The article investigates the chemical and rheological properties of bituminous binders extended with tall oil pitch (TOP), a bio-oil by-product from the pulp and paper industry. Bio-extended binders were formulated to incorporate different percentages of TOP, reaching the target penetration grades. Comprehensive chemical analyses, including Fourier-transform infrared FTIR spectroscopy and SARA (saturates, aromatics, resins, and asphaltenes) analysis by thin-layer chromatography with flame ionisation detection (TLC-FID), were conducted to investigate the compositional changes induced by TOP addition. Laboratory ageing of the binders was carried out. Rheological characterisation was performed using dynamic shear rheometer (DSR) to assess the impact on viscoelastic behaviour. The results indicate that TOP-extended bituminous binders exhibit distinct chemical signatures from bitumen, with notable differences in functional groups and SARA fractions. Furthermore, the incorporation of TOP changes the viscoelastic behaviour of binder. The specific impact and its extent seem to depend on the temperature and frequency range as well as the content of TOP in the binder. These findings are expected to contribute to the development of more sustainable asphalt pavements, highlighting the potential of TOP as a viable extender for bituminous binders. 

To verify the justification for an amendment of European StandardEN 14770:2023, this study investigates the effect of trimming on measured shear modulus and phase angle of bituminous binders using Dynamic Shear Rheometer (DSR). Six bituminous binders were analysed, including penetration grade neat bitumen and modified bitumen with polymer and wax. More than 400 DSR measurements (with trimming versus without trimming) were conducted at 10 rad/s at different temperatures. The comparisons between test results indicate that the effect of trimming on DSR measurements depends on the plate size used for the measurement. With the plate-plate geometry PP25 (diameter 25 mm and thickness 1 mm), whether trimming the specimen or not does not affect the DSR measurement repeatability or make a difference larger than the repeatability of the standard test method. However, with the plate-plategeometry PP08 (diameter 8 mm and thickness 2 mm), the trimming process has a more significant effect, particularly on shear modulus |G*|. But the effect of trimming as a single factor does not exceed the reproducibility limits of the standard test method. 

This paper investigates the use of a plant-based bio-oil in bituminous binders as a partial replacement of petroleum-based bitumen for asphalt mixtures. Its effects on the ageing behaviour of bituminous binders and asphalt mixtures are studied. A total of six bituminous binders and their asphalt mixtures were prepared and analysed in laboratory, including three different binder formulations with varying percentages of bio-oil and their respective reference binders. Both the bituminous binders and asphalt mixtures were subjected to ageing protocols in laboratory. Softening point test, rheological and dynamic mechanical analyses were conducted to evaluate the changes in properties of the materials before and after ageing. The results indicate that the mechanical properties of aged binders and mixtures show very similar relationships as between the fresh materials, but the relationships after ageing are at changed levels due to the laboratory conditioning. This supports further studies to verify their functional performance in asphalt pavements.

here have been efforts in Sweden to convert and transform single carriageway roads into collision-free roads. The structural design and cost-effectiveness of these roads have mainly been performed using empirically derived pavement design methods. Currently, the Swedish Transport Administration (STA) is financing a project aimed at developing and implementing a mechanistic-empirical (M-E) pavement design approach for Swedish conditions. This is expected to impact long-term pavement performance and subsequently, the total life cycle cost (LCC) of projects. This paper examines, through design alternatives, the impact of a pavement design method on the total LCC of a road project. This is achieved by designing and analyzing an actual flexible pavement structure using two empirical pavement design methods and one M-E pavement design method. A life cycle cost analysis (LCCA) was employed to estimate future maintenance and rehabilitation (M&R) and road user costs, as well as initial construction and end-of-life costs. The cost estimation was conducted considering various combinations of interest and inflation rates that are expected to reflect current and future cost trends. The analyses have shown that the M-E pavement design approach delivered the least LCC, but this LCC is observed to vary considerably depending on the inflation and interest rates employed.

Polymer-modified binders are widely used in asphalt pavements, but their long-term performance and recyclability depend on how they age under both thermo-oxidative and photo-thermal conditions. Within RILEM TC 307-PPB, Task Group 2 (TG2) has set up an interlaboratory programme to compare a reference RTFOT+PAV ageing condition (PAV40) with a well-defined RTFOT+UV condition (UVA72) for two industrial SBS-modified binders with different SBS contents. Ageing was carried out centrally at TU Delft and the binders were characterised in ten laboratories using FTIR spectroscopy, BTSV rheological measurements and fluorescence microscopy. FTIR band indices indicate that PAV40 and UVA72 bring both binders to a similar overall oxidation level, while the balance between matrix oxidation and polymer-related changes depends on SBS content. BTSV results show comparable high-temperature stiffening for PAV40 and UVA72, with binder-dependent but modest differences. The interlaboratory data reveal larger scatter of FTIR indices for UVA72, and additional tests on solid and homogenised UV-aged films point to finite UV ageing depth and sampling/homogenisation procedures as important contributors. Fluorescence microscopy provides a qualitative microstructural counterpart and confirms the sensitivity to preparation protocols. Together, these findings offer an interlaboratory reference for relating UV and PAV ageing of SBS-modified binders and underline the need for clearly defined UV ageing and sampling procedures in future TG2 pre-standardisation work.

Bitumen is a complex material with specific visco-elastic properties. Modifiers are now commonly used to enhance the performances of asphalt materials. This makes bituminous binders even more complex with different phases and interphases in the binder. Within the RILEM TC 272-PIM, the TG1 aimed at investigating complex bituminous binders through multiple testing. An inter-laboratory program was conducted with 17 laboratories. Seven binders were evaluated, in two groups, one with polymer modified bitumen and the second with liquid additives. In addition to conventional property measurements, extensive efforts were undertaken to investigate fundamental physical properties, including rheological measurements, chemical, thermal, and morphological characterisations. Current conventional tests, used for binder characterisation, were initially developed for pure bitumen. The extensive experiment, conducted by TG1, clearly highlights the limits of conventional properties, and brings more fundamental understating how the morphology of complex bituminous binders can affect the overall behaviour of bituminous binders in a wide range of conditions. This chapter first describes the experimental plan as conducted by the different laboratories. After that, it displays in detail the results of each test for each group of binders and includes some comparisons between parameters according to the expected conditions and performances. Already numerous standalone publications have been published for specific test results to address variability and in-depth interpretation of outcomes. The results discussed in this chapter are mostly focusing on the relevance of each test to better distinguish between complex bituminous binders and not addressing variability of results.

Replacing petroleum-based bitumen with alternative bio-based binders in asphalt mixtures is a promising solution for green transition of road construction industry. The mechanical performance of bio-extended bituminous binders and asphalt mixtures is not yet fully understood, in particular with respect to dynamic mechanical behavior due to traffic and environmental exposures. As bio-binders differ in their chemical compositions, their physical properties and mechanical behavior may vary and differ significantly from bitumen-based materials. This paper aims to contribute to this important topic by evaluating a spherical indentation test as a quasi-nondestructive tool for viscoelastic characterization of the asphalt mixture containing bio-extended bituminous binder. Asphalt indentation tests are more sensitive to the binder phase properties as compared to standard macro-scale asphalt tests and may thus be a potentially useful tool for monitoring binder properties from the measurements performed on asphalt mixtures without extracting the binder.

The carbon footprint of bio-extended bituminous binders aiming for pavement decarbonisation was quantified using a “cradle-to-pavement” life cycle assessment. The binders were extended with a plant-based bio-oil. By biogenic carbon accounting, the impact of biogenic carbon flow was analysed through different approaches. The results indicated that using the bio-oil as a bitumen extender slightly increases the fossil global warming potential (GWP) of asphalt pavements, by about 1%. Both the absolute GWP levels and the effect of polymer modification on average annual GWP are variable, depending on the input data. When the “−1/+1” approach is adopted, two of the three analysed cases showed a lower average annual GWP of asphalt pavements with polymer-modified bitumen while one analysed case showed almost unchanged average annual GWP. All analysed cases confirmed that the biogenic carbon accounting by the “−1/+X” approach reduces the total and average annual GWP significantly for the cases with biogenic components.

Tall oil pitch (TOP) is widely available as a by-product, but not sufficiently valorized and has potential as a bitumen extender. In this research, three types of TOP were used to prepare bio-extended binders of two grades based on the penetration and softening point of target neat binders. The chemical, rheological, and fatigue behaviour of bio-based binders and reference binders were investigated and compared. The optimum TOP contents were inversely determined based on penetration and softening point fitting equations. New C = O and C–O–C stretching can be found in bio-based binders. Different TOPs can significantly increase the viscous response of asphalt binders, resulting in better low-temperature properties but reduced high-temperature properties. A high amount of TOP can significantly reduce fatigue resistance. This work reveals that TOP can work as extenders for bitumen, but the performance of bio-based binders is affected by the TOP type and amount.

Attenuated Total Reflection Fourier Transform Infrared spectroscopy has become a popular spectroscopic technique in bituminous binder analysis. However, comparable results are not obtainable yet due to differences in devices, measurement routines, sample preparation procedures, and spectral evaluation. Thus, the Task Group 1 of the RILEM TC 295-FBB: “Fingerprinting bituminous binders using physicochemical analysis” focuses on bringing this method towards pre-standardization. This study evaluates the reproducibility and consistency from round robin test, where 21 participating laboratories performed six different preparation techniques on three different binders in an unaged, short-term, and long-term aged state. A total of 6461 spectra were recorded and evaluated for their mean, standard deviation and coefficient of variation (CV) in the spectral region between 1800 and 600 cm−1. The results show that the solid sample preparation methods provide excellent reproducibility, with a coefficient of variation below 2%. Only the solvent method showed a higher coefficient of variation at 7.18%. Outliers with a high CV were detected and categorized into two groups: one where only one of the four samples differed and the other where all 16 spectra showed slight scattering in the overall absorption. The consistency of the method is significantly influenced by the accuracy of sample preparation, which is crucial for minimizing differences in slope, baseline, and noise in the spectra. These findings show the excellent reproducibility of these sample preparation methods and will be further examined to establish universal indices for evaluating effects such as ageing, bringing the method closer towards standardization.