High Percentages of Reclaimed Asphalt Affect the Performance of Asphalt Binder

More than 90 percent of the road and highway network in the United States is paved with asphalt concrete. Maintenance and periodic rehabilitation require a continuous supply of aggregates and asphalt binder, both of which are becoming increasingly scarce and expensive. Recycling and reusing these resources can reduce costs and improve sustainability. The most common recyclable material used in road construction is reclaimed asphalt pavement (RAP), which is milled asphalt surface layers that have been removed from existing pavements before new asphalt overlay is placed. Reclaimed asphalt roofing shingles (RAS) are another potential source of asphalt binder.There is growing interest in allowing significantly higher percentages of RAP and RAS in asphalt mixes used on state and local roadways. However, making this change has raised concerns regarding how these composite binders may influence the performance and durability of asphalt mixes, depending on the blends of different virgin and reused binders. Researchers at the UC Pavement Research Center investigated the use of higher percentages of RAP and RAS as a partial replacement for the virgin binder in new asphalt mixes and their effect on pavement performance in California. This research brief summarizes findings from that study.View the NCST Project Webpag

Structural performance and sustainability assessment of cold central-plant and in-place recycled asphalt pavements: A case study

This paper aimed at assessing the structural performance and sustainability of cold recycled asphalt pavements. Four cold recycling technologies were investigated, including the cold central-plant recycling with emulsified and foamed asphalt binders (i.e., CCPR-E and CCPR-F), and the cold in-place recycling with emulsified and foamed asphalt binders (i.e., CIR-E and CIR-F). Firstly, the laboratory tests were conducted to comprehensively evaluate the dynamic modulus, rutting, and cracking performance of cold recycled asphalt mixtures. Subsequently, these laboratory results were used to determine the inputs of cold recycled asphalt mixtures for the Pavement ME Design program, which was employed to predict the pavement performance. Meanwhile, the National Center for Asphalt Technology also constructed four cold recycled pavement sections in the field. The monitored and predicted pavement performance showed similar trends in the first two years, but the Pavement ME Design program over predicted the rut depth of these sections. The pavement performance results confirmed that the bottom-up fatigue cracking was a negligible distress mode for cold recycled asphalt pavements. In the following, the life cycle cost analysis and life cycle assessment were conducted to evaluate the four different cold recycling projects. The life cycle cost analysis results demonstrated that all of the four cold recycling projects yielded less net present values than the HMA project. The life cycle assessment data indicated that the cold recycling technologies reduced the energy consumption by 56–64%, and decreased the greenhouse gas emissions by 39–46%. Finally, this study found that the overlay and asphalt treated base thicknesses and climatic conditions had significant impact on the performance of cold recycled asphalt pavements

Impact of Rejuvenators Type on Physical Properties of Aged Asphalt Cement

Recycling can be considered as one of the measures of sustainable methods. The physical traits of the asphalt mixture under the influence of accelerated aging (Long and Short–Term) for asphalt concrete were assessed. Asphalt cement (40-50), aggregate with 12.5 mm nominal extreme size and limestone dust as filler of the mineral was used for the preparation of asphalt concrete mixture. At the optimum content of the asphalt and asphalt of 0.5 percent below and above the optimum value, specimens were prepared by using Marshall Method. Two types of polymers as recycling agents were used (Polyethylene of Low Density and Crumb Rubber) with (0.5, 1 and 1.5) % by weight of the binder. The indirect tensile test was used for the mixtures at 25 ºC and double punch test at 60 ºC. It was determined that the use of (asphalt binder mixed with rubber) as the agent of recycling showed improved performance than the other kind of recycling agent. The indirect tensile strength at 40 ˚C of the recycled mixture was higher than that the control mixture. Punching shear strength was decreased by 84 %, temperature susceptibility was decreased by 69.6 % and the resistance to moisture damage increases by3.3 % at optimum asphalt content

Multi-recyclability of asphalt mixtures modified with recycled plastic: towards a circular economy

Although asphalt pavements modified with recycled plastic have demonstrated enhanced performance, their recyclability remains under-explored, which is crucial under the scope of a circular economy. To address this, the present study investigates the multi-recyclability of asphalt mixtures, both with and without a recycled plastic modifier, at a recycling rate of 50% over two cycles using an open-loop and a closed-loop model. The research utilised an innovative recycled plastic modifier made from hard waste plastics, incorporated into the mixture via the dry method. To ensure control over consistency and variables while also considering the novelty of the recycled plastic modifier, the reclaimed asphalt pavements (RAPs) were prepared using a loose asphalt mixture ageing protocol. Additionally, a rejuvenator made of vegetal derivatives was used as the recycling agent, considering the high recycling rate over each cycle. The comprehensive evaluation of volumetric and mechanical performance revealed that asphalt mixtures containing the recycled plastic modifier performed comparably to unmodified mixtures over two recycling cycles. Furthermore, all the recycled mixtures exhibited superior performance in resistance to rutting, moisture susceptibility, and fatigue compared to the conventional asphalt mixture. Overall, it can be inferred that the asphalt mixture modified with recycled plastic is capable of being recycled over multiple life cycles without compromising its mechanical and performance characteristic

Materials Characterization and Economic Considerations of Cold-Mix Recycled Asphalt Pavements

Recycling of asphalt pavements has become a common rehabilitation and maintenance process since the mid 1970s. The state of the art of designing and constructing pavements composed of recycled materials has now advanced to a point where recycling is considered as an alternative to conventional procedures for most paving projects. An in-depth evaluation of cold-mix recycling techniques was undertaken and the findings are presented in this report. The variability of the existing materials found in city streets and county roads throughout the State of Indiana was evaluated by means of laboratory test procedures. The data obtained from these experiments were statistically analyzed and the results were examined and discussed in an attempt to characterize those pavements. The significance of various factors believed to influence the final performance of cold recycled mixes, was determined by means of extensive sampling of various types of asphalt pavements from counties and cities within the State. Reclaimed asphalt pavement materials (RAP), with asphalt contents, aggregate gradation, recovered asphalt penetration and viscosity properties, etc., closely resembling values obtained from field-core samples, were used in the laboratory in a series of mix design procedures. These laboratory studies were performed in an attempt to determine the effects that factors such as mixing water, recycling agent content, gradation of the RAP, curing time, etc., will have on the performance of cold recycled mixes produced with existing asphalt pavement materials from Indiana\u27s county roads and city streets. A detailed analysis and discussion of the main factors that affect the selection and implementation of urban and rural pavements cold recycling, is presented by means of information and findings reported in the literature. A set of guidelines for cold-mix recycling of county roads and city streets asphalt pavements in Indiana, is recommended with the objective of directing and informing county and city engineers of the advantages and disadvantages and potential applications associated with asphalt pavement cold-mix recycling

Investigating the Blending Mechanism and Strength Development of 100% Hot In-place Recycled Asphalt Mixtures

The current tendency in the asphalt paving industry is to increase the utilization of recycled asphalt pavement (RAP). Hot in-place recycling (HIR) is a promising approach to consume 100% RAP from the existing pavement for pavement surface rehabilitation in the field. However, some concerns remained regarding the utilization of HIR techniques in pavement rehabilitation: 1. Whether it is cost-effective to apply the in-place recycling techniques to pavement rehabilitation compared to the conventional HMA surface milling & filling? 2. How to improve the performance of the asphalt mixtures with HIR technique? 3. How much RAP binder can be available for coating the aggregates during HIR? 4. What are the bonding mechanisms, the influence of effective asphalt content and properties on the performances of the HIR mix? 5. What are the contributions of the immobilized RAP binder? To better understand the pavement performance and recycling efficiency during HIR procedure, the overall objective of the proposed doctoral study is to investigate the blending mechanism and strength development of asphalt mixtures during HIR technique. The research scopes are to (1) investigate the blending mechanism of HIR mixes relating to binder mobilization and mixture mechanical properties; (2) develop an approach to quantify the recycling efficiency of HIR mixes; (3) explore the mechanism of bonding, effects of the degree of blending, and properties of effective binder in HIR mixes; (4) investigate the effects of immobilized RAP binder on asphalt-aggregate interactions and the performance of 100% recycled asphalt mixtures. The results of this study provide a better understanding of the significance of mobilized and immobilized RAP binder on the recycling efficiency of 100% recycled asphalt mixtures

Rheological and Chemical Characteristics of Asphalt Binders Recycled using Recycling Agents and Nanoparticles

The reuse and recycling of materials, especially materials derived from nature, is necessary for a sustainable environment and world. Asphalt mixture is a combination of asphalt binder and aggregates, both of which originated from nature. The reuse and recycling of aged asphalt materials (RAP) is widespread. However, a large portion of these materials is wasted. One primary reason for the reluctance to use a high percentage of RAP in recycled asphalt is uncertainty in the long-term performance of recycled asphalt pavement. To improve the long-term performance of recycled asphalt, new additives and Recycling Agents (RA) are used to modify the binder’s properties. However, different RAs will change the recycled binder’s properties differently, resulting in different long-term recycled binder properties. Therefore, this study was conducted to correlate the chemical indices and rheological properties of the recycled binder using different recycling agents. Furthermore, the performance of recycled binders was evaluated to predict the long-term performance of recycled binders according to their unaged and initial properties. The results showed that the chemical indexes (carbonyl and sulfoxide) of recycled binders can be used to predict the long-term performance of recycled binders. These results could also be used to select the proper RA in the recycling of RAP material. Also, an asphalt design procedure based on the chemical indices of binders was developed for use by practitioners and researchers. The previous design method was based on Performance Grade tests, while the developed method is mostly based on the chemical properties of binders, and its tests are easier and more economical. Furthermore, the incorporation of RAP percentage in the unmodified PG 67-22 binder was limited to 20% by the Florida Department of Transportation due to uncertainty in the long-term performance of recycled asphalt. To increase the percentage of RAP in recycled asphalt, new additives are used to modify the asphalt binder. One of the newly introduced additives is nanoclay particles, which were applied in the recycling of RAP and were investigated in this study. The results showed an increase in the incorporation of RAP percentage in the nanomodified binder by 30% compared to using unmodified (neat) asphalt binder. The improved properties of the nanomodified binder compared to the unmodified binder proved the feasibility of using a nanomodified binder in severe weather conditions and roads that experience higher loads and traffic

Modulus Kekakuan Lentur Dan Sudut Fase Campuran Material Perkerasan Daur Ulang Dan Polimer Elastomer

Pavement Flexural Stiffness Modulus and Phase Angle tend to bend due to over load of vehicle. Using Reclaimed Asphalt Pavement (RAP), in this case asphalt recycling will decrease deformation endurance of asphaltic mixture. The lower deformation endurance of asphaltic mixture, the worse asphaltic mixture quality is. Therefore modified of asphalt recycling, must be done to improve deformation endurance of asphalt. This research using Styrene-Butadiene-Styrene (SBS) which is elastomer polimer as asphalt modifier. Variation of SBS polimer are 2.5% and 5% of asphalt weight and variation of RAP are 20% and 30% of mixture weight. The value of Flexural Stiffness Modulus and Phase Angle was determined by Fatique testing using Four Point Loading Apparatus. According to the result, the highest Flexural Stiffness Modulus is 5,763.67 MPa which found in variation RAP 30% and SBS 5%. This mixture composition also have the lowest Phase Angle that is 23.33°. The result showing that the stiffness will be increase by adding Reclaimed Asphalt Pavement (RAP) and SBS Polimer

EQUIVALENT THICKNESS COEFFICIENT OF COLD CENTRAL PLANT RECYCLING PAVEMENT STRUCTURE

        This research focuses on the equivalent relationship between cold central plant recycling mixture and hot mix asphalt. In this paper, the pavement surface condition index (PCI) was calculated by the road surface conditions investigating, which was used as the evaluation standard. The unreasonable data were removed by SPSS software. The existing decay equation of pavement performance was simplified by MATLAB, and optimized by the Marquardt and global optimization methods. The survey data were fitted nonlinearly by 1stOpt software. Ultimately, the multivariate nonlinear regression optimization equation of the equivalent thickness coefficient was established. The results show that the cold central plant recycling with the emulsified asphalt (CREA) pavement equivalent thickness coefficient is 0.587. The cold central plant recycling with the foamed asphalt (CRFA) pavement equivalent thickness coefficient is 0.632. In addition, the performance of 10 cm cold central plant recycling pavement is equivalent to 6 cm the traditional hot mix asphalt pavement. The dispersion of the CREA is greater than that of the CRFA significantly