Warm Mix Asphalt Additives Research Articles

Assessing bonding and debonding properties of Evotherm modified bitumen with natural aggregates using surface free energy approach

ABSTRACT An incongruous pairing of aggregates and bitumen can result in early pavement failures such as stripping, raveling, and fatigue cracking. Surface free energy (SFE) assessments of aggregates and bitumen offer a means to evaluate the compatibility of the aggregate-bitumen system. It is important to emphasise that the SFE of both bitumen and aggregates significantly influences the determination of a compatible aggregate-bitumen combination. In this study, the moisture damage resistance of unmodified bitumen types (VG20, VG40) and modified bitumen types (PMB40, CRMB60) incorporating chemical-based warm mix asphalt (WMA) additives, specifically Evotherm, was investigated. The SFE approach was utilised to gain insights into their performance. In the laboratory, the static contact angle and SFE parameters of both unmodified and modified bitumen, with and without Evotherm, were determined using the Sessile drop method. Five different aggregate types were employed to calculate SFE performance parameters. Subsequently, the SFE performance parameter of forty combinations of aggregates and bitumen was calculated. As part of the assessment of moisture damage resistance, the compatibility ratio (CR) parameter was estimated using the dry adhesion energy, bitumen cohesion energy, wet adhesion energy, and wettability of different combinations of bitumen with aggregates. From the result, Evotherm addition to base bitumen (excluding VG20) significantly improved CR across various aggregates. Notable increases were observed for VG40, PMB40, and CRMB60 after Evotherm addition, with improvements of 66.67%, 48.48%, and 64.54% respectively for basalt aggregate. PMB40+EM with basalt aggregate exhibited the highest CR and Tensile Strength Ratio (TSR), suggesting superior moisture damage resistance compared to other bitumen combinations.

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.

Diffusion mechanism explorations on the sustainable warm mix asphalt and synchronous rejuvenated SBS-modified asphalt binder using the free volume theory

The blending degree, dominated by the diffusion process between virgin and rejuvenated asphalt, profoundly affects the performance of recycled mixtures. However, research on the blending degree in Warm Mix Asphalt (WMA) containing Styrene-Butadiene-Styrene-modified asphalt (SBSMA) mixtures remains relatively underexplored despite its significant impact on pavement performance. To this concern, a predictive model for characterizing the diffusion behavior of the WMA modified SBSMA and synchronous rejuvenated SBSMA was developed based on the free volume theory, which was validated by the pulsed field gradient nuclear magnetic resonance test. Based on the predicted diffusion coefficients, the influences of WMA additives, rejuvenator types, and temperatures on diffusion behavior were systematically investigated. Results indicated that the diffusion coefficients were affected by the interaction of WMA additives, rejuvenator types, and temperatures. The presence of the WMA additive and the increase in diffusion temperature were able to improve the blending degree by increasing the diffusion coefficient. Rebalancing the unstable colloidal structure of SBSMA can enhance the diffusion coefficient of the WMA modified SBSMA twice than that of untreated one. After further reconstruction of small SBS fragments into the triblock copolymers, the blending between the WMA modified SBSMA and synchronous rejuvenated SBSMA was completed in the form of mutual diffusion, showing the highest diffusion coefficients (10−7).

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.

Laboratory and Field Performance Evaluation of Cracking of Airfield Warm Mix Asphalt with Reclaimed Asphalt Pavement at the National Airport Pavement and Materials Research Center

The U.S. Federal Aviation Administration is exploring initiatives to decrease transportation greenhouse gas emissions by developing carbon reduction strategies, including using low-embodied carbon materials, such as reclaimed asphalt pavement (RAP), in airport pavement construction. However, verifying RAP’s viability for airfield pavements with laboratory and field performance measures is essential. This study compared the cracking susceptibility of a P-401 hot mix asphalt and warm mix asphalt (WMA)+RAP airfield mixes using laboratory performance tests and conducted a preliminary evaluation of pavement responses from accelerated pavement testing (APT) fatigue tests. The observations and outcomes presented in this paper found that adding 20% of recycled materials with WMA additives had a decreasing impact in mix performance but did not overly affect the asphalt mix properties, as cracking properties from the different test procedures were found with comparable outcomes. Additional observations from strain gauges and temperature probes in the National Airport Pavement and Materials Research Center test cycle 2 APT fatigue test sections showed that the maximum tensile strains in the WMA surface lane 5 south section were consistently higher than those in the WMA+RAP lane 6 south section, which may be because of the higher load level that it was exposed. Additionally, the hardened or aged RAP binder in the entire lane 6 south section may have increased its stiffness, resulting in lower strain levels than in the lane 5 south section. Notably, both sections showed an increase in tensile strains with an increase in asphalt concrete temperature, which confirmed the temperature dependency behavior of asphalt concrete.

Evaluation of the influence of warm additives modified by Vestenamer polymer on the performance of stone matrix asphalt containing crumb rubber

This study aimed to evaluate the impact of Vestenamer polymer and warm mix asphalt (WMA) additives (Zycotherm, Sasobit, and PAWMA) on the resilient modulus and rutting behavior of crumb rubber (CR)-modified stone matrix asphalt (SMA) using resilient modulus and wheel tracking tests. The resilient modulus test illustrated that CR-modified SMA mixtures containing WMA had a greater resilient modulus than the control mixture. Also, Sasobit had the highest effect on enhancing the resilient modulus. The wheel tracking test revealed that in each percentage of CR, WMA additives decreased the rutting depth of SMA mixtures, and Sasobit represented the lowest rutting depth among WMA additives. By adding 8, 12, and 16% CR, the rutting depth of SMA was reduced by 30.57%, 50.03%, and 64.76%, respectively, compared to the control sample. Therefore, the application of CR-modified SMA mixtures containing Sasobit can have a considerable impact on improving the rutting resistance of asphalt pavement.

ASPHALT BINDERS EMPLOY VARIOUS ORGANIC ADDITIVES: PHYSICAL AND RHEOLOGICAL QUALITIE

Several studies aim to reduce surface temperatures and improve the performance of hot mix asphalt. These studies have occurred to reduce the global warming phenomena and economic concerns. We're researching how organic materials affect the viscosity of modified asphalt. Asphaltan A, Asphaltan B, Asphaltan C, and T-grade are organic additives. temperatures with the asphalt binder were employed in the current study. These organic additives were used to improve the characteristics of hot-mix asphalt. In addition, it increases the durability, and lifespan of pavement and reduces mixing and compaction temperatures. A penetration grade bitumen of 40/50 was used in this study. Then, pure bitumen was added to the organic additives to modify binders containing varying concentrations of each additive. Physical properties were performance at different levels of additives. In the research, conventional bitumen/asphalt should be adjusted due to climate conditions, strong traffic loads, and growing axial loads. As a result, asphalt mixtures comprehending bitumen with a high penetration index are less prone to low-temperature cracking and irreversible deformation. Traditional asphalt studies found that bitumen samples with the softening point of warm mix asphalt additives were greater rate, and were less susceptible to temperature changes. The introduction of organic compounds increased the penetration and softening point of the asphalt substantially. This indicated that the stiffness and thermal expansion of the binder had gotten better.

Presentation of machine learning methods and multi-objective optimization of fracture indices for asphalt rubber mixtures containing wax-based warm mix additives modified by nano calcium carbonate

Warm mix asphalt (WMA) additives have been proposed to overcome the high viscosity problem of crumb rubber modified asphalt (CRMA) binders. Various additives have been used to improve the low-temperature cracking performance of asphalt mixtures, but no study has been conducted to present the optimum additive content in CRMA binders in different loading modes. Therefore, this research aims to present the optimum content of nano calcium carbonate (NCC) to improve the fracture toughness and energy of asphalt rubber mixtures containing WMA additives (slack wax (SW) and polypropylene wax (PPW)). The semi-circular bend (SCB) fracture test was applied under pure mode I, mixed mode I-II, mixed mode II-I and pure mode II loadings at subzero temperature. Machine learning methods, including multivariate regression (MVR) and artificial neural network (ANN) models of group method of data handling (GMDH) and multilayer perceptron (MLP), were used to provide the prediction models of effective stress intensity factor (Keff) and fracture energy (Gf). Finally, the multi-objective optimization of Keff and Gf was performed to obtain optimum NCC content. The results indicated that in MVR model, the outputs had a small correlation with laboratory values, so that R value of MVR was 0.8406 and 0.8011 for Keff and Gf, respectively. Also, it was revealed in MVR that NCC had the highest impact on Keff and Gf significantly. GMDH model results showed that the relationships between predicted and laboratory values of Keff and Gf are appropriately described with R value of 0.9546 and 0.9229 for Keff and Gf models, respectively. In MLP model, different layer structures of the feed-forward neural network were developed to obtain the most accurate structure. It was indicated that MLP with 4–22–1 and 3–19–1 structures had a higher accuracy for Keff and Gf prediction models with R value of 0.9951 and 0.9978, respectively. Finally, by the use of the best model relationships, the results of the multi-objective optimization indicated that 4.91% and 6.37% NCC were the design optimum contents resulting in a maximum of Keff and Gf simultaneously for SW and PPW-modified CRMA mixtures. Moreover, the optimum NCC contents in loading modes of mode mixity Me of 1, 0.8, 0.4 and 0 were 3.62%, 5.12%, 4.08% and 3.42% for SW-modified CRMA mixtures and 4.35%, 6.51%, 7.19% and 2.84% for PPW-modified CRMA mixtures, respectively.

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.

Full-component cascade utilization of waste cooking oil in asphalt materials

Resources utilization of waste has become a global challenge with both environmental and economic issues. To realize the refinement recycling of waste cooking oil (WCO), a novel strategy was proposed in this work for the cascade utilization of different components of WCO in asphalt materials. Given the characteristics of each component in WCO, the analysis and verification were carried out for WCO as aged asphalt rejuvenators, warm mix asphalt additives, and thermal storage materials for asphalt thermoregulation. The results show that WCO components can be classified into three categories based on the nature of the fatty acid esters, namely waxy components, light oil components, and heavy oil components. Both light oils and heavy oils demonstrate great potential as rejuvenators of aged asphalt in terms of rheological properties and microscopic characteristics. Furthermore, it is worthy of expectation to select appropriate WCO components for performance recovery according to the actual aging degree of asphalt pavement. The waxy components of WCO can be applied for asphalt thermoregulation and warm mix asphalt additives after hydrolysis and ammonolysis respectively, which is conducive to improving the durability of roads, reducing the energy consumption and volatile organic compounds emissions during the construction process. The findings of the study contribute to the sustainable development of highway engineering and the recycling of waste resources.

Zeolite-Like Warm-Mix Asphalt Additive: Dosage Optimization Based on Asphalt Binder Characterization

Abstract The major objective of this research was to augment the temperature reduction characteristics of the recently developed sodium aluminate tetraethyl ammonium hydroxide montmorillonite (STEAM) warm-mix asphalt (WMA) additive by optimizing 8 dosages of 20 STEAM variants mixed with one viscosity graded-30 base asphalt binder. As the first step in the optimization process, a series of molar combinations of sodium aluminate and tetraethyl ammonium hydroxide were blended with constant concentrations of weights of montmorillonite (MMT) and water. The Fourier transform infrared (FTIR) spectroscopy test was performed on all the 20 STEAM variants to derive the hydroxyl functional groups and understand if they have potential in reducing the mixing and compaction temperatures of the STEAM-modified asphalt binder. The FTIR results indeed indicated that hydroxyl bonds increased with increasing MMT content, as a consequence of MMT releasing itself when mixed with the base asphalt binder. Next, the STEAM additives were mixed with the base binder at 8 dosages with 2 molar ratios covering 20 STEAM-modified asphalt binders on which penetration, softening point, and rotational viscosity tests were performed mainly to establish the ASTM Ai-VTSi relationships. Depending on the combination of molar ratio and dosages, the STEAM-modified asphalt binders demonstrated a decrease of about 3°C–8°C of mixing and compaction temperatures. Furthermore, the STEAM additive that exhibited highest reduction in mixing temperature was blended with dense-graded aggregate gradation to produce a STEAM-modified asphalt mix, which reduced the production temperature by 10°C based on the equivalent mixture performance criterion while also demonstrating stiffness performance similar to that of a control mix. Overall, the optimized indigenous STEAM WMA additives proved to be water-containing, zeolite-like products that have immense capacity in minimizing the working temperatures, albeit further studies should focus on tapping the full potentiality of several STEAM combinations to render the products as globally acceptable “green” paving materials.

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.

Effects of finer gradation, temperature, warm mix additives, and compaction methods on density and performance of asphalt mixtures

The pavement service life can be extended by producing asphalt mixes that are easier to compact and are more likely to result in higher in-place density during construction. Some potential strategies to improve compactibility and increase density include finer gradation, warm-mix asphalt (WMA) additives, increasing binder content, and increasing the asphalt mixing and compaction temperatures. In this study, the cracking and rutting performance of a more economical mix design method with finer gradation was quantified and compared with the standard mixes. The effect of using WMA chemical additives on the compactibility and performance of HMA mixes was also determined. Besides, the impact of temperature and high binder content were investigated on both gyratory compacted, and roller compacted samples in the laboratory. The results indicated that WMA mixes provided significantly higher (1.5 to 2 times higher than the HMA levels in some cases) cracking resistance than the corresponding HMA mixes.

Effect of chemical warm-mix additives on asphalt binder rheological and chemical properties in the context of aging

Warm-Mix Asphalt (WMA) has achieved gradually increasing popularity among researchers and agencies because of the environmental and economic benefits associated with lower production temperatures. An ongoing research study sponsored by the Oklahoma Department of Transportation (ODOT) is focusing on evaluating how different chemical WMA additives and the associated lower production temperatures impact asphalt binder and mixture properties and exploring potential relationships between asphalt rheology and chemistry in the context of chemical WMA and various aging conditions. This manuscript presents partial findings from this study that involved testing of two binder types (modified and unmodified binder) and four different WMA additives (chemical additives). Different aging conditions were simulated by changing the Rolling Thin Film Oven (RTFO) temperature, and by subjecting the binder to different cycles of Pressure Aging Vessel (PAV) aging. Frequency and Temperature Sweep tests by a Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests were performed for rheological characterization, while Fourier Transform Infrared Spectrometer (FTIR) test was conducted for chemical characterization. Analysis of the test results indicated that while all the WMA additives can improve the rheological and chemical properties of control binders at original and RTFO conditions, two additives cause inferior properties after 20 h, 40 h, and 60 h of PAV aging, indicating possible higher aging susceptibility and long-term performance concerns. Good correlations (R2 greater than 0.8) observed between binder rheological parameters and chemical indices indicate the existence of fundamental relationships between asphalt binder’s engineering properties and chemical make-up, which also supports the possibility of using FTIR as a quick screen or fingerprint tool for binder selection and comparison. Two new rheological parameters have been proposed for evaluation of the polymer-modified binder in this study. This was important to address the presence of multi-transition behavior in modified binders. These two parameters show consistent trends with increasing aging conditions.

Understanding the moisture sensitivity of warm-mix asphalt binders based on bond strength

Moisture damage in asphalt mixtures is typically attributed to the loss of bond strength at the interface of the asphalt binder and aggregate matrix. Selecting an appropriate combination of materials that resist moisture-induced damage is therefore critical. This concern is of utmost importance when asphalt mixtures are prepared at lower temperatures (i.e. warm-mix asphalt (WMA) mixtures). An attempt was thus made to quantify the impact of moisture on asphalt mixtures prepared using four different WMA additives and two aggregates through bond strength tests. The results showed that WMA binders imparted similar or even higher bond strength than the base asphalt binder, regardless of the aggregate source and moisture exposure (wet or dry). The use of WMA additives improved the moisture sensitivity (evaluated through the bond strength ratio), despite lower production temperatures, compared with the base asphalt binder (VG30). Statistical analysis showed that the asphalt binder type significantly affected the bonding mechanism and moisture sensitivity. Based on the ranking protocol used in this study, use of the chemical-based WMA additive Rediset showed the best performance compared with other WMA additives in VG30.

Effects of Asphalt Binder Additives and Industrial Fillers on the Mechanical and Functional Properties of Open Graded Friction Course

Open graded friction course (OGFC) is widely recognized for its environmental and safety benefits (e.g., water drainage and noise reduction). However, based on durability concerns, many states have limited the use of OGFC. The objective of this study was to evaluate the effectiveness of warm mix asphalt (WMA) additives, by-products (i.e., crumb rubber [CR]), and industrial fillers (i.e., Portland cement and fly ash) in enhancing the laboratory performance of OGFC mixes. To achieve this objective, a comprehensive experimental program was conducted to evaluate the performance of eight mixes at three distinct stages (i.e., production, construction, and service). A suite of laboratory tests was conducted including draindown, prediction of compaction energy, Cantabro abrasion loss, Hamburg wheel tracking, Texas overlay, modified Lottman, and boiling tests to evaluate production, compaction, and OGFC resistance to raveling, permanent deformation, cracking, and stripping damage. Results indicated that CR, Portland cement, and fly ash significantly enhanced OGFC durability while maintaining adequate functional performance. In addition, results also showed that the use of an organic WMA additive considerably reduced the production temperature and compaction effort required to place the mix at the desired density while showing a significant improvement in OGFC durability.

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.

Optimizing the Dose of Warm-Mix Asphalt Additives by Maximizing the Asphalt-Aggregate Adhesion Measured via Surface-Free Energy

Warm-mix asphalt (WMA) is a group of technologies focused on reducing the viscosity of the asphalt binder (or binder) to produce asphalt mixtures at a reduced temperature compared with that specified for conventional hot-mix asphalt mixtures. The WMA technologies include two main groups: foaming and additives. The additives can be classified as synthetic-chemical or natural-based. This study aims at assessing the feasibility of optimizing the WMA additives dose by maximizing the adhesion between the asphalt binder and the aggregate at their interface in WMA mixtures. Adhesion is quantified using energy parameters derived from surface-free energy measurements (SFE), including three WMA additives (Carnauba wax, a natural-based warm-mix additive, Sasobit, and Evotherm). Accomplishing this objective required measurements of SFE for four different asphalt binders, and corresponding WMA-modified asphalt binders were performed. The results suggest the possibility of identifying a WMA-additive dose that maximizes adhesion at the binder–aggregate interface in terms of resistance to fracture (i.e., adhesive failure) and moisture damage, and the wettability of the binder. In addition, the results showed that the inclusion of Carnauba wax as a warm-mix additive yielded equivalent adhesion at the binder–aggregate interface compared with the response of the other commercially available WMA additives evaluated (i.e., Sasobit and Evotherm). Additional studies at the mixture level are recommended to validate further the conclusions obtained in this study.

Exploring the consequences of reduced aging on the performance of warm mix asphalt binders

ABSTRACT Warm mix asphalt (WMA) technology has proven to be a viable alternative to asphalt pavement production due to its lower mixing and compaction temperatures. However, the performance of asphalt binders is a concern linked to WMA technology due to its reduced aging effect. This study investigates the impact of redcued aging temperature on the performance of two different WMA additives blended with VG30 binder. Fourier transform infrared spectroscopy (FTIR) was performed to check changes in chemical composition of asphalt binder due to aging. Performance of the WM modified asphalt binders was assessed using linear amplitude sweep (LAS), multiple stress creep and recovery (MSCR), and bitumen bond strength (BBS) tests. FTIR analysis showed that used WMA additives increases the aging resistance of asphalt binder. Test results revealed that the application of Rediset enhanced the fatigue performance compared to neat and Sasobit modified asphalt binder. On the other hand, Sasobit decreased the non-recoverable creep compliance (Jnr) and increased the percent recovery (%R), whereas the contrary trend was observed with the addition of Rediset. It was found that Rediset exhibits the antistripping properties thereby improving the bond between asphalt binder and the aggregate, even at reduced production temperature.