Download or read book Long Term Effectiveness of Recycling Agents to Improve Performance Properties of Asphalt Concrete written by Mahsa Tofighian and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recycled materials such as reclaimed asphalt pavement (RAP) have been incorporated into asphalt mixtures for many years. However, their usage has increased over time as they are seen as a way to reduce the cost of asphalt mixtures, save energy, and protect the environment. Similarly, there has been a growing focus on the utilization of recycled asphalt shingles (RAS) in asphalt mixtures, a pursuit undertaken by various state highway agencies. However, unless appropriate precautions are taken, as the proportion of RAP and RAS in the asphalt mixture is raised, the mixture becomes more brittle, leading to a higher risk of cracking and raveling in the asphalt pavement. Furthermore, the mixture becomes less workable and more challenging to compact in the field, increasing the potential for premature field failure. One strategy to incorporate more RAP and RAS into asphalt mixtures involves the use of specialized recycling agents (RAs), known as rejuvenating agents. Over time, asphalt mixtures undergo aging during construction and over the extended service life of asphalt pavements, resulting in the oxidation of the mix and the loss of a significant portion of the maltenes in the binder composition. Maltenes contribute to the softening effect of the binder, and these recycling agents, when used appropriately, are expected to compensate for this reduction in maltenes. The ultimate result of this rebalancing of components is the softening of the aged binder and an improvement in its resistance to cracking. This study investigates the long-term impact of bio-based and petroleum-based recycling agents (RA's) on recycled asphalt binders with varying levels of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) content, specifically low (15%) and high (30%) RAP content and 0% and 5% RAS content. The rejuvenated binders underwent short-term and long-term aging through the use of a Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV), respectively. The performance characteristics of these modified binders at various aging stages were assessed using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The study revealed that all RA's used in this research maintained their effectiveness even after long-term aging, though the degree of effectiveness varied. Additionally, the results indicated that the petroleum-based RA required a higher dosage to achieve the same effect as the bio-based RA's. The findings from this research also demonstrated that when rejuvenators are added to mixtures with a high RAP content or a combination of RAP and RAS, the mixture's performance is enhanced in terms of low-temperature cracking and fatigue cracking. Nevertheless, it is crucial to extend this work to field pilot projects to ensure the effective application of these rejuvenating products.
Download or read book Engineered Frameworks for Evaluating the Use of Recycling Agents in Surface Asphalt Mixtures for Virginia written by Jhony Habbouche and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, several state highway agencies have introduced special provisions and specifications to allow the use of higher contents of reclaimed asphalt pavement (RAP) in asphalt surface mixtures. The challenges associated with high RAP mixtures can be addressed through the use of additives such as recycling agents (RAs) and/or softer binders. Currently, there are no specific guidelines or specifications available to evaluate the acceptability of RAs in Virginia. The purpose of this study was to evaluate the short- and long-term effectiveness of RAs in improving the performance of asphalt mixtures, particularly those with high RAP contents. Another objective of the study was to establish a performance-based framework to determine the acceptability of a specific RA product for inclusion in the Virginia Department of Transportation’s Approved Product List. Both objectives were achieved by benchmarking recycled binder blends (Phase I) and mixtures (Phase II). These were then compared in terms of laboratory performance to commonly used virgin asphalt binders and mixtures in Virginia. Moreover, a comprehensive review of the literature and information from state departments of transportation and RA suppliers on the current state of the practice regarding the use of recycled materials and RAs in asphalt mixtures was summarized. Component materials, including three virgin asphalt binders, RAP and aggregate materials from three different sources, and six RAs, were collected and tested. Phase I involved testing virgin and RAP binders; combinations of virgin binder and RAP binder; and combination of virgin binder, RAP binder, and RAs. A total of 26 binder blends were evaluated at various aging conditions through numerous rheology- and chemistry-based tests. In Phase II, 10 asphalt mixtures were designed and evaluated for durability, resistance to rutting, and resistance to cracking at various aging conditions. Cross-scale evaluation of asphalt binder and mixture testing data was established. Finally, preliminary verification was performed using data collected from various field trials constructed in Virginia. Based on the binders and mixtures tested in this study, the effectiveness of RAs in improving the properties of asphalt binder blends is specific to the product being used and to the targeted temperatures or conditions. Moreover, RAs can enhance the performance and increase the use of recycled materials in asphalt mixtures provided that the correct and suitable dosage of RA product is determined through a performance-based testing framework. The study recommends the following: (1) adopting the streamlined frameworks presented in this study to determine the acceptability of a given RA; (2) further validating the presented framework using different component materials; (3) employing balanced mix design tests to assess the performance characteristics of surface mixtures (with A and D designations) with RAs and drafting a roadmap; (4) collecting and further evaluating the field performance of all trials involving high RAP, RAs, and/or softer binders; (5) investigating the availability and activity of binders, especially with RAs, in RAP materials; (6) evaluating and establishing a protocol to assess the consistency of RAP materials; and (7) quantifying the environmental and economic impacts of using surface mixtures with high RAP contents and/or RAs.
Download or read book Characteristics of Asphalt Binders written by and published by . This book was released on 1996 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Properties of Recycled Asphalt Concrete Hot Mix written by Elton R. Brown and published by . This book was released on 1983 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recycling of aged asphalt concrete pavements has been demonstrated to be cost-effective and to reduce the demand for natural resources such as aggregate and asphalt. Because of the advantages derived when using recycled materials, the capability to predict long-term performance is needed so that optimum benefits can be obtained. This study was undertaken to evaluate the laboratory performance to recycled asphalt concrete mixtures and to compare these results to those measured for conventional asphalt concrete mixtures. Results of this study indicated a satisfactory comparison between laboratory performance of recycled mixtures and conventional mixtures. Fatigue analysis indicated that conventional mixtures would provide the greatest fatigue resistance in thick asphalt concrete layers at lower temperatures, while the recycled mixtures would provide the greatest fatigue resistance in thin asphalt layers at higher temperatures. Water susceptability was shown to be related more to aggregate type than to mixture type. The data show that recycled mixtures prepared with the recycling agent produced mixtures with the lowest durability and poorest low temperature performance when compared with the recycled mixtures prepared with AC-5 or compared with the conventional mixtures.
Download or read book Asphalt Binder Aging Methods to Accurately Reflect Mixture Aging written by Ramon Francis Bonaquist and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Asphalt binders experience aging that occurs in two distinct stages under quite different conditions: (1) short-term during construction (plant mixing, storage, placement, and compaction) and (2) long-term during the service life of the pavement. The TRB National Cooperative Highway Research Program's pre-publication of NCHRP Research Report 967: Asphalt Binder Aging Methods to Accurately Reflect Mixture Aging documents research conducted to improve laboratory binder conditioning methods to accurately simulate the short-term and long-term aging of asphalt binders, and to calibrate the improved procedures to the aging that occurs during mixture production, transport, and placement as well as during the service life of the pavement structure.
Download or read book Federally Coordinated Program of Highway Research Development and Technology written by and published by . This book was released on 1983 with total page 838 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recycling Materials for Highways written by National Research Council (U.S.). Transportation Research Board and published by Transportation Research Board National Research. This book was released on 1978 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This synthesis will be of special interest and usefulness to design engineers, materials technologists, and others seeking information on the potential use of recycled materials in design, construction, rehabilitation, and maintenance of pavements, bases, and other components of the highway system. Detailed information is presented on procedures for pavement recycling."--Avant-propos.
Download or read book Asphalt Mixture Components written by and published by . This book was released on 1998 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Binder Rheology and Performance Outcomes of Recycled Hot mix Asphalt Using Different Rejuvenation Agents written by Kerry Jean King and published by . This book was released on 2015 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research presented in this thesis investigated the effect of various rejuvenation agents on the performance of hot-mix asphalt (HMA) surfacing mixes containing high levels of recycled asphalt pavement (RAP) material (30%). The research aimed to develop testing methodologies for evaluating the mechanical performance properties of HMA mixes and for the characterisation of extracted binder properties. The methodologies were used determine the effects of various rejuvenators on the mechanical performance properties and binder properties fundamental to the long-term performance of pavement surfaces. A testing methodology was developed to investigate the performance properties of five HMA mixes including four mixes that were rejuvenated using different rejuvenation agents and one control. The mechanical testing methodology provided a comprehensive assessment of mix properties that are fundamental to the long-term performance of recycled pavements. A methodology for the characterisation of extracted binders was developed to evaluate properties that had a significant effect on the performance of the binder and therefore the overall mix. The binder properties were compared to results obtained from mechanical performance tests to establish a relationship between binder rejuvenation and performance observations. The results obtained from mechanical testing demonstrated that the cracking resistance of recycled mixes could be significantly improved through the use of rejuvenation agents. Rejuvenation also decreased the stiffness of the mix and had a negative effect on the resistance of a mix to permanent deformation. From the characterisation of the binder, it was found that rejuvenation agents altered the rheological properties of the binder but did not have a notable effect on chemical composition. The rheological performance parameters of the binder correlated to the mix performance observed from mechanical tests. Overall this research has shown that rejuvenation agents can be utilised to enhance the performance of recycled mixes by restoring binder properties.
Download or read book Evaluation of Long term Field Performance of Cold In place Recycled Roads written by and published by . This book was released on 2007 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cold in-place recycling (CIR) has become an attractive method for rehabilitating asphalt roads that have good subgrade support and are suffering distress related to non-structural aging and cracking of the pavement layer. Although CIR is widely used, its use could be expanded if its performance were more predictable. Transportation officials have observed roads that were recycled under similar circumstances perform very differently for no clear reason. Moreover, a rational mix design has not yet been developed, design assumptions regarding the structural support of the CIR layer remain empirical and conservative, and there is no clear understanding of the cause-effect relationships between the choices made during the design/construction process and the resulting performance. The objective of this project is to investigate these relationships, especially concerning the age of the recycled pavement, cumulative traffic volume, support conditions, aged engineering properties of the CIR materials, and road performance. Twenty-four CIR asphalt roads constructed in Iowa from 1986 to 2004 were studied: 18 were selected from a sample of roads studied in a previous research project (HR-392), and 6 were selected from newer CIR projects constructed after 1999. This report summarizes the results of a comprehensive program of field distress surveys, field testing, and laboratory testing for these CIR asphalt roads. The results of this research can help identify changes that should be made with regard to design, material selection, and construction in order to lengthen the time between rehabilitation cycles and improve the performance and cost-effectiveness of future recycled roads.
Download or read book Effect of Recycling Agents on the Structural Performance of Recycled Asphalt Concrete Materials written by Dallas N. Little and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Superpave Mix Design written by Asphalt Institute and published by . This book was released on 2001-01-01 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Long Term Performance of High Recycled Asphalt Pavement RAP Mixes and Development of Models for RAP Binder Contribution and Aging written by Logan Dale Cantrell and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recycled asphalt pavement (RAP) is one of the most recycled materials in the United States. It provides many environmental and economic benefits, but RAP usage has stagnated recently. The advancement in rejuvenators and performance testing renews the ability to increase RAP levels and address cracking concerns. This study investigated the use of RAP in asphalt concrete and if it could be increased beyond current limits without adversely affecting long-term performance. These results provide evidence and tools for increasing RAP both in the mix design and production stages. Additionally, the models developed can make implementing performance testing in production much more feasible. Field constructability and performance were first evaluated to ensure current high RAP (HR) mixes are performing adequately. This systematic approach found that HR mixes performed equal or better than low RAP (LR) typical mixes with lower density deviation and less longitudinal cracking. Then, super high RAP (SHR) mixes, with RAP levels up to 100%, were designed using current WSDOT volumetric design standards. SHR mixes were statistically similar in rutting and cracking performance to typical 20% RAP mixes except for polymer modified binder mixes with RAP levels above 80% due to an overall reduction in polymer and degradation of polymer cross-linking. Cracking performance could be improved with the slight addition of a virgin binder. With SHR mixes showing potential, models based on mix mechanics were developed to aid in implementation. First, a model to predict RAP binder contribution (PRBC) was developed based on mix performance testing. Lab results showed that the mix with a neat virgin binder with softer RAP contributed more than the modified virgin binder with stiffer RAP. The model was then adjusted for use with plant mixes and showed HR mixes, and V binders with more PRBC than LR mixes and H binders. An aging model was then developed to predict cracking performance as a mix aged. Next, a logarithmic-based model was chosen to predict aged CTIndex results, which characterizes both oxidative aging and polymer degradation. Finally, a 3D model was created to predict the effects of both RAP addition and aging on CTIndex samples.
Download or read book Moisture Damage in Asphalt Concrete written by Russell G. Hicks and published by Transportation Research Board. This book was released on 1991 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: This synthesis will be of interest to pavement designers, construction engineers, maintenance engineers, and others interested in avoiding or limiting moisture damage in asphalt concrete. Information is provided on physical and chemical explanations for moisture damage in asphalt concrete, along with a discussion of current practices and test methods for determining or reducing the susceptibility of various asphalt concrete components and mixtures to such damage. Moisture damage in asphalt concrete is a nationwide problem which often necessitates premature replacement of highway pavement surfaces. This report of the Transportation Research Board describes the underlying physical and chemical phenomena responsible for such damage. Current test methods used to determine the susceptibility of asphalt concretes, or their constituents, to moisture damage are described and evaluated. Additionally, current practices for minimizing the potential for moisture damage are examined.
Download or read book Sustainable Materials for Pavement Infrastructure written by Louay Nadhim Mohammad and published by . This book was released on 2019 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the price of liquid asphalt continuously climbs, methods are being sought to decrease material costs, which will also have less impact on ecological systems without compromising material or pavement performance. The use of recycled materials is one method that can replace a percentage of their virgin counterparts, thus reducing the negative impacts on the environment. Asphalt mixture performance is affected by the level of blending that occurs between aged and virgin asphalt binders. The interaction and compatibility of recycling agents (RAs) with recycled asphalt shingles (RAS) and reclaimed asphalt pavements (RAP) have not been thoroughly evaluated since the 1970s. To characterize laboratory mixture performance through their mechanistic and volumetric properties, a suite of tests was conducted to evaluate the low, intermediate, and high temperature performance of conventional asphalt mixtures and mixtures containing RAS and/or RAP with and without RAs. Also, the asphalt binders’ molecular structure was correlated with their cracking potential through binder fractionation. With respect to the mixes without RAs, results indicate that RAS binder does not fully blend with the virgin binder. The actual availability factor was found to range from 35 to 46%. Also shown was an improvement in rutting performance, with no adverse effects to intermediate temperature or low temperature performance because the mixtures are comprised of approximately 90% virgin asphalt. For mixtures containing RAs, a modified mixture design change was developed to improve blending between the aged and virgin asphalt binders. The actual availability factor was found to range from 50 to 100%. It was determined that RAs adversely affected the intermediate and low temperature properties of the mixtures studied due to the increase in the recycled binder content utilized within the mixture. In terms of low temperature properties, the use of soft binder performed similar to mixtures containing no RAs. The concentration of the high molecular RAS species exceeds 40% in which 25% of these are highly aggregated with apparent molecular weights approaching 100K. The use of RAs did not significantly dissociate the very high molecular weight species, and thus failed to improve mixture cracking resistance. In addition, Fourier-Transform Infrared Spectroscopy (FTIR) results were inconclusive.
Download or read book Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios written by Amy Epps Martin and published by . This book was released on 2020 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: "More than 90 percent of highways and roads in the United States are built using hot-mix asphalt (HMA) or warm-mix asphalt (WMA) mixtures, and these mixtures now recycle more than 99 percent of some 76.2 million tons of reclaimed asphalt pavement (RAP) and about 1 million tons of recycled asphalt shingles (RAS) each year. Cost savings in 2017 totaled approximately $2.2 billion with these recycled materials replacing virgin materials. The TRB National Cooperative Highway Research Program's NCHRP Research Report 927: Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios presents an evaluation of how commercially available recycling agents affect the performance of asphalt mixtures incorporating RAP and RAS at high recycled binder ratios."--
Download or read book Strategic Highway Research Program written by and published by . This book was released on 1986 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt:
