2nd International Workshop on the Use of Biomaterials in Pavements

In recent years, a number of innovative bio-binders have been made available in the UK, which incorporate biogenic components. These biogenic components partially replace traditional petroleum-refined bitumen in asphalt production. The introduction of these bio-binders has significant potential to decarbonise asphalt production and support the achievement of Net Zero targets within the sector. National Highways (NH) has set out an ambitious plan to achieve net zero carbon for construction and maintenance activities in its road network. As part of this plan, a surface course trial containing polymer modified (PMB) bio-binders was undertaken on the A30 on Strategic Road Network (SRN) in England. This represented the first surface course installation of PMB bio-binders on the SRN.

Two Thin Surface Course Systems were installed each incorporating a different commercially available PMB bio-binder. In addition, a control section incorporating a conventional PMB was installed to enable the performance and carbon footprint to be compared. All trial sections were successfully installed in February 2023. Laboratory assessment demonstrates the trial sections with bio-binders achieve the end performance requirements for a Thin Surface Course System in the UK. The initial results indicate that the incorporation of the bio-binder has significant potential to reduce the carbon footprint of bituminous surface courses.

Asphalt pavements are crucial in the road networks of many countries. Annually, these networks require significant economic resources for development and maintenance. However, the constant restriction of these resources necessitates the exploration of alternatives to enhance their durability. Aging processes, induced by oxidation of organic components during construction and throughout their lifespan, significantly affect asphalt behavior. This aging process leads to a reduction in asphalt’s viscoelastic properties, making it brittle and prone to cracking. To address this, various natural antioxidants have been analyzed, and one such additive is Kraft Lignin, a biopolymer abundantly available as a byproduct of the paper industry. This study aims to present the experience and results of using Kraft Lignin as an antioxidant agent in CA-24 asphalts widely employed in Chile. Characterization of Lignin included its elemental composition and particle morphology. Different proportions of Lignin (0, 10, 20, and 30%) were mixed with asphalt by weight. Asphalt-Lignin samples underwent short-term aging using the RTFOT test and long-term aging through the PAV test. To analyze the impact of incorporating Kraft Lignin, rheological properties were evaluated by dynamic shear rheometer, determining the complex modulus (G*) and phase angle (δ). Results indicate beneficial behaviors at high temperatures, enhancing resistance to rutting. However, considerations arise at low temperatures related to fatigue resistance.

One recent low carbon technology which has the potential to reduce the carbon footprint of asphalt is the use of biogenic binders. To fully realise the potential of bio-binders and to achieve net zero it is recognised that there is a need for bio-binders to be compatible with warm-mix asphalt and reclaimed asphalt. A laboratory investigation was therefore undertaken to assess the performance of a commercially available bio-binder in conjunction with Reclaimed Asphalt (RA) and Warm-Mix Asphalt (WMA).

In total four mixes were assessed incorporating incremental changes to examine the performance of the bio-binders with warm-mix additives and increasing RA content (up to 20% RA). Performance testing was conducted on the binders, bituminous mixtures and recovered binder properties. This paper presents the results of the bituminous mixture testing and concludes the mixes incorporating a Polymer Modified Binder (PMB) bio-binder in conjunction with WMA and up to 20% RA has demonstrated comparable performance to the control surface in terms of wheeltracking, water sensitivity, cantabro abrasion loss, fracture toughness and fatigue. The only significant difference observed was in relation to the ITSM for the RA mixes, which is attributed to the RA content. Carbon footprint analysis has also confirmed that combination of bio-binders in conjunction with 20% RA and WMA can deliver significant carbon reductions.

An increasing number of researchers and industrial partners have turned towards biomasses as promising materials for bitumen substitution. This exploration has led so far to a number of patented bio-binders from different stream sources, as well as test tracks and small-scale applications. Considering the relatively short period of research behind these materials, the research community has not yet optimised the design and production of a bio-binder that can completely or partially substitute bitumen in a successful and efficient way. This short review provides an overview of the approach and results of the most significant bio-binder patents and applications thus far. The overview covers a range of materials like natural resin, microalgae and lignin, and innovations like coloured pavements and test tracks with combined bio-materials. It highlights that some materials resulted in good cracking and rutting resistance, while others reported viscoelastic properties similar to bitumen. Finally, this short review stresses the need for a deeper understanding of the fundamental principles and the interaction mechanisms of the materials, which are essential for future research and applications of bio-sourced materials in the asphalt field.

This study focuses on synthetic clear binders used in the manufacture of colored roads. We present here an innovative formulation of a biosourced clear binder used to create colored road infrastructures with a low carbon footprint. We display both the validation of this biosourced formulation on a laboratory scale and the worksite resulting from its development. We also investigated the chemical aging of this type of binder using high-resolution mass spectrometry (HRMS) to understand the evolution of biosourced molecules under climatic exposure. This study brings hindsight on the degradation mechanisms specific to biobinders and highlights the need to anticipate the aging of these new binders.

The sustainability in construction activities is in prime focus of present-day infrastructure development. The sustainability involves reuse of existing materials and optimum utilization of resources. In this direction, the present study evaluated the performance of control mix (0% RAP) and 40% recycled asphalt mix with waste wood bio-oil (WBO) as rejuvenator (40% RAP). Superpave based mix design was carried out and further, the mixes were subjected for rutting, fatigue and moisture damage resistance evaluation using Indirect Tensile Asphalt Rutting Test (IDEAL-RT), Indirect Tensile Cracking Test (IDEAL-CT), and Tensile Strength Ratio (TSR) test, respectively. The detailed analysis revealed that the addition of WBO affected the rutting resistance of 40%RAP mix, however, statistically no significant difference was observed. The cracking resistance of 40%RAP mix was found to be higher than control mix at intermediate temperature. The moisture damage resistance of both the mixes satisfied the Asphalt Institute’s (MS-2) minimum criteria (>80%). The quadrant plot indicated that the both the mixes fall under “stiff mix” category. Overall, it can be concluded that the RAP mixes composed of WBO improves the cracking performance without significant adverse effects on the rutting and moisture damage resistance. The study also emphasizes the application of simple performance tests in QA/QC process for industry practitioners.

The ageing behavior of asphalt mixtures containing RAP and rejuvenators and its effects on the performance properties of the asphalt mixes have not yet been systematically investigated. In this study, three types of asphalt mixes with three different bio-based rejuventors and with a soft paving grade bitumen 160/220 (reference variant R0) were investigated. In order, to find out the ageing resistance of rejuvenated asphalt, the performance properties of asphalt mixes were determined before and after the long-term ageing of asphalt mixes. The resistance of asphalt mixes against low temperature deterioration was investigated by means of the thermal stress restrained specimen test (TSRST), uniaxial tensile test (UTST) and fatigue cracks by means of indirect tensile test (ITT).

The determined performance properties of asphalt after ageing show that asphalt mixes with RAP and rejuvenators can have better performance at low temperature and similar fatigue properties compared to asphalt mixes produced with virgin material.

In order to promote in-depth research on biomass materials in road applications, this paper comprehensively reviews the research and application of pavement biomass materials on. Classifying pavement biomass materials into three categories—bio-oil, bio-fiber, and bio-filler—based on different application forms, we conducted a comprehensive analysis and summary of the performance of these materials. The analysis results indicate that the low-temperature performance of asphalt modified with general bio-oil is effectively enhanced. To further improve it, consideration could be given to the addition of styrene-butadiene-styrene (SBS) or other compatible biological components for composite modification. For the bio-asphalt mixture, there is a general improvement in low-temperature crack resistance and fatigue resistance, although there may be a trade-off with reduced high-temperature stability and moisture resistance. As a rejuvenator, bio-oil can restore the high-temperature performance of aged asphalt and enhance its low-temperature properties. The addition of bio-fibers significantly improves the stability of asphalt and the high-temperature stability, low-temperature crack resistance, and moisture resistance of the mixture. Most bio-fillers can enhance the stability of asphalt and the fatigue resistance of asphalt mixtures. In conclusion, biomass materials are widely used on pavement, showing the potential to reduce dependence on petroleum products and possessing significant developmental prospects. Future research can focus on the following aspects: establishing a unified system for the joint preparation of biomass materials and bio-asphalt, enhancing standardization; strengthening microscopic research to expedite the identification and extraction of effective components in bio-oil; intensifying research in the field of bio-oil regeneration, specifically in resisting secondary aging; exploring more effective compound formulations.

The road infrastructures allow different type mobilities, and social and economic interactions and activities. However, current road infrastructure systems are rarely imagined and designed to overcome the main societal and environmental challenges such as the GHG emissions or the lack of finite and sometimes critical raw resources. Therefore, troubles due to their construction and lifetime cannot be ignored. It is thus central to identify methods to mitigate their overall undesired impact and make them more sustainable over the years. The valorisation of biomaterials, mainly from wastage of different industries, has emerged as a way to make the current transport infrastructure more sustainable. Toward the use of biomaterials as alternative pavement materials it is hence central to identify current barriers and encouraging opportunities to their implementation in the current research and practices ecosystem. Using a literature review and meta-analysis methodology, the goal of the study is to raise awareness and consciousness on the likely limitations in the development of pavement with biomaterials, the changes opportunities and the required areas of research to consider to overcome the identified barriers, and propose a roadmap allowing to reach a cutting-edge development toward sustainable pavement research during the full cycle of the materials.

In response to climate challenges an energy transition is ongoing which exerts indirect pressures on the availability of petroleum-based construction materials, particularly within the road industry. Urgently transitioning to non-petroleum-based infrastructure materials is paramount, given the uncertainties surrounding crude oil supply and the compelling demand for environmentally sound alternatives. This paper describes the CIRCUROAD value chain collaboration program the Netherlands has adopted for exploration of bio-circular binders as viable substitutes for bitumen in road construction. In the collaboration, parties across the value chain work together: road owners, contractors, producers, knowledge institutes and raw material suppliers. Collaborative endeavors aim to expedite this transition, guided by roadmaps delineating commercialized technologies, explorative developments, and carbon capture strategies. Sustainability perspectives from Dutch stakeholders underscore the imperative of circular regulations and emission-free materials. International collaboration is deemed essential to achieve sustainability objectives while meeting economic and performance benchmarks.

This paper conducts a comprehensive Life Cycle Assessment (LCA) of bio-reused asphalt pavements, focusing on three distinct technologies. The assessment evaluates various environmental impact categories, including climate change (global warming potential), metal depletion, freshwater consumption, freshwater eutrophication, ionizing radiation, land use, and terrestrial ecotoxicity. Comparisons against a baseline reveal significant differences in impact category indicators. Findings indicate that all technologies demonstrate a reduction in the climate change indicator (global warming potential) when considering biogenic carbon. Similarly, there is a consistent decrease observed in the metal depletion indicator across all technologies. However, an increase is noted in several impact category indicators, including freshwater consumption, freshwater eutrophication, ionizing radiation, land use, and terrestrial ecotoxicity, compared to the baseline. Of particular importance is the identification of land use as the most critical impact category indicator when compared with the baseline. This highlights the necessity of using waste biomass or biomaterials which are by-products from other industries to optimize the environmental performance of bio-reused asphalt pavements.

This article focuses on the production and yield of lignin as a biomaterial for pavement, emphasizing its importance as a sustainable alternative to reduce the use of non-renewable sources and mitigate environmental impacts. Lignin, a component found in lignocellulosic materials, can be incorporated into asphalt binders to bring environmental and economic benefits. The study analyzes different methods of lignin extraction from various types of wood and aims to identify the most effective approach for obtaining this component. The research highlights lignin as a promising modifier, showcasing improvements in the mechanical and environmental properties of asphalt.

Reclaimed asphalt pavement (RAP) results from asphalt road pavement maintenance and requires proper disposal to avoid environmental issues. Regarding this, the recycling of RAP is essential to mitigate the consumption of natural resources. In addition, a cold mixture reduces the energy spent when compared with a HMA (Hot Mix Asphalt). The management of RAP meets the environmental criteria of ESG, Environmental, Social and Governance. Furthermore, there are so many studies that report the good mechanical performance of this material to be reused. The stabilization of 100% RAP using an organic rejuvenator agent is proposed in this study, to be used in pavement shoulders and localized repairs. The stages of this study included sample preparation, laboratory tests analysis, construction of an experimental section and its assessment after four years. The laboratory results and de assessment of the experimental section shows that is feasible to use 100% of RAP stabilized with organic rejuvenator agent for pavement shoulder lanes.

Waste tyres (WTs) represent a significant challenge in recycling and disposal, given their high generation rate and low degradability under environmental conditions. One of the promising alternatives for recovering WTs is their thermal fractionation by pyrolysis. This way, multifunctional liquids that can improve the rheological and self-healing properties of aged asphalt binders are obtained. This research uses WT mixtures from light vehicles (WT-L) and mining trucks (WT-M) to produce asphalt rejuvenators through pyrolysis technology. Then, the rejuvenator was optimised by thermal fractionation via distillation to create an improved pyrolytic rejuvenator (PR) to improve the rheological and self-healing properties of aged bitumen. The effect of different doses of PR (3%, 6%, and 9%, by weight of asphalt binder) on the rheological properties of the bitumen at different ageing levels was measured by frequency-temperature tests in a DSR device. Main results showed that the rejuvenator obtained by pyrolysis at 465 ℃ and distillation cut-off between 160–200 ℃ contains aliphatic hydrocarbons and aromatic families, with a significant proportion of terpenes (~34%). It was also proven that the incorporation of PR-1, in doses between 3% and 6%, positively affected the restoration of the rheological properties of PAV samples up to a primary ageing state. To conclude, the optimised pyrolytic rejuvenator can successfully restore aged asphalts, making it a potential agent to promote more durable and sustainable asphalt pavements.

This study focuses on exploring sustainable pathways for generating bitumen substitutes from renewable biomass, particularly microalgae residues. Microalgae, investigated for biofuel manufacturing due to their high yields on non-arable lands, can potentially create significant waste, emphasizing the need for waste valorization. Recent findings indicate that hydrothermal liquefaction (HTL) can transform microalgae residues into a viscoelastic hydrophobic material resembling petroleum-based bitumen. HTL, simulating natural petroleum formation conditions, offers advantages by converting wet biomass without energy-intensive drying.

The article aims to evaluate the ecotoxicological hazards associated with biobinders derived from HTL of microalgae for road construction. Materials used include Scenedesmus and Spirulina microalgae residues, processed through HTL in batch and continuous reactors. The resulting water-insoluble phases exhibit rheological properties similar to conventional bitumen.

Rheological measurements confirm the similarity in properties between the water-insoluble fraction from HTL on microalgae and conventional bitumens. Ecotoxicity assessments, including leaching tests and standardized aquatic impact measurements, reveal significant toxicity in mixes with both biobinders compared to the control mix with conventional bitumen. The study concludes that, at present, using HTL-processed biobinders for pavement materials might not be environmentally advisable, emphasizing the need for further investigation and process adaptation to prevent the formation of harmful chemical species.

Cold recycling techniques provide an eco-friendly solution for restoring aged asphalt pavements, minimizing non-renewable material usage. Limited to low-traffic areas, its effectiveness depends on weather and seasonality. Various research focus on bio-sourced materials to substitute bitumen, but ensuring compatibility and solving aging issues are crucial for manufacturing durable pavements with these alternatives. The aim of this work is to validate the use of biosourced emulsion for cold in-place recycling with the same level of performance as conventional bituminous solutions. The effectiveness of the mixtures was assessed using a simple compression test, considering two different conditions (temperature of 18 ℃/relative humidity of 50% and temperature of 35 ℃/relative humidity of 20%) over a 90-day curing period. The results indicate that the mix with biomaterial emulsion has comparable performance to the mix with conventional emulsion and highlight the direct influence of temperature and water loss on the characteristics of the materials.

Encapsulated rejuvenators have become a promising way to crack-healing autonomously in bituminous materials. This work covers the synthesis of a biobased capsule as an additive to promote extrinsic self-healing in aged asphalt. With this objective, capsules with polynuclear microstructure were synthesised using alginate biopolymer as encapsulating material and sunflower oil as a rejuvenator. The thermal and mechanical stability of the capsules were evaluated by thermogravimetry and compressive tests. Four dense asphalt mixtures were manufactured to assess the capacity of the capsules. Capsules were added in 0.0%, 0.125%, 0.25%, and 0.5%wt content. The effect of the capsules in recovering the mechanical strength of cracked asphalt mixtures was evaluated based on a 3-step process, including mechanical cracking, capsule activation, and quantification of the healing level. The self-healing capacity of the non-encapsulated rejuvenator on aged bitumen was also assessed. The main results showed that the capsule design was thermally and mechanically stable to be incorporated in asphalt mixtures. Moreover, the sunflower oil effectively diffused into the cracked-aged bitumen with a softening effect that promoted its closure. Finally, the addition of capsules at 0.25% wt. Loading significantly improved the self-healing ability of the asphalt mixtures.

The transportation of cargo is essential for the development of any country. The good condition of roads is therefore essential for the efficient flow of production. They are usually paved with asphalt, which comes from the distillation of petroleum, which is a finite material. Therefore, it is important to enhance research efforts aimed at exploring biomaterials capable of substituting a portion of the asphalt binder. Thus, the objective of this study is to evaluate the impact of wood-derived biomaterials, such as lignin and tannin, interfere with the adhesion of asphalt binders to aggregate and whether there is an influence on solubility. For this purpose, they were mixed with 50/70 asphalt binder at concentrations of 3%, 6% and 9% in relation to the mass of the binder. The solubility evaluation reveals that lignin is less soluble in water than tannin. The adhesiveness tests concluded that the mixtures of 50/70 binder with tannin or lignin and basalt aggregate obtained satisfactory results for all the samples. The mixtures made with granite all looked unsatisfactory for both biomaterials. However, the degree of unsatisfaction differed between the samples. Accordingly, water solubility does not affect the adhesion of the binder to the aggregate. Furthermore, in the case of granite aggregate, there was an improvement in adhesiveness in samples with higher levels of tannins. This was not evident in the samples with lignin, since the improvement in adhesion occurred at lower levels.

The objective of this study was to prepare microcapsules containing modified vegetable oil and assess the rheological properties of asphalt incorporating these microcapsules for potential use in self-healing processes. Initially, castor oil was epoxidized (ECO) through chemical modifications to its side chain. The microcapsules were prepared using the in-situ polymerization method, and their chemical characteristics were evaluated. Dynamic shear rheology (DSR) and amplitude linear sweep tests were performed to study the rheological properties and self-healing ability of asphalt containing microcapsules. The results showed that the microcapsule material was successfully synthesized. Furthermore, thermal analysis showed that the microcapsules can withstand high temperatures, which is reflected in possible resistance during the construction of the asphalt pavement. Rheological tests showed that microcapsules containing bio-oil provide better resistance to cracking, in addition to having the ability to restore the properties of an aged binder.

This study analyses the diffusion transport of sunflower oil as a rejuvenator through biopolymeric microcapsules for asphalt self-healing. The capsules were synthesised via emulsification and ionic gelation using sodium alginate, resulting in spherical capsules with an average diameter of 1.17 mm. Multiscale analysis incorporating morphological, mechanical, chemical, and transport characterisations provided insights into capsule stability, composition, and controlled release properties. Scanning Electron Microscopy confirmed the formation of polynuclear capsules without damage and with a polymeric appearance. Fourier-Transform Infrared Spectroscopy verified the preservation of the key functional groups during the encapsulation process. The compression test showed appropriate stability, with yield forces of 6.143 N. Controlled capsule fracture-release enabled diffusion transport modelling, revealing zero-order release kinetics of sunflower oil through the capsule matrix with a diffusion coefficient of 4.80 × 10^–6m²/s. This study, including novel measurements of oil released from ruptured capsules, contributes to an understanding of the activation and release phenomena of encapsulated rejuvenators for asphalt self-healing.

The development of road infrastructure is indeed a critical component for the economic growth and quality of life improvements in modern societies. However, the construction and maintenance of conventional asphalt roads have significant environmental impacts, including high energy consumption, greenhouse gas emissions, and the use of non-renewable resources. The urgent need for sustainable solutions in road infrastructure is driven by the necessity to mitigate these impacts. In this context, this study investigates the epoxidation of castor oil and its application as a bio-additive in asphalt binders, focusing on rheological properties. The tests revealed that the epoxidized castor oil (ECO) modification can better resist rutting, meaning that the material becomes more elastic and less prone to permanent deformation, which is a desirable property for asphalt. Furthermore, an increase in the fatigue resistance of the modified samples was observed, particularly at a concentration of 2%, which showed to be more resistant to cracking. The results of this research suggest that bio-based additive derived from castor oil in asphalt binders aligns with the growing trend towards sustainability in the construction industry.

The utilization of oleic additives as modifiers for asphalt binder presents itself as a viable and environmentally friendly alternative. This study assessed the physical and rheological characteristics of asphalt binder, graded as penetration 50/70, modified through the inclusion of five vegetable oils (copaiba, cotton, linseed, soybean, and corn) at concentrations of 1% and 3%. The analyses, conducted both pre- and post-short-term aging (RTFO), encompassed Penetration, Softening Point, Rotational Viscosity, Performance Grade (PG), and Multiple Stress Creep Recovery (MSCR) tests. The findings indicated the suitability of soybean, copaiba, and linseed oils for warm mixtures, exhibiting potential environmental and energy advantages. Cotton, linseed, and soybean oils exhibited promising prospects for enhancing recycling in asphalt mixtures, with all modified binders meeting standard traffic requirements. The utilization of 3% of these vegetable oils stands out for its practicality, offering sustainable alternatives for pavement construction and the potential for cost reduction in production processes. Overall, soybean and linseed oils were noteworthy for their significant softening and stiffness-reducing effects on the binder.

With the increasing popularity of the low-carbon and environmental protection concept, bio-based materials have gained attention from researchers. This study assessed the effects of adding three distinct biomaterials (carnauba and beeswax waxes, sunflower and canola vegetable oils, and pinus and eucalyptus lignins) on the mechanical performance, addressing stiffness and moisture susceptibility in dense asphalt mixtures. The additives were incorporated at a ratio of 3% relative to the weight of the asphalt binder, which had a 50/70 penetration, and were used in mixture production. Performance evaluation included tests for tensile strength by diametral compression, resilient modulus, and damage induced by moisture. The results indicated that asphalt mixtures with lignin show tensile strength and resilient modulus comparable to wax-containing mixtures. All formulations, except those with beeswax, proved suitable for field application, with the latter recommended for use in low rainfall regions, accompanied by an adhesion enhancer. On the other hand, mixtures with vegetable oil are suitable for low-traffic roads, given their high flexibility and low resilient modulus. The study highlighted distinct behaviors of these biomaterials regarding stiffness and moisture damage, emphasizing lignin as ideal for roads subjected to higher stresses and wax/vegetable oil for mixtures with high stiffness, such as those composed of recycled material.

Bio-binder was formulated using vegetable solvent and pine resin. The final product met the Brazilian penetration grade specification, presenting low viscosity at high temperatures, allowing warm mix and compaction. Its behavior at high temperature shows enhancement of rutting resistance in relation to asphalt cement pen grade 50/70. The transparence of this binder allows the natural color of mineral aggregates to be exalted. It can be used to enhance visibility and driving safety, to reduce lighting costs in tunnels and to indicate differences in bus lane and cycle track. Normally, it is applied in a small thickness as a colored pavement. The function of colored wearing course is not structural, requiring less performance in terms of fatigue resistance. The addition of thermoplastic polymer in the bio-binder could improve the rheological properties, however, resulted in viscosity increase. The nonmodified option allows the warm mixes production, allowing greenhouse gas emission and carbon fingerprint reduction. The mechanical properties of bio-binder warm mixture without polymer in the laboratory were superior to the hot mix with traditional pen grade 50/70. The rutting resistance increase was confirmed by flow number result. The stiffness at intermediate temperature was high, which requires structural analysis and fatigue tests to evaluate its employ in high volume traffic roads. Moreover, the properties of bio-binder related to fuel resistance were better than mixes containing asphalt binder.

This study aims to partially replace the conventional asphalt binder with a bio-oil to achieve a novel and sustainable value chain for paving materials commonly used in Nordic countries. For this purpose, the penetration and softening point of bituminous binders were measured to determine the optimum replacement rate of bio-oil. Fourier-transform infrared spectroscopy (FTIR) and linear amplitude sweep (LAS) test were used to evaluate the chemical and fatigue properties of the bio-extended binder. The results indicate that penetration and softening point values have an exponential and linear relation with the bio-oil content, and the optimum replacement rate was determined as 6%. The infrared spectra show that the chemical composition of the bio-extended binder is largely similar to that of the target asphalt binder while exhibiting new weak peaks due to the addition of bio-oil. The bio-extended binder showed inferior fatigue performance to the target asphalt binder, which raises concerns about the selection of bio-oil, formulation of bio-extended binder, etc. In summary, the use of bio-extended bituminous binder can be practicable. Still, proper bio-oil selection and formulation should be guaranteed, and the binder material behavior needs to be evaluated beyond the conventional penetration and softening point tests.

This study aimed to evaluate the impact of a new biopolymer, which includes epoxidized benzyl soyate (EBS), in a field experiment on the National Center for Asphalt Technology (NCAT) Test Track. For the study, the surface layer of Section W10 was milled and inlaid with a new asphalt mixture with an EBS bio-polymer binder in 2018. This section was compared to a control section (E5A) in the seventh and eighth research cycles (2018 through 2024). The surface layer of E5A was also paved with an asphalt mixture produced based on the same mix design, but it used a styrene-butadiene-styrene (SBS)-modified PG 76-22 binder. The test sections were monitored weekly for rutting, cracking, smoothness, and macrotexture under truck traffic. In addition, asphalt binders and plant mixtures were sampled during construction for a comprehensive laboratory evaluation to assist the field evaluation. Results indicated that the new biopolymer could be used by itself or with other modifiers to modify asphalt binders to achieve performance grades like conventional SBS-modified asphalt binders. The laboratory test results indicated that the mixture modified with biopolymer was less resistant to cracking and stiffer. However, the field performance revealed different results. After 20 million ESALs of trafficking, both test sections have shown good field performance thus far. Both sections exhibited good rutting with final rut depths below 5.0 mm. Low-severity cracking was observed in both sections, with 2.7% of the lane area in Section E5A and 3.4% of the lane area in Section W10.

This paper presents an evaluation of the effect of ultraviolet (UV) radiation on the rheological and mechanical behavior of a wood-based bio-binder (Bio A) designed for total substitution of asphalt binders. Bio A comes from pine wood resin biomass. UV aging simulation was done on short-term aged samples. Frequency and temperature sweep tests were carried out to assess the rheological properties of the aged biomaterial, while linear amplitude sweep tests and poker chip tests were used to evaluate its susceptibility to cracking. The results were compared to a petroleum-based asphalt binder taken as reference. The analysis of the results showed that UV aging had higher impact on Bio A than in the asphalt binder, as UV radiation increased the elasticity of the material but reduced its ductility, which makes the bio-binder more susceptible to fatigue and thermal cracking.

Physicochemical properties of biobinders from slow pyrolysis of unpretreated and pretreated agricultural lignocellulosic biomass (sugarcane bagasse, straw, and rice husk) were analyzed. Results showed pH of ≤3, water content of 7–10%, and FTIR indicated phenols, ketones, and aromatics as the main constituents of biobinders. Rheological analysis revealed similar behavior of biobinders derived from pretreated sugarcane bagasse (Bio-SBc) and rice husk (Rio-RHc) compared to the neat petroleum-based asphalt binder (AC 30/45). Further characterization via GC-MS and TGA/DTG demonstrated distinct chemical composition and lower thermal stability of Bio-SBc and Bio-RHc compared to AC 30/45. Biobinders are constituted mainly by o-cresol, guaiacol, 3-ethylphenol, creosol and 4-ethylguaiacol with molecular weight distribution between 80–160 g/mol while AC 30/45 is predominantly composed of hydrocarbons.