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The Life Cycle Assessment (LCA) of asphalt pavements are associated with significant uncertainty resulting from variability in the quantity and impact of individual components, the quality of data for each component, and variability of asphalt durability. This study presents a framework to quantify and incorporate the uncertainty of LCA and asphalt durability data into LCA of asphalt surfacings. The suggested framework includes: estimating the uncertainty of asphalt production processes by the pedigree matrix method, conducting a deterministic LCA, applying Monte Carlo Simulation (MCS) to estimate the probability density functions (PDFs) of the considered impacts using the uncertainty data, deterministic solution, and asphalt durability. This framework was applied to six asphalt mixtures; the results show that there is significant uncertainty in the processes that contribute to the environmental impacts. They also showed that considering asphalt durability and its uncertainty is critical and can significantly change the results and interpretation of LCA. [ABSTRACT FROM AUTHOR]

The road pavement industry, worldwide, has often shown reluctance in quickly implementing innovative practices; however, in the case of raw material consumption, a cultural change is necessary and, in this sense, sustainability assessment could play a major role. Along these lines, this research study aims to provide evidence to all the involved stakeholders (material producers, pavement contractors, and road authorities) of how life cycle-based techniques can be crucial in evaluating whether the adoption of asphalt mixtures with high contents of reclaimed asphalt (RA) for wearing courses is actually a sustainable practice for major European roads. An evaluation framework composed of a life cycle assessment, to calculate the carbon footprint of both pavement materials and pavement activities, and a life cycle cost assessment, performed to determine the overall economic burden of the related road pavement surface courses and maintenance strategies over a sixty-year analysis period, is presented and applied to selected case studies. These were developed together with three major European national road authorities and include scenarios involving the construction of road surfaces with asphalt mixtures containing up to 90% RA. Results have shown that whenever high-content RA mixes do not under-perform against conventional mixtures, up to 50% CO2eq savings can be registered and up to 60% economic cost reductions can be reported. The durability of road pavement layers remains a key parameter for any road pavement sustainability assessment exercises; therefore, in order to adapt the obtained results to other contexts, researchers should always consider conducting a sensitivity analysis of the reference service life and/or road authorities should somehow request road pavement durability as a pre-requisite within procurement practices. [ABSTRACT FROM AUTHOR]

The binder content of rubberised asphalt mixtures is usually increased compared to that used in conventional asphalt. This increase is deemed important to compensate for the reduction in the actual bitumen due to the existence of rubber particles. This study presents the results of performance evaluation conducted on different rubberised Stone Mastic Asphalt (SMA) mixtures produced using different types and contents of rubberised bitumen. The energy ratio (ER) computed from Superpave Indirect Tensile (IDT) tests was used to evaluate the cracking resistance of asphalt mixtures while the rutting behaviour was evaluated using the Repeated Load Axial Test (RLAT). The indirect tensile stiffness and strength were used to evaluate the moisture susceptibility. Using the same binder content for rubberised SMA mixtures as used in the conventional mixtures can still give superior performance properties. Adding crumb rubber to softer base bitumen can produce asphalt mixtures with superior cracking and rutting resistance. [ABSTRACT FROM AUTHOR]

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°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°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°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. [ABSTRACT FROM AUTHOR]

Even though alternative paving materials, like rubberized asphalt, are sometimes present in specifications, these are still not widely adopted from road agencies mainly due to a lack of experience, reticence in changing work habits and, often, a lack of evidence of real gains in the change. Authors believe that performance-based laboratory characterization is a solution to highlight differences with conventional asphalt mixtures. Hence, this research wants to highlight the differences between designing asphalt mixtures modified with engineered crumb rubber (ECR) on the basis of conventional indirect tensile testing (ITS), as prescribed by Italian specifications, and by means of performance-related characterization. ECR allows to asphalt mixtures to be modified through a dry process without inconveniences such as uncontrolled swelling and the generation of fumes; on the other hand, performance-related characterization focuses on highlighting rutting behavior by using a basic approach, still based on ITS, and a more advanced viscoplastic methodology using the asphalt mixture performance tester (AMPT). As a result, performance-related characterization is necessary to highlight clear gains in the rutting behavior of the asphalt mixtures modified with ECR. Advanced methodology by means of AMPT provides a fine-tuned characterization; however, the basic approach by means of ITS already highlights the differences in performance. ECR could be widely used to improve the properties of dense mixtures for roads with low traffic; in fact, it solves many of the practical issues of adding crumb rubber through a dry process and greatly improves paving material properties compared to conventional asphalt mixtures, with an increase in cost of only 10%. [ABSTRACT FROM AUTHOR]

Polymer additives are widely used to improve the performances of road bitumen and mixtures including their oxidative resistance. However, their effect on the oxidative mechanism remains unclear. This study includes the investigation of the changes in the rheological response of Polymer Modified Bitumen (PMBs) prepared with the Styrene Butadiene Styrene (SBS) copolymer and Sulphur as cross-linker. The bitumen samples were aged in the Rolling Thin Film Oven (RTFO) and in multiple cycles of Pressure Aging Vessel (PAV). The rheological properties were measured by means of the Multiple Stress Creep and Recovery (MSCR) test. Results show that in the case of cross-linked SBS modified bitumen the polymer phase mitigates the effect of hardening of the bitumen phase on the rheological response as a function of the polymer concentration. Adversely, in the SBS modified bitumen without cross-linker, the effect of the polymer vanishes after the RTFO.

The current need to move towards more sustainable technologies in the construction sector has promoted the investigation of using alternative materials in asphalt mixtures for pavements. Biomaterials, used as biobinders, have shown their potential as partial replacement of bitumen in asphalt mixtures as solution to decreasing the demand for fossil-fuel-based binders as well as CO2 emissions. However, more research is needed to increase the replacement of bitumen in asphalt mixtures. In this investigation,biobinders are used as full replacement of virgin bitumen and as recycling agent within asphalt mixtures with high Reclaimed Asphalt (RA) content. Blends of biobinders and RA binders, and bio-recycled asphalt mixtures, were produced, subjected to ageing and rheologically characterised. The results show that the rheological properties of binders' blends seem adequate for their use, while the bio-recycled asphalt mixtures seem to have a faster ageing than conventional ones, hence their full-scale application still remains a concern. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present a novel approach for the continuous monitoring of pavement condition through the use of combined piezoelectric sensing and novel condition-based interpretation methods. The performance of the developed approach is validated for the detection of bottom-up fatigue cracking through full-scale accelerated pavement testing (APT). The innovative piezoelectric sensors are installed at the bottom of a thin 102 mm (4 in.) asphalt layer. The structure is then loaded until failure (up to 1 million loading cycles in this study). The condition-based approach, used in this work, does not rely on stain measurements and allows users to bypass the need for any structural or finite-element models. Instead, the data compression approach relies on variations in strain energy harvested by smart sensors to track changes in material and structural conditions. Falling weight deflectometer (FWD) measurements and visual inspections were used to validate the observations from the sensing system. The results in this paper present a first large-scale validation in pavement structures for a piezopowered sensing system combined with a new response-only based approach for data reduction and interpretation. The proposed data analysis method has demonstrated a very early detection capability compared to classical inspection methods, which unveils a huge potential for improved pavement monitoring. [ABSTRACT FROM AUTHOR]

Laboratory scale mechanical performances on six plant produced mixtures; three semi-dense surface courses and three dense binder courses modified with engineered crumb rubber (ECR) using the dry process are presented. The two types of mixtures produced and investigated fulfilled for the most part, the requirements of the Swiss and/or US standards regarding volumetric properties, water sensitivity and rutting. In advanced testing where no requirements exist, the dense ECR mixtures performed similar to the reference polymer modified mixtures and slightly worse for semi-dense mixtures in high temperature tests, where the binder becomes viscous in the rubber-binder composite and its ability to transfer loads is reduced. The ECR mixtures performed similarly or better than the reference in low temperature tests. Across the advanced testing data set, all obtained results were well within acceptable values for both ECR and reference polymer mixtures indicating that crumb rubber can effectively replace polymer in asphalt mixtures. [ABSTRACT FROM AUTHOR]

Using bio-binder and bio-additives as recycling agents for asphalt mixtures with high-content of reclaimed asphalt (RA) is proving to be feasible. It is still not clear whether this combination might provide new known hazardous emissions from airborne binder fumes. The health hazard related to airborne bitumen fume generation is primarily relevant for paving crews, whereas there is little opportunity for exposure for asphalt plant workers. In this study, measurements of gaseous organic compounds from airborne binder fumes of selected bio-asphalt mixtures have been measured during the laboratory mixing process by using a thermo-mixer equipped with a chimney at University Gustave Eiffel. Parameters studied are the binder nature, mix formula, and mixing temperatures. Results show that generally combining bio-based materials and RA is as safe as using conventional bitumen and RA; however, thanks to this approach, it was possible to identify a strong link between bituminous materials' composition and their emission potential. [ABSTRACT FROM AUTHOR]

Purpose: Although the impact of road pavement surface condition on rolling resistance has been included in the life cycle assessment (LCA) framework of several studies in the last years, there is still a high level of uncertainty concerning the methodological assumptions and the parameters that can affect the results. In order to adopt pavement carbon footprint/LCA as a decision-making tool, it is necessary to explore the impact of the chosen methods and assumptions on the LCA results. Methods: This paper provides a review of the main models describing the impact of the pavement surface properties on vehicle fuel consumption and analyses the influence of the methodological assumptions related to the rolling resistance on the LCA results. It compares the CO emissions, calculated with two different rolling resistance models existing in literature, and performs a sensitivity test on some specific input variables (pavement deterioration rate, traffic growth, and emission factors/fuel efficiency improvement). Results and discussion: The model used to calculate the impact of the pavement surface condition on fuel consumption significantly affects the LCA results. The pavement deterioration rate influences the calculation in both models, while traffic growth and fuel efficiency improvement have a limited impact on the vehicle CO emissions resulting from the pavement condition contribution to rolling resistance. Conclusions and recommendations: Existing models linking pavement condition to rolling resistance and hence vehicle emissions are not broadly applicable to the use phase of road pavement LCA and further research is necessary before a widely-used methodology can be defined. The methods of modelling and the methodological assumptions need to be transparent in the analysis of the impact of the pavement surface condition on fuel consumption, in order to be interpreted by decision makers and implemented in an LCA framework. This will be necessary before product category rules (PCR) for pavement LCA can be extended to include the use phase. [ABSTRACT FROM AUTHOR]

The addition of recycled tyre rubber as a modifier to enhance the mechanical properties of bitumen has proven to provide asphalt mixtures with better mechanical performance. However the rubberised bitumen presents the limitation of requiring higher manufacturing and compaction temperatures. This could be solved by subjecting the tyre rubber to sort of pre-treatments such as: Adding warm-mix additives and/or using partial devulcanisation. These solutions have the potential of lowering the overall environmental impact of the asphalt pavement, however it is still not clear whether these can be detrimental for the rubberized asphalt binder mechanical properties. This paper investigates the effect on fatigue and healing properties of rubberized bitumen blended with pre-treated crumb rubber. An innovative combined fatigue and healing analysis will be presented and used to compare the several rubberised binders with a neat bitumen. The analysis consists in conducting time sweep tests by means of dynamic shear rheometer, by applying repeated cycles of stress or strain loading at selected temperatures and loading frequency. The healing potential of binders was evaluated by introducing short rest periods after a certain number of load pulses. At last, the unique energy parameter obtained using the Ratio of Dissipated Energy Change approach, was applied to obtain a unique index that could provide combined information for both fatigue binder damage and healing phenomenon. The results showed that the analysed rubberised bitumens show having better fatigue and healing performance when compared to the straight-run bitumen. [ABSTRACT FROM AUTHOR]

In order to provide a new method to study the migration behavior of coarse aggregates in the compaction process of asphalt mixtures, the "Intelligent Aggregate Attitude Acquisition System (IAS)" is developed based on 3D printing technology and wireless intelligent sensing technology, and the "Intelligent Attitude Aggregate (IAA)" is prepared as the acquisition terminal. The Superpave Gyratory Compaction (SGC) test and the Internet of Things (IOT) wireless sensor technology are combined to collect and analyze the attitude data of an SMA-20 asphalt mixture built in IAA at different compaction stages, and the migration behavior of coarse aggregate in the compaction process is quantitatively characterized. The result shows that the IAA is suitable as a "tracking aggregate" to study the aggregate transfer behavior in asphalt mixtures. The IAA in the upper layer tends to move vertically downward, while the particles in the lower layer tend to move horizontally and spatial rotation in the process of rotating compaction. With the increase in asphalt content, the lubrication effect between aggregate particles is obvious, and the friction resistance of aggregate particles decreases when it is embedded downward. Affected by shear force in the process of rotary compaction, the aggregate particles are easier to overcome friction and cause large horizontal migration and spatial rotation. With the increase in compaction temperature, the viscosity of asphalt binder decreases, and the contact friction between aggregate particles decreases. The asphalt content has a significant effect on the displacement in the horizontal plane Dxoy of the aggregate. The asphalt content and compaction temperature have significant effects on the spatial rotation angle Φ of aggregate, but the asphalt content has a greater impact on it. [ABSTRACT FROM AUTHOR]

The pavement engineering industry, having realized the significance of the impacts that it imposes on the environment through the production, construction and management of its products and assets, has been driven towards a more sustainable and circular way of operating. This has partly been through asphalt recycling, which is an area that many road authorities have prioritized. However, not all the National Road Authorities (NRAs) and/or sector stakeholders seem to be adequately familiar with the Circular Economy (CE) concept. This paper attempts to assist the transition of NRAs to a more circular way of doing business, by analyzing the current situation of CE within national/regional authorities and NRAs. To do so, a questionnaire was sent to different NRAs and an online search was conducted to identify the ways that NRAs communicate their CE practices. Findings indicate that, although the majority of the NRAs are familiar with CE as a concept, not many actions have been taken so far towards its holistic implementation. Finally, there is a significant lack of CE expertise and communication within these bodies. [ABSTRACT FROM AUTHOR]

The aged properties of Reclaimed Asphalt (RA) binders are one of the main factors working against their utilisation in high-RA content (>30%) mixes for surface courses. Fatigue cracking is the main distress of surface courses that are manufactured with a high percentage of RA. This investigation presents results of the rheological and fatigue results of different asphalt mixtures and their recovered binders. The binders were recovered from asphalt mixtures that had been manufactured in asphalt plants using different amounts of RA with contents up to 60% with and without rejuvenators. Two different sources of RA were used, representing a moderately aged RA and an extremely aged RA. The Dynamic Shear Rheometer (DSR) was used to assess the fatigue-characteristics of the binders using time sweep tests while the fatigue characteristics of their mixtures were assessed using the Indirect Tensile Fatigue Test (ITFT). The fatigue data was analysed based on the cumulative dissipated energy approach in addition to traditional fatigue analysis. Results have shown that the ageing condition of RA significantly affects the fatigue properties of recovered binders. Binder and asphalt mixture fatigue results showed that RA contents up to 60% can produce comparable fatigue performance compared to lower percentages of RA in road surface course if the aged RA binder is sufficiently rejuvenated. [ABSTRACT FROM AUTHOR]