources (granite and dolomite), two base asphalt binders (VG30 and PMB40), and five WMA additives categorized under organic, chemical, and foaming technologies were used. Moisture damage in WMA mixtures was found to be a function of aggregate type and base asphalt binder. Rediset, a chemical WMA additive, showed higher moisture resistance in comparison to other technologies. Appreciable correlations were found between BSR and TSR (R2 ranged from 0.61 to 0.72). This study suggests a minimum BSR of 0.7 for satisfactory performance against moisture damage.

Interlayer bonding properties of warm recycled asphalt pavements

The need for sustainable road infrastructures has led to great interest in Warm Mix Asphalt (WMA) technologies, which allow the production, lay-down and compaction of asphalt mixtures at reduced temperatures, about 40°C lower than traditional Hot Mix Asphalt (HMA). The use of WMA ensures lower emissions and is also beneficial in the recycling of Reclaimed Asphalt (RA) deriving from the milling of end-of-life pavements. One of the main concerns regarding WMA is the possible poor adhesion between the pavement layers that could be caused by the reduced working temperatures during the paving operations. However, almost no data are currently available in literature on this aspect, which thus could represent a deterrent to the wide application of WMA by road agencies. In this regard, this paper focuses on the investigation of the interlayer bonding properties of warm recycled asphalt pavements constructed along various Italian motorways and national roads using different WMA chemical additives. The Interlayer Shear Strength (ISS) was measured at different pavement interfaces (wearing-binder, binder-base) and time intervals by testing extracted cores with ASTRA and Leutner equipment. The results show that the interlayer bonding properties of WMA pavements are comparable to HMA pavements and are not affected by the WMA additive type. Moreover, ISS depends on the properties of the tack coat applied between the layers and increases over time due to aging effects, especially when the interface is below an open-graded friction course (OGFC). These findings further encourage the use of WMA as environmentally sustainable technologies for the construction and maintenance of asphalt pavements.