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Asphalt mixtures are multi-phase composites composed of aggregates, bitumen, mineral powders, and voids, and various structures are intertwined during the compaction process. Most of the traditional research focuses on the macro-scale domain, and it is difficult to obtain the internal structure of asphalt mixture in different compaction processes. With the continuous development of digital image technology, the influence of the meso-structure of the asphalt mixture on the compaction quality of the asphalt mixture has become a new means to evaluate the performance of the asphalt mixture. In this paper, different numbers of compactions are selected to represent different stages in the compaction process, the digital images of specimens in different compaction stages are obtained by industrial CT scanning technology. Then, the images are processed and reconstructed in three dimensions using improved image segmentation methods, and the position characteristics and geometric information of coarse aggregate are obtained by combining the Oriented Bounding Box (OBB). The meso-response characteristics of the skeleton structure of the asphalt mixture during compaction were studied. The influence of the internal structure of the mixture on the compaction quality of the mixture was obtained, which is of great significance for the study of improving the durability of the pavement. The results show that the "effective coordination number" (the number of aggregate particles that can transmit force in the skeleton structure) is greatly related to the aggregate size. With the compaction process, the centroid of coarse aggregate in the upper layer of the specimen reflects the overall downward movement trend. The inclination angle of the aggregate spindle tends to be in the range of 80°~100°; the anisotropic amplitude of the xy plane increases, and the direction of the aggregate spindle becomes more and more consistent. With the increase in the number of rotational compactions, these four parameters showed obvious rules, indicating that this meso-characteristic index could well characterize the compaction quality of the asphalt mixture in the compaction process. [ABSTRACT FROM AUTHOR]

Graphene can significantly improve the mechanical performance and durability of a bitumen composite. However, the underlying reinforcement mechanism of this enhancement is not yet clear. Here, we use molecular dynamics (MD) simulation to study the mechanisms of tensile fracture and shear fracture in a graphene-reinforced bitumen composite. Two representative volume elements were developed from a single-crystal graphene-reinforced bitumen composite: graphene in the parallel plane and orthogonal plane. The MD results show that graphene in the orthogonal plane is better able to support and transmit shear loads, as evidenced by a 33% higher shear strength than graphene in the parallel plane. Under tensile loading, the failure type of the base bitumen and the graphene in the parallel plane is cohesive; for the graphene in the orthogonal plane, the failure type is adhesive. The shear failure for graphene in the parallel plane is an adhesive failure, which typically occurs at the graphene–bitumen interface. The shear failure for graphene in the orthogonal plane and for base bitumen is likely to be a cohesive failure. The results of the pull-off test validated the results of the simulation, which indicated that the interlayer sliding of graphene and the fracture of the bitumen matrix are the failure modes of a graphene-reinforced bitumen composite under tensile loading. This study provides atomic-level insight into the mechanical reinforcement mechanism of graphene-reinforced bitumen, and can contribute to the future application of advanced carbon nanomaterials in transportation infrastructure. [ABSTRACT FROM AUTHOR]

Quantifying recycled asphalt binder availability in recycled asphalt pavement (RAP) mix design is very essential, as the widely adopted 100% RAP binder availability assumption in RAP mix design never holds correct. Depending on the mix production condition, recycled binder stiffness, and virgin binder properties, the degree of binder availability in the mix is always partial. The present study proposes a simple procedure to estimate the degree of recycled binder availability in RAP mix design. In the proposed methodology, the designer needs to compare optimum binder content of bituminous mixes prepared using white rock aggregate gradation and virgin aggregates, along with mixes designed by blending black rock gradation and virgin aggregates blended in proportion to achieve the target white rock gradation. The binder content in the RAP fraction used in the blending exercise was determined using ignition oven method. RAP mix designs were performed for RAP material collected from two different sources, and design was performed for three mixing durations in a laboratory pug mill—60, 120, and 180s. The mixes were prepared with 50% RAP incorporation level. RAP material was conditioned at 110°C for 2 h, whereas virgin aggregates were superheated to 175°C. Using the methodology proposed, RAP binder availability was found to vary between 92.5% and 96.6% for softer RAP material, 75.9% to 91.5% for mixes incorporating stiffer RAP. With increasing mixing time, even though the total active binder content did not change significantly, a mixture performance test quantified the implication of increased RAP binder availability in mixes. A higher degree of binder activation resulted in mixes being rut resistant, while the same mixes exhibited relatively higher cracking susceptibility. Recycling of bituminous mixes has been considered as one of the sustainable practices in the highway construction industry. In a recycled bituminous mix, the milled material contributes good quality aggregates, and aged bituminous binder. The amount of aged bituminous binder that can be mobilized in the recycling process largely depends on mix production condition, milled, and virgin material property. The paper presents a simple methodology to quantify the degree of bituminous binder which becomes available in recycled mix design. The methodology can be used by mix designers to account for appropriate adjustment in virgin binder grade selection. The knowledge of degree of binder availability would also enable, if one targets to synthesize recycled mixes of a definite binder content. The paper also investigated the implication of different degree of binder availability on mix performance, arising due to different mixing time (production condition) and milled material property. [ABSTRACT FROM AUTHOR]

In this research, the properties of two tailings solvent recovery unit (TSRU) samples, one bitumen froth sample and two aggregates, are evaluated using various laboratory tests. The TSRU-modified mixtures are prepared at different concentrations of bitumen froth (0%–6% of weight of mixture increasing in 1% intervals) where TSRU materials were added based on optimum moisture content of the mixture. The properties of the mixtures are investigated using indirect tensile strength and Marshall stability tests. The results show that TSRU modification results in a higher tensile strength. The granular layer thickness can be reduced by 42% and 60% for modified samples made with both aggregates. It should be noted that the modified samples fail to meet the soaked indirect tensile strength requirement. A potential solution to improve the indirect tensile strength of the soaked mixture is using cementitious additives such as Portland cement. [ABSTRACT FROM AUTHOR]

Considering the characteristics of steel slag, the effective relative density of steel slag was measured by the impregnation method. By the volume substitution method, the asphalt mixtures with different steel slag content were prepared for replacing the coarse aggregates. According to the technical requirements of the ultra-thin friction course, the road performance and the function characteristics of the steel slag asphalt mixture were evaluated. The test results show that with the increasing of steel slag content, the performance indexes of dynamic stability, maximum tensile strain and tensile strength ratio of asphalt mixture are increased with latter decreasing. When the steel slag content is 50%, the comprehensive performance of asphalt mixture is the best. With the increasing of the placement time of test specimens, the high temperature performance index of the steel slag asphalt mixture is increased slightly, while the low temperature crack resistance index and water stability index are decreased. The skid resistance and abrasion resistance of asphalt mixture are significantly improved with the addition of steel slag. The impermeability of the mixture is reduced, while the water seepage coefficient values of several steel slag asphalt mixtures can still meet the requirements of the standard test methods of bitumen and bituminous mixtures for highway engineering (JTG E20—2011). [ABSTRACT FROM AUTHOR]

Durability of bituminous mixes is affected by presence or intrusion of moisture into it. The intrusion and amount of trapped moisture largely depend on the air voids present in the mixes. This study explores the combined influence of air voids and hydrated lime (HL, as anti-stripping agent) on moisture-induced damage of bituminous mixes prepared from two different aggregate sources. The aggregates used in the study are siliceous sandstone and basalt. Tensile Strength Ratio (TSR) test was used to determine the moisture susceptibility of bituminous mixes. A higher value of TSR depicts that the mixes are more moisture resistant. TSR was reaffirmed to be lowest at an air void range of about 5% to 13% which is termed as pessimum air void range. At this air void range, moisture gets trapped within the mix, resulting in moisture-induced damage. TSR results showed that bituminous mixes prepared with siliceous sandstone is more susceptible to moisture-induced damage as compared to mixes prepared with basalt. Boil water test reconfirmed the results. Use of HL in bituminous mixes improved its moisture-induced damage resistance only marginally. Thus, moisture-induced damage control at pessimum air void range using anti-stripping agent is not always sufficient. Observations show that air void plays a critical role in moisture-induced damage and control of air void during construction needs to be ensured. [ABSTRACT FROM AUTHOR]

This study aims to enhance the performance of the microsurfacing mixture and evaluate the parameters affecting this mixture. For these purposes, the effects of pure bitumen types for producing bitumen emulsion, types of aggregates, and the percentages of bitumen emulsion and emulsifier on the microsurfacing mixture are investigated. Three different types of pure bitumen with penetration grades of 40–50, 60–70, and 85–100 were used to make bitumen emulsion. In addition, limestone and siliceous aggregates, 0.9%, 1.2%, 1.5% emulsifier, and 9%, 10%, and 11% bitumen emulsion were used for test samples. The microsurfacing mixture was then evaluated by cohesion, wet track abrasion, loaded wheel, and mixing time tests. The results revealed that increasing the percentages of bitumen emulsion, emulsifier, limestone aggregates, and bitumen emulsion made from softer pure bitumen increased the microsurfacing mixture's breaking time. Moreover, the test sample containing bitumen emulsion made from harder pure bitumen, limestone aggregates, and lower emulsifier percentages showed a better setting time, which is suitable for a quick traffic reopening system. In addition, using limestone aggregates, pure bitumen with a lower penetration grade and a higher emulsifier percentage declined the optimum bitumen emulsion percentage. It also enhanced the microsurfacing mixture's resistance to abrasion, rutting, and moisture sensitivity. Overall, using limestone aggregates and bitumen emulsion made from harder pure bitumen improved the microsurfacing mixture performance, preventing some distresses, including rutting, stripping, bleeding, and aggregates' polishing, which can lead to the longer service life of this mixture. [ABSTRACT FROM AUTHOR]

• Examines the degradation behaviour of elastomeric BGMs exposed to MSW leachate. • Compares the BGM degradation in MSW leachate to air and water immersion. • Compares the durability of two BGMs with different thicknesses. • Estimates the time nominal failure at field temperatures using Arrhenius modelling. The effect of thickness (4.8 and 4.1 mm) on the degradation of two bituminous geomembranes (BGMs), when immersed in a synthetic leachate is investigated over a period of 33 months. Based on the data collected at four different temperatures (20, 40, 55, 70 °C), it is shown that the 4.1 mm has slightly faster degradation than the 4.8 mm thick BGM. Due to the reduced conditions of the examined leachate, the degradation in the chemical and rheological properties of the bitumen coat was relatively lower than in air and water immersion. However, the presence of a surfactant in the leachate increased the degradation of the polymeric back film and the reinforcement layer responsible for the mechanical properties of the BGM. The time to nominal failure of the two BGMs is predicted at a typical range of landfill liner temperatures using Arrhenius modelling. The predictions at temperatures >20 °C suggest that the examined BGMs may not be suitable for the containment of solid wastes containing surfactants due to the fast degradation in their mechanical properties. [ABSTRACT FROM AUTHOR]

Stone Mastic Asphalt (SMA) pavements have advantages such as increasing durability and resistance to cracks. Gap-graded SMA pavements are more preferred because they reduce rutting and delay fatigue cracks. In SMA pavements, the filler and bitumen ratio is higher than conventional asphalt pavements. In addition to the positive aspects of SMA pavements, there are also some negative aspects that need to be taken care of. The bitumen draindown during the time it takes from the production in the plant to the application on the road. The draindown of the bitumen causes disruption of the homogeneity in the pavement. In addition, as a result of laying the SMA mixture on the road with a paver and compacting it with a roller, the bituminous binder rises from the pavement to the surface and desorption. In this study, the effect of using different aggregates and bitumen for fiber and non-fiber SMA mixtures with constant gradation on the percentage of draindown was investigated. As a result of the Schellenberger bitumen draindown tests, it was observed that the increase in the specific gravity and softening point of the bitumen decreased the drain down percentage. In mixtures prepared from the same refinery bitumen with different aggregates, it was found that a decrease in bitumen absorption of aggregates increases the draindown percentage, but an increase in the peeling strength of aggregates and the use of aggregates from the Sedimentary Rock class in the fine aggregate part of the mixture reduces the draindown percentage. [ABSTRACT FROM AUTHOR]

In this study, the suitability of developing and applying different types of geogrids to increase road-subbase bearing capacity was investigated. Textile products obtained from natural jute fibers were transformed into a geogrid and used in the road subbase. Studies have revealed that natural fibers, typically obtained from agricultural waste, can be spontaneously degraded via natural processes. Therefore, the jute textile geogrid surface was coated with bituminous materials. In addition, commercially available geogrid materials made using basalt fibers were included as a road-subbase reinforcement in the study for a comparative analyze. The study was performed on a subbase material used in the subbase of a road. The developed and commercial geogrids were classified into different sample groups and subjected to ground tests. In the first group, tests were conducted on the road subbase material without using a geogrid. Thus, the basic physical properties and the California bearing ratio (CBR) values were determined and used as a reference for the bearing strength parameters of the ground. The second group was tested using the basalt geogrid on the same subbase material. The third group was subjected to the same tests using an uncoated geogrid developed with natural jute fibers. Finally, the fourth group was exposed to the same tests after the surface of the jute-fiber geogrid was coated with bitumen. Thus, four sample groups, including a reference (control), were evaluated for comparison. Test results indicated that the bearing strength of geogrid samples with natural fibers increased by 39.7% and 48.5% compared to control samples for CBR values of 2.5 and 5 mm, respectively. In addition, the bearing capacity of bitumen-coated natural jute-fiber geogrid samples increased by 17.8% and 22.4% for CBR values of 2.5 and 5 mm, respectively. After analyzing the bearing capacity of basalt geogrid samples, increases of 6.68% and 5.05% were obtained for CBR values of 5 and 2.5 mm, respectively, compared with reference samples. [ABSTRACT FROM AUTHOR]

In the production of asphalt mixtures, the possibility of recycling rubber grits has appeared for decades. A rubber bituminous mixture appearing as a special Hungarian patent greatly reduced the viscosity problems of rubber bitumen mixtures, resulting in a bitumen type that is easily transportable and does not require special equipment, The asphalt mechanical properties of the MOL rubber bituminous mixture are excellent both in the field of plastic deformation, cold behavior, and fatigue properties, so they are real competitors to polymer-modified bituminous mixtures. New research possibilities have emerged for use at reduced production temperatures, as a so-called WMA asphalt mix, in which case the first experimental – wheel tracking and cold behavior test - results are also encouraging. [ABSTRACT FROM AUTHOR]

This study focused on the preparation, structural characterization and evaluation of some dynamic and rheological properties of a new type of mastic material, clay-mastic, which consists of bituminous binders mixed with mineral fillers. For this purpose, mastic samples were prepared by mixing conventional bitumen (50/70) with organo-montmorillonite (OMMT) in various proportions. X-ray powder diffraction (XRD) spectra and scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images of raw clay (MMT), organo-clay (OMMT) and raw bitumen with the prepared mastics were taken, and the changes in the crystallographic properties of the clay and its dispersion characteristics in the bitumen matrix as well as the changes in the morphological properties of the mastic samples were investigated comparatively. In addition, penetration, softening point, flash point, dynamic viscosity, dynamic shear rheometer (DSR) and Fraass breaking point tests were carried out together with those of base bitumen in order to evaluate the properties of the prepared mastic samples in terms of dynamics and rheology. A comparison of the images of raw clay and organo-clay indicated delamination based on surface modification in clay layers in those belonging to organo-clay, and diffractograms of prepared mastic samples showed that the characteristic smectite peak of Montmorillonite shifted to the left gradually with an increasing clay ratio. This shows that due to the successful lyophilic modification on the clay surface, the effective intercalated and even exfoliated dispersion of the clay layers in the bitumen matrix can occur. The penetration viscosity number (PVN) values, defined as a function of penetration and dynamic viscosity, and the penetration index (PI) values, defined as a function of penetration and softening point, were found to be within a well-accepted thermal stability range for all of the prepared mastic samples. For this reason, it was concluded that the sensitivity of the samples to temperature decreased with the addition of organo-clay, thus providing applicability in a wider temperature range. The Fraass breaking point and dynamic viscosity values of the prepared mastic samples decreased and increased, respectively, with an increasing clay ratio, meaning that the addition of organo-clay lead to an increase in the crack resistance of the samples at low temperatures and a decrease in their permeability. [ABSTRACT FROM AUTHOR]

It is desirable for the work done in any construction process to be both cost-effective and durable. A thorough consideration of the matter reveals that the optimization of real-world problems involves multiple objectives. Bituminous hot mixtures, which are widely used in motorway construction, consist of aggregate and bitumen. The ratio between the different types of aggregate and bitumen forms the input to the real-world problem defined in this article, and the results of a test of the obtained asphalt in three different fields form the output. Our aim is to optimize these three outputs simultaneously to obtain a solution space with the most appropriate inputs. To optimize this problem, a new multi-objective optimization approach is proposed and tested in various ways and is finally adapted to the hot mix asphalt problem. Since the mathematical model of the objective function for this problem is fairly difficult, a fuzzy logic expert system is developed to act as the objective function. We believe that our approach to solving complex problems such as these forms a significant contribution to the literature. [ABSTRACT FROM AUTHOR]

A 23 factorial design experiment was conducted to study the influence of pre-heating temperature (HT) for manufacturing sample, bonding temperature (BT) onto rheometer, and trimming state (Trim) of the sample on complex shear modulus (G*) and phase angle (δ) using a dynamic shear rheometer on unmodified bitumen of types 50/70, 70/100, and two 160/220 from various sources. In addition, the black diagram and 2S2P1D model were used to evaluate the viscoelastic properties of bitumens. Findings show that the G* is more sensitive to the changes than the δ. Additionally, it was found that the 8 mm parallel plate diameter had a higher sensitivity to the trimming state than the 25 mm. The tested factor HT generally did not have a statistically significant impact on the results of the tested materials, except for 160/220_I. At practically all the temperatures tested for 50/70 and 160/220_II, the G* dropped by increasing the factor BT from a lower to a higher value. The Trim:BT interaction has the greatest impact on all materials and temperatures on G*, except for 160/220 at lower temperatures. However, in the case of δ, the Trim:BT interaction has the most significant effects for 70/100 and 160/220_II. The black diagrams show no discernible differences, which may be a result of the limited range of changes made to the variables. [ABSTRACT FROM AUTHOR]

In this study, B50/70 penetration grade original bitumen was modified by adding nanoclay at 2%, 4%, 6%, and 8% ratios. Subsequently, penetration, softening point, and rotational viscometer tests were performed on non-aged and short-term aged samples. The effect of nanoclay addition to bitumen on the susceptibility of bitumen to high temperature was evaluated with different equations. Since the central focus of the study is to assess the temperature susceptibility and the reaction to thermal changes of the nanoclay added bitumen, a differential scanning calorimetry experiment was performed on the samples, and the temperature susceptibility criteria that are obtained from the binder experiment results such as penetration index, viscosity–temperature susceptibility, and pen-vis number were calculated. In addition, the temperature range in the rotational viscometer experiment was kept broad, and measurements were made at 10 °C increments. By fitting these measurements into the Arrhenius equation, activation energies of original and modified bitumen were obtained. The results revealed that adding nanoclay improved the temperature susceptibility, high-temperature performance, and the resistance properties to aging of the binders. [ABSTRACT FROM AUTHOR]

Disposal or incineration of waste low-density polyethylene (LDPE) bags is a major problem, as it causes pollution. The pavement over time gets deteriorated by vehicular traffic, which mostly results in rutting and other distresses. This research is based on the performance evaluation of hot mix asphalt (HMA) modified with LDPE. Aggregates National Highway Authority Pakistan (NHA) gradation B, bitumen grade 60/70 and waste LDPE bags from the dump yards of Islamabad (Pakistan) were used in this study. Penetration, ductility and softening-point tests were conducted with bitumen modified with different contents of waste LDPE bag flakes; i.e., 0%, 2%, 4%, 6% and 8% to figure out the optimum modifier content (OMC). Marshall testing was performed for the determination of optimum bitumen content (OBC). Using OBC and incorporating LDPE contents as a replacement for OBC, HMA samples were tested for performance evaluation, including rutting resistance and moisture susceptibility and compared with the performance of unmodified HMA. It was observed that 4% of LDPE as a replacement for OBC in the HMA can be used as OMC and yielded better performance results than unmodified asphalt mix. Rutting resistance was improved by 20.86% and tensile strength ratio (TSR) for moisture susceptibility evaluation was above the specified limit of 80%. [ABSTRACT FROM AUTHOR]

To obtain a bitumen emulsion paste with a good bitumen film structure and rapid drying rate, the effect of cement content, cement type, and emulsion type on the drying and film formation of bitumen emulsion paste was studied. The drying and film formation mechanism of emulsion was employed to study the drying curve of bitumen emulsion paste. Results indicate that the drying and film formation process of bitumen emulsion paste can be divided into three stages. The solid volume fraction of the beginning of the final stage (ϕ2) and the maximum particle volume fraction (ϕm) are proposed to evaluate the drying and film formation quality of bitumen emulsion paste. Higher values of ϕ2 and ϕm indicate a denser particle packing state and lower residual water content of the final stage, which are beneficial to the drying and film formation quality of bitumen emulsion paste. The ϕ2 and ϕm of bitumen emulsion paste differ slightly with the increasing content of ordinary portland cement. However, these quantitative indexes vary significantly with changing bitumen emulsions with different values of ϕ2 and ϕm. Compared with ordinary portland cement, sulfoaluminate cement can lead to a noticeable decrease in ϕ2 and ϕm ; thus, its addition is harmful to the film structure of bitumen emulsion paste. Overall, to obtain a bitumen emulsion paste with a good bitumen film structure and rapid drying rate, a bitumen emulsion with good drying and film formation quality is recommended. [ABSTRACT FROM AUTHOR]

This study evaluates the performance of Polyethylene Terephthalate (PET)-modified hot mix asphalt. Aggregate, bitumen of grade 60/70 and crushed plastic bottle waste were utilized in this study. Polymer Modified Bitumen (PMB) was prepared using a high shear laboratory type mixer rotating at a speed of 1100 rpm with varying PET content of 2%, 4%, 6%, 8% and 10%, respectively. Overall, the results of preliminary tests suggested that bitumen hardened with the addition of PET. Following optimum bitumen content determination, various modified and controlled HMA samples were prepared as per wet and dry mixing techniques. This research presents an innovative technique to compare the performance of HMA prepared via dry and wet mixing techniques. Performance evaluation tests, which include the Moisture Susceptibility Test (ALDOT-361-88), Indirect Tensile Fatigue Test (ITFT-EN12697-24) and Marshall Stability and Flow Tests (AASHTO T245-90), were conducted on controlled and modified HMA samples. The dry mixing technique yielded better results in terms of resistance against fatigue cracking, stability and flow; however, the wet mixing technique yielded better results in terms of resistance against moisture damage. The addition of PET at more than 4% resulted in a decreased trend for fatigue, stability and flow due to the stiffer nature of PET. However, for the moisture susceptibility test optimum PET content was noted to be 6%. Polyethylene Terephthalate-modified HMA is found to be the economical solution for high volume road construction and maintenance, besides having other significant advantages such as increased sustainability and waste reduction. [ABSTRACT FROM AUTHOR]

The quality of bitumen is standardized by conventional tests. With the development of new techniques, rotational and oscillatory measuring systems are applied to evaluate bitumen under defined geometric, temperature, frequency, stress, and strain conditions that correspond to loads during asphalt production and service. Several studies have focused on determining the effect of composition on bitumen properties at service temperatures. However, there is a lack of information related to the effect of composition on viscosity at higher temperatures, which influences production processes. The different types of bitumen, samples of 50/70, 35/50, 45/80-75, and 25/55-60 bitumen, had different viscosity values in intervals corresponding to a confidence level of 95%. The viscosity–temperature relationship in temperature range of 120 to 180 °C was observed in values of 3.87 and 3.70 for unmodified bitumen and 3.09 and 3.22 for modified bitumen. The effect of differences in SARA fractions content on the variation in viscosity using regression analysis showed the importance of asphaltenes (direct correlation) and aromates (negative correlation) contents for 50/70 bitumen with a coefficient of linear regression above 0.7. In comparison, the strong effect of saturates and asphaltenes (negative correlation) and resins was identified for 45/80-75 bitumen samples with correlation of 0.5 to 0.7. [ABSTRACT FROM AUTHOR]

Environmental safeguards promote innovative construction technologies for sustainable pavements. On these premises, this study investigated four hot mix asphalt (HMA) mixtures—i.e., A, B, C, and D—for the railway sub-ballast layer with 0%, 10%, 20%, and 30% reclaimed asphalt pavement (RAP) by total aggregate mass and a rejuvenator additive, varying the bitumen content between 3.5% and 5.0%. Both Marshall and gyratory compactor design methods have been performed, matching the stability, indirect tensile strength, and volumetric properties of each mixture. Dynamic stiffness and fatigue resistance tests provided mechanical performances. Laboratory results highlighted that the RAP and the rejuvenator additive increase the mechanical properties of the mixtures. In addition, the comparative analysis of production costs revealed up to 20% savings as the RAP content increased, and the life cycle impact analysis (LCIA) proved a reduction of the environmental impacts (up to 2% for resource use-fossils, up to 7% for climate change, and up to 13% for water use). The experimental results confirm that HMA containing RAP has mechanical performances higher than the reference mixture with only virgin raw materials. These findings could contribute to waste management and reduce the environmental and economic costs, since the use of RAP in the sub-ballast is not, so far, provided in the Italian specifications for railway construction. [ABSTRACT FROM AUTHOR]

The utilization of recycled materials is an important issue in the context of environmental protection. The large amounts of recycled material recovered from the demolition of asphalt road structures indicate the need to find new ways of utilizing them. In the case of road renovation projects, large amounts of recycled materials are, in most cases, recovered in the form of reclaimed asphalt pavement (RAP), reclaimed concrete (RC) and recycled aggregate (RA). To focus on the effects of the use of recovered materials (RAP, RC and RA), the same composition was used for all of the analyzed mixtures in terms of foamed bitumen (FB) and Portland cement (CEM) content. The scope of laboratory tests included the specification of the following parameters: the amount of air void content Vm, the determination of axial compression strength at +25 °C, indirect tensile strength (ITS) at +25 °C, water resistance, TSR, water and frost resistance, WRW+M stiffness modulus (IT-CY) at 13 °C, dynamic dynamicmodulus. The plan of the experiment assumed addition recycled material in quantities between 20% and 80% in increments of 20%. The obtained results indicate that both the type and quantity of recycled material significantly affect the properties of the cold-recycled mixture with foamed bitumen. Using reclaimed asphalt pavement and recycled cement concrete guarantees high levels of stiffness in the recycled mixture. Howeverin the case of recycled aggregate, the authors did not observe any visible changes in the dynamicdynamic modulus, irrespective of the loading conditions. It was also indicated that it is necessary to reduce the quantity of reclaimed asphalt pavement in the composition of the FB-RCM mix to maintain the required air void content. [ABSTRACT FROM AUTHOR]

In previous studies, different additives and modifiers have been studied to improve the properties of asphalt concrete mixtures, whose main failures are plastic deformation and cracking. In this research, the improvement of the properties of asphalt concrete mixtures were investigated by introducing residual plastics as a substitute for virgin bitumen, which improves the sustainability of the mixtures. Furthermore, the results obtained from these new mixtures were compared with a mixture designed with polymer-modified bitumen (PMB). Ten experimental designs were tested with three types of waste fibre plastics from a municipal solid waste treatment plant and two percentages of bitumen replacement (15% and 25%). The experimental testing plan included air void characterization, moisture sensitivity, stiffness and fatigue resistance, among others. An increase of approximately 5% in voids could be observed when introducing the plastic material and therefore some tests were carried out to over-compact the specimens. The results showed an improvement in the mechanical performance of the experimental mixtures, highlighting the resistance against plastic deformations, which even reached similar values to the mixtures made with PMB. [ABSTRACT FROM AUTHOR]

One of the primary methods for bitumen and heavy oil recovery is a steam-assisted gravity drainage (SAGD) process. However, the mechanisms related to wettability alteration under the SAGD process still need to be fully understood. In this study, we used MD simulation to evaluate the wettability alteration under a steam injection process for bitumen and heavy oil recovery. Various oil droplets with different asphaltene contents were considered to determine the effect of an asphaltene content on the adsorption of the oil droplets onto quartz surfaces and wettability alteration. Based on the MD simulation outputs, the higher the asphaltene content, the higher the adsorption energy between the bitumen/heavy oil and quartz surfaces due to coulombic interactions. Additionally, the quartz surfaces became more oil-wet at temperatures well beyond the water boiling temperature; however, they were extremely water-wet at ambient conditions. The results of this work provide in-depth information regarding wettability alteration during in situ thermal processes for bitumen and heavy oil recovery. Furthermore, they provide helpful information for optimizing the in situ thermal processes for successful operations. [ABSTRACT FROM AUTHOR]

The effect of elevated temperatures on the degradation of an elastomeric bituminous geomembrane (BGM) when exposed to air and deionized (DI) water at temperatures between 22 and 85 °C is investigated using immersion tests. The changes in the mechanical, chemical and rheological properties of the BGM are examined over approximately two years under different ageing conditions. It is shown that the BGM exhibited different degradation rates in its different components when exposed to elevated temperatures that are dependent on the incubation media. In air, the BGM exhibited thermo-oxidative degradation in the elastomeric bituminous coat that changed the bitumen glass transition temperature and increased its rigidity. Further degradation led to the brittleness of the bitumen coat before any degradation in the tensile and puncture strengths of the BGM. In contrast, exposure to DI water resulted in faster degradation of the mechanical properties of the BGM, while the bitumen coat exhibited substantially less degradation than in air. Arrhenius modelling is used to estimate the degradation times of the BGM at a range of field temperatures for both media. • Degradation behaviour of an elastomeric BGM is examined over two years in air and DI water at elevated temperatures. • The BGM exhibited different degradation rates in its different components when exposed to elevated temperatures. • Exposure to air resulted in faster thermo-oxidative degradation in the elastomeric bituminous coat than in DI water. • The degradation in the mechanical properties was faster in DI water than in air. • Estimates of the time to nominal failure of the BGM are presented at a range of field temperatures. [ABSTRACT FROM AUTHOR]

Changes in the properties of bitumen binders that occur as a result of aging have a huge impact on the durability of products produced from them. In particular, asphalt pavements, which constitute the most common use of petroleum bitumen, are susceptible to damage resulting from the increasing stiffness of the bitumen during its life cycle. Increased stiffness of asphalt pavements reduces the pavement resistance to low-temperature cracks and fatigue cracks, ultimately leading to the loss of their functional properties and the need for road repair. The rate of changes in bitumen properties is influenced by many factors, the most important of which are environmental conditions, technological parameters of binder processing, and physicochemical properties. The greatest impact on minimizing the adverse effect of aging is the use of bitumen suitably resistant to aging, and changing the technological parameters of its application. This article reviews the literature and standardized test methods of bitumen aging, with a focus on the methods that are most often used in practice, to evaluate the suitability of bitumen for use in road construction. The presented methods are limited to aging simulation. This mini-review presents the most important stages of aging procedures, their advantages and limitations, as identified by the authors of this publication for different types of bitumen. Moreover, the most important directions of developments in the field of new laboratory aging tests are highlighted. The suggestions are based on the industrial practice of the authors of this review, taking into account identified demands for quality control in the industry. [ABSTRACT FROM AUTHOR]

Selecting the optimum amount of modifiers added to bitumen to modify its characteristics has always been one of the most important steps of such researches. In this study, the response surface method is used to design the experiments and to determine the optimal combination of different percentages of waste LDPE and crumb rubber. Waste LDPE in the amounts of 3%, 5%, and 7% and crumb rubber in the amounts of 1%, 3%, and 5% are used as the modifiers. In addition, the central composite design method is used to select the optimal combination of waste LDPE and crumb rubber. Polymer percentage is the most effective parameter in this research. The results show an optimum point of approximately 3% waste LDPE and 3% rubber powder. It can be the optimal point and has the best performance at low temperatures in this combination of modified bitumen percentages. However, the exact optimal point is obtained as 3% recycled plastic and 2.02% rubber powder after the optimization process. [ABSTRACT FROM AUTHOR]

Bitumen is a petroleum residue that is extensively used as a pavement material. Rutting at high temperatures is one of the limitations of bitumen in warmer regions. The aim of this study is to improve the performance and increase the temperature susceptibility of neat bitumen. In this study, polyethylene glycol (PEG) and nano ZnO have been used to modify the properties of neat bitumen. Four samples were prepared by incorporating PEG and nano-ZnO with a standard laboratory mixer. Polyethylene glycol with 2%, 4%, 6%, and 8% by weight were mixed initially with neat bitumen along with nano ZnO (1.5% and 3%). To check its applicability in the road construction industry, the blends were subjected to mechanical properties tests such as ductility, flash point, fire point, softening point, and penetration test. It was investigated that decrease in ductility ranges from a maximum of 143 (neat bitumen) to a minimum of 83 (8 wt%). Softening point increased from 54°C to a maximum of 59°C (8 wt%). Flash and fire point increase first and then decrease; the optimum content was found to be 6%. The structural properties of blends were investigated using X-ray diffraction. The spectra show there is a shift of peaks in polymer-modified bitumen (PMB) as compared to neat bitumen, which leads to homogeneous mixing. The shift of peaks is because of an increase in interlayer spacing of neat bitumen and a decrease in Bragg's angle. FT-IR analysis shows the presence of peaks in the range of 3000–2800 cm−1 which confirms the presence of additives in modified bitumen. SEM analysis was conducted to check the quality of dispersion and to investigate the microstructure. ZnO nano particles affect the mechanical properties of samples. The physical properties of polymer-modified bitumen (PMB), PEG, and nano ZnO blends enhance the stiffness of samples at high temperatures. [ABSTRACT FROM AUTHOR]

In recent years, both dry and wet processes to include waste rubber (WR) in bituminous mixtures have had little success in Italy due to technical and economic reasons. However, the necessity to recycle this waste material and the increasing interest in low-noise emitting pavement is encouraging researchers and stakeholders to explore new solutions. In this context, a hot-mix asphalt (HMA) manufactured with polymer-modified bitumen and fine WR added through a dry method has been recently developed. This paper deals with the rheological characterization and modeling of this innovative HMA, in comparison with two reference mixtures, with ordinary polymer-modified bitumen and with an asphalt rubber binder produced through a wet process. The complex modulus was measured through uniaxial cyclic compression tests at different temperatures and frequencies. The Huet-Sayegh rheological model was used to simulate the experimental data. The results showed that the time-temperature superposition principle is valid, despite the presence of polymers and WR. The Huet-Sayegh model allows a good fitting of the dynamic modulus and loss angle data to be achieved. The viscous response of the mixture including polymer-modified bitumen and rubber powder is higher than the other HMAs, which is mainly associated with the nature of the modifiers, the binder content in the mix and the less severe short-term aging. [ABSTRACT FROM AUTHOR]

Asphalt pavements inevitably deteriorate over time, requiring frequent maintenance work to ensure the proper serviceability of the road network. Small interventions, such as resurfacing for pavement preservation, are preferable to reconstruction at the end of roads' in-service lives as they limit environmental- and economic-related impacts. Thin asphalt overlay (TAO) mixture represents a suitable maintenance solution to restore the functional properties of road surfaces. Due to the increasing awareness of the depletion of non-renewable resources and the importance of promoting the circular economy, this study evaluated the possibility of using fully recycled TAO mixes by investigating their volumetric and mechanical properties. Two eco-friendly TAO mixes were designed using recycled aggregates from reclaimed asphalt pavements, a municipal solid waste incinerator, and steel slags in order to meet EN 13108-2 requirements. The TAO mixes differed in regard to the type of bituminous binder (neat/SBS-modified bitumens) and fibres (natural/synthetic) employed. The preliminary results demonstrated that the presence of recycled aggregates did not negatively affect the workability and the mechanical performances of the two sustainable mixtures in terms of stiffness, tensile resistance, rutting and moisture susceptibility. Of these, the TAO mix with neat bitumen and synthetic fibres showed enhanced mechanical performance highlighting the structural effects of the used fibres. [ABSTRACT FROM AUTHOR]

The moisture resistance of dense- and gap-graded bituminous mixes prepared with the replacement of virgin aggregates and fresh bitumen with reclaimed asphalt pavement (RAP) was evaluated using indirect tensile strength (ITS) and resilient modulus (Mr). The mechanistic analysis was performed to estimate the effect of moisture resistance on the fatigue performance of thin and thick pavement sections designed with dense- and gap-graded bituminous mixes. The ITS ratio and Mr ratio results indicate that the resilient modulus ratio is more sensitive to moisture damage in bituminous mixes than the ITS ratio. In addition, the results of the fatigue life ratio indicated that the gap-graded mix prepared with different RAP content has better resistance to moisture-related cracking in thick pavement sections than the dense-graded mix. However, the effectiveness of gap-graded and dense-graded mixes prepared with different RAP content on moisture-related cracking depended on the subgrade strength for thin pavement sections. [ABSTRACT FROM AUTHOR]

Activated carbons are widely used especially in the removal of harmful contents of gases and liquids. Activated carbons constitute one of the important import items for our country. It is foreseen that the production of activated carbons from cheap, easily available and abundant raw materials of various organic origins will make significant contributions to the country's economy. In this study, it is aimed to evaluate semi-bituminous coals (Gediz-Kütahya) containing high sulfur as an alternative area of use in the production of activated carbon. In the study where ZnCl2 was used as the activation chemical, the effects of different working parameters (chemical/coal ratio, impregnation time and grain size) on activated carbon production were investigated. Various properties such as BET surface area, pore distribution, SEM surface properties, adsorption capability etc. of the obtained activated carbon were determined. Comparisons of the obtained activated carbon with the imported activated carbons still used commercially were made, and it was determined that there were significant similarities in properties. Optimum production operating parameters, 1/1 ZnCl2/coal mixture ratio, 24 hours impregnation time and +2 mm particle size coal is treated at 650 oC for 60 minutes under N2 atmosphere, with 733 m2/g BET surface area, micro and meso porosity activated carbon with a total pore volume of 0.460 cm3/g was obtained. As a result of the adsorption tests of the obtained activated carbon, it was determined that 99.2% of the Cu2+ ions in the solution could be removed. It has been understood that the obtained activated carbon can be used in many sectors. [ABSTRACT FROM AUTHOR]

The effectiveness of weight ratio of mineral filler to effective bitumen in the fatigue performance of asphalt mixture with integral granules was investigated based on experiments on bitumen mastic (mixture of bitumen and mineral filler passed through sieve grade 200). The experiments included a dynamic shear rheometer, elastic recovery, linear amplitude sweep tests and other performance tests on asphalt mixture, such as fatigue of indirect tensile and resilient modulus test for assessing the medium temperature with various mineral fillerto-bitumen ratios of: 0.4, 0.6, 0.8, 1.0, 1.2, 1.4 and 1.6 for bitumen 70-16 PG. Based on this project, the weight ratio of mineral filler to effective bitumen according to Iran Management and Planning Organization (IMPO-234) and SHRP-A407 standard and based on fatigue performance of asphalt mixture was separated and modified. So, to control and modify the medium temperature, the maximum weight ratio of filler to effective bitumen should be considered, which is equal to 0.8. The results of this research showed that for controlling the fatigue performance, the rheological behavior of bitumen mastic should be considered beside the asphalt mixture performance and the bitumen rheological behavior. [ABSTRACT FROM AUTHOR]

Nanosilica (NS) has been involved in many investigations over bituminous materials. Although nanosilica is variable in size and type, most literature has failed to consider or acknowledge its type and/or size impacts. Hence, this research focused on this knowledge gap by considering 20-nm, 20-nm with couplant, and 60-nm NS types for some index, rheological shear, and creep tests. Tests were conducted at virgin, short-term, and long-terms aging conditions as well. Estimations of rutting and fatigue resistances were found to be promising at different extents. Generally, 60-nm NS was better for rutting, whereas 20-nm NS was more efficient for fatigue. Initially, dry blending was considered during sample preparations. However, wet blending was also used later for extra samples and limited shear oscillation tests. Some discrepancies in dry-prepared results were found to be attributed to mixing conditions. Outcomes of experiments after wet blending showed more consistent and reliable direct relationships between sample properties and NS contents. Hence, coarse NS at higher ranges, typically at 8% usage, was more efficient than other batches. [ABSTRACT FROM AUTHOR]

The carbon footprint reduction mandate and other eco-friendly policies currently in place are constantly driving the trend of the synthesis and application of sustainable functional materials. The bitumen industry is not an exception to this trend and, every day, new technologies that facilitate safer, cost effective and more sustainable industrial processes and road paving operations are being researched and brought to light. A lot of research is currently ongoing to improve bitumen's properties due to its use as a binder in road paving processes. Over the years, the most common method to improve bitumen's properties has been with the use of additives. The major drawback in the use of these additives is the fact that they are substances of strong chemical nature which are either too acidic, too basic or emit toxic fumes and volatile organic compounds into the environment. In the long run, these chemicals are also toxic to the road pavement personnel that carry out the day to day industrial and paving operations. This led researchers to the initiative of synthesizing and applying biomaterials to be used as additives for bitumen. In this light, several studies have investigated the use of substances such as bio-oils, natural waxes, gum, polysaccharides and natural rubber. This literature review is aimed at classifying the different bio-based materials used to improve bitumen's properties and to provide a deeper knowledge of the application of these biomaterials in bitumen technology. In general, we highlight how the research efforts elaborated herein could potentially foster safer, sustainable, eco-friendly approaches to improving bitumen's properties while also promoting a circular economy. [ABSTRACT FROM AUTHOR]

In order to conserve non-renewable natural resources, waste cooking oil (WCO) in bitumen can help lower CO2 emissions and advance the environmental economy. In this study, three different components of WCO were isolated and then, together with polyphosphoric acid (PPA), used separately as bitumen modifiers to determine the suitability of various substances in WCO with PPA. Conventional tests, including penetration, softening point temperature, and ductility, and the dynamic shear rheology (DSR) test, including temperature sweep and frequency sweep, were used to evaluate the influence of WCO/PPA on the traditional performance and rheological properties at high and low temperatures. The results indicate that WCO reduced the ductility and penetration value, when the use of PPA increased the softening point temperature and high-temperature performance. Compared to reference bitumen, the rutting factor and viscous activation energy (Ea) of bitumen modified with 4% WCO and 2% PPA has the most significant increase by 18.6% and 31.5, respectively. All components of WCO have a significant impact on improving the low-temperature performance of PPA-modified bitumen. The performance of the composite-modified bitumen at low temperatures is negatively affected by some waxy compounds in WCO, such as methyl palmitate, which tends to undergo a solid–liquid phase change as the temperature decreases. In conclusion, the inclusion of WCO/PPA in bitumen offers a fresh approach to developing sustainable pavement materials. [ABSTRACT FROM AUTHOR]

The main goal of this study is to evaluate the field performance of crumb-rubber-modified asphalt mixtures used as a surface layer on high-volume traffic roads. For this purpose, several road sections were constructed under different climate conditions and using control mixtures (manufactured with traditional SBS polymer-modified binders) and crumb-rubber-modified mixtures. After the construction of the different road sections, cores were taken at different periods of their service life (up to 63 months) and they were tested in the laboratory in order to assess the evolution of the density, stiffness and fatigue resistance of the layers. Based on the results obtained from tests, it can be concluded that under real severe traffic and climate conditions, asphalt mixtures manufactured with crumb-rubber-modified bitumen offer ageing and mechanical performance very similar to that offered by asphalt mixtures manufactured with traditional SBS-modified bitumen. Based on these considerations, this application can be an interesting solution to minimize environmental problems caused by end-of-life tires in landfills. [ABSTRACT FROM AUTHOR]

Rejuvenators as environmentally-friendly materials can restore the properties of aged bitumen physically or chemically. A proper dosage of a rejuvenator can achieve the desired properties of bitumen. Thus, this study proposed a method, the empirical double-logarithmic formula and calibration, based on physical properties to determine the appropriate rejuvenator dosage within aged bitumen for the desired properties. Three different rejuvenators were selected to restore recycled/aged bitumen extracted from reclaimed asphalt pavement (RAP) to a similar level as that of neat bitumen with penetration of 70–100 (reference bitumen). The initial estimation of rejuvenator dosage was determined by the viscosity of rejuvenators and recycled bitumen using an empirical double-logarithmic formula; the penetration and softening point of one rejuvenated bitumen were applied to calibrate the rejuvenator dosage within recycled bitumen. After the determination of the rejuvenator portion within recycled bitumen, rejuvenated bitumen was compared with reference bitumen regarding penetration, softening point, Fraass breaking point, complex modulus, phase angle, and PG upper temperature; the properties of rejuvenated bitumen over aging degree (short-term aging and long-term aging) were also compared with that of reference bitumen using softening point, Fraass breaking point, complex modulus, phase angle, rutting factor, and fatigue factor. It was found that this method can accurately calculate the rejuvenator dosage in recycled bitumen with a few available physical parameters; the rejuvenated bitumen showed similar equivalent properties as reference bitumen, and the three rejuvenators have a lasting effect on recycled bitumen. Therefore, this method is recommended for calculating the rejuvenator dosage of recycled bitumen due to its convenience and less demand for tests. [ABSTRACT FROM AUTHOR]

Fatigue resistance is of paramount importance for bituminous materials and so it is the effect of applying rest periods, as this is a more realistic representation of the traffic loading. To this end, to evaluate the healing potential, storage rest periods were introduced during a series of fatigue tests. In this study, the healing investigation was performed on the asphalt and mortar scale, aiming to assess the effect of reclaimed asphalt binder (RAB) on the healing potential. For the mortars, the healing indices derived under different damage levels and rest periods were modelled into a healing master curve, describing the healing index as a function of damage level and rest time. The asphalt tests revealed that the mixtures containing RAB showed higher healing potential compared to the control mix, attributed mainly to the existence of a softer blend as a result of partial blending. Furthermore, chemical indicators were considered to assess the healing potential of the binder blends and compared to the results of the healing tests. For the mortars, the 70% RAB samples showed the lowest healing potential, reflecting the full effect of very high RAB content, when the RAB is fully blended with the virgin binder. [ABSTRACT FROM AUTHOR]

Research on waste tire pyrolysis carbon black (PCB) in bitumen mixtures indicates that it has excellent high-temperature rutting resistance; however, the degradation of low-temperature crack resistance and water stability of PCB-modified asphalt limits its wide application. Therefore, the low-temperature crack resistance and water stability of PCB-modified hot-mix asphalt (HMA) were enhanced by addition of waste chicken feather (WCF). Based on the response surface methodology (RSM), a variance analysis (ANOVA) and P-value test of the model response coefficient were carried out, and the performance prediction models of percentage air voids (VV) in bituminous mixtures, 30-min Marshall stability (MS), and 48-h MS were obtained. The interaction effects of different independent variables on response variables were analyzed. In addition, the optimal solutions of multiresponse variables obtained by the response optimizer were 0.20% PCB content, 0.36% WCF content, shearing time of 5.78 min for WCF, and 6.66% asphalt–aggregate ratio. The corresponding performance index prediction values were 4.00% VV, 12.80 kN 30-min MS, and 12.65 kN 48-h MS. The road performance test results demonstrated that incorporating WCF improved the high-temperature rutting resistance, low-temperature crack resistance, and water stability of PCB-modified hot-mix asphalt. This study provides a precise performance prediction model for adding PCB and WCF to HMA. [ABSTRACT FROM AUTHOR]

Increased heavy-vehicle traffic, higher traffic volumes, and temperature changes lead to distresses such as stripping, rutting, fatigue cracks in asphalt pavements, increasing the cost of road maintenance. Therefore, it is inevitable that the properties of bitumen and asphalt mixtures must be improved. Polymer modification is one of the methods to improve bitumen properties. In the present paper, styrene butadiene styrene (SBS), styrene-butadiene rubber (SBR), and low-density polyethylene (LDPE), along with Sasobit wax, were used to modify the bitumen. For that purpose, we used tests, including conventional bitumen tests and linear amplitude sweep (LAS) tests. The results of the present study showed that the polymer mentioned above improves the rutting index of the base bitumen. Based on the bending beam test results, polymer additives and Sasobit have no positive effect on the low-temperature performance of the base bitumen. The LAS test results were used to compare PMBs' fatigue performance, and it was evident that SBR had the most significant effect on increasing the fatigue life of the base bitumen. In the meantime, Sasobit increases the fatigue life of PMBs at high strain levels. [ABSTRACT FROM AUTHOR]

Foamed bitumen stabilisation is a unique pavement treatment option for improving new granular materials or rehabilitating existing granular layers that have exceeded their serviceable life. As a type of expedient construction technology, the application of foamed bitumen stabilisation technology to Australian pavements is exceptionally promising, with the product of the stabilisation process being a flexible material for use as base and subbase course, but with an increased modulus and reduced susceptibility to the effects of moisture ingress. Increasing demands on pavements, compounded with quality unbound pavement materials proving more difficult to acquire is necessitating the hauling of materials over long distances and this significantly increases typical pavement construction and maintenance costs. However, stabilisation of existing, marginal and non-standard granular materials can offer a logistically convenient and cost-effective solution. This paper reviews the design, construction and characterisation of foamed bitumen stabilised granular material for pavements. First, the technology of foamed bitumen stabilisation is summarised and then the design and production practices are reviewed, before concluding with future developments for stabilisation practices. [ABSTRACT FROM AUTHOR]

Background: Mechanical characterization of materials that solely relies on global responses may overlook important local behavior that significantly affects the characterization of material properties. Field displacements such as from digital image correlation (DIC) can provide high-fidelity experimental data, which combined with finite element method (FEM) can form DIC-FEM inverse method that can better account for complex mechanical properties of materials. Despite its capability, the DIC-FEM inverse method has been mainly applied to an elastic-dominant regime even though inelastic deformation is important in many engineering materials. Specifically, the DIC-FEM inverse method has not been fully extended to viscoelastic materials due to the complex representation of the time-dependent modulus. Objective: This study aimed at establishing a DIC-FEM inverse framework to identify constitutive properties of homogeneous elastic and viscoelastic materials. Methods: Two example materials (i.e., polyetheretherketone (PEEK) and a viscoelastic fine aggregate matrix (FAM) with a bituminous binder) were selected for the elastic and viscoelastic investigation, respectively. Both were experimentally tested using three-point bending incorporated with DIC. FEM simulated the experiment and the Nelder-Mead nonlinear optimization algorithm was implemented to solve the inverse problem. Results: The DIC-FEM inverse method successfully identified Young's modulus of an example linear elastic PEEK and the linear viscoelastic relaxation modulus of FAM. Conclusions: The resulting DIC-FEM inverse method is applicable to various materials with inelastic deformation and can be extended to localized behavior induced by microstructure heterogeneity and fracture. [ABSTRACT FROM AUTHOR]

For the first time, by atomic force microscopy (AFM) methods, micro- and nanofragments of micronized powder elastomeric modifier (PEM) formed at the short-term (3 min at 160 °C) interaction of PEM with hot bitumen have been demonstrated. It is the technology of high-temperature shear-induced grinding of a worn-out tire's crumb rubber or its co-grinding with styrene–butadiene–styrene (SBS) block copolymer which provides the creation of the PEM structure inclined to rapid degradation in hot bitumen. The formation just after the preparation process of a new structure of a modified binder, more resistant to external effects, is supported by the data of rheological tests. Performance tests for a modified binder using Superpave standard adopted by the road industry for bituminous binders showed an extended temperature range, resistance to rutting, and low-temperature and fatigue cracking. The better resistance to low-temperature and fatigue cracking is certainly related to energy absorption and crack growth stopping in the presence of micron and submicron resilient PEM fragments in accordance with the mechanism of increasing impact toughness in plastics. [ABSTRACT FROM AUTHOR]

This study focussed on investigation of fundamental properties of cuplump-modified bitumen (CMB) modified with an additive Ethylene Bis Stearamide (EBS) wax. EBS is a non-polar long fatty acid bis-amide with two central amide groups. The properties evaluated included conventional and rheological properties of CMB. The properties were tested using Viscometer, penetrometer, Ring and Ball softening tester and dynamic shear rheometer (DSR). Results indicated that viscosity of bitumen increases with the EBS addition. Greater temperature rutting resistance, softening point, stiffness and complex modulus were observed with EBS addition compared to the unmodified one. [ABSTRACT FROM AUTHOR]

One major research topic is to characterize the mechanical behaviour of actual reinforced pavement structures from laboratory experimentation and take it into account for the design. This investigation aims to verify the effect of fiberglass geogrid presence on interface linear viscoelastic (LVE) behaviour separately and as a system along with the bituminous mixture layers. To conduct the research, two different fiberglass geogrids, with ultimate tensile strength (UTS) of 100 and 50 kN/m, and tack coat made of straight-run bitumen and modified by polymer were combined for the fabrication of three reinforced configurations. In addition, two unreinforced configurations were also fabricated. The first was a single layer slab and the second was a double-layered slab composed of two bituminous mixtures (same type) bonded layers by a tack coat. Complex modulus tests were carried out in specimens cored in two different directions, vertically (V) and horizontally (H) cored. The experimental data were fitted using the 2 Springs, 2 Parabolic Elements and 1 Dashpot (2S2P1D) model. The test results showed that all interfaces' complex modulus obtained for V specimens were LVE. Moreover, complex viscous properties of the interfaces were obtained from the used binder. The interface containing polymer modification presented the highest stiffness. • Interface and bituminous mixture complex modulus could be obtained separately from a single reinforced specimen. • Interfaces containing geogrid or not presented linear viscoelastic behaviour that could be modelled using 2S2P1D. • Bitumen type and amount play an important role in interfaces LVE behaviour. • The tack coat containing SBS-modified bitumen increased the interface stiffness. • Considerable low level of geogrid mobilization was observed at small strain amplitudes tension-compression tests. [ABSTRACT FROM AUTHOR]