Open Graded Asphalt Friction Course: State of the Practice

Open Graded Friction Course (OGFC) has been used since 1950 in the United States to improve the frictional resistance of asphalt pavements. However, experience of states with this kind of mix has been widely varied. While many transportation agencies have reported good performance, many others have stopped using OGFC due to poor performance. This report presents the results of a survey of state transportation agencies in the USA carried out to determine where OGFCs have been used, why they are used in some places and not others, mix design and construction practices, OGFC's performance history, and problems encountered. The survey showed that significant improvements have been observed in the performance of OGFCs since their introduction in the 1950s. These improvements have been achieved with the help of good design and construction practices. Although experience of transportation agencies with OGFC has been widely varied, half of the agencies surveyed in this study indicated good experience with OGFC. More than 70% of the agencies which use OGFCs reported service life of eight or more years. About 80% of the agencies using OGFCs have standard specifications for design and construction. A vast majority of agencies reporting good experience use polymer modified asphalt binders. Also, gradations of aggregates used by these transportation agencies tend to be somewhat coarser compared to gradations used earlier and gradations used by the agencies which had bad experience with OGFC. It seems that good design and construction practice is the key to improved performance of OGFC mixes. An improved mix design procedure is needed to help the transportation agencies adopt these good practices. Graphs, tables, appendix. 31p

00% recycled hot mix asphalt: A review and analysis ARTICLE in RESOURCES CONSERVATION AND RECYCLING · JULY 2014 100% recycled hot mix asphalt: A review and analysis

a b s t r a c t A holistic evaluation of the feasibility of producing 100% recycled mixtures is presented. Eleven technologies readily available for producing 100% Reclaimed Asphalt Pavement (RAP) hot asphalt mixtures are described in the article and the complementary video (http://youtu.be/coj-e5mhHEQ). The recorded performance of 100% RAP mixtures is analyzed along with identification of typical high RAP distresses. Recommended mix design procedures and the best RAP management strategies are described. A cradleto-gate analysis of environmental effects indicated 18 kg or 35% CO 2 eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses

Finite Element Modeling of Rejuvenator Diffusion in RAP Binder Film – Simulation of Plant Mixing Process

In order to sustain the needs of the 21st century civil infrastructure, we need a paradigm shift in recycling – from current 20-40% to 100% (zero waste). The main hindrance to successful recycling of high Reclaimed Asphalt Pavement (RAP) content mixes is the lack of confidence which stems from a lack of understanding of the rejuvenation and diffusion process that is supposed to occur when a recycling agent is added to an aged asphalt mix. This research presents finite element simulation of rejuvenator diffusion into an aged asphalt binder film. Five different rejuvenators and aged RAP binder were tested to obtain the required input data for simulation – viscosity at different temperatures and molecular weight. The simulation was run assuming 100% RAP mixture and three different temperatures were simulated for three rejuvenator dosages. The final viscosity for complete diffusion and the required time to reach this state was determined. The results show significant differences in the softening potential of different rejuvenators and helps in the estimation of temperature range to reach homogeneous rejuvenator concentration within the binder film before the production process is completed. The simulation results are compared with mechanical tests of binder penetration and mixture creep compliance to confirm the softening effect

Review of Very High-Content Reclaimed Asphalt Use in Plant-Produced Pavement: State of the Art

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

Adaptation to Flooding and Mitigating Impacts of Road Construction − a Framework to Identify Practical Steps to Counter Climate Change

Adaptation and mitigation are the two critical actions that are needed to counter the looming threats of climate change on transportation. For roadways, flooding constitutes one of the most important impacts of climate change, and adaptation to build more resilient roadways must be made. For a proper adaptation, the first step is a way to properly assess the vulnerability of roadways to flooding. Road construction impacts the environment negatively through emissions and energy consumption, and a proper way to determine the practical methods to reduce the impact is also necessary. This paper presents a framework to assess the vulnerability of roadways to flooding and evaluate the impact of different changes in construction on energy consumption and emission. Two system dynamics based models were developed and results of the simulations have been presented. Simulation tools for these two models have also been developed and made available on the public domain. The results of the simulation point out the beneficial effects of providing low permeability and dense and thick surface layers to reduce vulnerability to flooding and that of using drier aggregates, reducing heat losses, reduced mix temperatures and extension of pavement lives on the emission and energy consumption during roadway construction

Evaluation of Different Recycling Agents for Restoring Aged Asphalt Binder and Performance of 100% Recycled Asphalt

Because of aged binder, high reclaimed asphalt pavement (RAP) content mixes are susceptible to cracking failures and are less workable than virgin mixtures. The potential of six differently originated recycling agents was evaluated in this study to restore the desired binder properties using conventional binder test methods and the results were compared with performance-related test results of 100 % RAP mixture. Binder test results showed that application of organic products require much lower dose to provide the same softening effect as petroleum products. The workability of binder and mixture was improved compared to RAP, but remained lower than that of reference virgin mixture. All rejuvenated mixtures proved to be very rut resistant. Low temperature performance ofRAP, measured by creep compliance at -10 C, was improved with the application of all recycling agents and RAP mixes rejuvenated with waste vegetable products even performed equal or better than virgin mixture. Organic oil and both waste vegetable products provided the best performance in binder and mixture fatigue resistance tests as measured by linear amplitude sweep and fracture work density respectively. Overall, the organic products outperformed the petroleum based additives in most tests, which partly can be attributed to un-optimized recycling agent dose. It was observed that penetration test may be a good indicator for initial selection of optimum dose since the results provide indication of rut resistance as well as fatigue performance of mixture and can be easily predicted using an exponential relationship that was developed in the research

Use of Rejuvenators for Production of Sustainable Hot Mix Asphalt with High Reclaimed Asphalt Content

In order to sustain the needs of the 21st century civil infrastructure, we need a paradigm shift in recycling – from the current 20-40% to 100 % (zero waste). The research is aimed at developing a simple method for evaluation of rejuvenators’ effectiveness for production of up to 100% RAP mixtures. Because of the presence of stiffer (aged) binders, high RAP content mixes are perceived to be more susceptible to fatigue and thermal cracking failures than virgin mixtures. Appropriate choice of rejuvenator may allow recovering the properties of aged binder by reconstructing the chemical composition of the aged binder. Twelve differently originated rejuvenators were evaluated in the study to restore aged RAP, including different types of plant oils, waste derived petroleum oils, engineered products as well as bio based rejuvenators. Empirical binder test methods were used on extracted binder to determine softening efficiency of the rejuvenators and the rejuvenation quality. 100% RAP rejuvenated mixtures were tested at wide range of in-service temperatures including evaluation of low temperature and fatigue cracking, moisture susceptibility and rut resistance. The test results have shown that at least five rejuvenators are capable of reducing the binder viscosity to the required level and significantly improving the performance of RAP mixture. Future stages of the research will include mix design optimization to achieve the performance of virgin mixture and development of simple acceptance criteria for choosing rejuvenator

100% Recycled Hot Mix Asphalt: A Review and Analysis

A holistic evaluation of the feasibility of producing 100% recycled mixtures is presented. Eleven technologies readily available for producing 100% Reclaimed Asphalt Pavement (RAP) hot asphalt mixtures are described in the article and the complementary video (http://youtu.be/coj-e5mhHEQ). The recorded performance of 100% RAP mixtures is analyzed along with identification of typical high RAP distresses.Recommended mix design procedures and the best RAP management strategies are described. A cradleto-gate analysis of environmental effects indicated 18 kg or 35% CO2eq savings per t of produced 100% RAP asphalt mixture compared to virgin mix, while cost analysis showed at least 50% savings in material related expenses

Evaluation of Rejuvenator's Effectiveness with Conventional Mix Testing for 100% Reclaimed Asphalt Pavement Mixtures

This paper presents research evaluating the effectiveness of rejuvenators for production of very high (40% to 100%) reclaimed asphalt pavement (RAP) content mixtures. Nine differently originated softening agents were tested; these included plant oils, waste-derived oils, engineered products, and traditional and nontraditional refinery base oils. Two different dosages of the agents were added to binder extracted from RAP to evaluate their softening potential through testing of kinematic viscosity and penetration at two different temperatures. At 25°C the softening efficiency varied by a factor of 12 between the most and least effective rejuvenators. Consistency results at different temperatures were used to express temperature susceptibility by means of penetration index (PI), penetration-viscosity number, and bitumen test data chart of the softened binders. The PI results varied measurably depending on the rejuvenator and supported the low-temperature mixture test results, showing that PI may be a good and simple measure of rejuvenation effectiveness. Low-temperature mixture embrittlement was evaluated at -10°C through determination of the indirect tensile strength and creep compliance for rejuvenated 100% RAP mixture samples. It can be concluded that four of the nine tested rejuvenators reduced extracted binder consistency to the necessary level and reduced susceptibility of RAP mixtures to low-temperature embrittlement. Of the four, two engineered products tested had notably different performance but neither was superior to similar generic oils

Use of Rejuvenators for Production of Sustainable High Content RAP Hot Mix Asphalt

Aged binder is the main obstacle for increasing the use or Reclaimed Asphalt Pavement (RAP) in production of asphalt pavements. RAP binder is much stiffer and therefore high RAP content mixes are perceived to be susceptible to fatigue and thermal cracking failures. Appropriate choice of rejuvenator may allow reducing the binder viscosity to attain the desired mixture workability and recover the necessary performance properties of the aged binder. Six differently originated rejuvenators were added to extracted binder at 12% dose including aromatic extract, waste engine oil, tall oil, organic oil, waste vegetable oil and waste vegetable grease. The rejuvenation potential of these products was evaluated by performing multiple empirical as well as performance tests and the results compared with a virgin binder. The rejuvenators proved to soften the extracted binder to the level of virgin and the kinematic viscosity results show that the optimum compaction temperature can be reduced by 15°C to 25°C compared to extracted binder. Performance Grade (PG) test results showed that none of the rejuvenators reduced the high PG of extracted binder to the level of virgin binder indicating increased rutting resistance. At the same time most are able to reduce low PG from -12°C of the extracted binder to at least the required -22°C. The low temperature performance correlated well with penetration index, proving that thermal cracking should not be an issue at appropriate rejuvenator dose. The binder fatigue performance was evaluated through Linear Amplitude Sweep (LAS) test. Only waste vegetable products were able to increase the fatigue resistance to the level of virgin binder at a 12% dose using LAS test while the Superpave G*·sinδ indicated that all rejuvenators pass the minimum fatigue requirement