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The useful life of pavements determines the design of asphalt mixtures. However, premature structural failures and low durability are one of the main problems in pavement engineering today. The action of loads produced by traffic, exposure to environmental factors and the inadequacy of conventional designs of asphalt pavements are some of the main problems associated with the durability of the pavement. The modification of asphalt binders is an alternative that has been used for some years to improve the properties of bituminous material. Among the modifying materials are elastomers, a class of polymers with elastic properties that can be heattreated. In this study, the asphalt was modified by wet means by adding 5, 10 and 15% of Thermoplastic Polyurethane (TPU) by weight of the binder. Subsequently, standard samples were prepared with the characterized constituents and mixtures with the modified asphalt cement. Consequently, tests were carried out to obtain the optimal mixture that improves the properties of conventional pavement. The results show that the optimal TPU addition content is 5%. With this percentage, the modified binder presented a greater elastic recovery of up to 5.60% and a reduction of up to 42.6% in penetration compared to conventional asphalt. In addition, using the Marshall method, it was determined that the stability of the modified mixtures was much higher than that of standard mixtures for light, medium and heavy traffic; so, they will have a higher resistance to deformation and better fatigue behavior. [ABSTRACT FROM AUTHOR]

Shakedown limit has been perceived as a useful guidance in pavement structure design against rutting. However, temperature, as one key factor influencing the shakedown limit of asphalt pavements, has barely been considered. In this paper, the shakedown phenomenon was first identified from wheel tracking tests for a pavement structure consisting of a dense bituminous macadam layer and a granular layer at 40°C. Based on a previously developed shakedown approach and the material elastic and plastic properties obtained through a series of tests, lower-bound shakedown limits of the layered system were determined and compared with the wheel tracking test results. Following that, an empirical relation between temperature and cohesion of asphalt mixture was suggested. A temperature-dependent shakedown approach was then proposed which can quickly obtain the shakedown limits of asphalt pavements over a range of temperatures. Results show that the shakedown limits decrease markedly with increasing temperature, accompanied by a shift of the failure mode from a granular layer failure to an asphaltic layer failure. One effective and economic way to enhance the pavement performance under high temperature is improving shear strength properties of asphalt mixtures. By using this method, pavement stability against rutting can be evaluated efficiently at any temperature. [ABSTRACT FROM AUTHOR]

To produce cationic bitumen emulsions, bitumen is used, whose penetration is not lower than 90 mm-1. Such bitumen has a small plasticity interval, which leads to a deterioration in its heat resistance at elevated temperatures and narrows the scope of application of emulsions based on it. Based on the review of emulsion modification methods, the modification has been proposed that involves mixing the finished bitumen emulsions with aqueous cationic latex. The process of interaction between a bituminous emulsion and an aqueous cationic latex has been considered. A mechanism for the disintegration of the modified bitumen emulsion on the surface of mineral materials was proposed. The emulsifiers have been selected and the composition of the aqueous phase has been chosen based on the analysis of surface tension isotherms. The influence of the modification on the properties of bitumen emulsions was investigated. It was established that the main physicochemical characteristics of the interphase surface accept similar values for the aqueous phase and emulsions based on it. It has been proven that the introduction of aqueous cationic latex quite moderately affects the basic physical-mechanical properties of emulsions, which makes it possible not to change the main technological parameters when using them. It was established that increasing the concentration of the polymer in the emulsion has a positive effect on the physicalmechanical properties of the binder. With an increase in the concentration of the polymer to 6 % the softening temperature increases by 16 °C, elasticity is 74 %, and the holding capacity at minus 25 °C is approaching 100 %. Improving the physical-mechanical properties of residual binder as a result of emulsion modification could increase the durability of layers in a roadbed based on bitumen emulsions and expand the scope of their application in the construction and repair of motorways. [ABSTRACT FROM AUTHOR]

This study examines the effect of weathering on bituminous composites containing polyphosphoric acid (PPA). PPA has been commonly used in bitumen to increase bitumen's stiffness and elastic properties. However, the effect of PPA on bitumen's properties is highly affected by the interplay between PPA and other bitumen modifiers such as liquid and solid additives. Wax-based additives generally reduce PPA's efficacy, and a mineral additive such as montmorillonite (MMT) clay increases PPA's efficacy. MMT has been typically used to enhance the resistance of a bituminous matrix to aging. This paper uses laboratory experiments to evaluate changes in the properties of bitumen containing PPA and MMT when exposed to water. Samples were conditioned in water at 60°C for up to 100 h, and their thermomechanical properties were evaluated at different intervals. The study results showed that the presence of PPA in bitumen alleviates the swelling of MMT when montmorillonite-doped bitumen is exposed to water. However, extended water exposure reduces the elastic properties of bitumen. This is attributed to PPA's losing its branches as water promotes the separation of PPA's branches from its backbone, leading to a reduction in binding energy between bitumen and PPA. The latter was reflected in a rapid loss of bitumen's elasticity, healing capacity, and shear thinning, as water conditioning continued. [ABSTRACT FROM AUTHOR]

In the article bitumen and asphalt concrete qualitative properties depending on using rubber, the crumb is considered. Bituminous binders' comparative physical and mechanical characteristics containing modified crumb are given. It is proved that the increase in the quantity of Kulantau vermiculite leads to a decrease in the thickness of bitumen films on the particle surface. The modification by rubber crumb allows to increase the quality of the bitumen binder, durability of the coatings and to reduce the cost of asphalt coatings, as well as to utilize largetonnage rubber products waste. [ABSTRACT FROM AUTHOR]

In this study acidic sludge was refined by a novel method that involves neutralization and extraction of organic compound by a waste solvent. Study on refined sludge indicated that sulfuric acid and major of impurities were removed from sludge. Moreover, resin and asphaltene and accordingly ductility of sludge increased. In continue, different amounts of sludge residue were added to vacuum bottom for bitumen preparation. Test results indicated that sludge residue improved mechanical property and elastic modulus of bitumen. Thermal tests illustrated fine thermal stability of blends at production temperature. Also, aging data described reasonable durability for samples. Consequently, by this approach not only hazardous acidic sludge was eliminated from environment but also it improved mechanical properties of bitumen. [ABSTRACT FROM AUTHOR]

Back in 1993, Strategic Highway Research Program introduced new mix design method known as SUPERPAVE that is an acronym of Superior Performing Asphalt Pavement. Superpave caters filed performance of bituminous mixes and Superpave gradation chart includes 0.45 power line, restricted zone and control points. In Superpave, the gradation that compliance with the restricted zone was considered less rut resistant as compared to gradation passing outside the restricted zone. This study targets three types of gradations that passed above, below and through the restricted zone. The results show that the gradation passing through the restricted zone not only satisfy Superpave volumetric requirements but also performs better against rutting as compared to gradation passing outside the restricted zone. Resilient modulus (MR) measured through indirect tensile strength setup that defines the elastic properties of bituminous mix under repeated load test. Laboratory study was conducted to find factors that affect the gradation. Two-way factorial design was carried out by using Minitab-15 statistical software and the results reflected that the individual factor i.e. loads duration and temperature as well as interaction of factors has significant effect on the performance of HMA. [ABSTRACT FROM AUTHOR]

This study intended to evaluate the use of waste stone sawdust filler with asphalt binders and compare the mechanical properties of the waste filler-asphalt mastic with those of the asphalt mastic produced using the typical limestone filler. The mastics were prepared at four filler-to-asphalt ratios by volume of asphalt binder: 0.05, 0.10, 0.20, and 0.30. A dynamic shear rheometer (DSR) strain-controlled frequency sweep test was used to evaluate the properties of the control asphalt binder and the mastics. The test used a constant strain of 10% and loading frequencies of 10, 5.6, 3.1, 1.78, 1.0, 0.56, 0.31, 0.178, and 0.1 Hz and was conducted at wide range of temperatures: 10, 20, 30, 40, 50, 60, and 70°C. The test measured the complex shear modulus (G∗) value and the phase angle for the binder and the mastics. The findings of this study showed that the stone sawdust filler demonstrated higher resistance to fatigue and rutting behavior than the limestone filler. However, the elastic behavior of the two asphalt mastics was nearly similar and increased with the increase in volume ratio. It was also found that the best-fit model described the relationship between the volume ratio and each of G∗/sin  δ and G∗cos δ, and the mastic-to-binder modulus ratio was the exponential model with high coefficient of determination (r2). The differences in the G∗ value between the limestone filler and the stone sawdust filler were relatively insignificant particularly at low loading frequencies and high temperatures. Finally, the mastic-to-binder modulus ratio decreased with the increase in loading frequency. [ABSTRACT FROM AUTHOR]

Properties of cement-stabilized gravel modified by emulsified asphalt under freezing and thawing cycle conditions were investigated by adjusting the dosage of cement. Mercury intrusion porosimetry (MIP) and Scanning electron microscopy (SEM) were introduced to analyze the influential mechanism. The results indicate that cement emulsified asphalt stabilized gravel with 5 wt % of cement performed well in both mechanics and frost-resistance. Although the addition of emulsified asphalt would lead to a partial decrease of strength, it can extend the process of strength loss and improve the freezing resistance. The main reason for this is that the permeability can be improved by the filling effects of emulsified asphalt. The frost-heave stress caused by the phase transition of water can also be remitted by emulsified asphalt, the elasticity modulus of which is much lower than the matrix. The generating speed of the micro crack can also be slowed down by emulsified asphalt. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the effect of the warm compaction modifier on the physical and rheological properties of High-viscosity High-elasticity modified asphalt and SBS modified asphalt. Three types of asphalt binder with different concentrations (at 0.3%, 0.5%, 0.8% by weight) of the warm compaction modifier were studied respectively. The influence of the warm compaction modifier on the physical and rheological properties was evaluated by penetration, softening point, and ductility and Dynamic Shear Rheometer (DSR) test. It was evident that the addition of the warm compaction modifier had a significant effect on the stiffness and elasticity behavior of the asphalt both at high and intermediate temperatures. It is indicated by DSR analysis that the warm compaction modifier could increase stiffness and fatigue behavior compared with base modified asphalt. Based on the physical and rheological tests, the concentration of warm compaction modifier was recommended to be at 0.3% by the weight of base modified asphalt. [ABSTRACT FROM AUTHOR]

In this paper, experimental support is provided showing the importance of polyaromaticity on the elastic properties of bituminous binders. Especially the size of the polyaromatic structures seems to play a crucial role. The observations indicate that larger conjugated aromatic structures provide stronger interactions and relate to the elastic behaviour at longer loading times or up to higher temperatures, while smaller aromatic structures determine more the elastic behaviour at short loading times or at low temperatures. In addition to aromatic interactions, natural wax can, upon crystallization, also induce increased elastic effects, especially at low frequencies. A large variety of binders was investigated: bitumen from straight distillation, visbreaking, solvent deasphalting and oxidation were included in the sample set. Average levels of aromaticity were determined by Fourier transform infrared (FT-IR) spectroscopy and by refractive index measurements. Chromatography combined with UV-visible absorption spectroscopy was used as an indicator of the average size of the aromatic structures. Rheological properties were determined using a dynamic shear rheometer, in a temperature range from 0 up to 90 °C. Good relations were observed between the phase angle measurements, at specific test conditions of frequency and temperature, and UV-vis absorption levels at specific wavelengths. [ABSTRACT FROM AUTHOR]

Highlights: [•] The orthotropic property of the PBM creates an elliptical blister propagation front. [•] The orthotropic material property of the PBM is measured using biaxial test. [•] We determined the energy for elliptical adhesive blister propagation. [•] Blister propagation is proportional to orthotropic ratios of the two elastic moduli. [ABSTRACT FROM AUTHOR]

Abstract: In this study, rheological and mechanical properties of bituminous binders and hot mixtures modified by different polymeric additives, Kraton D1101, Kraton MD243 and Evatane®2805, were examined. In all samples, the amount of the polymeric additive was kept constant at 4wt.% of the bituminous binder. The experiments showed that with the addition of the polymer to binder, Marshall stability, retained Marshall stability, indirect tensile strength, tensile strength ratio, stiffness and fatigue life values of the bituminous hot mixtures increased. The effect of the EVA on stiffness modulus and fatigue life was found to be notable. When toughness index values were compared, it was detected that mixtures with SBS- Kraton MD243 demonstrated the highest elasticity, while those with EVA-Evatane®2805 showed the least. The rheological experiments on the binders figured out that by the use of MD243, a new type of styrene–butadiene–styrene additive, low viscosity values could be obtained. This implies that if MD243 is utilized to bituminous mixtures, an effect on bituminous mixtures similar to that created by D1101 addition could be obtained by consuming less amount of energy. [Copyright &y& Elsevier]

Abstract: This paper presents numerical application of a modified Huet-Sayegh (MHS) model for modeling the response of bituminous materials. The model consists of elastic, viscoelastic and viscous response elements. Application of the model for describing the frequency domain response of bituminous materials is presented. To utilize the model for time domain use, a numerical approach is proposed. The proposed numerical approach utilizes the Grünwald Letnikov definition of fractional derivatives. The formulation is first discussed for one dimensional case, and then generalized into three dimensional forms by decoupling the deformation into deviatoric and volumetric components. The 3D formulation is finally implemented into a commercially available strain-controlled finite element program, ABAQUS. For this purpose, a user material subroutine (UMAT) code has been scripted in FORTRAN language. After performing various simulations to verify the UMAT code, application of the material model in performing meso-mechanistic computations for porous asphalt layer is presented. Simulation results are used to illustrate the significance of the linear dashpot in the MHS model. Moreover, results that were obtained from the UMAT code are compared with corresponding results obtained with the built-in material model in ABAQUS. Good agreement in results has been observed. The results have demonstrated the model accuracy and the suitability of the proposed numerical approach to allow the model use in finite element environments. [Copyright &y& Elsevier]

Abstract: The chemical and rheological properties of two asphalts selected from different sources (Urals, Russia; Cold Lake, Canada) were investigated. Analyses of chemical (elemental composition, fractional composition, molecular weights) and physical properties (complex viscosity, loss tangent, shear compliance) were performed on all original and aged (rolling thin film oven test, RTFOT; pressurized aging vessel, PAV) samples. The analyses of the chemical properties of both asphalts revealed higher asphaltene content, higher heteroatom content, and lower aging susceptibility of the Cold Lake asphalt (less significant changes in group composition). Based on its chemical composition, the Cold Lake asphalt was expected to perform better in the rheological tests than the Urals asphalt. The rheological tests confirmed this hypothesis and revealed better low- and high-temperature properties of the Cold Lake asphalt and a slower deterioration of its physical properties upon oxidative aging. [Copyright &y& Elsevier]

• A biphasic random generated model was introduced to simulate microstructure of modified bitumen. • Using 2D or 3D heterogeneous viscoelastic FE models of the BBR test resulted in identical outputs. • Addition of crumb rubber having lower modulus than bitumen improved critical cracking temperature. This paper uses a heterogeneous micromechanical model to evaluate the resistance to thermal cracking in bituminous composites containing granular particulates. Thermal cracking is mainly caused by temperature fluctuations leading to accumulated stress that exceeds the strength of the materials. The presence of various granular particulates significantly affects a material's strength and capacity to release stress. Here, we use a two-dimensional heterogeneous numerical finite element model to evaluate and predict the thermal cracking characteristics of bitumen containing granular particulates such as crumb rubber and taconite. To develop the model, randomly distributed polygons using the Delaunay triangulation method were used to represent taconite and crumb rubber inside a bitumen matrix. The elastic properties of taconite and crumb rubber were assigned to the particulates, and the viscoelastic properties of the bitumen were modeled using a Prony series by implementing a simple fractional viscoelastic model. The study results showed that the flexural creep stiffness and creep rate calculated by the model were in good agreement with the measurements of experiments: the maximum errors were 6.15% for bitumen containing crumb rubber and 13.72% for bitumen containing taconite. Considering that flexural creep stiffness and creep rate are commonly used as indicators of thermal cracking resistance, the newly developed heterogeneous micromechanical model can be used to evaluate the thermal cracking resistance of bituminous matrices containing granular particulates. The model was further used to study the effects of temperature, elasticity, and concentration of particulates on the cracking resistance of the bituminous matrix. For instance, it was found that introducing 16% particulates with an elasticity of 1.02 MPa (representing crumb rubber) to bitumen improves its critical cracking temperature from −25 °C to −29.3 °C. This model provides insights to help the design of bituminous composites with desired cracking resistance properties by incorporating the proper particulates. [ABSTRACT FROM AUTHOR]

Elastic properties of bitumen reservoir change dramatically during thermal production, due to varying temperature and pressure conditions, which affect both the pore fluid and the rock frame. The effect of bitumen on the elastic properties of bitumen sands is widely studied, while the frame effect is commonly ignored. The influence of frame under different pressure and temperature conditions is investigated through laboratory measurements. Natural and artificial samples are compared to investigate the role of rock frame in their elastic properties. Samples with the same bitumen but different porosities are also compared, which reveals that the distinctions between the samples vary with temperature. Theoretical models are also applied to inspect the influence of rock frame, indicating the weak frame. In the end, two samples from Alaska and Alberta are compared, justifying the roles of bitumen and rock frame during the heating process. Our results reveal that rock frame of bitumen sands is quite loose, which may even damage during the heating process; and its influence on the rock elastic property is temperature dependent: at low temperature, its influence is insignificant, while at high temperature, its contribution is more important. These results suggest that for seismic monitoring of bitumen reservoir production, we should emphasize the temperature effect at the early stage and pay more attention to the pressure effect at the later stage of thermal production. • Artificial samples have similar acoustic velocities as natural samples. • The contribution of frame to the moduli of the rock is small at low temperature. • The influence of frame on the rock moduli varies with temperature. • The bitumen sands' frame is loose, and most grains are suspended with only a few contacts. • The influence of frame on the rock moduli increases with temperature. [ABSTRACT FROM AUTHOR]