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Hot-gas drum heating (HDH) of bituminous mixtures is a new approach to heating bituminous mixtures that is influenced by the parameters of the hot gas and drum. A fluid thermal numerical model was developed to evaluate the effects of heating bituminous mixtures with HDH using a finite-volume method (FVM). The FVM was verified through the heating test of a bituminous mixture. The effects of the drum rotating speed and hot-gas speed on the efficiency of heating the bituminous mixture during HDH were analyzed using Fluent. The results indicated that the drum rotating speed directly influenced the formation of a bituminous-mixture curtain, which had a significant effect on the efficiency of heating the bituminous mixture. The efficiency of the heat exchange between the hot gas and the bituminous mixture was high, with full contact between the hot gas and the bituminous mixture. With an increase in the hot-gas speed, the heating time became shorter; however, the rate of hot-gas utilization was reduced. A symmetrical temperature distribution and a superior heating efficiency of the bituminous mixture were achieved when the drum rotating speed was 7 rpm and the hot-gas speed was 1.4 m/s. [ABSTRACT FROM AUTHOR]

The rheological properties of bitumen largely influence the performance of the pavement. Determination of rheological properties of bitumen depends on thermal equilibrium time. The main objective of this study is to evaluate the effect of Evotherm, a chemical warm mix additive on the thermal equilibrium time of bituminous binders. The bituminous binders used for this study included two unmodified binders, a polymer-modified bitumen (PMB) and a crumb rubber-modified bitumen (CRMB). The thermal equilibrium times for bituminous binders with and without Evotherm were measured using a dynamic shear rheometer. The results indicate that the thermal equilibrium time primarily depends on the type of binder, wherein the asphaltene content, presence of polymer and rubber influence thermal equilibrium time. The higher thermal equilibrium times observed for the Evotherm-modified PMB40 binder and Evotherm-modified CRMB60 binder in unaged condition can be attributed to a change in morphology and chemical interaction respectively upon the addition of Evotherm. Lesser thermal equilibrium time exhibited by short-term aged Evotherm binders can be because of the reduced formation of ageing compounds due to reduced short-term ageing temperature and presence of Evotherm. The linear regression model well predicted the thermal equilibrium time based on test temperature and softening point of binders. [ABSTRACT FROM AUTHOR]

The use of sustainable materials in road construction has been gaining popularity to provide a better future for the next generations. This study investigates the possible use of two common sustainable road construction materials, recycled asphalt pavement (RAP) and recycled tire rubber (RTR), for pavement maintenance applications. Mixtures were produced either with combined RAP and RTRs or 100% RAP with petroleum-based (RAP-A) and bio-based (RAP-B) rejuvenating oils. Because pavement maintenance applications such as pothole patching have traditionally been performed with cold mixtures (CM), a typical cold patching mixture was also investigated along with six hot asphalt mixtures. RTR mixtures were produced using different rubber modification technologies. They were manufactured using crumb rubber wet (WET), crumb rubber dry (DRY), devulcanized rubber (DEV), and crumb rubber terminal blend (TB) technologies. Each RTR-modified mixture included 40% RAP and approximately 12% rubber content by weight of the binder. The performance of the mixtures was compared using dynamic modus (DM) testing for linear viscoelastic characterization, flow number (FN) testing for rutting potential, and tensile strength ratio (TSR) testing for moisture susceptibility. The cost-effectiveness of different mixtures was performed using the life cycle cost analyses (LCCA) approach for bituminous materials. The results showed that any recycled hot-mix asphalt outperformed the CM. The 100% hot RAP mixture with petroleum-based rejuvenator performed as well as any combined RTR-RAP mixtures, and it became the most cost-effective alternative for pavement maintenance applications. [ABSTRACT FROM AUTHOR]

The presence of water badly affects the moisture susceptibility of the reclaimed asphalt Foamed Bituminous Mix (FBM). The present study is mainly emphasized to assess the moisture susceptibility of reclaimed asphalt FBM, Where RAP is being incorporated as a replacement of fresh aggregates. Moisture susceptibility of the mix is evaluated in terms of tensile strength ratio (TSR) and resilient modulus ratio, subjected to different conditioning procedures namely AASHTO T283, modified IDOT, TG-2 guidelines, and MIST. Further data analytics and regression modeling are also carried out to determine the moisture susceptibility of the mix and to check the statistics among the variables. The findings show that the incorporation of RAP in the FBM improves moisture resistance. Further, FBM containing 100% RAP shows the least moisture susceptibility in terms of TSR and Mr ratio irrespective of any conditioning type. Moreover, MIST conditioning may be preferred to assess the moisture sensitivity as it simulates the field pore pressure effects. Further, mathematical analysis is carried out to predict the moisture susceptibility of mix. Adjusted R square coefficient indicates a better fit of the prediction model developed. Overall, the study may be helpful to highway professionals in analyzing the conditioning procedures and determining the moisture sensitivity of the reclaimed asphalt Foamed Bituminous Mix. [ABSTRACT FROM AUTHOR]

The conventional design approaches for reclaimed asphalt pavement (RAP) mix follow blending rules to select the grade of the virgin binder for hot recycled bituminous mixtures. The interactions of RAP binder with the virgin binder are highly complex in the presence of the rejuvenator. Identifying the optimal proportion of RAP binder, virgin binder, and rejuvenator is often a trial-and-error procedure, involving considerable experimental data collection. The current research study proposes the statistical-based design of experiments (DoE) framework to design ternary RAP binder blend, develop response surface prediction models, and optimize the proportions to meet targeted binder properties of viscosity grade (VG30) binder. A desirability-based multiple response optimization is carried out, and the optimal blend proportions with target binder properties are arrived at with different desirability levels. A total of 13 RAP binder blends are formulated using the I-Optimal algorithm in the current study. Experimental data such as softening point, high-temperature performance grade (PG), and linear viscoelastic parameters in the temperature range of 46°C to 70°C and frequency range of 0.1 to 50 Hz are collected. The binder blends are evaluated using master curve parameters and relaxation spectrum. The response surface models are developed for two measured parameters (high-temperature PG and softening point), three computed master curve parameters, and four relaxation spectrum parameters. These models capture the possible individual component effects and combined component effects on the final RAP binder blend through linear and nonlinear terms. A desirability-based simplex optimization is adopted to identify combinations of constituents at various levels of desirability that comprises only direct measurements, direct measurements and master curve parameters, and direct measurements, master curve parameters, and relaxation spectrum. Using this proposed approach, a wide range of solution zones are identified with various levels of desirability. Reclaimed asphalt pavement (RAP) consisting of aged bitumen coated on mineral aggregates is used for recycling in pavement construction. Many challenges exist related to the optimal use of such material. The aged binder may need to have the required properties suitable for recycling. Generally, rejuvenators are added to the RAP to enhance the properties of aged binder. However, how much rejuvenator should be added is unclear. Aged bitumen from different sources of RAP can have different degrees of aging. In addition, it may not be easy to estimate the extent of blending of the RAP with the virgin materials (aggregates and bitumen), as it is linked to the characteristics of aged binder and the choice of fresh bitumen and rejuvenator. Also, the aged bitumen, when mixed with a rejuvenator and virgin bitumen, may not necessarily result in a final mix with bitumen that meets the requirements. As can be seen, the choices are entirely diverse and varied. This research attempts to solve such issues using a statistics-based tool called design of experiments (DoE). Using such a tool, this study demonstrates how to optimally choose the proportions of virgin bitumen, RAP bitumen, and rejuvenator. This work presents a methodology that can be implemented efficiently using commercial software by any asphalt mix designer. [ABSTRACT FROM AUTHOR]

To effectively utilize waste mask materials in road engineering and minimize resource waste, the melt-blown fabric (MBF) of waste masks was utilized to modify the virgin bitumen. The preparation process of MBF-modified bitumen was investigated, and the physical and rheological properties of bitumen were measured. Subsequently, the blending mechanism during preparation and the dispersion morphology of the modifier were explored. Finally, the pavement performance of the mixture was investigated, and a radar chart analysis was performed to quantitatively assess the effects of MBF modification. Results suggested that the recommended preparation process of shear time, shear rate, and shear temperature was 170 °C, 4000 r/min, and 15 min, respectively. MBF enhanced the high-temperature stability of the binder and weakened the temperature susceptibility. The modification was primarily a physical process. No network structure and agglomeration formed in the bitumen after modification. The addition of MBF significantly improved the resistance of the asphalt mixture to a high-temperature deformation and water damage but harmed its low-temperature crack resistance. The comprehensive assessment results of 0% ( f 1 ), 1% ( f 2 ), 3% ( f 3 ), and 5% ( f 4 ) MBF to improve the properties of the mixture were in the following order: f 3 > f 4 > f 2 > f 1 , where the impact of 3% MBF was the most significant, followed by 5% and 1% MBF. [ABSTRACT FROM AUTHOR]

Examples of nanostructured fluids (NSFs) used as highly specialized "brush‐on, wipe‐off" detergents for the removal of graffiti coatings resistant to removal are water‐in‐oil nanoemulsions that have been stabilized with nonionic saccharide surfactants. Nanodetergents with safe, ecofriendly ingredients were produced using high‐pressure homogenization (HPH). These ingredients included D‐limonene or 3‐methoxy‐3‐methyl‐1‐butanol, esterified vegetable oils, and alkyl polyglucosides (APG). Responsive surface methodology (RSM) optimization was used to identify the most efficient detergents for removing stubborn graffiti coatings. Two different types of black paint containing nitrocellulose or bitumen as components to strengthen the paint properties were used to create a stubborn graffiti coating on a marble surface. The effectiveness of the nanodetergents in removing the stubborn graffiti coatings was evaluated, and the results revealed a considerable variation in the pace at which the coatings could be removed by the nanodetergents, despite the fact that both paints strengthened with different additives showed similar surface properties. It was found that alkyl polyglucosides are highly efficient in stabilizing water‐in‐oil nanoemulsion systems, including diverse solvent types. These nanoemulsions can be used as specialized "brush‐on, wipe‐off" detergents for the precise removal of different graffiti coatings, which require a specified action period to prevent destroying the underlying original substrate. [ABSTRACT FROM AUTHOR]

The escalating quantities of waste are coming from old bituminous road pavements in Thailand has led to significant environmental and economic challenges. This research explores an innovative solution by investigating the feasibility of using Reclaimed Asphalt Pavement (RAP) as a substitute for natural coarse aggregate in roller compacted concrete (RCC). This study explores optimal proportions between cement to RAP-specifically at ratios of 1:6, 1:8, and 1:10-to achieve maximum dry density. The research includes essential tests, such as dry density and maximum compressive strength assessments, to determine the suitability of the material for compacted concrete production. Intriguingly, the research reveals that the 1:6 ratio not only has the highest dry density and maximum compressive strength but also may minimize environmental impact. These findings align with the ACI 325.10R-95 standard (1995), presenting a promising alternative for engineering applications and contributing to the responsible use of reclaimed materials. [ABSTRACT FROM AUTHOR]

Conventional rejuvenation techniques, such as adding oil-based substances, are proved very effective to improve some properties of aged styrene-butadiene-styrene modified asphalt (SBSMA), including low-temperature cracking resistance and fatigue characteristic. However, its significant reduction of high-temperature properties needs to be closely focused on because it is related to the deformation resistance to rut. The major reason is that these rejuvenators play as viscosity-reducing agents to physically soften the aged SBSMA binder, whereas it does not work to repair the molecular structure and properties of aged SBS. Therefore, this study adopted polyurethane (PU) prepolymer as reactive chemical together with tall oil (TO) as common asphalt rejuvenator for the physicochemical rejuvenation of aged SBSMA. A series of tests including Fourier transform infrared (FTIR) spectra, softening point, viscosity, dynamic shear rheology (DSR), and multiple stress creep recovery (MSCR) were carried out to identify the above-mentioned issues. The results obtained showed that the chemical rejuvenation of PU contributes to fix the molecular structure of SBS degradation products in the aged binder, which is able to improve the high-temperature deformation resistance and elastic recovery of aged SBSMA binder. TO can help supplement partial loss of light components for a better workability of PU rejuvenated binder. Surprisingly, limited use of TO will not significantly decrease the elastic recovery of PU rejuvenated SBSMA at high temperature based on the physicochemical rejuvenation effects. The research achievements can address the worrying issues, especially the early-stage rutting deformation resistance, in terms of fresh rejuvenated SBSMA mixtures. [ABSTRACT FROM AUTHOR]

As materials undergo large-scale yielding or exhibit large sizes of fracture process zone in the crack tip region, multi-parameter fracture concepts should be employed to describe the complex crack-tip stress-strain fields. Fracture resistance curves (R-curves) are an established tool in characterizing the entire fracture process of such materials. However, for complex materials such as bituminous mixtures, the development of these curves is subject to experimental and computational intricacies. In this research, a framework is developed to automate the construction of R-curves for normal and rubberized asphalt concrete (AC) mixtures. AC mixtures are produced using PG58–22 and PG58–28 binders. Limestone and siliceous aggregates are used, and three binder contents are considered for the mixtures. Single-edge notched beam (SE(B)) fracture testing is conducted on AC beams with two different notch patterns. A convolutional neural network (CNN) model is developed and trained over 1260 test images with varying temperatures, notch geometries, and setups. The CNN model was used to detect the growing crack on the beam surface and each crack-detected image was sent to an image processing framework to measure the crack length. Crack extension increments were calculated and synchronized with test time and magnitude of load, load-line displacement, and cumulative fracture energy, and the R-curve could be constructed. A training accuracy of 0.91 was obtained for the model and a loss of below 0.10 as a result of a hyperparameter tuning indicating reliable classifications by the CNN architecture. The R-curves showed desirable agreement for control mixtures at temperatures of 0 °C and −15 °C. As the mixtures are rubberized, the R-curves showed favorable agreement in the crack blunting phase, transition zone, as well as the unstable propagation phase at −20 °C. Cohesive energy magnitudes were compared for the two methods with a Pearson coefficient of 0.81 while fracture rate and fracture energy magnitudes showed favorably close magnitudes with coefficients of 0.89 and 0.98 respectively. • R-curves of asphalt concrete mixtures were constructed using an automated procedure. • Image data pre-processing is conducted using CNN to classify images containing cracks. • The accuracy of the CNN model was enhanced to 0.91 after hyperparameter tuning. • The R-curves for rubberized mixtures were desirably close in all fracture phases. [ABSTRACT FROM AUTHOR]

• Performing temperature sweep test to generate master curves for viscoelastic properties of bitumen. • Optimizing the number of frequencies and temperatures to develop master curves of asphalt mortar and mixture. • Reducing the time and cost of dynamic modulus test without missing the accuracy of master curves. This study aimed to assess the feasibility of substituting temperature sweep tests for frequency sweep tests and explore the potential of utilizing fewer temperatures and frequencies in dynamic modulus tests to formulate viscoelastic properties master curves. The results indicated that master curves derived from temperature sweep tests mirrored the trends and values obtained from frequency sweep tests, presenting a viable alternative for constructing viscoelastic properties master curves of bitumen. Furthermore, models fitted to dynamic modulus test results at three temperatures and three frequencies exhibited comparable primary parameters, values, and trends to those derived from the complete dataset. The model fitted on reduced data demonstrated robust performance with correlation and R-squared values exceeding 0.95. Considering a marginal increase of about 5% in Residual Standard Error (RSE) values when using the reduced dataset, generating master curves with fewer test results underscored the feasibility and reliability of the original master curves. [ABSTRACT FROM AUTHOR]

This paper provides an overview of rubber bitumen (RB) modification mechanisms, factors affecting storage stability, and characterization methods. The focus is on summarizing the methods to improve the storage stability of RB. Results indicate that the modification of RB primarily involves swelling and degradation. The settling velocity of crumb rubber (CR) is influenced by the particle size, density, and bitumen viscosity. To evaluate the storage stability of modified bitumen, widely applicable and preferred methods include softening point and rheological property tests. The storage stability of RB can be improved by increasing the swelling rate of CR, promoting crosslinking between CR and bitumen, and reducing CR agglomeration. Commonly used improvement methods include CR selection, the Terminal Blend (TB) curing process, adding modifiers, solubilization blending, the screw extrusion process (SEP), chemical reagent activation, and physical energy activation. The TB curing and SEP are more suitable for engineering-scale applications and yield improved results. However, high production temperatures may compromise the mechanical properties of CR, leading to drawbacks such as high energy consumption and environmental pollution, a problem requiring further exploration. Utilizing bitumen analogs rich in aromatic fractions as solubilizers for CR pretreatment has emerged as an effective option, offering advantages such as simplicity, resource conservation, and favorable improvements. Future research should focus on a deeper investigation of these processes. [Display omitted] • Methods to improve the compatibility of crumb rubber with bitumen are summarized. • Different characterization methods for storage stability are evaluated. • Reducing the crosslink density of rubber improves rubber bitumen storage stability. • Solubilization blending can be considered a sustainable and capable approach. [ABSTRACT FROM AUTHOR]

[Display omitted] • All-atom simulations are impractical for bitumen microscale phenomena; we introduce a United Atom model alternative. • The force field surpasses other UA models when modelling large molecules, mirroring geometric, thermodynamic, and kinetic properties. • The force field features 17 bead types and 287 potentials, covering a variety of molecules for bitumen modelling. • The force field achieves a 100-fold increase in performance in MD simulations of bitumen. • The force field allows microsecond, micrometer MD simulations for bitumen SARA phase separation exploration. This paper presents a United Atom (UA) force field for simulating hydrocarbon molecules in bituminous materials, integrating explicit hydrogens into beads with their parent atom. This method simplifies all-atom molecular models, significantly accelerating Molecular Dynamics (MD) simulations of bitumen by 10 to 100 times. Key advantages include halving the particle count, eliminating complex hydrogen interactions, and decreasing the degrees of freedom of the molecules. Developed by mapping forces from an all-atom model to the centers of mass of UA model beads, the force field ensures accurate replication of energies, forces, and molecular conformations, mirroring properties like pressure and density. It features 17 bead types and 287 interaction types, encompassing various hydrocarbon molecules. The UA force field's stability, surpassing all-atom models, is a notable achievement. This stability, stemming from smoother potential energy surfaces, leads to consistent property measurements and improved stress tensor accuracy. It enables the extension of MD simulations to larger spatiotemporal scales, crucial for understanding complex phenomena such as phase separation in bituminous materials. This foundational work sets the stage for future developments, including refining parameters and introducing new bead types, to enhance the modeling capabilities of the force field, thereby advancing the application and understanding of bituminous materials. [ABSTRACT FROM AUTHOR]

• The new approach to fatigue life determination, based on pseudo strain energy density was developed. • The energy consumed to counteract the healing effect is considered in this approach. • The new test procedure for Dynamic Shear Rheometer was proposed and named: Discontinuous Linear Amplitude Sweep test (named D-LAS) • Various asphalt mastics were evaluated according to the newly developed method. • Fatigue life of tested mastics exhibits logarithmic growth with an increase in the duration of rest periods. Rest periods between cyclic loads can lead to recovery of damage and extension of fatigue life. This phenomenon is referred to as healing. Healing is clearly observed in bituminous materials, such as asphalt mastics, which belong to the components of asphalt mixtures. Due to the nature of road pavement traffic loading, which is characterized by series of intermittent pulses with rest periods, consideration of healing is necessary for accurate fatigue life estimation. Nevertheless, the vast majority of existing methods relies on relationships established using continuous load conditions. The paper presents a new approach to fatigue life determination, based on pseudo strain energy density. Two components of energy released in fatigue test are considered: the energy responsible for damage growth and the energy consumed to counteract the healing effect. Theoretical derivations were verified in experimental tests, which were performed on asphalt mastics using the Dynamic Shear Rheometer (DSR). It was shown that fatigue life increases with the duration of rest periods on a linear-log scale. Moreover, fatigue life and healing abilities of the analysed asphalt mastics were affected by the type of bitumen and filler, as well as the ageing process. [ABSTRACT FROM AUTHOR]

Volatile organic compound (VOC) emissions are becoming an increasingly significant issue because of the increasing demand for bitumen in road engineering. This study attempted to develop a type of fume-suppressed bitumen with good comprehensive performance. Initially, 1, 2, and 3% organic montmorillonite and 2, 3, and 4% waxy warm-mix agents were utilised to modify bitumen. Subsequently, the fume suppression and physical and construction performances of the modified bitumen were evaluated, and the modified bitumen with the best comprehensive performance was determined. On this basis, constant- and variable-temperature heating modes were designed to verify the fuel suppression performance of the modified bitumen thoroughly. Finally, the modification mechanism of modified bitumen was investigated via atomic force microscopy. The results indicate that the modifier had the greatest impact on the ductility of the modified bitumen in terms of its physical performance. Although waxy warm mixed agents increase VOC emissions, organic montmorillonite can inhibit this effect. The modified bitumen, composed of 2% organic montmorillonite and 2% waxy warm mix agent, has the best comprehensive performance, with a 40.6% emission reduction rate under constant temperature heating mode and 46.4–28% range from 200 ℃ to 120 ℃ under another mode. The waxy warm mix agents and organic montmorillonite-modified bitumen developed into continuous and dispersed phase systems, respectively, leading to variations in the modified bitumen's physical performance and VOC emission capacity. In contrast, the composite-modified bitumen exhibited a two-phase structure with the surface morphology of an 'egg tray'. This unique structure enhances the heating surface area and facilitates heat conduction, improving the bitumen performance during construction. [Display omitted] • Consideration was given to the VOC emission reduction effect caused by the decrease in viscosity of bitumen. • The efficacy of fume suppression asphalt was verified in two heating modes. • A fume suppression asphalt with commendable comprehensive performance was designed. [ABSTRACT FROM AUTHOR]

Quality of aggregate material reflects the physical, chemical and mineralogical properties of source rock. Limestone is main source of crushed rock aggregate, which is largely used by construction industry. There are few geological formations in Kohat-Potwar province which qualify the specific criteria for utilization as aggregate in building material. Khairabad Limestone exposed in Kalabagh area in Western Salt Range contains colossal quantity of minable aggregates. That's why, we quantitatively examined this limestone of Paleocene age through several physical, chemical, mineralogical, engineering and mechanical tests to evaluate its aptness as aggregate material. AASHTO, ASTM, BS and NHA designated engineering tests including Los Angles Value (26.59%), Aggregate Impact Value (13.91%), Aggregate Crushing Value (12.84), soundness value (1.84%), coating and stripping of bitumen (96.4%), specific gravity (2.7), water absorption (0.83%), unit weight (1.65 g/cm3), total (elongation + flakiness) index (22.78%), and petrographic analysis (ASR and ACR) revealed that it is highly feasible aggregate resource with suitable properties. Investigated reserve is vast and thick enough to provide aggregate material to nearby local construction as well as national megaprojects. It would be a good contribution to the rising demand of construction materials in the country. [ABSTRACT FROM AUTHOR]

In this paper, micromechanical models are used to predict the 3D viscoelastic behaviour of asphalt mixtures (with volume fraction of aggregate particles up to 87%) from the mechanical properties of their constituents. To fulfil the objective of study, complex modulus tests are conducted on bituminous materials at three different scales: bitumen, asphalt mastics and asphalt mixtures. The volume fraction of particles varies from 0% (bitumen) to 15%, 25%, 35% (asphalt mastic) and up to 87% (asphalt mixture). In the experimental program, complex modulus of bitumen, asphalt mastic and asphalt mixtures at different temperatures, frequencies are measured. For asphalt mixtures, measurements of complex Poisson's ratio are also performed. The rheological model 2S2P1D is used to simulate the 3D viscoelastic behaviour of tested bituminous materials. From the experimental results and simulations, two micromechanical models (self-consistent and generalized self-consistent model) are used to predict the complex modulus and complex Poisson's ratio of asphalt mixtures. The obtained results show that both micromechanical models give the good prediction of complex modulus for asphalt mastic where the volume fraction of aggregate particles is lower than 35%. At asphalt mixture scale where the volume fraction of particles is up to 87%, only simulation using the generalized self-consistent model can show good results. The prediction using the generalized self-consistent model at the mixture scale can be applied for both complex modulus and complex Poisson's ratio. In addition, the prediction of complex modulus and complex Poisson's ratio of asphalt mixtures becomes better when the asphalt mastic instead of bitumen is considered as viscous matrix. ● Relationships between 3D LVE properties of asphaltic materials are built. ● Large volume fraction of filler/aggregate is considered (from 0 up to 87%). ● Rheological model parameters are linked with volume fraction of filler/aggregates. ● Complex modulus/complex Poisson's ratio is predicted using micromechanical models. ● Asphalt mastic instead of bitumen is considered as the matrix phase of mixture. [ABSTRACT FROM AUTHOR]

Bitumen-aggregate interfaces are the weak points in asphalt mixtures determining the material failure. Previous studies were focused on interfacial failure without a clear understanding to the coupled size effects of bitumen film thickness and aggregate roughness on the failure mechanisms. This study investigates the bitumen-aggregate interface failure mechanisms with the coupled size effects and provide a mechanistic model for interface pull-off strength prediction. Pull-off tests were conducted at five levels of aggregate roughness (0.803 µm-22.09 µm) and four bitumen film thicknesses (30 µm-60 µm). A modified Kendall model was developed to predict the interface pull-off strength, addressing the coupled size effects. Results indicate that a thin bitumen film thickness (30 µm-40 µm) and a low surface roughness (<2.36 µm) yield a higher pull-off strength(1225–1470 N). Thicker bitumen films showed more cohesive debonding, reducing the pull-off strength. When aggregate roughness increases but remains below 2.36 µm, the contact area increases, resulting from an interlocking effect between bitumen and aggregate. Beyond 2.36 µm, aggregate surface spines appear and puncture bitumen film, causing a decreased contact area and decreased pull-off strength. The modified Kendall model can accurately (within a 10 % error) predict bitumen-aggregate interfacial pull-off strength accounting for the coupled size effects of the bitumen film thickness and aggregate surface roughness. [Display omitted] • Thinner bitumen film causes higher interfacial bonding before being punctured. • Lower roughness (<2.36 µm) reduced interfacial bonding by less contact areas. • Higher roughness (>5.01 µm) reduced interfacial bonding by punctured bitumen films. • Interfacial pull-off strength is modeled by a mechanistic model with size effects. [ABSTRACT FROM AUTHOR]

The high global need for non-renewable resources such as bitumen for the construction of flexible pavements is a foremost concern in the pavement industry. Thus, researchers are looking for novel approaches such as bio-modifiers to reduce dependency on bitumen. This study investigated the effect of the modified waste cooking oil beads (MWCOBs) as a bio-modifier on the rheological properties, morphological properties, and chemical characteristics. The waste cooking oil (WCO) was pre-processed and modified at two ratios (45:55 and 50:50) with the SBS to form the rubbery material (MWCOBs). The base bitumen (BB) with 60/70 grade was blended with five percentages of MWCOBs for each ratio (5%, 10%, 15%, 20%, and 25%). The results indicated that viscosity has systematically increased with increasing content of MWCOBs and provided a better response at higher temperatures. Adding 5 wt% of MWCOB-A and MWCOB-B improves the viscosities to 513 cp and 562 cp at 135 ℃ respectively compared to 429 cp of BB. The incorporation of the MWCOBSs substantially enhances the elasticity and stiffness of modified bitumens. Additionally, based on the rutting and fatigue parameters, the incorporation of the MWCOBs provides enhanced performance. The 15 A and 15B demonstrated a performance grade (PG) 76 with failing temperatures of 76.2 °C and 78.7 °C respectively. However, 5B exhibited fatigue failure at 13 °C, whereas all other modified bitumens demonstrated fatigue parameter values below 5000 kPa. The separation indices (SIs) based on complex modulus at a temperature of 64 °C of modified bitumen are within the specified range regardless of the 25 A and 25B with SIs of 1.27 and 1.36 respectively. The master curve of 15 A demonstrated higher stiffness at a lower frequency than other bitumen curves and is less stiff at a higher frequency. The field emission scanning electron microscope (FESEM) investigation showed that the MWCOBs are dispersed in the base bitumen and produced a homogeneous matrix. In conclusion, the modified bitumen 15 A and 10B have shown optimal rheological performance and could be utilised as a sustainable bio-modifier. • Modification of waste cooking oil in the form of beads significantly enhanced the bitumen performance. • WCO promotes the swelling and homogenous distribution of SBS, thus improving the storage stability of modified bitumen. • MWCOBs-modified bitumen improved the viscoelastic properties of modified bitumen. • MWCOBs-modified bitumen decreased the rutting and improved the fatigue performance. [ABSTRACT FROM AUTHOR]

Bitumen materials will occur a physical hardening effect when stored isothermally in a low-temperature environment, and ignoring the physical hardening factor has become one of the important reasons for premature cracking of asphalt pavement during the service period. This paper investigates the response of bitumen binder and bitumen mastic to physical hardening effects at different storage temperatures and times using the bending beam rheometer and dynamic shear rheometer. The response of the material to physical hardening effects is analyzed through temperature index system changes, mathematical model fitting, and stiffness master curve fitting. Results indicate that the response of the material to physical hardening effects can be classified into two stages: the rapid growth and the gradual stabilization periods. The response time of these two stages is related to factors such as aging degree and storage temperature. The physical hardening effect will cause the temperature loss of the material at low temperature, and its influence law on T S 60 = 300 MPa and T m 60 = 0.300 is different. It is recommended to extend the isothermal storage time specified in the test from 1 h to 9 h, considering the time cost and the change in temperature index. Moreover, the stiffness master curve study revealed the occurrence of the "tail drift" phenomenon. • Physical hardening effects cause temperature loss in bitumen, even over a grade. • Recommend extending BBR test storage to 9 h for better scientific validity. • "Tail drift" occurs during the fitting of the stiffness master curve. • The Logistic model can well fit the S and m values in the physical hardening process. [ABSTRACT FROM AUTHOR]

The interaction forces were investigated between matrix bitumen and four kinds of aggregates, including basalt, granite, limestone A, and limestone B in various pH solutions. The aim was to accurately evaluate the water damage resistance of bitumen mixtures at macroscopic and microscopic levels with a conjunctive method of boiling water tests, atomic force microscopy (AFM) colloidal probe technique, zeta potential measurements, and molecular dynamics simulation. Macroscopic evaluation was conducted through indoor water-boiled flaking rate tests to analyze the flaking rate and adhesion class of bitumen and aggregate. The microscopic forces were measured by AFM probe technique between bitumen and aggregate, zeta potential measurements were carried out and the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was employed to interpret the bitumen–aggregate interaction behaviors. Molecular dynamics simulations were considered to explain the interface binding tendency between bitumen and aggregate. The AFM force measurements showed that the long-range repulsion forces changed to attractive forces and high adhesive forces with the pH change from 4 to 6. However, the strong long-range repulsive forces were decreased, compounded with a relative low adhesion in the alkaline solution. The long-range force between granite and bitumen was a strong attraction, and adhesion was strong when the solution pH was 4, which is a more special phenomenon. It may be due to the electrostatic attraction between the positive charge on the granite surface and the negative charge on the bitumen surface. Zeta potential values of bitumen droplets and aggregate particles exhibited an overall decreasing trend with increasing solution pH, and the variation of surface potential value is consistent with the variation trend of long-range force between aggregate and bitumen. The microscopic forces between bitumen and aggregate measured by AFM were validated by molecular dynamics simulations, revealing a strong correlation between debonding work and interfacial forces. The results indicate that the adhesion between aggregates and bitumen in aqueous solution followed the order: limestone A > limestone B > basalt > granite, and alkaline conditions are not conducive to preventing water damage in bitumen mixtures. It provides insights into the water stability mechanism of bitumen-aggregate at macroscopic and microscopic scales, offering theoretical support for preventing water damage in bitumen pavements. • The adhesion of limestone to bitumen is better than that of granite and basalt. • The alkaline conditions are not favorable for preventing water damage in bitumen mixtures. • The DLVO theory provides a good explanation of the bitumen-aggregate adhesion mechanism. • Molecular dynamics simulation results are consistent with the results obtained from the AFM test. [ABSTRACT FROM AUTHOR]

Supplementary Cementitious Materials (SCMs) have been widely accepted in the concrete industry due to their varied advantages. However, the same reflects little in the case of Cementitious Stabilized Aggregates (CSA). The present work focuses on the potential and practical application of SCMs in CSA based on laboratory-based growth and performance analysis followed by their design aspects and economic advantages. Fly ash and Crushed Granulated Blast Furnace Steel Slag (GBFS) were chosen at 30% and 50% by weight of cement as partial replacement to cementitious material to prepare a cementitious stabilized mix of aggregates. Mechanical and microstructural properties were then assessed through critical tests like Unconfined Compression Strength (UCS), Flexural Strength (FS), Flexural Modulus (FM) and Thermogravimetric Analysis (TGA) over subsequent curing periods. Results from these tests revealed improved performance on including SCMs in significant proportion when compared to cement mix of aggregates. Power-law relationships proved optimal for comprehending strength and stiffness growth in CSA. Mixes with SCMs exhibited higher growth coefficients and growth rates for UCS, FS and FM. TGA data showed higher bound water loss %, indicating increased hydration for SCMs mixes. Composite pavement design revealed a 5 mm increase in the bituminous layer for cement-fly ash mix, while it remained unchanged for cement and cement-GBFS mix. Economic analysis demonstrated SCM cost savings of 6% to 16% in the CSA layer in mixes with SCMs. [Display omitted] • Performance Evaluation of fly ash and GBFS-infused CSA through FM, FS and UCS. • Results showed enhanced mechanical performance, supported by TGA findings. • Simulated power-law relationships in CSA for strength and stiffness behaviour. • Composite pavement design with SCMs-infused CSA showed significant cost savings. [ABSTRACT FROM AUTHOR]

This study has focused on the effect of cement kiln dust (CKD) as a waste filler on the rheological and nano-mechanical properties of bituminous mastic in comparison with limestone powder (LSP) as an ordinary filler. Mastics were prepared using three filler to bitumen (F/B) ratios including, 0.4, 0.8 and 1.2. The strategic highway research program (SHRP) standard and multiple stress creep recovery (MSCR) test methods were used to evaluate the behavior at high performance temperatures. Also, SHRP standard and time sweep methods were performed to evaluate the fatigue behavior at medium performance temperatures. Low temperature properties were examined by bending beam rheometer. Field emission scanning electron microscopy (FESEM) was used to evaluate the quality of filler distribution in the mastic. Furthermore, the nano-mechanical properties of mastics were examined by atomic force microscopy (AFM) including topography roughness, elastic modulus and adhesion force. Fundamental evaluations with AFM indicated that, at a constant F/B ratio, CKD filler with a higher fineness and specific surface area showed higher elastic modulus and lower adhesion than LSP. Also, the FESEM analysis for filler distribution showed the highest homogeneity coefficient at F/B ratio of 0.8. A significant relationship was observed between SHRP rutting parameter and creep variables in MSCR method. Both methods indicated a superior rutting resistance for CKD than LSP. Although, there was no clear relationship between SHRP fatigue parameter and the time sweep outcomes. • Rheological and nano-mechanical properties of mastics containing CKD compared with LSP. • Quality of filler distribution in mastic was evaluated with EDS and definition of HC parameter. • Adhesion force, stiffness, and phase changes were studied by AFM. • Rheological properties of mastics examined by MSCR, time sweep and SHRP standard methods. • CKD with finer gradation outperformed LSP in rutting resistance, and the opposite was true for fatigue. [ABSTRACT FROM AUTHOR]

The utilization of waste plastics as an additive in warm mix asphalt (WMA), which is an environmentally friendly technology, by pyrolysis method is an emerging concept. In this study, WMA additive was synthesized from char (C) and wax (W) products obtained from the pyrolysis of polypropylene (PP) type waste plastics. Seven different pyrolysis modified bitumen were prepared as PP 6%C, PP 6%C-3%W, PP 6%C-6%W, PP 6%C-10%W, PP 3%C-6%W, PP 1%C-6%W and PP 6%W. Base bitumen and Sasobit® 3% (by weight of bitumen) modified bitumen were used as control groups. The rheological properties of the binders were investigated by Rolling Thin Film Oven, Pressure Aging Vessel, Rotational Viscometer, Dynamic Shear Rheometer and Bending Beam Rheometer tests, and the morphological properties were analyzed by Scanning Electron Microscope, Fourier Transformed Infrared Spectroscopy and Zeta Potential analysis. Asphalt mixture performance characteristics were evaluated by Marshall Design, Hamburg Wheel Tracking and Thermal Stress Restrained Specimen Tests. Binder test results demonstrated that with the addition of PP 6%C-6%W and Sasobit® 3%, the viscosity of bitumen decreased significantly and accordingly the plant temperature reduced by 14ºC and 9ºC. Besides, PP 6%C-6%W modified bitumen performed better than base bitumen at low, medium and high temperatures. Sasobit® 3% improved the high temperature performance of the bitumen. The additive-bitumen modification mechanism involved physical process. Furthermore, the additives were well distributed in bitumen and no agglomeration was observed. WMA-1 (PP 6%C-6%W) and WMA-2 (Sasobit® 3%) have 5% and 9% higher Marshall stability than hot mix asphalt (HMA), respectively. Moreover, the addition of PP 6%C-6%W and Sasobit® 3% increased the rutting resistance of the mixture by 9% and 21%, respectively. Moreover, PP 6%C-6%W improved the low temperature performance of the mixture by decreasing fracture temperature by 3ºC and increasing the fracture strength by 15%. All in all, PP pyrolysis products have strong indicators to become a WMA additive. [Display omitted] • The addition of Sasobit ® 3% and PP 6%C-6%W reduced the bitumen viscosity and, consequently, mixture's plant temperature. • PP 6%C-6%W and Sasobit® 3% increased both Marshall stability and rutting resistance of the mixture. • PP 6%C-6%W also enhanced the low temperature cracking resistance of the mixture. • WMA additives are uniformly distributed in bitumen and do not agglomerate. • The additive-bitumen modification mechanism is in the form of physical blending. [ABSTRACT FROM AUTHOR]

Non-bituminous binders with sustainable characteristics have been developed as potential roofing materials. A vegetable colophony rosin ester, waste cooking oil, waste crumb rubber and a blend of recycled high-density polyethylene (HDPE) and polypropylene (PP) have been used for binder formulations. Rheological, calorimetric and technological characterizations have been performed to assess the compatibility among binder components and optimal compositions. Additionally, thermal conductivity, heat capacity and solar radiation tests have been performed on selected non-bituminous and bitumen-based binders. Solar radiation experimental set-up has been simulated by Computational Fluid Dynamics (CFD) in order to get a deeper insight into heat transmission mechanisms involved. A binder formulation composed of 40 wt% maleic-modified rosin ester, 32 wt% waste oil, 20 wt% crumb rubber and 8 wt% recycled HDPE/PP blend has shown suitable mechanical properties and solar behaviour for roofing materials. The use of recycled thermoplastics and elastomers imparts material with a hybrid character, showing enhanced flexibility and softening points, respectively, at low and high in-service temperatures. Its solar behaviour is comparable to that of the modified bitumen, with a similar heat absorption from Sun (about 30 %) but lower heat storage capacity at ambient temperature. • Non-bituminous binders designed with sustainable characteristics for roofing. • Binder formulated with a rosin ester and wastes from cooking oil, tyre and HDPE/PP. • Binders show good flexibility and viscoelastic moduli in a wide temperature range. • Compared with bitumen, binder absorbs similar heat from Sun but stores less energy. [ABSTRACT FROM AUTHOR]