Designing a toolbox for bitumen to answer the need for tomorrow's pavement

The asphalt industry is facing some key challenges. There is a need to move towards more sustainable and environmental friendly solutions to construct the pavements for tomorrow. This has to answer the market needs for greater performance with improved warranties, increased safety and less impact on environment, all in required budget constraints. At the same time, there is an even greater diversity in binders, petroleum based binders from different sources or processes for which bitumen quality may be affected. Up to now, specifications and characterisation for asphalt binders have been designed for known petroleum-based bitumen. With complex binders, more fundamental understanding and properties have to be considered to really capture the long-term benefits in road and airport engineering. And finally, beyond the technical requirements, sustainable aspects need to be part of the design including circularity, environmental impacts, health and safety amongst others. This is an important paradigm where new technologies are needed and adjustment of designing materials. Thus, the need for new solutions are becoming increasingly common practice. Designing the exact solution may depend on various parameters such as the nature of the modifier, the dosage level, or the expected effects on the binder, on the asphalt mix and finally on the pavement. It can be viewed as a toolbox where different options can be selected and combined together to adjust the properties of the binders that fits the need for pavement applications. Through some examples with the specific use of polymers and bio-based additives, an example of general framework will be discussed to be served as a toolbox to design materials to bring the frontiers of road and airport engineering a step further to the future

Evaluation of chemical composition and physical properties of bituminous binders and fractions

Bituminous binders are foreseen as colloidal dispersed systems characterised by high chemical complexity containing a plethora of molecules classified into maltenes and asphaltenes. The effect of these fractions on the overall response of bituminous binders remains elusive. This research selected two binders from the same refinery but with different paving grades. First, Dynamic Shear and Bending Beam Rheometers were employed to assess their rheological properties, and results were consistent with the physical measurements conducted on binders to address low to high temperature rheological response. Then, the binders and their fractions were individually analysed in a Fourier transform infrared spectroscopy and differential scanning calorimetry to elucidate their chemistry associated with the structural changes. No significant difference could be noticed in the infrared spectra of binders, even if they displayed diverse physical properties. Differences may be identified in asphaltenes, an observation which is also supported by calorimetric measurements where steric hindrance occurred upon heating. Maltenes contributed significantly to the glass transition of both binders, while the impact of asphaltenes on the heat capacity changes in glass transition was limited. The findings from this research could be used to establish a new analytical approach for bituminous binders to understand the differences in the physical properties of binders based on their chemistry.Pavement Engineerin

The use of rejuvenators as an effective way to restore aged binder properties

The amount of Reclaimed Asphalt recycling using rejuvenating agents has increased recently due to environmental and economic constraints. Rejuvenating agents are now regularly used to restore the aged binder properties similarly to those of a virgin binder. The current European specifications for asphalt paving bitumen use only empirical testing. Such procedure is appearing not sufficient to address the effect of rejuvenating agents. More advanced rheological analysis using DSR and BBR equipment appears promising. Parameters such as viscous to elastic transition (VET) from DSR or the difference between the creep stiffness and m-value critical temperature (ΔTCR) from BBR provide apparent indication of a binder’s flexibility and ability to relax stresses in cases of rejuvenation. This paper investigates the effect of three various rejuvenators on aged binder behaviour and shows that the rejuvenation process has a large impact on the material properties. Particularly rheological measurements demonstrated that as the aging process progresses the variance in rejuvenated binder behaviour increases especially in terms of performance at intermediate (VET) and low temperatures (ΔTCR)

Empirical, rheological and chemical properties of recycled binder blends 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 with50% of rejuvenated RA binder (RAb) and virgin binder were subjected to different ageing levels: short (RTFOT), long (PAV for 20h) and prolonged (PAV for 60h). 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, while the other additives showed comparable results with the second industrial product

Multiple Stress Creep Recovery Test to Differentiate Polymer Modified Bitumen at High Temperature

The constant demand for high-performing and more reliable roads has led to an increasing use of complex bituminous binders such as polymer-modified bituminous binders, which has become a widespread practice for asphalt pavement. As a result, specification and testing have evolved to better distinguish between quality materials. In recent years, more focus has been devoted to better evaluating the rutting resistance of bituminous binders. The multiple stress creep recovery (MSCR) test has gained popularity over the last decade, especially for polymer-modified binders, bringing more advantages in discriminating amongst quality binders such as polymer-modified bitumen. Within the International Union of Laboratories and Experts in Construction Materials, Systems and Structures technical committee 272, Phase and Interphase of Behavior of Innovative bituminous Materials, and its TG1 task group, several binders were thoroughly evaluated, including two non-modified and two polymer-modified bituminous binders, under various testing conditions to address the high-temperature behavior. Five laboratories performed MSCR on short-term aged binders after performing the rolling thin film oven test, in the same temperature conditions for all binders. Despite the limited data set, the variability between laboratories was reasonable. The MSCR results were compared with softening point temperature, high-temperature performance grade criteria, |G*| / sin delta, and equi-modulus temperature. MSCR was able to distinguish between complex binders better as compared with conventional parameters. It generates multiple useful parameters, amongst which percent recovery and non-recoverable creep compliance are the most relevant. This paper presents the analysis of MSCR results and comparison with other test methods

RILEM TC272 PIM: phase morphology of bituminous binders with liquid additives

In the past years, the use of liquid additives as bitumen modifiers has increased to tailor the rheology of bitumen for a wide range of applications. Their chemical composition and mutual interaction result in specific phase morphologies in the binders. Hence, there is a need to evaluate the phase morphology of complex binders and the impact of additives on their physical properties. The RILEM Technical Committee 272-PIM ‘Phase and Interphase behaviour of innovative bituminous Materials’, Task Group TG1 assessed the phase and interphase properties of bituminous binders. Some preliminary results are presented on blends using three liquid additives and a neat 35/50 bitumen. The goal of formulating the blends was to achieve similar consistency of a pen grade 70/100 bitumen at the original state and to evaluate the binders at both original and after aging. Physical properties were evaluated through rheological characterisation using a dynamic shear rheometer (DSR) in a wide range of conditions. The phase morphology was assessed using atomic force microscopy (AFM). Differential scanning calorimetry (DSC) was also used for the characterisation of the thermal behaviour of the binders. While conventional properties, as obtained from the routine binder testing methods, hardly distinguish between blends, the cross-over temperature, derived from DSR measurements, enabled to dictate the impact of liquid additives on the physical properties of bituminous binders at intermediate temperature. AFM confirmed a difference in phase morphology between the blends, whereas some binders displayed new phases at original and aged conditions. Glass transition, as determined by DSC, also showed a difference in the low-temperature domain that may be explained with the difference in phase morphology. Overall, an in-depth understanding of microstructure morphology and glass transition behaviour of complex binders can assist in designing future specifications to distinguish durable bituminous materials better.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin