Warm Mix Asphalt Additives Research Articles

Improving Durability of Asphalt Pavements in Louisiana through Increased In-Place Field Density

The objective of this project was to evaluate the effects of increasing the initial in-place density of asphalt pavements on expected field performance and durability. This study was completed as part of the FHWA’s demonstration project on “Enhanced Durability through Increased In-Place Pavement Density.” Two approaches for increasing in-place density were explored: (i) the addition of an Evotherm warm-mix asphalt (WMA) additive at a dosage rate of 0.6% by the weight of mix; and (ii) the addition of 0.2% asphalt binder (Plus AC) to the design optimum asphalt binder content of standard dense-graded mixtures. The field component of the research involved three 4,000-ft long test sections representing control hot-mix asphalt (HMA) mixtures, Evotherm WMA mixtures, and the Plus AC HMA mixtures. Each test section included a binder and a wearing course for a total of six mixtures. Density measurements were determined in the laboratory from field cores taken at each test section. The high- and intermediate-temperature properties of field cores were evaluated using the Loaded Wheel Tracking and Semi-Circular Bending tests, respectively. Further, the Indirect Tensile Dynamic Modulus (IDT |E*|) test was conducted for full viscoelastic characterization of the asphalt mixtures. The two approaches considered in this study were successful in increasing field density, especially for the binder course mixtures. The two strategies for increasing in-place density also resulted in better than expected resistance to cracking and rutting, as well as an increase in mixture stiffness as measured by the IDT |E*|.

Field and simulated rutting behavior of hot mix and warm mix asphalt overlays

Research implementing new pavement technologies often focuses on material characterization; however, expanding the research to study and validate how new technologies influence pavement design is needed for continual improvement. Numerical analysis approaches use laboratory mixture data to predict field performance. This study compares predicted rutting by MEPDG design, estimated rutting from Finite Element (FE) simulations, and actual rutting performance in the field. Ten years ago, warm mix asphalt research was underway to measure the effect of warm mix asphalt (WMA) additives and lower production temperatures on performance. WMA benefits include reduced mixing/compaction temperatures, reduced fuel consumption, and improved compatibility. In 2009, three asphalt overlay projects were constructed in Iowa using both hot mix asphalt (HMA), and WMA mixes to compare their performance. A series of dynamic modulus tests were conducted to determine dynamic modulus and phase angles of HMA and WMA mixtures. The dynamic modulus results were used to develop FE viscoelastic simulations to predict the rutting of HMA/WMA pavement sections. Iowa’s pavement management system provided field rutting of WMA/HMA sections. Also, pavement sections were evaluated using mixture input parameters in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The results showed MEPDG based on linear elastic theories might overestimate the rutting of asphalt pavements, especially overlays placed on Jointed Plain Concrete Pavement (JPCP). In contrast, the FEM based on viscoelastic theories more accurately predicted the rutting of pavements. Calibration coefficients are proposed by this study, which may be useful for design engineers and industrial applications to correct and modify MEPDG overlay design thicknesses for HMA/WMA mixes placed on HMA and JPCP surfaces.

Production temperatures and mechanical performance of rubberized asphalt mixtures modified with two warm mix asphalt (WMA) additives

Studies show that warm mix asphalt (WMA) technology is a practical solution against the high production temperature of rubberized-asphalt (RA) mixtures. RA mixture containing WMA additive is considered as an eco-friendly technology contributing to noise reduction and performance optimization of asphalt mixtures. This study aims to introduce two organic WMA additives called slack wax (SW) and polypropylene wax (PPW) which are used to lower the production temperatures by reducing the viscosity of RA mixtures. Rotational viscosity (RV) as a common bitumen test (Equiviscous, ZSV, and S-ZSV methods), as well as tests related to mixtures including resilient modulus (Mr) and moisture susceptibility (TSR and MRR methods), were carried out on binder and mixture specimens. According to the results, 6% (by the binder’s weight) of both WMA additives reduced the mixing and compaction temperatures of the RA binder by about 20–25 °C. Also, CRM and both WMA additives improved the stiffness of mixtures by increasing the resilient modulus (Mr). In terms of moisture susceptibility, although nearly all specimens could pass the minimum requirement of SCDOT, both WMA additives and CRM caused a reduction in ITS value of wet mixtures and final TSR value. MRR test results followed a similar trend, though resilient modulus was more sensitive to moisture damage compared to ITS. The results suggest that PPW and SW are suitable and cost-effective warm additives that can be used in combination with CRM in areas with hot climates and low precipitation. Nevertheless, additional experiments should be done to further validate the performance of CRM mixtures with these two warm additives.

Influence of water on warm-modified asphalt: Views from adhesion, morphology and chemical characteristics

It has been proven that warm mix asphalt (WMA) has great potential for reducing the fuel consumption and polluting emissions during the construction of asphalt pavement. However, the moisture susceptibility of WMA is one of the main concerns associated with this material, and it limits the wide application of this technology. In this study, a styrene–butadienestyrene (SBS) modified asphalt was selected as a control binder, and two types of WMA additives with different dosages were used to prepare warm modified asphalt binders. Atomic force microscopy (AFM), dynamic shear rheometer (DSR), and fourier transform infrared spectroscopy (FTIR) tests were carried out to evaluate the influence of water immersion on the nano-adhesion properties, morphological characteristics, stiffness, and chemical constituents of asphalt with and without the WMA additives. The results showed that several changes in the asphalt resulted from water immersion, including a decline in the adhesion performance, the appearance of small bumps on the surface of the asphalt, an increase in asphalt stiffness, and the amount of oxygen-containing functional groups and polar components in the asphalt. In addition, the SBS modifier in the asphalt remained stable during water immersion. Considering the effects of the WMA additives, it was found in this study that the water-induced adhesion degradation, oxidative aging, and increase of the polar components in asphalt could be delayed with the use of Sasobit.

Effect of optimized short-term aging temperature on rheological properties of rubberized binders containing warm mix additives

This study investigates the effect of warm mix asphalt (WMA) additives and base binder, on the rheological properties of crumb rubber modified binder (CRMB-55) at higher temperatures. The rheological properties of the base binder VG-30, VG-40, and CRMB-55 are subjected to optimized short-term aging and compared with its unaged condition. WMA such as Sasobit and Rediset additives enhance the CRM binders by optimizing the mixing temperature by reducing it to 18 °C through the rotational viscometer (RV) test. This optimized temperature is implemented on the RTFO aging temperature at 177 °C and compared with both standard mixing temperature of 163 °C for the base binder and 195 °C for the crumb rubber modified binder to simulate the ideal mixing viscosity and to determine its rheological properties. In this study, the dynamic shear rheometer (DSR) is employed to measure the complex shear modulus (G*) and the phase angle (δ) of all the binders at various short-term aging temperatures. The Fourier transform infrared spectroscopy (FTIR) and the Scanning Electron Microscopy (SEM) are also applied to justify the effects of the WMA additives on the CRM binders in terms of chemically and morphological properties. It is identified that the two WMA additives can improve the rheological properties of the CRM binders more effectively by optimizing the short-term aging temperature, and greatly enhance the viscoelastic properties at the high-temperature condition for the CRM binders. It is found that Sasobit has the most remarkable effect on G* and δ at 177 °C RTFO-aged for CRMB-55 than with the Rediset WMA additives, and always suggest implementing this optimized short-term aging temperature for CRM binders before evaluating any rheological behaviour.

The Role of Additives in Warm Mix Asphalt Technology: An Insight into Their Mechanisms of Improving an Emerging Technology.

The asphalt industry’s incentive to reduce greenhouse gas emissions has increased since the 1990s due to growing concerns on environmental issues such as global warming and carbon footprint. This has stimulated the introduction of Warm Mix Asphalt (WMA) and its technologies which serve the purpose of reducing greenhouse gas emissions by reducing the mixing and compaction temperatures of asphalt mix. WMA gained popularity due to the environmental benefit it offers without compromising the properties, performance and quality of the asphalt mix. WMA is produced at significantly lower temperatures (slightly above 100 °C) and thus results in less energy consumption, fewer emissions, reduced ageing, lower mixing and compaction temperatures, cool weather paving and better workability of the mix. The latter of these benefits is attributed to the incorporation of additives into WMA. These additives can also confer even better performance of WMA in comparison to conventional Hot Mix Asphalt (HMA) methods. Even though there are recommended dosages of several WMA additives, there is no general standardized mixture design procedure and this makes it challenging to characterize the mechanism(s) of action of these additives in the warm mix. The effects of the addition of additives into WMA are known to a reasonable extent but not so much is known about the underlying interactions and phenomena which bring about the mechanism(s) by which these additives confer beneficial features into the warm mix. Additives in a certain way are being used to bridge the gap and minimize or even nullify the effect of the mixing temperature deficit involved in WMA processes while improving the general properties of the mix. This review presents WMA technologies such as wax, chemical additives and foaming processes and the mechanisms by which they function to confer desired characteristics and improve the durability of the mix. Hybrid techniques are also briefly mentioned in this paper in addition to a detailed description of the specific modes of action of popular WMA technologies such as Sasobit, Evotherm and Advera. This paper highlights the environmental and technical advantages of WMA over the conventional HMA methods and also comprehensively analyzes the mechanism(s) of action of additives in conferring desirable characteristics on WMA, which ultimately improves its durability.

Comparative Rheological and Mechanical Characteristics of Different Warm-Mix Asphalt Additives Under Aging Conditions

This study compares the rheological and mechanical characteristics of three different kinds of warm-mix asphalt additives (WMAA) namely: natural zeolite (NZ), synthetic zeolite (SZ) and manufactured zeolite (MZ). 40/50 Dora penetration grade bitumen and one dosage of each WMAA were chosen. The resultant WMA binders were subjected to penetration, softening point, ductility, elastic recovery, Furol viscosity, elastic modulus, temperature susceptibility, aging, cracking index, compatibility, extensional viscosity, and shear strength tests. Test results depict that the rheological and mechanical characteristics of NZ and MZ binders are better than SZ binder against resistance to high and low temperature effects.

Performance and Aging Characteristics of Hot Mixture Asphalt with Crumb Rubber and Warm Mix Asphalt Additives

In this study, the mixes prepared using crumb rubber (CR) and binders with warm mix additives were aged through various aging methods (1, 2, 3, and 4 weeks at 60°C in the laboratory; 2, 4, 6, 8, 10, and 12 months under the environmental conditions; and AASHTO R30) and examined in terms of performance and aging index. The indirect tensile strength (ITS), indirect tensile stiffness modulus (ITSM), and fatigue tests were applied to the pure and the CR, CR+Sasobit, and CR+Evotherm modified aged and nonaged mixes, and the aging indexes were determined according to the results obtained. According to the test results, CR+Sasobit was found to be the best mix in terms of mechanical properties. Using the warm asphalt additives in the CR modification was determined to decrease the aging indexes and retarded the aging. Also determined was that a high correlation exists between the aging at 60°C in the laboratory and the aging under the environmental conditions. Based on the fatigue test results, AASHTO R30 short-term aging (4 h at 135°C) was determined to cause structural deterioration in the mixes and yielded low load repetition relative to the pure mixes. Therefore, using this method for the short-term aging of the CR modified mixes would not be appropriate. When the tests applied were evaluated in terms of the aging indexes, the fatigue test was found to be the most sensitive method for detecting aging in the pure mixes and mixes with additives.

Rejuvenating effect of soft bitumen, liquid surfactant, and bio-rejuvenator on artificial aged asphalt

Challenges are existing when applying high percentages of reclaimed asphalt pavement (RAP) into construction as the aged RAP binder became more brittle, and stiffer after second-round usage. The bio-rejuvenator with dramatic environmental effects can alleviate stiffness and increases viscous components of aged RAP binder and is becoming popular in the incorporation with RAP. Unfortunately, till now, there is no research available to fully characterize and compare the regenerating effect between bio- rejuvenator, soft bitumen, and warm mix asphalt additives on high artificial RAP binder. To overcome this issue, in this study, a bio-rejuvenator and the other two rejuvenators including soft bitumen and Evotherm-DAT, were used to quantify the difference on regenerating effects of asphalt binder with different contents of artificial RAP binder. Penetration, softening point, rotational viscometer, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) test were performed to characterize the basic properties, workability, and rheological properties of prepared samples. Test results showed that the bio-rejuvenator had the most effective rejuvenating impact, while its improvement on low-temperature performance was limited when it was used on binder containing 80% of artificial RAP binders. In addition, Evotherm-DAT had a significant softening effect on binder containing 30% of artificial RAP binders. Finally, it was found that Evotherm-DAT and bio-rejuvenator can perform well when maximum artificial RAP binder contents were 50% and 80%, respectively. The results of this study indicate possible uses of three different rejuvenators to improve the rejuvenating performance on the high percentage of RAP binder.

Multi-scale study on the high percentage warm-mix recycled asphalt binder based on chemical experiments

With the development of the transportation industry, the requirements for the warm mix asphalt (WMA) involving high percentage of reclaimed asphalt pavement (RAP) are becoming increasingly high due to its benefit in energy cost and environment. This paper focuses on the chemical properties and multi-scale research of the high percentage warm-mix recycled asphalt (WMRA) binder. Three contents of RAP binder, 30%, 50% and 70%, and two types of warm-mix asphalt additives i.e., polyethylene wax (R) and surfactant (M) were considered. The Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) tests were carried out on the recycled asphalt binders in this paper. The results showed that there was no reverse reaction of aging in the recycling process, and no patterns of change were found between the content of RAP binder and the carbonyl index/sulfoxide index. The increase in the large molecular size (LMS) distribution of the three types of WMRA binders after short-term aging was generally higher than that after long-term aging. After aging, the change in the LMS of the RAP-R binder was relatively large, and the anti-aging performance was weaker than that of the RAP-M binder. The RAP-R binder improved the low-temperature performance of the binder and showed middle-temperature stability, but its anti-aging properties were worse than that of RAP-M binder. There were clear correlations between the glass-transition temperature and the stiffness modulus, between the complex shear modulus and the weight average molecular weight, and between the rotational viscosity and the LMS. However, the correlation between the aging index and the BBR stiffness modulus was not applicable to the recycled binder. This study lays a foundation for evaluating the performance of WMRA binder at the microscopic level and exploring the mechanisms of warm-mix recycling.

Laboratory Characterization of Asphalt Binders Containing a Chemical-Based Warm Mix Asphalt Additive

Abstract Different technologies, namely foamed asphalt, synthetic waxes, zeolites, and chemical additives, are used to produce warm mix asphalt (WMA). This study was undertaken to evaluate the effect of using different amounts of an amine-based chemical WMA additive on the rheology, performance grade (PG), and moisture-induced damage potential of an asphalt binder (PG 58-28). Superpave specifications were used to evaluate the rheological properties and PG of the asphalt binder. Also, a mechanistic approach-based on the surface free energy (SFE) method was used to evaluate the moisture-induced damage potential of the asphalt binder combined with commonly used aggregates in an asphalt mix. It was found that the dynamic viscosity of the asphalt binder was not significantly affected after blending it with the WMA additive. It was also observed that the Superpave high-temperature PG and the rutting factor did not reduce by an increase in the WMA additive content. However, the continuous low-temperature PG of the asphalt binder decreased with an increase in the amount of WMA additive. Furthermore, it was found that the fatigue resistance increased after blending the binder with the WMA additive. The SFE results of the asphalt binder revealed that the WMA additive used in this study reduced the moisture-induced damage potential of the asphalt mixes. However, the extent of this improvement was found to largely depend on the aggregate type. The outcomes of this study are expected to help better understand the influence of amine-based chemical WMA additives on rheological and long-term performance of asphalt mix.

Rheological properties of bitumen containing nanoclay and organic warm-mix asphalt additives

In recent years, utilization of warm mix asphalt (WMA) proven to be an environmental way for reducing carbon dioxide emissions in the production and laying process of asphalt mixtures by decreasing the mixing and compaction temperatures. On the other hand, increasing traffic volumes cause asphalt pavements exposed to higher stresses, which could lead to premature distresses. In order to improve the resistance to distresses and alleviate the drawback of WMA mixtures, modification of the bituminous material has grown significantly. In this research, Sasobit as a warm mix asphalt additive and nano-montmorillonite k10 as a bitumen modifier used to modify the 60/70 and 40/50 pen-grade bitumen. The contents of Sasobit were selected are 0%, 2.5%, 3.5% and 4%, while for nano-montmorillonite k10 these percentages are 0%, 2.5%, 3.5% and 5% (by weight of pure bitumen). The objective of this study is to investigate the effect of additives on the conventional and rheological properties of bitumen. To achieve this goal, conventional tests, rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rheometer (BBR), and direct tension tests were conducted to characterize the properties of pure and modified bitumen. The results indicated that Sasobit has a negligible effect on fatigue and low temperature cracking resistance. Conversely, when increasing the amount of nano-montmorillonite k10, these properties were improved. The results showed that nano-montmorillonite k10 improves the rheological properties of bitumen and reduced drawback effect of Sasobit, especially in low temperature cracking performance.

Evaluation of Warm Rubberized Stone Mastic Asphalt Mixtures through the Marshall and Gyratory Compactors.

Stone mastic asphalt (SMA) mixtures exhibit excellent behaviour; they are highly resistant to reflective cracking and permanent deformation, as well as providing the wearing surface with an optimal texture. However, the production and compaction temperatures are similar to conventional mixtures, which means that there is a significant consumption of energy, as well as greenhouse gas emissions. Warm mix asphalt (WMA) technology, which has been developed over the last few years, might allow lower temperatures without compromising the mechanical behaviour of the mixtures. Also, over the last few decades, rubberized asphalt has proved to be effective in improving the performance and being environmentally suitable, but it requires higher production temperatures than conventional mixtures. In this study, several tests were performed to evaluate the effect of a chemical WMA additive on the compactability and water sensitivity of rubberized SMA mixtures with both the Marshall and the gyratory compactor. The investigation has shown that the gyratory compactor is more suitable for studying compactability and the water sensitivity of rubberized SMA with WMA additives.

Influence of Selected Warm Mix Asphalt Additives on Cracking Susceptibility of Asphalt Mixtures.

Warm mix asphalt (WMA) has been widely accepted as a future asphalt paving technology. Besides clear advantages, there are still some concerns regarding durability and long-term performance of pavements made with this type of asphalt mixtures. One of the most important issues is low temperature behaviour of WMA because certain additives used for temperature reduction can affect bitumen properties. This paper presents the evaluation of low-temperature properties of laboratory-produced asphalt concrete for wearing course with selected WMA additives. One type of bitumen with paving grade 50/70 and five WMA additives of different nature (organic, surface tension reducer and combination of both) were used in this study. The production and compaction temperature of mixtures containing WMA additives was 25 °C lower in comparison with the temperature of the reference mix. To assess the susceptibility of WMA to low-temperature cracking, Semi-Circular Bending (SCB) and Thermal Stress Restrained Specimen Test (TSRST) were used. Supplementary rating was made by analysing Bending Beam Rheometer (BBR) test results of asphalt binders.

Performance Evaluation of Crumb Rubber Asphalt Modified with Silicone‐Based Warm Mix Additives

This research was conducted to elucidate better understanding of the performance of crumb rubber asphalt modified with silicone‐based warm mix additives. Two different silicone‐based warm mix asphalt (WMA) additives (herein Tego XP and Addibit) were used to prepare crumb rubber modified (CRM) warm mix asphalt binders. The viscosity of these CRM binders was measured at different temperatures and shearing rates. Furthermore, softening point and penetration tests, Multiple Stress Creep Recovery (MSCR), Time Sweep (TS), Atomic Force Microscopy (AFM), Frequency sweep (FS), and Fourier Transform Infrared (FTIR) tests were also conducted on prepared samples. Based on these robust and rigorous laboratory experiments, it was established that viscosity of CRM binders was reduced by addition of Tego XP and Addibit WMA additives. However, WMA additives had different influence on rheological properties of the binder. CRM binder with Tego XP improved resistance to rutting of the binders but would degrade the fatigue performance. On the contrary, viscoelastic continuum damage (VECD) model results and those of phase angle approach revealed that the binder with Addibit improved resistance to fatigue cracking of the binders but had no adverse effects on high temperature rutting performance. FTIR test results established a presence of polydimethylsiloxane (PDMS) in CRM binders with Tego XP and Addibit. PDMS is a well‐known hydrophobic organic and inorganic polymer that is water repellent; therefore, binders containing these silicone‐based warm mix additives could be beneficial in resisting moisture damage in asphalt binders and mixtures. Morphology of CRM binders with and without WMA revealed good distribution of the rubber particles in asphalt binder matrix. Further addition of WMA increased surface roughness of the binder, which can be correlated to changes in microstructure properties of the binder. Therefore, the study concluded that addition of Tego XP and Addibit reduces viscosity and improves mechanical properties of the asphalt binder.

Research on Rheological Properties of High‐Percentage Artificial RAP Binder with WMA Additives

With the development of pavement recycling technology, the requirement of reclaimed asphalt pavement (RAP) is substantially increasing. Warm‐mix recycled asphalt (WMRA) technology has made great progress, which can effectively decrease the working temperature and improve the RAP content. In this study, the rheological properties of recycled binders with incorporation of high‐percentage artificial RAP binder (30–70%) were evaluated using two types of warm‐mix asphalt (WMA) additives, i.e., polyethylene wax (R) and surfactant (M). The dynamic shear rheometer (DSR) and beam bending rheometer (BBR) tests were conducted on the recycled binders. The results showed that the temperature and frequency played an important role in determining the complex shear modulus of the high‐percentage WMRA binders. The dependency of phase angle on frequency increased after the long‐term aging. The WMA additive R had a relatively huge impact on the rheological properties of asphalt, which mainly occurred before the PAV aging of recycled asphalt binder; the WMA additive M had no significant impact on the rheological properties of recycled asphalt binder. The WMA additive R enhanced the low‐temperature rheology of recycled asphalt binder, while the WMA additive M enhanced the high‐temperature rheology of recycled asphalt binder. Both of these types of WMA additives improved the antifatigue performance of recycled asphalt binder. The increased content of RAP binder improved the high‐temperature performance and reduced the low‐temperature performance of the recycled asphalt binder. However, it had no obvious impact on the fatigue performance. In addition, there was a good linear relation between the RAP binder content and the two indexes of the multiple stress creep recovery (MSCR) test.

Use of Recycled Material in WMA- Future of Greener Road Construction

Sustainable road construction practice requires an asphalt mix technology that is environmental friendly, energy-efficient, economical and protective for humanity and health. India and many other countries are using Hot Mix Asphalt (HMA) technology for asphalt road construction. HMA has several disadvantages like high production temperature (155˚C to 165˚C), which increases Green House Gas (GHG) emissions. These emissions increase Global Warming and severely affect the respiratory system of paving crew workers. Warm Mix Asphalt (WMA) technology can reduce the mixing and compaction temperature by around 30˚C in comparison to HMA. WMA has many advantages over HMA like fuel-saving, reduced emissions, improved visibility at the site, more incorporation of Reclaimed Asphalt Pavement (RAP). RAP is the old aged flexible pavement material that can be recycled back to construct a new pavement. Researchers found two major issues with the use of RAP in asphalt mixes such as high emission during mixing of RAP with virgin aggregate and premature cracking due to aged (stiff) binder. WMA may resolve these two issues, first by reducing binder’s viscosity at lower production temperature (reducing high emissions during production of asphalt mix) and second, reducing secondary aging of RAP aged binder. Some WMA additives also works as rejuvenators and provide good coating. This paper discusses the WMA technology, it’s classification, mix design guidelines for WMA, era of recycling, use of RAP and Reclaimed Asphalt Shingles (RAS) into WMA and role of rejuvenators in WMA.

Rutting and fatigue performance evaluation of warm mix asphalt mastic containing high percentage of artificial RAP binder

This study investigated the rutting and fatigue performance of asphalt mastics containing high percentage of artificial reclaimed asphalt pavement (RAP) binder and two types of warm mix asphalt (WMA) additives, R and M. The filler/asphalt ratio (F/A) ranged from 0.0 to 1.5 and the recycled asphalt binder was blended with 50% artificial RAP binder. The Superpave high-temperature performance grade test and multiple stress creep recovery (MSCR) test were carried out to evaluate the rutting resistance of recycled asphalt mastic. An approach to determine the optimum filler/asphalt ratio was also proposed based on the MSCR parameter Jnr-diff. The fatigue performance under strain-controlled and stress-controlled load modes was investigated by linear amplitude sweep (LAS) test and time sweep test. It was found that artificial RAP binder, WMA additive M and mineral fillers could improve the high-temperature performance while the incorporation of WMA additive R would offset the advantage of artificial RAP binder in rutting resistance. The fatigue test results indicated that the effects of artificial RAP binder, WMA additives and mineral fillers on the fatigue cracking resistance of asphalt mastic exhibited different dependencies on the load mode. Besides, the energy-based approaches might be more acceptable for evaluating the fatigue life of asphalt materials according to time sweep test results.

Fatigue performance of long-term aged crumb rubber modified bitumen containing warm-mix additives

Recently warm mix asphalt (WMA) technologies have been introduced to rubberized asphalt mixtures to decrease the required construction temperatures and to alleviate the hazardous gas emissions. Rubberized asphalt pavements combining with WMA have the potential to improve the long-term pavement performance. This study aims to investigate the fatigue performance of crumb rubber modified bitumen (CRMB) containing warm-mix additives using different characterization methods. The effects of crumb rubber modifier (CRM) content (5%, 10%, 15% and 22% by weight of base bitumen) and warm-mix additives on the binder fatigue performance were investigated. Various laboratory tests, including frequency sweep tests, time sweep (TS) tests and linear amplitude sweep (LAS) tests, were conducted on the long-term aged binders to obtain indicators of fatigue performance. Results show that there is a good correlation between the measured fatigue life determined by TS tests using the dissipated energy concept and the predicted fatigue life determined by LAS tests using the simplified viscoelastic continuum damage (S-VECD) theory. However, the traditional Superpave fatigue parameter and the G-R parameter cannot characterize accurate enough the fatigue performance of modified binders. CRMB binders exhibit superior fatigue performance compared to the neat bitumen. The effects of warm-mix additives on the fatigue performance are different for neat bitumen compared to CRMB binder. Based on the findings in this study, rubberized asphalt mixture combining with WMA additives is expected to have a promising long-term fatigue performance.

Effect of Warm Mix Asphalt Additives on Freeze-Thaw Resistance of Crumb Rubber Modified Bituminous Mix

Effect of Warm Mix Asphalt Additives on Freeze-Thaw Resistance of Crumb Rubber Modified Bituminous Mix - written by Er. Shah Fahad Riyaz , Er. Parvinderjeet Kaur , Er. Usman Khan published on 2019/12/19 download full article with reference data and citations