Full-scale validation of bio-recycled asphalt mixtures for road pavements

Recycling of asphalt has become a well-established practice in many countries, however the road pavement industry remains a bulk consumer of extracted raw materials. Novel solutions that find root in circular economy concepts and life‐cycle approaches are needed in order to enable optimisation of infrastructure resource efficiency, starting from the design stage and spanning the whole value chain in the construction sector. Itis within this framework that the present study presents a full-scale validation of asphalt mixtures specifically designed to ensure durability of flexible road pavements and at the same time enabling the reuse of reclaimed asphalt pavement (RAP) through the incorporation of bio-materials as recycling agent. These bio-recycled asphalt mixtures have been first designed in laboratory and subsequently validated in a real scale experiment conducted at the accelerated pavement testing facilities at IFSTTAR. Four pavement sections were evaluated: three test sections with innovative bio-materials, and a reference section with a conventional, high modulus asphalt mix (EME2). Two tests were realized: a rutting test and a fatigue test and for each of them the evolution of bio-recycled asphalt mixtures properties as well as the pavement deteriorations were recorded and studied. Evolution of the bio-asphalt mixtures was monitored for a 5 months period after paving by a bespoke nondestructive micro-coring, extracting and recovering methodology developed at the Western Research Institute (WRI). The structural health of the pavement sections was monitored through periodic falling weight deflectometer (FWD) as well as with strain gages and temperature sensors. As a result the three tailored bio-asphalt mixtures performed similarly or better than the control mixture, both in terms of property evolutions and durability

Rheological Behaviors of Waste Polyethylene Modified Asphalt Binder: Statistical Analysis of Interlaboratory Testing Results

This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders' rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer-based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28 degrees C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28 degrees C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70 degrees C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders

Performance of a sustainable asphalt mix incorporating high RAP content and novel bio-derived binder

The recent drive to find ways to increase sustainability and decrease costs in asphalt paving has led researchers to find innovative ways to incorporate more recycled materials and bio-derived binders into mixes with varying success. A new novel bio-derived binder made from refined pine chemistry stabilised with a polymer can increase the sustainability of asphalt mixes while maintaining pavement performance. Laboratory performance testing was conducted on asphalt mixes containing 50% Reclaimed Asphalt Pavement (RAP) by mix weight and the novel bio-derived binder. Results show that the bio-derived binder outperforms the conventional 50/70 pen grade binder mixes with respect to resistance to thermal cracking and adequately passes all requirements for pavements with 20-year design loadings of less than 30 million ESALs. This research shows that asphalt mixes containing 50% RAP and a bio-derived binder can be designed to pass performance criteria at low, intermediate, and high temperatures without the need of neat bitumen

Empirical, Rheological and Chemical Properties of Aged Binder with Rejuvenators at Different Ageing Levels

The use of Reclaimed Asphalt (RA) into new asphalt mixtures becomes an inevitable step for sustainable infrastructure. Saving natural, non-renewable materials, such as bitumen and aggregates, the asphalt industry is moving forward with more recycling. Although asphalt is a 100% reusable material, high recycling rates are not yet easily achievable due to many limitations, going from technical specifications through RA properties to asphalt plant capabilities. The rate of RA, which may be used within a new asphalt mixture, depends on many aspects: variability, moisture and fines contents, presence of polymers, brittleness of aged binder, etc. The latter is directly linked to the degree of the RA binder ageing. As higher RA content increases the asphalt mixture stiffness, the material becomes more brittle and prone to cracking. The use of recycling additives is taking recycling to the next level by solving these issues. With the growing need of the industry for asphalt recycling agents, many products have appeared on the market with different effects. In this study, three asphalt recycling agents (two industrial and one alternative) were used as rejuvenators. Blends with 50% of rejuvenated RA binder (RAb) and virgin binder were subjected to different ageing levels: short (RTFOT), long (PAV for 20 h) and prolonged (PAV for 60 h). After each ageing level, physical, rheological and chemical properties were evaluated addressing the ageing behaviour of the additives used. Testing results showed that one industrial additive lost almost all its properties after prolonged ageing, whereas the other additives showed comparable results with the second industrial product

Aging of Bitumen and Asphalt Concrete: Comparing State of the Practice and Ongoing Developments in the United States and Europe

Aging is a crucial factor in pavement performance and being able to determine its effect on a mixture is necessary to link its initial properties to the properties over time in order to ensure the intended service life. This is becoming more important now that climate change leads to increased variation in weather conditions, while environmental considerations cause changes in the constituent materials that are used. As a result, past experience is becoming less reliable. In this paper, the USA and European approaches to aging are compared, showing that those contain the same test equipment and almost identical conditions for aging. This allows the exchange of data and experience. The current tests are suitable for binders and give an indication of the sensitivity to aging. For short term aging, Rolling Thin Film Oven Test (RTFOT) conditioning gives a reasonable indication of bitumen aging during asphalt concrete production and construction. This only holds for penetration grade binders during hot mix production and construction. For long term aging, because of the many variables involved, developing a single test method to characterize aging sensitivity seems impossible. However, using more elaborate protocols in existing, practical tests can provide more information and the necessary input for kinetic aging expressions. A pressure aging vessel (PAV) protocol for testing at two temperatures and time intervals, specifically at 90 and 100 degrees Celsius and for 20 and 40 hours, respectively, is suggested. Using the same conditioning in characterizing materials for pavement construction and research will facilitate the exchange of data and enable faster developments.Alternate title: Review of Asphalt (Concrete) Aging Tests in the US and Europe.Pavement Engineerin

Recommendations of RILEM TC 252-CMB: relationship between laboratory short-term aging and performance of asphalt binder

This recommendation reports on the effect of the Rolling Thin Film Oven Test (RTFOT) aging temperature on chemo-mechanical properties of asphalt binders for Warm Mix Asphalts. The RTFOT testing temperature should ideally replicate physical and chemical short-term aging of asphalt mixtures. The relevance of this was investigated in light of the increased use of warm mix asphalt technologies. The recommendations are based on round robin experiments performed by nine participating laboratories and consisting of a series of tests including experimental results on penetration, softening point temperature, Fourier Transform Infrared Spectroscopy and Dynamic Shear Rheology. The results indicate that the current RTFOT aging temperature does not replicate the aging in the mixture. For this reason, the TC recommends the selection of appropriate RTFOT aging temperatures in order to simulate binder aging as a result of various mixing technologies. The sulfoxide index is proposed as a measure of oxidative short term RTFOT aging

Effect of short-term ageing temperature on bitumen properties

© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. Properties of asphalt mixtures after ageing are fundamental parameters in determining long-term performance (e.g. durability) of these materials. With increasing popularity of reduced temperature mixtures, such as warm-mix asphalt, WMA, the question remains how a reduction in short-term ageing affects the properties after long-term ageing of bituminous materials. This paper aims to improve our understanding of the effect of asphalt manufacturing temperature on ageing and the resulting mechanical properties of bituminous binder by studying the effect of short- and long-term ageing of different bitumen samples as a function of short-term ageing temperatures. For this purpose, round robin experiments were conducted within the RILEM technical committee (TC) 252 chemo-mechanical characterisation of bituminous materials by 10 laboratories from 5 countries using four binders of the same grade (70/100 pen) from different crude sources. The short-term ageing was carried out using the standard procedure for rolling thin film oven test (RTFOT), but varying the temperatures. Long-term ageing was carried out using the standard procedure for pressure aging vessel (PAV) in addition to RTFOT. For the mechanical characterisation, rheological data were determined by using the dynamic shear rheometer (DSR) and conventional tests, with needle penetration and softening point using the ring and ball method. The results show that although different short-term ageing temperatures showed a significant difference in the mechanical properties of the binders, these differences vanished after long-term ageing with PAV