Asphalt Additives Research Articles

Elaboration of concrete blocks with addition of crushed asphalt pavement

The main objective of this research is to determine the mechanical behavior of crushed asphalt, considered as the excess material in the paving of roads in Colombia. Initially, this raw material must be ground and, later, articulated to elaborate blocks that can be used as dividing elements in the construction of any civil works project. For the execution of this experimental research, concrete cubes were developed with different percentages of crushed asphalt that were 25%, 50%, and 75% of recycled asphalt addition, considering the Colombian technical standards procedures to develop the mechanical and physical tests. The results indicated that samples with 25% recycled crushed asphalt were determined as the best replacement of the sample for the realization of the blocks which dimensions of 9 cm × 17 cm × 34 cm, with vertical perforations of 4 cm × 3 cm × 10 cm. Finally, tests related to water absorption, the mechanical resistance to compression gave very good results, concluding that concrete blocks with the addition of recycled ground asphalt material can be used in the construction industry with an emphasis on sustainable construction, thus allowing the development of new materials that provide an environmental care contributing thus to the efficient use of natural resources.

Influence of warm mix additive on internal structure of dry process crumb rubber modified mixtures

Performance of asphalt concrete depends highly on its internal structure, which is affected by production temperature, compaction effort and material properties. This study aims to evaluate the internal structure and performance of dry process crumb rubber modified mixtures with warm mix asphalt (WMA) additives. In order to evaluate the effect of WMA additive on these properties, dry process crumb rubber modified WMA mixtures were prepared under different production temperatures applying different compaction efforts. In addition, a radial inhomogeneity analysis tool is developed considering the size fraction and location of aggregate particles, while iPas software is utilized to quantify the contact zone properties. The performance of each test mixture is also evaluated through stability, rutting, and cracking tests. The study outcomes indicate that WMA additive reduces the segregation level of dry process crumb rubber mixtures. In spite of the favorable influence of the WMA additive, there seems a slight decrease in the total contact length and number of contact points of the samples. It is shown that both the control and the WMA mixtures can offer similar performances when compacted at lower temperatures or the same temperature under less compaction effort. The use of DryWMA allows for longer haul distance, less energy for production and limited exposure to fumes during construction.

Environmental assessment of warm mix asphalt incorporating steel slag and high reclaimed asphalt for wearing courses: a case study

ABSTRACT This study quantifies the potential environmental benefits associated with the incorporation of industrial by-products and recycled materials combined with warm mix asphalt (WMA) additives in wearing course mixtures for asphalt pavement construction. An electric arc furnace (EAF) steel slag-based mix and three recycled mixtures incorporating steel slag and fractionated reclaimed asphalt (RA) of varying contents (i.e. 25, 40, and 50%) were analyzed comparatively to reference hot mix asphalt (HMA) using the ‘cradle-to-gate’ approach. The results of this study indicated that the warm asphalt mixture incorporating steel slag and 50% RA is the most environmentally friendly alternative. The greatest environmental benefits result from the combined use of steel slag and reclaimed asphalt, which is attributed to lesser demands for raw material extraction, bitumen production, and resource supply. On the contrary, the contribution of lowering mixtures’ production temperature by 30°C is minimal.

Effect of different fibres on the performance properties of cold recycled mixture with asphalt emulsion

ABSTRACT Fibre is one of the most popular additives in hot mix asphalt (HMA). However, there are few research studies about the application of fibres in cold recycled mixture with asphalt emulsion. In this study, five popular fibres are introduced to the emulsion recycled mixture, including polyester fibre, polypropylene (PP) fibre, polyacrylonitrile (PAN) fibre, lignin fibre, and basalt fibre. The optimum pre-mixing water (OPW) content, optimum emulsion content (OEC) and optimum fibre content of recycled mixtures reinforced by fibres are determined. The indirect tensile strength (ITS), moisture susceptibility, bending cracking at low temperature, rutting and fatigue life of mixtures with these fibres are investigated. The test results indicate that the OPW and OEC of recycled mixture are influenced by types and contents of fibres. Although different fibres lead to obviously different ITS values, the optimum content for each fibre is near 0.3% by weight of RAP. All five fibres improve the performance properties of the emulsion recycled mixture. The improved percentages depend on the type of fibres. Polyester fibre has higher improvement on fatigue life than the other fibres. Therefore, polyester fibre is recommended as the most effective fibre to improve the emulsion recycled mixture.

Thermal and bonding properties of epoxy asphalt bond coats

Epoxy asphalt bond coat (EABC) is one of the thermosetting polymer-modified asphalts, which has been widely employed as a strong waterproof bonding layer between the asphalt concrete and the orthotropic steel bridge deck. In the present work, the influences of asphalt content on the phase separation, viscosity, thermal stability, viscoelastic behavior, mechanical performance, pull-off strength, and adhesive performance of EABCs were characterized by various instruments. Laser scanning confocal microscopy observations showed that phase separation occurring in EABCs depended on the curing time. The asphalt merged to form large spherical particles in the continuous epoxy phase during the cure reaction. The size of asphalt particles increased in the asphalt content. Viscosities of EABCs were higher than that of the pure epoxy and increased with the asphalt content in the initial curing stage. However, the opposite trend was observed in the latter curing stage. The presence of asphalt slightly improved the glass transition temperature and the damping properties of the pristine epoxy. For EABCs, the damping behaviors slightly increased with the asphalt content. The thermal stability of the pristine epoxy was enhanced by the incorporation of asphalt. The addition of asphalt decreased the mechanical, adhesive properties, and pull-off strength of the pristine epoxy. What’s more, these properties of EABCs decreased in the asphalt content.

Evaluation of Engineering Properties of Rock-Modified Asphalt Concrete

Abstract The addition of the naturally occurring Buton rock asphalt (BRA) into the asphalt mixtures should be more desirable not only for stiffening the base asphalt but also for the future perspective of pavement recycling. The aim of this article is to evaluate the engineering characteristics of the rock-modified asphalt concrete (RMAC) using comprehensive laboratory tests. Test results showed that the RMAC produced by the wet process generally had better performance in all engineering properties as compared with the RMAC prepared by the dry modification process. The high-temperature performance for the RMACs appeared to be better than that for the unmodified asphalt concrete, but the resistance to raveling of the asphalt mixtures was slightly sacrificed after the addition of the rock asphalt. In addition, it is found that the addition of the rock asphalt stiffened the asphalt to reduce the total viscoelastic response of asphalt mixtures, whereas the polymer modifier increased the elastic component to reduce the viscous component of the asphalt. It is recommended that the percentage of pure rock asphalt (PRA) be no more than 15 % on a weight base of the blend. The BRA content should not be more than 30 % by weight of the RMAC.

Effects of polyphosphoric acid (PPA), styrene‐butadiene‐styrene (SBS), or rock asphalt on the performance of desulfurized rubber modified asphalt

AbstractTo improve the performance of desulfurized rubber modified asphalt (DRMA), especially its high‐temperature performance, three modifiers (including polyphosphoric acid [PPA], styrene‐butadiene‐styrene [SBS], and rock asphalt) were selected to modify DRMA respectively. The conventional performance, rheological properties, chemical composition, and thermal decomposition were characterized to analyze the performance and modification mechanism of DRMA and its composites. Test results show that, the addition of PPA, SBS, and rock asphalt can all improve the high temperature of DRMA, among which the desulfurized rubber/rock asphalt compound modified asphalt (DRMA‐ROCK) has the best high‐temperature performance; however, its construction workability, storage stability, and low‐temperature performance are poor. In contrast, desulfurized rubber/PPA compound modified asphalt (DRMA‐PPA) not only has better high‐temperature performance, but also has excellent low‐temperature performance, storage stability, and fatigue performance. Fourier infrared spectroscopy (FTIR) test confirms that the modification process of DRMA by these modifiers is chemical modification, and the characteristic peak indexes obtained from FTIR also prove that DRMA‐ROCK has better high‐temperature performance but poor construction workability from the microscopic point of view. Furthermore, thermogravimetric analysis‐differential scanning calorimetry test shows that the addition of rock asphalt improves the thermal stability of DRMA, while PPA and SBS decrease its thermal stability. From the above results, it can be concluded that DRMA‐PPA has excellent comprehensive properties.

Coupled effects of warm mix asphalt (WMA) additives and rheological modifiers on the properties of asphalt binders

Asphalt pavements, as an essential element affecting the economic vitality of the countries, are widely used to construct the highways and expressways. Severe climate conditions and traffic loads can influence the service life of asphalt pavements and lead to distresses such as thermal cracking and rutting. Various types of modifiers are used in asphalt industry to enhance the resistance of the pavements to these distresses. Although these modifiers improve a wide range of physical and rheological properties, they increase the construction temperatures, leading to increased energy usage and greenhouse gas emissions. The warm mix asphalt (WMA) technologies provide several techniques and additives to reduce the construction temperature of asphalt pavements and decrease the required energy and air pollution in construction phase. This research aims to investigate the influence of Sasobit and Evotherm M1, as two of the commonly used WMA additives, on the performance of unmodified and modified binders. Three types of modifiers (i.e., polyphosphoric acid (PPA), styrene-butadiene-styrene (SBS), and ground tire rubber (GTR)) were used to modify the binders. The influence of modification on the performance of binders was evaluated through some conventional tests such as viscosity, softening point, and penetration grade. Moreover, the performance grading (PG) tests were conducted at a broad range of service conditions. The results indicate that, with some slight variations, the effects of WMA additives on rheological properties have insignificant dependency on the type of modification. Overall, Sasobit increases the stiffness of binders while Evotherm M1 shows negligible effects on the stiffness properties.

Performance evaluation of asphalt mixtures containing warm mix asphalt (WMA) additives and reclaimed asphalt pavement (RAP)

Global warming and reduced available energy resources have provided strong incentives to find alternative materials and technologies for the construction of pavements. Technologies such as asphalt recycling or warm mix asphalt (WMA) can provide several economic and environmental benefits. This research was initiated to investigate the mechanical and durability performance of WMA mixtures containing 0% and 50% reclaimed asphalt pavement (RAP) made with different types of WMA additives including Sasobit®, Kaowax®, Zeolite®, and PAWMA®. For this purpose, various mechanical tests including dynamic creep at 54.4 °C, resilient modulus at three temperatures of 5 °C, 25 °C, and 40 °C, indirect tensile strength (ITS) at 25 °C, and semi-circular bending (SCB) fracture at about 25 °C were conducted. The durability performance of the mixtures was evaluated by calculating the tensile strength ratio (TSR) to investigate the moisture susceptibility of the mixtures. The findings indicated that the mechanical performance of the mixtures depends on the type of WMA additive. Among all the WMA additives evaluated in this study, only PAWMA® decreased the resistance of asphalt mixture to moisture damage. Although the incorporation of RAP material into asphalt mixtures decreases the flexibility and cracking resistance of the mixtures, it leads to a significant improvement in resisting the damages associated with rutting. The mixture containing RAP and Kaowax® resulted in the highest flow number value, while the HMA mixture containing Zeolite® resulted in the lowest flow number value. Moreover, the incorporation of RAP material into asphalt mixtures was found to enhance the moisture damage resistance, the asphalt mixtures containing RAP and PAWMA® showed the highest resistance to moisture damage among all the mixtures studied in this research. In addition, the asphalt mixtures containing RAP and made with Sasobit®or PAWMA® showed the highest resilient modulus and cracking resistance among all the mixtures, respectively.

The effect of using activated dates seed on Hot Mix Asphalt performance

The increasing demand for construction materials and the need to improve the performance of asphalt mixes have led to the depletion of available resources of aggregates. Lots of aggregate alternatives had been studied to partially or fully replace aggregate in asphalt concrete mixes. Indeed, date seeds are found easily in Kuwait. Their properties; such as light weight, very low crushing strength, and low impact value; represent a potential domain to enhance asphalt mix performance. The main objective of this paper is investigating the possibility of using activated date seeds additives in Hot Mix Asphalt (HMA) as a partial replacement of Fine Aggregates (sand). A total of 3 asphalt concrete mixes with different percentages by weight were prepared. Physical and mechanical properties of date seeds and Fine Aggregates (sand) were determined and compared in the asphalt concrete mix design of ratios 7, 10, and 15%. Compressive Strength and Marshall Stability tests were performed to investigate the effect of activated date seeds additives on HMA. Eventually, the findings indicated that the ratio of 10% gave the highest Marshall Stability. On the other hand, the ratio of 7% found to give the highest retained strength index. a deeper statistical analysis is performed to evaluate the robustness and significance of studied factors on response variables represented in Marshal Stability and Flow. The first part of the analysis included recognizing data outliers in data sets and eliminating them to compare basic statistical values with raw data. The minor differences in these values implies minor variability in the measurement and indicates minimal experimental error. T-test analysis was performed to study the influence of date seed percentages on different performed measurements. ANOVA tests were also represented to demonstrate the statistical significance factors on considered response variables. The results supported the significant influence of the included measurements on Marshal stability and flow values.

Effect of wax-based warm mix additives on fatigue and rutting performance of crumb rubber modified asphalt

Nowadays, the use of crumb rubber modified asphalt (CRMA) has gained popularity among the contractors and construction agencies due to the addition of crumb rubber in bitumen, which can increase the life span of asphalt pavement. The experimental studies have also shown that CRMA binder can improve some mechanical properties of asphalt mixture such as rutting and fatigue resistance. However, as a result of higher viscosity in the CRMA binders, higher mixing and compaction temperatures are required. So, to overcome this problem, the use of warm mix asphalt (WMA) additives accompanied with rubberized binders has been proposed. Since it is believed that crumb rubber modifier (CRM) can improve the rheological characteristics of bitumen; therefore, there is a need to more investigate the properties of CRMA binder modified with WMA additives to ascertain its proper usage in pavement construction. In this regard, the main objective of this study was to investigate the effects of two wax-based additives, as Slack wax and Polypropylene wax, on fatigue and rutting resistance of the rubberized binders modified with 15% CRM. Accordingly, the obtained results indicate that both wax-based additives have the ability of reducing the viscosity of the rubberized binders at high temperatures. Also, 2% of Polypropylene wax increased the high temperature performance of rubberized binder up to one grade. According to the results of multiple stress creep recovery (MSCR) test, the lower Jnr3.2 and higher R% values represent that Polypropylene wax can improve the rutting resistance of the rubberized binder, so that the samples containing 2% of Polypropylene wax have a higher rutting resistance than the 4% and 6% samples. Moreover, the Linear Amplitude Sweep (LAS) test’s results indicated that CRMA binders containing 6% of Slack wax have considerably higher fatigue life compared to the control rubberized binder, particularly in low strain levels.

Role of Aggregate Gradation in Balancing the Performance of Asphalt Concrete Mixtures

Improving the durability and long-term performance of asphalt concrete (AC) has become a major concern, especially with the increase in the use of recycled materials, warm mix asphalt additives and modified binders. This paper presents an evaluation of different mix design approaches to balance the mechanical properties of AC mixtures. The current volumetric-based design method was enhanced with a performance-based analysis methodology that specifies the parameters from the overlay tester, Hamburg wheel tracking device and indirect tension tests. Two typical Superpave mixes from different plants that exhibited a poor performance, especially in cracking, were selected for this evaluation. The mixtures were first designed following the current volumetric-based design process and characterized under the proposed performance-based analysis. Two alternative approaches that consider the influence of the asphalt content and the aggregate gradation were explored to improve the engineering behavior of the mixtures. From this evaluation, two mixtures that could potentially yield optimal volumetric and balanced mechanical properties were developed. The optimization of the aggregate gradation is a promising approach to formulate a mixture with a balanced stability and durability, as judged by its rutting and cracking potentials.

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.

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.

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.