Bitumen Blends Research Articles

Functional and rheological investigations on hydrophilic nanoclay blended bitumen

Functional and rheological characteristics are two essential criteria for the success of any modifiers for the modification of bitumen. Recently, nanoclay has grabbed extensive attention as a key solution for enhancing the performance of bitumen. This study focuses on evaluating the dispersion, storage stability, high-temperature performance, and aging resistance potential properties of bitumen VG-30 modified with montmorillonite bentonite hydrophilic nanoclay (NC). Various proportions (0, 2, 4, 6, and 8% by weight of bitumen) of NC were blended with VG-30 using a high shear mixer (HSM). Various performance assessments, including kinematic viscosity by Brookfield Rotational Viscometer (BRV), multiple stress creep recovery (MSCR), high-temperature performance grade (PG), frequency sweep along with scanning electron microscopy (SEM) were conducted. SEM images and viscosity data analysis show that dispersion problem arises beyond 6% of NC addition while phase separation is in the acceptable range. Further, considerable increment in Superpave rutting parameter (G*/Sinδ) and recovery percentage (%R), and decrease in non-recoverable compliance (Jnr) was seen, resulted up to 30% improvement in rutting performance of the bitumen. Furthermore, the potential for aging resistivity resulted a significant drop in aging index (AI) values, suggesting that introducing NC to bitumen could significantly improve aging resistivity. Moreover, rheological approaches can be helpful to understand temperatures and frequency dependent aging behaviours of bitumen.

Novel base predictive model of resilient modulus of compacted subgrade soils by using interpretable approaches with graphical user interface

The flexible pavement system consists of layers that are made up of a blend of aggregates and bitumen. To design flexible pavement systems that are both safe and environmentally sustainable, it is essential to have an accurate understanding of the resilient modulus (Mr) of the compacted subgrade soil. Mr refers to the ability of the soil to resist deformation under repeated loads. Thus, a critical parameter affects the performance and longevity of pavement systems. This study employs machine learning (ML) algorithms such as individual and ensemble learners using an extensive database of 2813 data points. These include dry unit weight, weighted plasticity index, confining stress, deviator stress, moisture content, and the number of freeze-thaw cycles (FT). The individual or weak learners were incorporated to create strong and robust ensemble learners by employing techniques such as bagging, adaptive boosting, and random forest (RF). Ensemble learning methods were used to improve the performance of individual learners, such as support vector machine (SVM) and decision tree (DT), by combining their predictions. To achieve the highest R2 value, a total of twenty bagging and boosting sub-models were trained and optimized. The validation of the test data was carried out through K-Fold cross-validation, utilizing metrics such as R2, MAE, and RMSE. The developed models were rigorously tested using statistical indices (MAE, MSE, RMSE, and RMLSE) to verify their predictive accuracy, reliability, and trustworthiness. The findings indicate that the integration of bagging and boosting techniques improves the efficiency of individual machine learning (ML) models. The combination of RF and DT utilizing bagging resulted in the most reliable performance, achieving an R2 value of 0.9 and demonstrating minimum errors. In general, the implementation of the ensemble algorithm in ML improved the overall prediction accuracy of the model. Sensitivity analysis reveals that the prediction of the resilient modulus (Mr) of the subgrade is primarily influenced by dry density, confining stress, and deviator stress. Moreover, a graphical user interface (GUI) is developed for practical implantation.

Rheological aspects of solid-to-liquid phase transitions in paraffin wax/bitumen blends for thermal energy storage applications

This paper correlates the evolution of the rheological and thermal properties with microstructure during the phase change of a blend of bitumen with a selected paraffin wax, having a melting point centred around 60 °C, for the development of bituminous based membranes for thermal energy storage applications. For this purpose, temperature sweep tests within the linear viscoelastic range, stationary state flow curves, Differential Scanning Calorimetry (DSC), polarised optical microscopy observations and solar irradiation tests were performed. The reported rheological results clearly point out a gel-like behaviour for both paraffin and paraffin/bitumen blend that is preserved almost up to the end of the phase change interval. This is consequence of the development of a network of interconnected crystals of paraffin wax which progressively disappear as temperature increases. Interestingly, a weak gel structure is kept even at low crystallinity levels since only a few junctions among structures are necessary to build a spanning network. Finally, the large degree of crystallinity of paraffin wax retained in the bitumen/paraffin wax is behind its thermoregulation ability, as was corroborated by solar irradiation tests. Therefore, results indicated the great potential of these formulations for thermal energy storage and related applications.

Laboratory evaluation of cutback bitumen modified with cup lump rubber

Abstract This research introduces a novel approach to addressing challenges in conventional asphalt used for road construction by incorporating cup lump rubber into cutback bitumen. The study investigates the viscosity and flash point of the resulting cutback bitumen to identify the optimal solvent percentage for achieving a lower mixing and compacting temperature range. Various diluent percentages were tested, ranging from 40% to 50%, across temperatures from 30°C to 70°C. Results indicate that higher diluent percentages lead to decreased viscosity in the blended bitumen. The most efficient solvent content for producing cutback bitumen-modified cup lump rubber is identified at 45% and 50% by weight of the bitumen, offering a reduced mixing and compaction temperature range. However, higher diluent content increases volatility potential and reduces the flash point. Additionally, toxicity testing reveals that lead and zinc are consistently present in cup lump rubber-infused samples, albeit below hazardous waste limits set by TCLP. The absence of lead in unmodified cutback bitumen underscores its compliance with environmental safety standards. These findings underscore the minimal environmental impact of this innovative modified bitumen formulation.

Waste Cooking Oil as Eco-Friendly Rejuvenator for Reclaimed Asphalt Pavement.

Over 50 MioT of Waste Cooking Oil (WCO) was collected worldwide in 2020 from domestic and industrial activities, constituting a potential hazard for both water and land environments, and requiring appropriate disposal management strategies. In line with the principles of circular economy and eco-design, in this paper an innovative methodology for the valorisation of WCO as a rejuvenating agent for bitumen 50/70 coming from Reclaimed Asphalt Pavement (RAP) is reported. In particular, WCO or hydrolysed WCO (HWCO) was modified by transesterification or amidation reactions to achieve various WCO esters and amides. All samples were characterised by nuclear magnetic resonance, melting, and boiling point. Since rejuvenating agents for RAP Cold Mix Asphalt require a melting point ≤0 °C, only WCO esters could further be tested. Efficiency of WCO esters was assessed by means of the Asphaltenes Dispersant Test and the Heithaus Parameter. In particular, bitumen blends containing 25 wt% of WCO modified with 2-phenylethyl alcohol, showed high dispersing capacity in n-heptane even after a week, compared to bitumen alone (1 h). Additionally, the Heithaus Parameter of this bitumen blend was almost three times higher than bitumen alone, further demonstrating beneficial effects deriving from the use of WCO esters as rejuvenating agents.

Effects of rejuvenators and aging conditions on the properties of blended bitumen and the cracking behavior of hot asphalt mixtures with a high RAP content

The utilization of Reclaimed Asphalt Pavement (RAP) in asphalt pavement has obtained global popularity because of its cost-efficiency, technical advantages, and positive environmental influence. However, incorporating RAP requires careful consideration of cracking resistance because of the existence of age hardening of bitumen in RAP. For the mixtures containing high RAP contents, rejuvenators are often applied to enhance the performances of aged bitumen and the cracking of mixtures. This research aims to evaluate the effects of different rejuvenators on the rheological properties of bitumen and the cracking resistance of the mixture under short and long-term aging conditions. To achieve this goal, three rejuvenators - namely, RA1 (petroleum-based), RA2 (waste vegetable oil-based), and RA3 (modified soybean oil-based) were evaluated at contents of 0%, 4%, 12%, and 20%, respectively. The dynamic shear rheometer (DSR) test results show that, under unaged and rolling thin-film oven (RTFO) aging conditions, blended bitumen with RA1 and RA3 have higher G*/sinδ than RA2. Conversely, under pressure aging vessel (PAV) aging conditions, blended bitumen with RA1 and RA3 has lower G*sinδ than that with RA2. Regarding the cracking resistance, the indirect tension asphalt cracking test results show that, under short-term oven aging (STOA) conditions, the mixture using RA2 and RA3 has a higher cracking tolerance index (CTIndex) than the one with RA1. However, under long-term oven aging (LTOA) conditions, the mixture using RA1 has the highest CTIndex value. In addition, the high correlations between G*sinδ with CTIndex and post-peak slope (|m75|) and between the CTIndex and |m75| are observed.

Chemical and Rheological Properties of Bitumen Partially Substituted with Rice-Straw-Based Lignin from Bio-Ethanol Industry Residue

The objective of this study is to evaluate the changes in the chemical and rheological properties of bitumen when partially substituted, up to 15%, with rice-straw-based lignin materials, namely isolated lignin (IL) and fermentation residue lignin (FRL), obtained from second-generation bio-ethanol industry residues. Attenuated total reflectance-Fourier transform infrared spectroscopy was used to evaluate the alterations in chemical properties. The rheological properties that were assessed include Superpave upper performance grade (PG), rutting resistance using the multiple stress creep recovery test, and fatigue resistance using the linear amplitude sweep test. The results indicated that the addition of IL and FRL materials to the base bitumen is a physical process. Furthermore, IL and FRL substituted bitumen blends exhibited distinct trends for carbonyl (C=O) and sulfoxide (S=O) functional groups with ageing, depending on the chemical structure of the additive. Specifically, the IL materials showed a reduction in the rate of increase of ageing products and a decrease in the combined ageing index, up to 10% IL dosage, suggesting some antioxidant effect within the group. The addition of IL up to 15% dosage and FRL up to 10% dosage also led to an increase in the base binder high-temperature grade from PG70-XX to PG76-XX. Moreover, both IL and FRL materials enhanced rutting resistance and reduced fatigue resistance with an increase in dosage. It is worth noting that bitumen blends with different additives showed varying trends between chemical and rheological properties.

Crude Oil-Bitumen Blends: A Resource and Potential for Refining and Petrochemical Applications.

This paper looks at the potential of bitumen blends for refinery and petrochemical applications. Bitumen mixed with diluents and synthetic oils have refinery applications but this process is expensive with current realities, hence the need for cheaper alternatives. In this study, Bitumen was mixed with crude oils, condensate oil and the transport and product properties compared to standard pipeline specification and refinery application evaluated. Bitumen/oil blend ratio of (50:50) was found to pass the North American oil transport pipeline specification of viscosity less than 350 cSt. The bitumen blends were further upgraded via catalytic processes to study the potential of the products. The gas analysis of the products confirmed it is rich in methane and with other components such as carbon monoxide and carbon dioxide, which are potential for energy and syngas production. This confirms the economic potential of bitumen blends with reservoir oils as a candidate material for cost-effective downstream feed/refinery and petrochemical applications.

Do different chemical and rheological properties act as effective and critical indicators for efficiency evaluation of rejuvenated bitumen?

This study investigates the impacts of rejuvenator type/dosage and the aging degree of bitumen on the chemical and rheological properties of rejuvenated bitumen, and propose critical chemo-rheological indicators for evaluating rejuvenation efficiency. Moreover, the potential connections between essential chemical and rheological indices of rejuvenator-aged bitumen blends are explored. Results indicate that chemical indices show linear relationships with rejuvenator dosage and vary depending on the rejuvenator type and aging level of bitumen. All rejuvenators can regenerate certain rheological parameters of aged bitumen to varying degrees, but cannot restore the crossover modulus (Gc). Various rheological indices exhibit different correlations with rejuvenator dosage and sensitivity degrees to the discrepancy in rejuvenator type and aging degree of bitumen. Critical chemical and rheological indicators are proposed based on their sensitivity levels to influence factors, with the aromaticity index (AI), carbonyl index (CI), and sulfoxide index (SI) as effective chemical indices and the complex modulus (G*), crossover frequency (fc), and high-temperature master curve area (AMH) as critical rheological indices for rejuvenation efficiency evaluation. The study finds that the magnitude of rejuvenation efficiency for four rejuvenators is Bio-oil > Engine-oil > Naphthenic-oil > Aromatic-oil, and the linear correlations between the critical chemical and rheological indices, together with their rejuvenation percentages, are significantly affected by the rejuvenator type and aging level of bitumen.

Unraveling the critical indicators for evaluating the high-temperature performance of rejuvenator-aged bitumen blends

This study aims to systematically investigate the influence of rejuvenator type/dosage and the aging degree of bitumen on the rutting resistance, flow behavior, and elastic/creep potential of rejuvenated bitumen at high temperatures. The rutting parameter (G*/sinδ), rutting failure temperature (RFT) from Linear viscoelastic test (LVE), zero-shear viscosity (ZSV) from flow test, recovery percentage (R0.1, R3.2), creep compliance (Jnr0.1, Jnr3.2), and stress sensitivity parameters (Rdiff, Jnrslope) from multiple stress creep and recovery (MSCR) tests of rejuvenated bitumen are characterized. The results reveal that bio-oil rejuvenator weakens the high-temperature performance of aged bitumen maximally, followed by engine-oil and naphthenic-oil, while aromatic-oil rejuvenated bitumen exhibits the best rutting, flow, and creep resistance. The RFT index can most effectively evaluate and differentiate the rejuvenation efficiency of various rejuvenators on the high-temperature performance, which correlates well with ZSV, R3.2, Jnr0.1, Jnr3.2, Rdiff, and Jnrslope indices. Therefore, the RFT index is recommended as the critical indicator for evaluating the high-temperature performance of rejuvenated binders. The flow and MSCR characteristics of rejuvenated bitumen can be predicted based on RFT values. The determination of critical indicators is beneficial to compare the rejuvenation effectiveness of variable rejuvenators on the high-temperature performance of aged bitumen.

Towards critical low-temperature relaxation indicators for effective rejuvenation efficiency evaluation of rejuvenator-aged bitumen blends

The relaxation behavior affected by aging and rejuvenation plays a crucial role in its low-temperature cracking potential of bitumen. However, there are limited studies on the relaxation performance of rejuvenated bitumen under different rejuvenation conditions. This paper aims to propose critical indicators to assess the rejuvenation efficiency of low-temperature relaxation performance of various rejuvenated binders. The effects of rejuvenator type/dosage and aging level on relaxation parameters are investigated. The τ50s, t25%, and A are recommended as critical indicators based on their high sensitivities to influence factors and rejuvenation percentage scope. Additionally, molecular dynamic simulation outputs on virgin/aged bitumen and rejuvenators explain the difference in rejuvenation effectiveness of different rejuvenators. The results show that bio-oil rejuvenator exhibits the highest efficiency on regenerating the relaxation performance. All relaxation parameters of aged bitumen can be regenerated by adding rejuvenators. MD simulations reveal that the molecular mobility and free volume ratio of rejuvenators mainly cause the difference in rejuvenation efficiency on the relaxation property between various rejuvenators. The diffusion capacity of rejuvenator shows a more dominant effect on rejuvenation efficiency than fractional free volume.

Artificial Neural Networks (ANNs) for Vapour-Liquid-Liquid Equilibrium (VLLE) Predictions in N-Octane/Water Blends

Blends of bitumen, clay, and quartz in water are obtained from the surface mining of the Athabasca Oil Sands. To facilitate its transportation through pipelines, this mixture is usually diluted with locally produced naphtha. As a result of this, naphtha has to be recovered later, in a naphtha recovery unit (NRU). The NRU process is a complex one and requires the knowledge of Vapour-Liquid-Liquid Equilibrium (VLLE) thermodynamics. The present study uses experimental data, obtained in a CREC-VL-Cell, and Artificial Intelligence (AI) for vapour-liquid-liquid equilibrium (VLLE) calculations. The proposed Artificial Neural Networks (ANNs) do not require prior knowledge of the number of vapour-liquid phases. These ANNs involve hyperparameters that are used to obtain the best ANN model architecture. To accomplish this, this study considers (a) R2 Coefficients of Determination and (b) ANN training requirements to avoid data underfitting and overfitting. Results demonstrate that temperature has a major influence on ANN vapour pressure predictions, while the concentration of octane, the naphtha surrogate having, in contrast, a lesser effect. Furthermore, the ANN data obtained allows the calculation of octane-in-water and water-in-octane maximum solubilities.

Determination of the Properties of Natural Rubber Crumb –Modified Bitumen Blends (NRCMB)

Determination of the Properties of Natural Rubber Crumb –Modified Bitumen Blends (NRCMB)

Dynamic Viscosity Prediction of Blends of Paving Grade Bitumen with Reclaimed Bitumen

The recycling of reclaimed asphalt pavement is of significant economic and environmental benefits. In this case, however, the satisfactory performance of the final product needs scientific planning of the mixture and thorough quality control. Before its use, a number of tests must be performed to verify that the binder meets the relevant requirements and can be used in asphalt mixtures. The binder characteristics in the reclaimed asphalt pavement and the expected properties of the binder blend in the new asphalt mixture must be known. For its prediction and calculation, a European standard offers the calculation of the penetration or softening point of the binder blend in the mixture with reclaimed asphalt content. However, in some countries, the determination of paving grade bitumen types (categories) is based not on dynamic viscosity measured with DSR instrument, so other validated test and calculation methods are in force. A viscosity-based method has not yet been validated for paving grade bitumens standardized on a penetration basis, although this method is more advantageous in many aspects when monitoring daily production processes; it is much shorter and requires less material than measuring softening point or penetration. The article deals with the measurement of the dynamic viscosity of bitumen blends of asphalt mixtures made using reclaimed asphalts, determined with a dynamic shear rheometer at different frequencies (0.1–10.0 Hz sweep). Furthermore, the relationships between the different composition ratios of national paving grade bitumens classified on the bases of penetration level and bitumens from reclaimed asphalt pavement are examined.

Radio- and stable carbon isotope analysis reveals minimal assimilation of petrogenic carbon into an oligotrophic freshwater food web after experimental spills of diluted bitumen

Following an oil spill into water, bacteria can biodegrade petroleum hydrocarbons which could lead to petrogenic carbon assimilation by aquatic biota. We used changes in the isotope ratios of radio- (Δ14C) and stable (δ13C) carbon to examine the potential for assimilation of petrogenic carbon into a freshwater food web following experimental spills of diluted bitumen (dilbit) into a boreal lake in northwestern Ontario, Canada. Different volumes (1.5, 2.9, 5.5, 18, 42, 82, and 180 L) of Cold Lake Winter Blend (a heavy crude blend of bitumen and condensate) dilbit were applied to seven 10-m diameter littoral limnocorrals (approximate volume of 100 m3), and two additional limnocorrals had no added dilbit to serve as controls. Particulate organic matter (POM) and periphyton from oil-treated limnocorrals had lower δ13C (up to 3.2‰ and 2.1‰ for POM and periphyton, respectively) than the control at every sampled interval (3, 6 and 10 weeks for POM and 6, 8 and 10 weeks for periphyton). Dissolved organic and inorganic carbon (DOC and DIC, respectively) had lower Δ14C in the oil-treated limnocorrals relative to the control (up to 122‰ and 440‰ lower, respectively). Giant floater mussel (Pyganodon grandis) housed for 25 days in aquaria containing oil-contaminated water from the limnocorrals did not show significant changes in δ13C values of muscle tissue compared to mussels housed in control water. Overall, the changes in δ13C and Δ14C observed indicated small amounts (up to 11% in DIC) of oil carbon incorporation into the food web. The combined δ13C and Δ14C data provide evidence for minimal incorporation of dilbit into the food web of this oligotrophic lake, suggesting that microbial degradation and subsequent incorporation of oil C into the food web may play a relatively small role in the ultimate fate of oil in this type of ecosystem.

Use of Low-density polyethylene in flexible pavement

Plastic is found in abundance on earth due to its cheap capital cost and large-scale availability. Plastic waste is a mean to degrade our environment as it is also a source of many toxic gasses and is non-biodegradable. There must be some way to eliminate such a threat to our surroundings. The use of Low-density polyethylene such as bottles, polythene bags, and much more as a replacement in bitumen blend provides various benefits like an increase in resistance to deformation, increase in durability, strength, reduction in seepage, mitigating of pollution, and gainful for waste disposal.

Feasibility Investigation of Bitumen Properties by Blending of Coal Tar Pitch

There are numerous methods and additives available to improve the durability and quality of road bitumen. A coal tar obtained by coal coking was distilled in a laboratory into fractions of initial boiling point IBP-180℃ (gasoline-like fuel), 180℃ - 360℃ (diesel-like fuel), and >360℃ (residue or coal tar pitch). The coal tar pitch was added into road bitumen by up to 1 - 5 wt% and investigated the alteration of physical and chemical properties. The physico-mechanical properties of coal tar pitch and bitumen blends, as well as the chemical group composition, were determined using standard techniques (MNS) and the SARA method, respectively. Results of 3% coal tar pitch addition into bitumen enhanced ductility by 12.4% and softening point by 1.6℃. We found that blending with bitumen coal tar pitch as a modifier could improve bitumen properties.

The P-µ-T Cubic Equation of Viscosity for Reservoir Oils

Summary Oil recovery simulation sensitivity increases with heavier oils for the existing viscosity models, driving into higher levels of difficulty when fitting viscosity data for rising oil heaviness, particularly below the saturation pressure. Keeping in view the similarity of trends of viscosity and density with isothermal pressures for reservoir oils, the P-μ-T cubic viscosity model, which was developed for pure hydrocarbon components, was extended to reservoir oils. Two parameters in the P-μ-T cubic viscosity model for mixtures with pure and pseudocomponents are identified for adjusting the viscosity data fitting: Kc for controlling the viscosity gradient with pressure and the “ε” shifting trends for increasing viscosity direction. These two parameters are treated as the adjustable parameters required for fitting the viscosity data. A total of 129 reservoir oils from different sources are used to validate the reliability of the P-μ-T viscosity model. The default model (where ε and Kc are 1 and 45, respectively), extended to 71 light oils, resulted in 31% of average absolute relative deviation (AARD) in viscosity prediction. However, separate adjusted parameters are obtained per oil for more accurate viscosity data fitting. Application of the model in this work results in (post-fitting) AARD% of 2.86% average for 36 low-viscosity oil data, 5.68% for 9 high-viscosity oil data, 9% for five oil blends, and 4.11% for bitumen blends. The model gives an AARD of 3.06% in the undersaturated region and 3.79% in the saturated region for the oil considered. The model predicts better the viscosity above saturation pressure for low-viscosity oils and below saturation pressure for high-viscosity oils. A comparative analysis of the P-μ-T cubic viscosity model vs. other models demonstrates its ability to successfully capture viscosity trends of oil and blends in all viscosity ranges. For simplicity, the P-μ-T cubic viscosity model is proposed with only two optimizing parameters even though using a third parameter improves the matching in heavy oils.

Rheological multi-scale evaluation of RAP and RAS binders mobilisation in hot mix asphalt

The use of Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) in asphalt mixes is a constructive solution allowing economic, environmental and technical benefits. The objective here is evaluating the binder mobilisation rate of recycled materials by predicting the viscoelastic (LVE) behaviour of the asphalts from the LVE of their theoretical binder. The multi-scale approach adopted here goes from the binder scale to the mix scale. At the binder scale, after the extraction/recovery of RAP and RAS binders, several bitumen blends were produced and characterised by conventional and rheological tests. At the asphalt scale, the LVE behaviour of several mixes containing RAP and RAS was characterised using complex modulus test. Then, Shift-Homothety-Shift-time-Shift-transformation (SHStS) was applied allowing verifying the correspondence degree between the experimental behaviour and the predicted one. The results confirm that the totality of the RAP binder was mobilised and up to 50% in the case of RAS.

Recycled plastic modified bitumen: Evaluation of VOCs and PAHs from laboratory generated fumes

A key aspect when investigating the use of recycled plastics in bitumen relates considerably to the issues relating to occupational, health and safety for humans and the environment from a fuming and emissions perspective. This research investigates laboratory-generated fumes in the forms of volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs) generated from producing polymer modified bitumen using five different types of recycled plastics. A comparative analysis of recycled plastic modified bitumen fumes was conducted based on a series of optimized parameters, including working temperatures (160 °C, 180 °C and 200 °C) and polymer contents (1%, 2%, 4% and 6% by weight of bitumen) against neat bitumen and polymer-modified bitumen. Forty-eight volatile organic compounds (VOCs) and sixteen polycyclic aromatic hydrocarbons (PAHs) were quantified using gas chromatography–mass spectrometry (GC–MS). The results from the comparative analysis revealed that the incorporation of recycled plastics could reduce overall emissions from both VOCs and PAHs perspectives. The reduction in emissions can be attributed to the enhancement in thermal stability of the bitumen blend when recycled plastics are added. The reduction rate is heavily dependent on the type and source of recycled plastics used in the blending process. Furthermore, a specific compound concentration analysis of the top-four weighted compounds emitted reveals that the total concentration of emissions can be deceiving as specific compounds can spike when adding recycled plastics in bitumen despite a reduction trend for the overall concentration.