Bitumen Samples Research Articles

When Physical Chemistry Meets Circular Economy to Solve Environmental Issues: How the ReScA Project Aims at Using Waste Pyrolysis Products to Improve and Rejuvenate Bitumens

Urban waste management is a hard task: more than 30% of the world’s total production of Municipal Solid Wastes (MSW) is not adequately handled, with landfilling remaining as a common practice. Another source of wastes is the road pavement industry: with a service life of about 10–15 years, asphalts become stiff, susceptible to cracks, and therefore no longer adapted for road paving, so they become wastes. To simultaneously solve these problems, a circular economy-based approach is proposed by the ReScA project, suggesting the use of pyrolysis to treat MSW (or its fractions as Refuse Derived Fuels, RDFs), whose residues (oil and char) can be used as added-value ingredients for the asphalt cycle. Char can be used to prepare better performing and durable asphalts, and oil can be used to regenerate exhaust asphalts, avoiding their landfilling. The proposed approach provides a different and more useful pathway in the end-of-waste (EoW) cycle of urban wastes. This proof of concept is suggested by the following two observations: (i) char is made up by carbonaceous particles highly compatible with the organic nature of bitumens, so its addition can reinforce the overall bitumen structure, increasing its mechanical properties and slowing down the molecular kinetics of its aging process; (ii) oil is rich in hydrocarbons, so it can enrich the poor fraction of the maltene phase in exhaust asphalts. These hypotheses have been proved by testing the residues derived from the pyrolysis of RDFs for the improvement of mechanical characteristics of a representative bitumen sample and its regeneration after aging. The proposed approach is suggested by the physico-chemical study of the materials involved, and aims to show how the chemical knowledge of complex systems, like bituminous materials, can help in solving environmental issues. We hope that this approach will be considered as a model method for the future.

Bitumen reuse: physical and chemical approach to investigate the effectiveness of rejuvenators

This study investigates a cyclic reuse of bitumen. In the first life cycle, only virgin bitumen is used, which is reused in the second life cycle through rejuvenators. The reuse rates of the bitumen samples are 100%, so no fresh binder is added in the second life cycle. At the beginning of the research a calculation method based on the equi-shear modulus temperature T(|G*| = 15 kPa) is used to determine the optimal rejuvenator dosages. For the rejuvenators, a wide range of dosages between 6% and 48% is found, which displays the diversity of the products available on the market. For the evaluation of the rejuvenators' performances , a comprehensive investigation programme of physical and chemical methods is carried out. Results show that not only the rejuvenation effect but also the effect of the rejuvenator on subsequent ageing should be considered when evaluating the effectivness.

Experimental and Statistical Analysis of Bitumen’s Field Ageing in Asphalt Pavements

Field ageing gradients of bitumen samples recovered from 14 asphalt road sections were investigated via rheological and chemical characterizations and statistical analysis. The effects of air voids and environmental factors on the ageing gradient were evaluated using the field ageing and climate data. The effectiveness of the pressure ageing vessel (PAV) test was assessed in accelerating the bitumen’s long-term ageing by comparing with the field ageing data. Critical factors for field ageing were identified using statistical methods. A statistical model for the Glover-Rowe (G-R) parameter was formulated and verified by incorporating the screened key factors. Results indicate that a threshold air void content (around 6%) exists in differentiating the field ageing gradient patterns in the asphalt pavements. An increasing tendency is observed between the ageing gradient and annual days below 0°C. The chemical indices, stiffness-related indices, and G-R parameter can quantify the field ageing gradient of asphalt pavements. The PAV test can condition the bottom slices’ bitumen to the same ageing level as that in a pavement depth of 0.5–2 cm after 8 years’ field service. Pavement service life, binder content, minimum temperature, days above 32°C, and days below 0°C are the critical material and environmental factors that significantly affect bitumen’s complex shear modulus, crossover frequency, G-R parameter, and Δ Tc. The statistical model is verified with an acceptable mean absolute error of 28.1% and a R2 value of 0.95.

Novel waterproof bituminous coating using self-healing microcapsules containing ultraviolet light curing agent

Bituminous material is widely used in construction and building field, which often need excellent waterproof performance in the process of application. The aim of this work was to design a novel waterproof bituminous coating using self-healing microcapsules containing ultraviolet light curing agent. Core material of microcapsules was a compound of polyurethane acrylate (prepolymer 95 wt%) and 2-hydroxy-2-methyl-phenylacetone (initiator, 5 wt%). Morphology and chemical analysis showed that the cross-linked cured methylether-melamine–formaldehyde (HMMM) shell material protected core material under the condition of high temperature molding and avoid sunlight. The microcapsules had perfect spherical shape with a mean size of 20 μm and shell thickness of 2 μm. Microcapsules dispersed in bitumen homogeneously without agglomeration. No deboning was found in the interface between microcapsules and bitumen. Microcapsules resisted the temperature above 200 °C and remained the core material safety in shells. Through a man-made microcrack experiment, it proved that the bitumen sample with 3.0 wt% microcapsules completed a quick self-healing process with the help of ultraviolet light. Waterproof measurement also indicated that the microcrack in bituminous coating disappeared with the help of self-healing microcapsules under ultraviolet light. In other words, the rapid disappearance of microcracks can contribute to improving the waterproof performance of bituminous coating.

The hierarchical structure of bitumen of different aging states at the molecular level and nanoscale

The realistic structure of bitumen at the microscopic level, although of great value to researchers and practitioners, has not been thoroughly and quantitatively examined. This study characterized twelve bitumen samples of various origins and aging states by fraction analysis, scanning transmission electron microscope (STEM), and gel permeation chromatography (GPC). Microstructures greater than 10 nm in STEM images were evaluated by their coverage areas, the longest dimensions, and aspect ratios. Microstructures and molecules of bitumen solutions that pass the filter of a pore size of 0.2 μm and the filter of a pore size of 0.45 μm were evaluated by the overall distributions of GPC chromatograms and the proportions in different size ranges. Combined information from fraction analysis, STEM image analysis, and GPC results reveals the realistic distributions of microstructures and molecules in bitumen at the molecular level and nanoscale. The effects of compositional and structural changes of bitumen on viscosities of the bitumen and its maltene phase were also evaluated.

Mechanical Properties of Stone Mastic Asphalt Incorporating Nano Titanium Modified Asphalt Binder

Due to its rough surface texture, Stone Mastic Asphalt (SMA) can create great qualities, such as good skid resistance and better visibility during rainy days, as well as optimal light reflection. The service life of SMA, on the other hand, reduces owing to a rapid increase in traffic loads, heavy traffic, and environmental conditions. TiO2's stable qualities and optimal content can help to improve the performance of modified asphalt at a reasonable cost and with low filler content. This study explores the effect of nano titanium on the performance of stone mastic asphalt. Virgin bitumen is modified with 2% and 4% of nano titanium by bitumen weight. The physical properties of the bitumen are accessed by carrying tests such as penetration tests, softening points, and ductility. The results show that the modified bitumen samples of 2% Nano-TiO2 powder content for bituminous tests have enhanced hardness, consistency, and ductility. While for the performance tests for the SMA samples are abrasion, Marshall stability, resilient modulus, and dynamic creep. Overall, 2% Nano-TiO2 powder content has been determined for the optimum content and best performance, where it provides high stability, strength and enhances stiffness effectiveness, which can improve SMA performance. However, the findings show lack of awareness and research is a factor that does not receive special consideration from the industry or the government. Therefore, the sharing of ideas and technology for each continuous research is needed to improve construction quality.

Thermal ageing behaviour of isocyanate-based bitumen additive

Asphalt modification has been a good way to improve and prepare pavements to bear increasing traffic loads and temperatures; however, it is important that the additives used have a positive impact throughout the entire life cycle of the pavement. Since the performance enhancing capabilities of isocyanate-bitumen modification have already been documented, in this study, the focus lies on the ageing behaviour of this novel additive from a chemo-mechanical perspective. The chemical oxidative ageing was studied using infrared spectroscopy (ATR-FTIR), while the mechanical/rheological ageing, on the other hand, was studied using different tests performed with the dynamic shear rheometer (DSR), such as BTSV, frequency-temperature sweeps and cryogenic stress tests. Five different samples of unmodified, isocyanate-modified and SBS-modified bitumen were submitted to standard and extended laboratory short and long-term thermal ageing, respectively. Since the isocyanate-based bitumen modification has shown to enable warm-mix asphalt production, one variant was subjected to a short-term ageing at a lower temperature to consider this aspect. From a chemical perspective, the ATR-FTIR measurements show that the isocyanate-modified bitumen produced a higher chemical ageing after short-term thermal ageing compared to the SBS modification. However, on the long-term, this effect disappears. On a rheological level, the different methods used suggest that the mechanical ageing of the isocyanate-modification is comparable to the SBS modification. Moreover, a lower short-term ageing temperature appears to have a benefit on the chemical ageing but not on the mechanical/rheological ageing.

Introducing a Sustainable Bio-Based Polyurethane to Enhance the Healing Capacity of Bitumen

This paper introduces the in-situ formation of biomodified polyurethane in bitumen as a novel strategy to enhance the healing capacity and aging resistance of bitumen. Bitumen is a substance that is known to have the capacity for healing. Self-healing bituminous composites can recover their properties. An increase in bitumen’s healing capacity can be facilitated using various modifiers. This study examined the merits of using a biobased polyurethane to both improve the healing capacity of bitumen and to enhance its resistance to aging through in-situ polymerization of polyurethane. The effect of aging on healing capacity was examined by studying specimens before and after aging in the laboratory. To do so, thermomechanical analysis and spectroscopy were used to characterize bitumen containing a biobased polyurethane from castor oil. It was found that the biobased polyurethane was quite compatible with bitumen, and the presence of polyurethane improved the overall thermomechanical properties of the bitumen. To evaluate the extent of healing, a time-sweep rheometry test was used to create samples with specific initial damage degrees. The degree of damage was selected to be a 30%, 45%, or 60% reduction in complex modulus. A healing index was calculated for each of the three damage levels after a 60-min rest period. The study results showed that the introduction of biobased polyurethane not only improved the healing index, it also mitigated the negative effects of aging on bitumen’s healing capacity. Compared to samples of unmodified bitumen, the average healing index of samples containing biomodified polyurethane was 1.3 times higher at 16% in the unaged state and 3.5 times higher at 7% in the aged state. In addition, the samples containing biomodified polyurethane showed better resistance to aging as evidenced by average 72% and 50% lower increases, respectively, in carbonyl and sulfoxide (known products of aging in bitumen) when exposed to the same aging protocol.

Estimating the Thermal Conductivity of Asphalt Binders

Abstract Nowadays, there is a common worldwide interest in environmental issues and pavements. How to save energy and mitigate the urban heat island (UHI) effect are topics that are drawing the attention of different researches and industrial organizations. In road infrastructure, one of the important properties addressing environmental and UHI aspects of pavements is the determination of the thermal conductivity. Asphalt concrete represents the third most widely used resource in the world, with asphalt-paved roads being its principal usage. One of the most important components of asphalt concrete is bitumen. Bitumen is a viscoelastic material susceptible to temperature changes. The determination of the bitumen’s thermal conductivity becomes very important in understanding and improving its thermal performance. There are very few test methods and equipment to measure thermal conductivity of bitumen (asphalt binders). Some are expensive and require special equipment and instrumentation. This study developed and validated a simplified testing technique to measure thermal conductivity of asphalt binders. This test is a steady state–based method to estimate the thermal conductivity of asphalt binders using cylindrical samples poured into a silicon mold. The method was validated using material of known thermal conductivity. A total of 18 samples of different binder grades were tested, and the test results were repeatable and within known thermal conductivity values. Sensitivity analysis and accuracy of the proposed method were validated modifying the asphalt binder with a material with a very low thermal conductivity. This method to estimate thermal conductivity of bitumen samples was found to provide an affordable alternative test procedure with good accuracy and precision.

The Effect of a Chemical Warm Mix Additive on the Self-Healing Capability of Bitumen

Abstract Warm mix asphalt (WMA) technologies reduce the production temperature of hot mix asphalt allowing for mixing and paving at lower temperatures. As a result, the use of WMAs reduces emissions and allows for longer transport times. Because of the recent increase of chemical warm mix additives in industry, the effect of a chemical warm mix additive (cWMA) on the intrinsic self-healing ability of the bitumen was investigated. Bitumen specimens containing three concentrations of cWMA were evaluated at four aging levels (unaged, rolling thin film oven [RTFO]-163°C, RTFO-130°C, and RTFO+ pressure aging vessel [PAV] aged) using the simplified–linear amplitude sweep healing (SLASH) (linear amplitude sweep with a single rest period fatigue-healing) test. Results indicate that oxidative aging of bitumen is reduced with increasing cWMA concentration but may be more heavily influenced by the aging temperature. It was also observed that RTFO+PAV-aged bitumen samples demonstrate greater fatigue restoration ability compared to RTFO and unaged binders. Supplementary work using video-based analysis of dynamic shear rheometer samples revealed that issues may arise from the calibration of the cohesive failure damage level as described in the original LASH procedure because of significant changes in sample geometry observed during the amplitude sweeps for unaged and RTFO-aged material. These results demonstrate that LAS-based healing tests warrant further research to optimize loading and rest period parameters for a wider range of bituminous materials.

Economic and environmental impacts of utilizing lower production temperatures for different bitumen samples in a batch plant

The utilization of hot mix asphalt (HMA) for road construction necessitates high temperatures during mixing bitumen and aggregate at asphalt plant. The required (mixing) production temperature is calculated by the standard method (ASTM 2493). The application of this method for polymer modified bitumen (PMB) and warm mix asphalt (WMA) have tendency of higher temperatures. Therefore, some alternative methods suggested by literatures for the determination of production temperature for PMB and WMA have been implemented aiming to determine lower temperatures than the standard method (ASTM 2493). Moreover, the economic impacts of the determined production temperatures through different models are evaluated by the estimation of energy consumption in terms of electricity and natural gas costs for the batch type asphalt plants. Besides, the possible environmental effects are calculated by considering the carbon dioxide emissions. The results of this study have shown that the reduction in production temperatures led to a significant decrease in the total construction cost of each type of asphalt and a significant reduction in the estimated carbon dioxide emission. The results of this study can be used as a reference point for the estimation of both economic and environmental impacts of utilizing lower production temperatures for different bitumen samples.

A comparative study on efficacy of waste plastic and waste Rubber in bitumen

This study compares the use of recycled polyethylene terephthalate (PET) and crumb rubber (CR) when they are functionalized with waste vegetable oil and used as modifiers in bitumen. Granules of the same size were used for both modifiers, and both modifiers were treated with waste vegetable oil to enhance their compatibility with bitumen. The efficacy of the treatment was evaluated using Fourier transform infrared spectroscopy. Chemical analysis showed the appearance of intense peaks after bio-oil treatment for both oil-treated polyethylene terephthalate (PEToil-treated) granules and oil–treated crumb rubber (CRoil-treated) granules, indicating changes in the granules’ surface chemistry. Treated granules were introduced into bitumen to produce PEToil-treated bitumen and CRoil-treated bitumen. Then, the phase separation and the thermomechanical properties of the bitumen samples were studied. The results showed that PEToil-treated granules are more compatible with bitumen than are CRoil-treated granules, as evidenced by a lower separation index and a lower softening-point difference observed for PEToil-treated bitumen. PEToil-treated bitumen showed the higher viscosity and recovery; PEToil-treated bitumen increased the recovery by 47.36%, while no effect on the elasticity was seen when introducing the CRoil-treated into bitumen. The results also showed that bitumen containing PEToil-treated had better resistance to permanent deformation, while bitumen containing CRoil-treated showed better resistance to fatigue cracking. In addition, the moisture-induced shear-thinning index (MISTI) showed improvements in resistance to moisture damage when incorporating either PEToil-treated or CRoil-treated into bitumen, with PEToil-treated bitumen having greater resistance to moisture damage. Similarly, improved resistance against thermal-oxidative aging was observed for both PEToil-treated bitumen and CRoil-treated bitumen. Comparing the two bitumens after long-term aging, CRoil-treated bitumen had the lower increase in stiffness, and PEToil-treated bitumen had the lower decrease in phase angle. This in turn indicates that these two waste streams could complement each other, and that an optimized blend of PEToil-treated and CRoil-treated could lead to an enhanced performance while promoting resource conservation and recycling.

Influence of zinc oxide/expanded vermiculite composite on the rheological and anti-aging properties of bitumen

The bitumen modifier, zinc oxide (ZnO)/expanded vermiculite (EVMT) composite (ZnO/EVMT), was introduced into the bitumen with a dosage of 4%, 5%, and 6%. The surface morphology of EVMT and ZnO/EVMT was characterized by a field emission scanning microscope (FESEM). Further, the Superpave continuous grade of bitumen containing different amounts of ZnO/EVMT was determined by the dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test. The bitumen samples were aged by thin film oven test (TFOT), pressure aging vessel (PAV) aging test and ultraviolet (UV) aging test, and the influence of different amounts of ZnO/EVMT on both physical and rheological properties of the bitumen before and after aging were investigated. Moreover, the influence of ZnO/EVMT on the molecular distribution during aging was investigated by analyzing the change in the proportion of large molecular size (LMS) obtained from gel permeation chromatography (GPC). The FESEM result shows the ZnO particles are uniformly supported on the EVMT surface. Moreover, ZnO/EVMT slightly influences the high-temperature performance and improves the low-temperature cracking resistance of bitumen. In addition, no matter what aging method is adopted, ZnO/EVMT effectively increases the retained penetration and phase angle aging index, and decreases the viscosity aging index and complex modulus aging index of the bitumen, demonstrating the effectiveness of ZnO/EVMT in both resisting the thermo- and photo-oxidative aging of bitumen. Meanwhile, 6% and 4% ZnO/EVMT exhibit the best inhibitory effect on thermo- and photo-oxidative aging of bitumen, respectively. According to the GPC results, the composite inhibits the transformation of small molecules to large molecules during aging, resulting in a lower LMS increment and better anti-aging properties of the modified bitumen.

High-sulfur bitumen amplifies the effect of polyphosphoric acid

This study examines the effect of polyphosphoric acid (PPA) in bitumens with low-sulfur content and high-sulfur (10% sulfur) content. The recently lowered limit on the sulfur content of marine fuel will result in increased sulfur content of the bitumen remaining at the bottom of the barrel. Since the effect of PPA on bitumen's performance highly depends on bitumen’s composition, we hypothesize that high-sulfur bitumen, with an increased content of sulfoxide due to aging, will have higher intermolecular interactions with PPA leading to increase in bitumen’s elasticity. We used computational modeling and laboratory experiments to examine this hypothesis. Based on the results, under laboratory aging, the content of sulfoxide is increased for bitumen samples containing sulfur; a greater increase is observed for high-sulfur bitumen. Our molecular modeling, showed that H-bonding and H-transfer interactions of PPA’s terminal OH with sulfoxide’s polar group (S = O) are responsible for the effective interaction between the two components. The H-transfer interaction has a considerable binding energy (-70.0 kcal/mol), although it is not dominant. H-bonding interactions, with lower binding energy (−(17–22) kcal/mol), are dominant. The high concentration of sulfoxides and dominant contribution of H-bonding interactions can provide an impressive improvement in bitumen’s performance. Upon the introduction of PPA to each bitumen, high–sulfur bitumen showed about 22% increase in percent recovery, while low-sulfur bitumen showed about 12% increase in percent recovery. A higher percent recovery is an indicator of enhanced elasticity. This was also evidenced in a significantly higher complex shear modulus in high-sulfur bitumen compared to low-sulfur bitumen.

A Probable Connection between a Bitumen Sample from the Western Niger Delta and Isan Well Sample from the Lower Cretaceous (Neocomian) Shale

An earlier study of GC-MS analysis on bitumen samples from the Agbabu area in Western Niger Delta showed the significant presence of gammacerane and no Oleanane and is suggested to be generated from the Lower Cretaceous (Neocomian) source rock, however, twelve core samples were obtained from the geological survey of Nigeria for both optical geochemical and biomarker analysis, two of the samples from Isan-9 well indicated the presence of Botryococcus braunii a freshwater alga which is characteristic of a lacustrine lake type environment. The extracts from the same core showed m/z = 191 chromatogram with the significant presence of gammacerane which is diagnostic for stratified water columns and characterizes a typical lake environment. However, the m/z = 191 chromatogram also shows the presence of Oleanane which is diagnostic for vascular plant materials, this doesn’t corroborate with that of the Ise-2 well. The Isan-9 well source rock is suggested to have occurred due to the evolving structural geology of the continental shelf after the onset of the rifting, whereby the dominant lake-type environment in the Early Cretaceous was accompanied by a sediment fill of continental runoffs containing vascular plant materials. This implies that an ancient lacustrine lake system was gradually modified as a result of sedimentary infill. And that the bitumen is sourced from the lower Cretaceous Neocomian source rocks.

Investigation of wetting and hydrophobic properties of bitumen modified with different vegetable oils

In this study, the effects of oils obtained from vegetable products on the physical, mechanical and hydrophobic properties of bitumen were investigated. Within the scope of the study, six different vegetable oils were used for bitumen modification: hemp oil, flax seed oil, laurel ghee, centaury oil, castor oil, pine turpentine oil. These are 100% pure vegetable oils, obtained by using cold press method. The bitumen was modified by adding vegetable oils to bitumen with the proportions of 3%, 5% and 7%. Including the reference group, 19 sample groups were formed with six different vegetable oils by using three different mixing ratios. The physical and mechanical properties of the prepared bitumen samples were determined, according to their contact angles their sensitivity to water, surface wetting and hydrophobic properties were determined by using the IMAGEJ program. As a conclusion of the results of the studies, it has been introduced that different vegetable oils cause serious changes in the physical and mechanical properties of bitumen, and in addition, bitumen modified with vegetable oils can make a significant contribution to removal of water from the road surface which is a major problem for traffic safety.

Investigation of premature failure mechanism in pavement overlay of national highway of Bangladesh

Roadway is the economic lifeline of Bangladesh. Maintenance of this roadway is main challenge of Roads and Highways Department (RHD). Overlay is the most common maintenance practice for National Highways, which design life is five years. However, it’s been reported, the overlay failed prematurely with cracking and rutting within one year even 6 to 9 months in some cases. This study aiming to investigate the premature failure mechanism of national highway pavement. Several field investigations were done on national highway namely N2. A numerical parametric study was also conducted with variable interfacial bond condition, overloading and layers stiffness. To investigate the pavements failures, conventional fatigue and rutting criteria were considered. Laser crack measurement system showed that alligator cracking is dominant failure mode followed by rutting. Alligator crack pattern indicated about slippage failure and overloading induced fatigue failure. Core cutting confirmed that interface de-bonding and cracking are strongly related. Bitumen samples were found highly temperature susceptible which could be correlated slippage failure. Moreover, Base layer stiffness variation was observed from Dynamic Cone Penetration test. Numerical analysis revealed that poor interfacial bonding significantly affects horizontal and vertical strain distributions; subsequently reduce pavement life but only it is not enough to fatigue and rutting failure of N2 within one year. Overloading found more significant than de-bonding especially for rutting. Analysis also suggested that fatigue and rutting failure within one year should be associated by coupling effect of poor bonding and overloading. Variation of base layer stiffness might be exacerbated the coupling effect in N2.

Investigating the effect of ultraviolet aging on the healing capacity of bitumen containing taconite tailings

ABSTRACT Bitumen’s evolution during aging includes oxidation, aromatization, chain scission, and carbonation, which alter bitumen’s properties of diffusivity and thermal conductivity and consequently bitumen’s healing capacity. To improve bitumen’s healing capacity after aging, there is a need to revitalize aged bitumen and restore its properties. This study studies the effect of ultraviolet (UV) aging on the healing capacity of bitumen containing different dosages of taconite tailings (a material with metal oxide as its main component). In addition, it examines whether the healing capacity of aged bitumen can be restored post-aging with the help of a rejuvenator made from waste vegetable oil. A healing index was used to measure the evolution of healing capacity in bitumen samples during aging and rejuvenation, using rheometry and spectroscopy. The study results show that exposure to UV aging increases the chemical aging index and rheological aging index, which makes bitumen stiffer and increases bitumen's complex modulus. This study further shows that taconite tailings accelerate the aging process of bitumen and increase its thermal conductivity. It was found that despite the negative effect of taconite tailings on bitumen aging, the presence of taconite tailings increased the healing capacity of bitumen. Results showed the healing capacity of bitumen containing taconite after being exposed to UV aging for 100 h and 200 h was up to 55.09% and 53.53% higher than that of bitumen without taconite, respectively. The samples with a higher content of taconite showed a higher healing capacity. Also all samples regardless of taconite dosage had higher healing capcity when rejuvnetor was present.

Rutting Prevention of Bituminous Mastic Using Microencapsulation Phase Change Material

Rutting is a pavement degradation that can be alleviated by reducing temperature variations experienced by the pavement. These variations can be reduced by utilizing microencapsulated phase change material (MPCM). The objective of this study is to investigate the potential use of a paraffin-type MPCM in mixtures of bitumen mastics to prevent rutting. The studied mastic of bitumen and cement and mastic of bitumen, cement, and MPCM. Multiple stress creep recovery (MSCR) test parameters of stress levels (0–256 kPa) and recovery time (9–40 s) are investigated to determine rheology properties (Jnr and percentage recovery) of the mastics. Performance grade (PG) temperature sweep tests (40°C–80°C) are performed to evaluate complex modulus and phase angle of the mastics [G*/sin(θ)]. The results show that the presence of MPCM in the mastics leads to higher Jnr values and lower percentage of recoveries compared to those using only cement as the filler. Higher Jnr values indicate lower stiffness of the mastics. This result is also confirmed by the results of the temperature sweep tests. At 75% MPCM, the stiffness of the mastic is at the same level as that of pure bitumen. At higher temperatures, pure bitumen and all mastics become less viscous, while the presence of MPCM shows nonlinearity in the range of 40°C–50°C. This temperature range is apparently around the phase change temperature of the MPCM. The MSCR test also shows that at 40°C, mastics containing 50% MPCM or less have a complete elastic recovery, shown by their constant Jnr values. At 60°C, all mastics have lower Jnr values compared to the pure bitumen sample. Hence, it is expected that the presence of MPCM, while reducing temperature variations, does not jeopardize the rutting resistance of the pavement.

Asphaltenes as model compounds of the UIBs/AIBs detected in various astrophysical objects. Part 2 – Natural bitumens asphaltenes carbonization

A series of naturally occurring bitumen samples from Central-South Italy (Maiella and Rivello) as well as from Sicily (Ragusa and Modica area), were purified and analyzed by thermal analysis (TGA-DTG-DTA) and FT-IR spectroscopy. The asphaltene fraction of these bitumen samples was isolated and analyzed by thermal analysis and by FT-IR spectroscopy. Each asphaltene fraction was then subjected to carbonization in a sealed crucible using a DSC scan to 700 °C under N2 flow and the carbonization product was studied by FT-IR spectroscopy. The naturally occurring bitumen samples, their asphaltenes and the carbonization products were used as model compounds to match the UIBs/AIBs (Unidentified Infrared Bands or Aromatic Infrared Bands) band pattern of the interstellar medium and their evolution in different interstellar and circumstellar environments. The asphaltenes extracted from the bitumen samples represent a concrete example of model compounds for the MAONs (mixed aromatic/aliphatic organic nanoparticles) theorized as the most probable carriers of the UIBs/AIBs.