Asphalt is the most recycled material in the USA at a re-use rate of 99%. However, by average only 10-20% reclaimed asphalt pavement (RAP) is used in a given mix design and large part of the RAP is ...degraded for use in lower value applications. The amount of RAP in asphalt mixtures can be significantly increased with the application of good RAP management practice, readily available modern production technologies and advanced knowledge of mix design. This paper summarises the state-of-the-art approaches for increasing the amount of RAP in asphalt mixtures above 40%. The production challenges and common pavement distresses of very high RAP content mixtures are identified and methods to optimise the mix design as well as production technology in order to allow manufacturing of such sustainable mixtures are described. The best practices for RAP management and economic benefits of high RAP use are also discussed.
•The properties of HVRA are analyzed by rheological measurements.•The synergistic effect of HVA and RA provide adhesion in high temperature.•RAP deteriorates the performance of recycled PAC in low ...temperature.•HVRA has excellent fatigue resistance performance with increased strain.
The asphalt binder of permeable asphalt concrete has high requirements and there are few studies on mixing reclaimed asphalt (RA) with high-viscosity asphalt (HVA) for recycled permeable asphalt concrete. This study aims to research the wide-temperature-range rheological properties of high-viscosity modified reclaimed asphalt binder (HVRA) which is the bituminous binder in recycled permeable asphalt concrete. First, HVRA was prepared by mixing RA and HVA, wherein RA was extracted from reclaimed asphalt pavement (RAP) and HVA was prepared in the laboratory. Then, the properties of HVRA at multiple application temperatures were analyzed by basic indexes test, dynamic shear rheological test, and bending beam rheometer test. Finally, the comprehensive performance was contrastively evaluated by radar chart. The results revealed that the properties of HVRA are excellent when the high-viscosity modifier (HVM) content is 18 % and 20 %. Additionally, the rheological properties and fatigue resistance of the HVRA showed a decreasing trend with adding RA. Among them, considering rheological properties, the optimal content of HVM in HVA is 18 % − 20 %, and the optimal proportion of RA in HVRA is 10 % − 20 %. Furthermore, the fatigue performance of HVRA is significantly enhanced when HVM content is 18 %, especially the fatigue life of HVRA with 10% RAP is 5–9 times HVA containing 12 % HVM which is regularly used as the bituminous binder.
Reclaimed asphalt pavement (RAP) materials have been considered as one of the most sustainable options in the pavement industry. However, the low shear strength and high permanent deformation ...behaviour of RAP materials often limit their application in road bases. Stabilisation of RAP bases using high-density polyethylene (HDPE) geocell was hence attempted in this study to assess the efficacy of three-dimensional geosynthetic reinforcements in improving the resilient properties of RAP materials and mitigating permanent deformation of them. The present paper discusses the results from a series of large-scale repeated load box tests conducted to study the effectiveness of HDPE geocell-reinforced RAP bases (GRRB). The performance of the geocell reinforcement was evaluated based on various parameters including resilient deformation, cumulative permanent deformation, resilient modulus, traffic benefit ratio (TBR), and rut depth reduction (RDR) factors. Test results show that HDPE geocell layer increased the resilient modulus of the RAP base layer by 2.5-3.3 times and reduced the permanent deformation of RAP base by 70-80% when compared to the unreinforced RAP bases. Test results were then used to perform pavement design to quantify the base thickness reduction with geocell reinforcement.
•A pavement maintenance project at Southeast China is studied.•The variability of RAP obtained form 16 sources are analyzed.•RAP from 16 sources are grouped by cluster analysis.•The maximum addition ...of the grouped RAP sources is determined.
The variability of reclaimed asphalt pavement (RAP) materials obtained from different sources is a major concern for the industry when recycling RAP for recycled asphalt mixtures. Many efforts have been made to minimize RAP variability by pre-mixing, crushing, and sieving of the RAP stockpile. In this study, a perspective for reducing RAP variability is proposed by grouping RAP sources with similar material characteristics, which is expected to minimize such variability from the origin. To is end, an asphalt pavement maintenance project located in South China with 16 RAP sources was selected for the study. Furthermore, material characteristics including aggregate gradation, binder softening point, penetration, and dynamic viscosity of recovered asphalt, for RAP obtained from various sources are analyzed by testing on core samples. After the aggregate gradation is presented via Fréchet similarity, a K-means cluster analysis is conducted with the involvement of aggregate gradation, asphalt content, and softening point of recovered asphalt. Then, the RAP sources are grouped into three groups with similar material characteristics. The results show that there is a significant difference in RAP material characteristics even for the same pavement, and the procedure developed in this study helps to reduce the RAP variability while increasing the RAP maximum addition amount for producing recycled asphalt mixture. The results may be of interest to construction contractors and road management departments because this study was intentionally conducted for use in practical applications.
•The effects of warm mix asphalt (WMA) additives on the performance of asphalt mixtures are studied.•Asphalt mixtures were made with and without reclaimed asphalt pavement (RAP) materials.•The use of ...WMA additives allows for the incorporation of high amount of RAP without compromising the mechanical properties.•The properties of the mixtures significantly depend on the type of WMA additive.
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 cracking resistance of asphalt mixtures declines by adding RAP at 0 °C and 15 °C.•Glass fibers are beneficial for enhancing the cracking resistance of asphalt mixtures.•The positive effect of ...glass fibers can compensate for the adverse impact of RAP material.•The use of RAP material improves cracking performance at −15 °C.
Escalating the price of asphalt binder and environmental issues have led to an increasing desire to use high amounts of reclaimed asphalt pavement (RAP) material in asphalt mixtures. However, increasing the RAP content may have negative effects on some characteristics of asphalt mixtures, such as cracking resistance. Therefore, finding an approach to compensate for the negative impacts of RAP material may be considered as a solution to raise the RAP content in asphalt mixtures. Fibers are known as one of the modifiers that are added directly to the mixtures and enhance the cracking resistance of asphaltic materials. Therefore, in this study, the cracking behavior of asphalt mixtures containing different percentages of RAP material in combination with glass fibers was investigated using the semi-circular bending (SCB) fracture tests at temperatures of −15, 0 and 15 °C. The results showed that using up to 0.12% glass fiber leads to a significant enhancement in resistance of all mixtures against crack initiation and propagation. Moreover, it was found that the negative impact of RAP material on the crack resistance of asphalt mixtures is reversible to a great extent using 0.12% glass fiber, and 100% RAP mixtures are applicable without any significant reduction in crack resistance.
To reduce the cost of epoxy asphalt mixture (EAM) pavement and increase the performance of mixture with high reclaimed asphalt pavement (RAP) content, three different dry-method ...styrene-butadiene-styrene (SBS) modifiers and an epoxy polymer (EP) were employed in this study to enhance the properties of aged asphalt binder and prepare SBS-modified epoxy reclaimed asphalt (SERA) binders. The chemical interaction between the dry-method SBS and EP was analyzed, and the microscopic structure and mechanical properties of the SERA binder were evaluated. Additionally, a discussion on the initial material cost of the newly proposed SERA mixture (SERAM) was conducted. Results indicated that the degraded products generated by the oxidization of dry-method SBS undergo interactive reactions with the epoxy rings present on the epoxy resin molecules. Phase separation occurred both between EP and SBS-containing aged asphalt binder, and between SBS and aged asphalt binder. The addition of dry-method SBS to epoxy reclaimed asphalt (ERA) increased the size of the asphalt binder phase in the fluorescence images. At EP contents ranging from 30% to 50%, the incorporation of dry-method SBS led to notable improvements in the elongation at peak, low-temperature properties, and fatigue resistance of ERA binder. The SERA binder exhibited comparable or even superior properties in terms of tensile strength, low-temperature behavior, and fatigue properties when compared to virgin epoxy asphalt (EA) binder. However, dry-method SBS may have a negative impact on the high-temperature properties and curing time of the binder. Dry-method SBS with rejuvenation capacity exhibited the greatest improvement in elongation at peak, low-temperature properties, and fatigue properties of ERA. Compared to EAM, the utilization of SERAM results in material cost-savings of approximately 46 USD (9%) per ton of mixture.
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•The degraded products of dry-method SBS reacted with epoxy resin molecules.•Phase separation occurred between EP and asphalt, as well as between asphalt and SBS.•Dry-method SBS increased the size of the asphalt binder phase in micro-morphology.•Dry-method SBS enhanced elongation, fatigue, and low-temperature properties of ERA.•The use of SERAM achieves material cost savings of around 46 USD (9%) per tonne.
•Silo storage has a notable effect on the mix cracking and fatigue properties.•The SCB and IDEAL-CT tests are highly influenced by mix aging.•The FI and CTindex show good correlation for the tested ...mixes.•The FI correlates with the displacement at 75 percent peak load.•The FI and CTindex do not correlate with the fatigue life from the flexural beam test.
During production, hot mix asphalt plants can store mixes in silos for a few hours before they get transported to the job site. Additional aging and possible blending between RAP and virgin binders take place inside the silo which affect mix properties. This study addresses the impact of silo storage on mix fatigue and cracking performance. The flexural beam test has been widely established as a representative fatigue test, however due to its complexity, it is difficult to implement as a quality control test. The semi-circular bending test (SCB) and the indirect tensile asphalt cracking test (IDEAL-CT) are simple and quick tests that are currently being used by some state agencies to assess the cracking resistance of asphalt mixes. The ability of SCB and IDEAL-CT to predict fatigue-related cracking as compared to flexural beam testing is also investigated in this study. Four plant-produced mixes were collected before and after silo storage, and tested using flexural beam, SCB, and IDEAL-CT. It was noted that the SCB and IDEAL-CT are highly influenced by the mix stiffness, and the cracking resistance was reduced considerably with silo storage. This finding has important implications when using either of these tests for construction quality control and assurance. It was concluded that the flexibility index (FI) from the SCB and the cracking tensile index (CTindex) from the IDEAL-CT did not provide a direct measure of the fatigue performance as compared to the flexural beam test.
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•Rejuvenators can reduce performance grade to the level of virgin asphalt binder.•Use of appropriate rejuvenator dose allows to pass rutting requirement.•Rejuvenators improve mixture ...cracking resistance.•Workability or rejuvenated mixtures remained lower than for virgin mixture.
100% recycled hot mix asphalt lab samples were modified with five generic and one proprietary rejuvenators at 12% dose and tested for binder and mixture properties. Waste Vegetable Oil, Waste Vegetable Grease, Organic Oil, Distilled Tall Oil, and Aromatic Extract reduced the Superpave performance grade (PG) from 94–12 of extracted binder to PG 64-22 while waste engine oil required higher dose. All products ensured excellent rutting resistance while providing longer fatigue life when compared to virgin mixtures and most lowered critical cracking temperature. Rejuvenated samples required more compaction energy compared to virgin and some oils reduced moisture resistance slightly.
AbstractDry-lean concrete (DLC) lies below the wearing course of the rigid pavement section to overcome the major reasons for its failure, such as improper base support, seepage of underground water, ...and frost action. DLC is generally manufactured with a huge aggregate-to-cement ratio, which lies below the wearing course of the rigid pavement section. In this study, reclaimed asphalt pavement (RAP), a waste material, derived from the milling process of flexible pavement wearing course, has been used as a partial replacement of natural coarse aggregates in DLC made from portland pozzolana cement (PPC). Initially, the feasibility of using washed reclaimed asphalt pavement (WRAP) and comparing the results with dirty reclaimed asphalt pavement (DRAP) as a partial replacement of natural coarse aggregate has been investigated. It was found that WRAP gave better results as compared to DRAP for satisfying DLC conditions. The reason is demonstrated using SEM images showing variation in formation of CSH gel due to the presence of dust particles. Further, strength and durability properties (acidic environment, water absorption, and alkalinity) were determined to check its durability of WRAP-incorporated concrete (WRAPC). The percentage of WRAP and DRAP was varied from 0%–50% by weight of natural aggregate. Also, nondestructive tests like ultrasonic pulse velocity (UPV) and rebound hammer test were performed to determine the quality and dynamic young’s modulus of WRAPC. It was found that the optimal curing period and optimum WRAP addition were 21 days and 20% respectively. An equation has been developed to determine the optimum moisture content (OMC) for varying percentage of moisture and RAP content. The equation was validated with the results of researchers and a variation of only 3.3% was found. It was observed that 20% WRAP incorporated in DLC gives optimal results in terms of strength and durability.
