Warm Mix Additives Research Articles

Impact of adding warm asphalt mix additives on recycling milled coatings: performance evaluation.

The use of warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) technologies presents challenges in optimizing binder activation and mechanical performance in asphalt mixtures. This study aimed to evaluate the effects of three WMA additives (sunflower oil, WarmGrip®, and natural zeolite) and different RAP contents (30% and 70%) on the rheological and mechanical properties of recycled asphalt mixtures. The research focused on assessing the degree of RAP binder activation, determining the extent of partial activation, and analyzing the impact on tensile strength, moisture resistance, modulus, fatigue life, and deformation resistance. The methodology included chemical and rheological analysis of RAP and modified binders, as well as mechanical testing of recycled mixtures. Results indicated partial RAP binder activation, with 96.16% activation in mixtures containing 30% RAP and 80.77% in those with 70% RAP. Sunflower oil acted as a rejuvenator, reducing binder stiffness and decreasing the maximum PG temperature by 6 °C. The use of natural zeolite improved moisture resistance, resulting in TSR values 20% higher than those of conventional hot mixtures with the same RAP content (70%). Warm recycled mixtures demonstrated enhanced fatigue life and moisture resistance, particularly with WarmGrip®. Overall, the incorporation of WMA additives allowed for enhanced fatigue life and deformation resistance in recycled mixtures, enabling the use of up to 70% RAP without compromising mechanical performance. The findings support the potential of WMA and RAP additives to improve sustainability, cost-effectiveness, and durability in asphalt pavement construction.

Temperature control and energy-saving efficiency evaluation of low-energy warm-mix asphalt mixtures with composite additives

Traditional warm-mix asphalt (WMA) faces challenges in reducing mixing temperatures to achieve lower energy consumption. To address this challenge and meet global environmental goals, this study designs various composite warm-mix additives using commonly used additives and their optimal dosages. The viscosity reduction mechanisms of asphalt and asphalt mixtures are examined using viscosity–temperature and air voids-temperature curves. Regression equations for viscosity and voids as a function of temperature are developed to determine the optimal mixing temperature of WMA. The study integrates thermodynamic equilibrium equations with field data to quantify the energy consumption in producing composite WMA mixtures. The results reveal that WMA significantly reduces mixing temperatures, making it suitable for low-energy asphalt mixtures. The use of various composite additives enhances the mechanical properties of asphalt pavements. Optimal mixing temperatures are set as 60–100 °C for WMA in warm-paving applications, and 20–60 °C for WMA in cold-paving applications. Viscosity ranges from 0.17 to 0.28 Pa⋅s, with air voids varying from 6%–7% for WMA in warm-paving applications and 8%–9% for WMA in cold-paving applications. Controlling the mixing temperature improves energy-saving efficiency, achieving reductions from 47.1% to 97.6%. The study recommends the use of WMA (Sasobit/Evotherm/DAT) for warm-paving applications and WMA (Sasobit/Diesel oil) for cold-paving applications. This study provides valuable insights for developing energy-efficient and high-performance asphalt pavements.

THE EFFECT OF SBR LATEX AND WARM MIX AGENT ON THE PERFORMANCE OF DRY AND WET ASPHALT MIXTURES

Moisture damage has been identified as one of the most common causes of distress in asphalt mixes. The attachment between bitumen aggregate components deteriorates when water interacts at the interface, causing the binder to be stripped from the exterior of the aggregate and cohesive breakdown inside the asphalt binder. To reduce the moisture sensitivity of asphalt mixes, styrene-butadiene rubber (SBR) and antistripping warm mix additive (WMA) have been frequently utilized. Nevertheless, the application of SBR and WMA as a compound modifier has yet to be investigated thus this research aims to evaluate the influence of SBR and WMA i.e., ZycoTherm on the moisture resistance of asphalt mixtures. For this reason, several tests, including modified Lottman, resilient modulus, and dynamic creep, were used to assess the mechanical properties of the mixes in both wet and dry situations. The results found that the SBR improved the mechanical performance of the mixture in dry conditions, whereas using the ZycoTherm as a single modifier was more effective in improving the performance of the mix in dry conditions. However, the application of the compound modifier (SBR and ZycoTherm) could optimize the performance of asphalt mixtures in both conditions i.e., dry and wet.

Effects of Laboratory Ageing on the Chemical Composition and High-Temperature Performance of Warm Mix Asphalt Binders

Warm asphalt mixtures can suffer from decreased short-term high-temperature performance; therefore, introducing additional modifiers can mitigate this risk. This study investigates the effects of a liquid organosilane warm mix additive (WMAd) and grade-bumping polyethylene-based additive added simultaneously to asphalt binders on their chemical composition and its relationship with performance characteristics. Previous studies found relationships between the formation of certain chemical species during bitumen ageing and the increase in their viscosity, stiffness and other performance characteristics—the present work intended to verify these relationships when the two mentioned additives are used. Two asphalt binders were investigated—a paving-grade 50/70 binder and a 45/80-55 polymer-modified bitumen. The chemical analysis was performed using Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance mode and focused on the quantification of carbonyl, sulfoxide, polybutadiene and polystyrene structures in the asphalt binders subjected to laboratory short- and long-term ageing. Additionally, the relationships between asphalt binder performance and selected FTIR indices were evaluated using a dynamic shear rheometer. It was found that the investigated additives significantly affected the apparent contents of all evaluated chemical structures in the asphalt binders; however, these changes were not reflected in their performance evaluation.

The influence of oxidative aging and wax structure on bitumen physical hardening: Insights from model wax compounds

Physical hardening (PH) significantly affects bitumen's low-temperature performance. This paper investigates the effect of oxidative aging and wax structure on PH using 4-mm dynamic shear rheometer (4-mm DSR) and differential scanning calorimetry (DSC) tests. The results show that the wax chain length has a pronounced effect on the PH. Short-chain waxes, such as C18 and C24 affect the PH while longer-chain n-paraffins like C40 or Sasobit have almost no effect. In addition, the physical hardening index (PHI) is not linearly increasing with wax content but shows a maximum at a particular wax percentage. Wax-doped samples that crystallize before reaching the hardening temperatures typically show a reduced PHI compared to those with crystallization temperatures just below the hardening temperature. When crystallization and melting temperatures are not close to the hardening temperatures, the PHIs are typically reduced. Oxidative aging also influenced the PHI and in most cases the hardening decreased after aging. The highest PHI of almost all investigated samples occurs at 0 °C among the four typical temperatures. This investigation provides insights in the mechanism of PH and in the relations between wax contents, the hardening temperature, and the PHI. It also shows that while long-chain waxes used as warm mix additives, will not cause a PH risk, short-chain waxes present in pyrolyzed waste plastic, for example, should be handled with care. In addition, PH is also crucial for the intermediate service temperatures and not exclusively for thermal cracking at low temperatures.

Investigating the properties of a novel organic composite warm mix additive on SBS modified asphalt binder

This study investigated the effects of new organic composite warm mix additive on the performance and microstructure of SBS modified asphalt binder. Acmp, as an organic composite warm mix additive, was used to prepare warm mix SBS modified asphalt binders with different contents, and compared and analyzed with Sasobit and Evotherm warm mix additives. The rheological properties of asphalt binders were evaluated by rotational viscometer, dynamic shear rheometer and bending beam rheometer. The effects of the warm mix additives on chemical composition and microstructure of binders were analyzed by fourier transform infrared spectroscopy, thermogravimetric analysis and fluorescence microscope. The results showed that, Acmp had significant viscosity reducing effect, and 6 % Acmp reduced the rotational viscosity of binder by approximately 50 %. Acmp warm mix modified asphalt binder exhibited better low temperature performance compared to Sasobit and Evotherm, but Acmp had negative impact on the high temperature performance. Acmp was mainly composed of light components produced by the cracking of rubber powder and plastic powder, which were mainly short chain alkanes and did not affect the distribution of SBS in binder. These light components were well soluble in asphalt binder to improve its fluidity and were the main components that affected the performance of binders and achieved warm mix effects. Considering the performance of asphalt binder and mixture, Acmp is more suitable for pavements in cold regions, with a recommended dosage of 5 % of asphalt mass. The findings validate the effectiveness of organic composite warm mix additives and contribute to the exploration of more efficient new warm mix technologies.

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.

Effects of warm-mix additives, anti stripping agent, and graphene nanoplatelet on the cracking resistance, moisture susceptibility, and cost effectiveness of stone mastic asphalt

Moisture and cracking damages are two of the most common asphalt pavement distresses in the United States. The use of stone matrix asphalt mixture has gained popularity due to its high durability, resistance to permanent deformation and cracking, and reduced noise pollution. Warm-mix additives and nanomaterials have also gained significant interest as promising asphalt binder additives. In order to achieve enhanced resistance to moisture and cracking in extremely wet regions, this study investigated the effects of three warm-mix additives, an anti-stripping agent, and one nanomaterial (graphene nanoplatelet) on the cracking and moisture resistance performance of stone matrix asphalt. Fourier transform infrared spectroscopy and sessile drop tests were used to evaluate the functional groups and moisture susceptibility of the modified asphalt binder blends, respectively. The indirect tensile asphalt cracking test and the modified Lottman tests were used to evaluate the mixtures' resistance to cracking and stripping damage. A cost-effectiveness analysis as well as a two-dimensional performance interaction diagram were employed based on the laboratory performance of the mixtures. Results indicated that the graphene nanoplatelet modification of the asphalt binder had the highest wettability potential, adhesion, and debonding properties, as well as moisture resistance potential compared to other additives. In terms of mixture cracking performance, both the graphene nanoplatelet and a chemical warm-mix asphalt significantly improved the mix cracking performance by 34.1 and 30.0 %, respectively, compared to the control mix. However, the graphene nanoplatelet modification had a tensile strength ratio of 0.76, which is below the acceptance threshold of 0.80 set by AASHTO T 283 for moisture damage resistance of asphalt mixture. Overall, all mixtures with warm-mix additives showed adequate cracking and stripping damage resistance performance and are expected to be cost-effective.

Characterization of wax precipitation in wax-doped asphalt binders by variable-temperature polarized light microscope and improved viscosity algorithm

Wax precipitation and crystallization at low temperatures limits the use of wax warm mix additives in asphalt binders. In this study, variable-temperature polarized light microscopy (VT-PLM) was used to conduct in-situ observation and quantitative evaluation of the low-temperature precipitation of four waxes in asphalt binders. A novel DSR viscosity method was also used to test the wax precipitation temperatures (WPTs) of wax-doped asphalt binders. The results showed that different waxes exhibit different optical properties and shapes after low-temperature crystallization. There are plateau temperatures (about 20–30 °C) during the cooling process. Below the plateau temperatures, the tendency for crystallized waxes to continue growing are no longer obvious. In addition to an asphalt binder with 5 % F-T wax, the WPTs obtained by the novel viscosity method are significantly higher than those obtained by the VT-PLM method, indicating that the viscosity method is more sensitive.

Development of sustainable pavement: an experimental study of stone mastic asphalt prepared with warm mix additives and reclaimed asphalt pavement

Development of sustainable pavement: an experimental study of stone mastic asphalt prepared with warm mix additives and reclaimed asphalt pavement

Thermal Oxidative Aging Effect on Chemo-Rheological and Morphological Evolution of Crumb Rubber Modified Asphalt Binders with Wax-Based Warm Mix Additives

Wax-based warm mix additives can decrease the viscosity and improve the workability of crumb rubber (CR)-modified asphalt, but the mechanism of influence on the aging performance of CR-modified asphalt is not clear. To investigate the thermal aging behavior and mechanism of wax-based warm mix CR-modified asphalt, polyethylene wax (PEW) and polyamide wax (PAW) were mixed to prepare warm mix CR-modified asphalt. The effect of thermal aging on the rheological and mechanical properties was characterized by a basic property test, frequency sweep test, and multiple stress creep recovery test. The chemical composition changes during aging were then analyzed by Fourier transform infrared spectroscopy and gel permeation chromatography. Finally, the phase morphology during thermal aging was observed by fluorescence microscopy. The results showed that compared with the degradation of CR, the oxidative aging of the asphalt binder played a dominant role in the process. Not only did PEW and PAW attach to the asphalt surface in the form of crystallization to prevent its reaction with oxygen but they also promoted the dissolution of CR, and released polymerization chains, thereby enhancing the antiaging properties of CR-modified asphalt. Furthermore, the antiaging of PAW/CR-modified asphalt was better than that of PEW/CR-modified asphalt, because the amide group of PAW reacted with CR-modified asphalt to form a polymer structure.

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.

Cracking resistance of crumb rubber modified green asphalt mixtures, using calcium carbonate nanoparticles and two by-product wax-based warm mix additives

Common procedures to incorporate the recycled crumb rubber (CR) in asphalt binders take a long time and use a high-temperature heating process, which makes these rubberized mixtures even more expensive and environment-unfriendly than conventional mixtures. In trying to make a cheaper and greener asphalt mixture, in this paper, the CR incorporation heating process and its duration were lowered (140–150°C in 15 minutes), and the effect of these changes was studied on the pavement's tensile/shear cracking resistance. Because the main disadvantage of using CR is the increase of viscosity, two by-products, slack wax (SW) and polypropylene wax (PPW) were used to correct the viscosity; also their effect on fracture toughness (Keff) and fracture energy (Gf) was assessed. As results showed that the following process decreases the cracking resistance, calcium carbonate nanoparticles (CCN) in different contents were added. Results show that adding 15% CR reduces Keff and Gf by about 18 and 16%, respectively. Adding the SW and PPW further reduces them by about 8 and 16%, respectively. In this condition, adding CCN in optimal content (about 5%) compensates for these reductions. Although these greener asphalts have the same cracking resistance as the control mixture, the environmental and cost-effectiveness analysis shows the developed materials are greener and cheaper.

Effect of synthesized warm mix additive and rejuvenator on performance of recycled warm asphalt mixtures

In this study, a warm mix additive (composed of diamine and fatty acid amine) and a rejuvenator (consisting of styrene-butadiene-styrene and aromatic elements) were synthesized to facilitate the incorporation of 50% recycled asphalt pavement (RAP) in warm mix asphalt for the surface layer and 100% RAP in cold asphalt mixtures for the base layer. The effect of WMA and rejuvenator-modified asphalt binder was performed through rotation viscosity, dynamic shear rheometer, and bending beam rheometer. Simultaneously, the performances of RAP-modified asphalt mixtures were assessed using dynamic modulus, overlay test, and flow number test. Constructing two testbed roads provided a real-world evaluation of two surface mixtures and two base mixtures. The results indicated that modifying asphalt binder PG 64–22 with 2.0% warm mix additive (WMA) and 5.0% rejuvenator upgraded the performance grade to PG 76–22, significantly improving rutting resistance, and reducing 40% creep stiffness. The asphalt mixture with 50% RAP, modified with WMA and rejuvenator, demonstrated a better resistance to rutting and low-temperature cracking compared to the original mixture. Both surface and base mixtures met field application specifications, exhibiting excellent performance after a year of service, as confirmed by pavement condition surveys, and falling weight deflectometer tests, thus highlighting the potential for sustainable and high-performance recycled asphalt solutions in road construction.

Comparative study of typical asphalt binders in Xinjiang region modified with warm mix additives

Xinjiang’s representative asphalt binders, such as Karamay and Tahe asphalt, lack sufficient research on warm-mix additive modification effects. Given their unique microstructure and molecular composition differences, comprehensive investigations are essential for a nuanced understanding of these binders. This study added Sasobit and Evotherm warm mix additives to Karamay 90# asphalt and Tahe 90# asphalt, respectively. The evaluation of diverse warm mix additives’ impact on diverse asphalt binders involved viscosity, softening point, penetration tests, Fourier transform infrared (FTIR) and analysis of saturate, aromatic, resin, and asphaltene (SARA) fractions. Additionally, molecular models of asphalt were constructed using Materials Studio software, based on the SARA test data. Molecular models of Sasobit and Evotherm were also developed, representing organic wax and a cationic quaternary ammonium surfactant, respectively. Conducting molecular dynamics simulations of warm mix additives and two asphalt molecules yielded valuable insights into solubility parameters and the radial distribution function (RDF). This approach enabled a thorough and comparative exploration of the modification mechanisms employed by various warm mix additives on different asphalt types at a molecular scale. The results indicate that, Evotherm excelled in enhancing high-temperature asphalt performance, while Sasobit surpassed it in low-temperature. The viscosity reduction by Sasobit proved more effective for K90, while for T90 asphalt, the trend was reversed with Evotherm exhibiting superior performance. The solubility parameter in MD simulations consistently correlates with asphalt viscosity results. Sasobit showed enhanced compatibility with K90 asphalt, while T90 asphalt demonstrated greater suitability for modification with Evotherm.

Impact of Sasobit on Asphalt Binder’s Performance under UAE Local Conditions

Asphalt pavements are the backbone of the transportation system. In light of the rising costs of energy and materials and the growing emphasis on sustainable infrastructure, there has been a push to enhance the performance of asphalt pavements. One of the primary methods for achieving this goal is the incorporation of warm mix additives into the asphalt binder. This study investigated the impact of Sasobit on the asphalt binder by adding 2% and 4% of Sasobit, by weight, to the asphalt binder. The following tests were conducted: penetration, softening point, rotational viscosity, and high-temperature performance. The results demonstrated that the addition of Sasobit at 2% and 4% concentrations resulted in a 25% and 30% reduction in penetration, respectively, accompanied by a 26% and 71% increase in the asphalt binder's softening point, as well as a 17°C and 36°C rise in the softening point, respectively. Additionally, the viscosity at 135°C and 165°C and the mix and compaction temperatures decreased by 30% and 25%, respectively. Utilizing the outcomes mentioned above, AASHTOWare simulations were conducted to assess the impact of local climate conditions and gradation. The simulations demonstrated that adding Sasobit resulted in enhanced service life, as evidenced by the International Roughness Index, permanent deformation, and bottom-up fatigue. The simulations and test results collectively indicate that Sasobit's incorporation could be advantageous for local asphalt pavements. The authors recommend further testing the effect of Sasobit on the performance of asphalt mixes in rutting, fatigue, and moisture damage.

The role of bio-based additives in achieving sustainability in asphalt pavements

Increased service demands from asphalt pavements due to ever-increasing volumes, coupled with the aging of highway networks, and calls for improved sustainability across the industry, have rendered the need for smart and sustainable pavement material and design more important than ever. While chemical warm mix additives and rejuvenating technologies have been utilized in pavement materials at various scales of research and practice in the past, in recent years bio-based additives have emerged as increasingly practical solutions for potentially achieving more sustainable pavements, offering the prospect for high performance combined with environmental and economic sustainability. Adaptation of chemical warm mix additives and rejuvenators in practice requires a working knowledge on the definitions, relevant evaluation criteria available to the practitioner, and, perhaps most importantly, demonstrated experience of successful application in practice. The present study will review current efforts underway in the industry to incorporate bio-based chemical warm mix additives and rejuvenators in performance-based design methods for HMA and WMA, using real world Balanced Mix design (BMD). Examples including comprehensive research being carried out in conjunction with NCAT and MnROAD research and test facilities will be reviewed to illustrate the utilization of such concepts in practice today.

A Fundamental Study on the Development of a Polymer Modified Rejuvenator and Warm-mix Additives Asphalt Mixture with Low CO<sub>2</sub> Emission and High Performance

A Fundamental Study on the Development of a Polymer Modified Rejuvenator and Warm-mix Additives Asphalt Mixture with Low CO<sub>2</sub> Emission and High Performance

Compactability and Performance of Warm-Mix Additives at Lower Than Traditional Compaction Temperatures

Compactability and Performance of Warm-Mix Additives at Lower Than Traditional Compaction Temperatures

Effect of Sasobit/Waste Cooking Oil Composite on the Physical, Rheological, and Aging Properties of Styrene–Butadiene Rubber (SBR)-Modified Bitumen Binders

The modifying effects of polymer on bitumen low-temperature performance are substantially compromised by the thermal breakdown of styrene–butadiene rubber (SBR) polymer during bitumen mixture production operations. The efficacy of the utilization of Sasobit/waste cooking oil (Sasobit/WCO) as a warm-mix additive has been demonstrated in mitigating the adverse consequences of thermal aging on SBR-modified bitumen binder (SB) while preserving the binder’s original performance characteristics. However, few studies have been conducted to further investigate the rheological properties and aging resistance of SB modified with Sasobit/WCO compounds. In this work, three additives—Sasobit, WCO, and Sasobit/WCO composite—were selected, and their effects on the physical and rheological characteristics of SB as well as the temperatures at which the mixtures were prepared were assessed. In addition, by using dynamic shear rheometers (DSR) and bending beam rheometers (BBR), the effects of this innovative warm-mix addition on the performance grade (PG) and aging resistances of SB were evaluated. According to the results, Sasobit/WCO composites outperform Sasobit and WCO in lowering the mixture preparation temperature. Sasobit/WCO also improves both the high- and low-temperature performance of SB simultaneously. Compared to hot-mix asphalt mixtures, the addition of Sasobit/WCO reduces the preparation temperature of the bitumen mixtures by 19 °C, which in turn helps to minimize the negative effects of temperature aging on the functioning of the SB. Additionally, the Sasobit/WCO composite addition can improve the SB mixture’s resistance to thermal cracking. After the introduction of Sasobit/WCO, the high-temperature PG of SB was raised by two levels, regardless of whether the warm-mix impact was taken into account. With the addition of Sasobit/WCO, SB’s resilience to short-term aging was enhanced.