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Acid sludge is an environmental pollutant that is produced daily in large amounts in used engine oil refineries. Recycling this waste is the primary goal of this paper. This study used 'washing with water' and 'neutralization with quicklime' methods to prepare acid sludge for use in bituminous materials as huge potential disposal. The neutralised sludge by the 'washing with water' method was added to bitumen in the wet blending process at 10, 20, and 30 wt%. This product is brittle without proper adhesion and cohesion and cannot meet the standard limits as an acceptable binder. It performs like long-term aged bitumen, reducing penetration and ductility and increasing the aging potential and viscosity. In another method, the neutralised sludge by adding quicklime was added to the asphalt mixture to replace fine aggregates in 50, 75, and 100 wt%. Using this product decreases the aging potential and moisture susceptibility up to 36.4, and increases rutting resistance up to 34.7%, indirect tensile strength up to 17.3%, and resilient modulus up to 17.3%. Despite the presence of large amounts of heavy metals in acid sludge, using this product in asphalt mixtures is an economical and completely hygienic solution for disposing of acid sludge. [ABSTRACT FROM AUTHOR]

This study investigated the effect of waste toner as a cost-effective enhancement modifier on short-term aging and moisture resistance of asphalt binders and mixtures. Moreover, the mechanism of asphalt binder aging and moisture resistance was reviewed, aiming to provide promising evaluation methods for assessing short-term aging resistance of asphalt binders as well as moisture resistance of asphalt binders and mixtures. First, the aging resistance of neat and toner-modified asphalt (TMA) binders was evaluated using three approaches: rheological aging index (RAI), viscosity aging index (VAI), and chemical functional group indices based on data obtained from Fourier transform infrared spectroscopy (FTIR) analysis. To measure viscoelastic and viscosity characteristics of neat and TMA binders, a dynamic shear rheometer (DSR) and a viscometer were employed, respectively. Second, the moisture resistance of asphalt binders and mixtures were investigated based on analyzing the infrared spectrum and tensile strength ratio (TSR), respectively. The findings indicated that modifying binder with low percentages of waste toner enhanced the short-term aging resistance. Also, TMA binders containing 12% of waste toner presented a significant improvement in moisture resistance of asphalt binders and mixtures. [ABSTRACT FROM AUTHOR]

• Predicting J nr and %R of modified bitumens deterministically by using MGGP based on MSCR test results. • Predicting probability of different traffic levels by using logistic regression technique. • Determining the critical dosages of crumb rubber, SBS, and PPA modifiers that alter the traffic levels. This study aims to develop deterministic and probabilistic prediction models for the multiple stress creep and recovery (MSCR) test. For this purpose, crumb rubber, polyphosphoric acid, and styrene–butadiene–styrene bitumen modifiers have been used with different dosages to modify high-temperature performance of PG 58–28 and PG 64–22 base bitumens. The MSCR test has been performed at different temperatures. Deterministic models are developed by the multi-gene genetic programming technique for each modifier individually, and the non-recoverable creep compliance (J nr) and percent recovery (R) parameters are predicted. The accuracy of deterministic models is suitable and the performance of R models has been better than J nr models. Furthermore, a comprehensive probabilistic model has been developed by using the logistic regression technique to predict different traffic levels. The accuracy of the probabilistic model is 0.85. The sensitivity analysis has been performed on this model and the effect of changes in the modifier dosage and temperature on the traffic levels have been investigated. Results show that using the probabilistic model, it is possible to find a range of modifier's dosage in which the traffic level is desired. [ABSTRACT FROM AUTHOR]

• 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]

• Fractional viscoelastic model can characterize low-temperature mechanical behaviour of bio-modified bitumen. • Bio-modifiers effects on bitumen's properties is highly source dependent. • Bio-modifiers have positive effect on bitumen performance at low service temperatures. • Bio-modifiers enhance bitumen behaviour during both creep-loading and relaxation. Cracks associated with large temperature fluctuation especially in cold regions are among prevalent pavement distresses. Binder rheology is typically found to the key factor affecting low temperature cracking resistance. Recognizing the importance of binder properties, many road authorities are requiring the use of special additives to enhance low temperature properties of binder to alleviate low temperature cracking problems. However, most of these modifiers are petroleum-based products with unstable price and depleting resources. Therefore, the asphalt industry is looking for renewable alternatives for modifying bitumen and improving its low temperature performance. Accordingly, this paper incorporates laboratory experiments and modeling to study merits of modifying bitumen with several bio-binders to enhance low temperature properties of bitumen. To investigate rheological properties at low temperatures, an extended bending beam rheometer test was used incorporating a simple fractional viscoelastic model based on the general power law. The data collected during loading and unloading portion of the test was used to evaluate the effect of introduction of bio-modifiers on low temperature properties of bitumen. The experimental results showed that introduction of bio-modifiers to bitumen significantly enhanced bitumen behavior both during creep loading and relaxation. The results of finite element modeling based on the extended bending beam rheometer geometry and boundary conditions proved that the simple fractional viscoelastic model can accurately characterize low-temperature mechanical behavior of bio-modified bitumen. [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]

• Measuring LVE properties of bituminous composites through a multiscale simulation. • Multiscale simulation has more accuracy than the generalized self-consistent scheme. • 3.35 mm is the best mortar cutting size to find mixture behavior with NMAS of 19 mm. Viscoelastic properties of asphalt mixture were studied through a multi-scale approach, including bitumen, mastic, mortar, and mixture length scale. Biphasic and triphasic finite element modeling were employed to construct the heterogeneous models of bituminous composites, including matrix, inclusions, and air voids. The 2S2P1D model consisting of two springs, two parabolic creep elements, and one dashpot was fitted on the output of the numerical model, i.e., dynamic modulus (E*) and phase angle (δ), to accurately determine the Prony series. Then, the data of each scale was utilized as a matrix for the next scale's model. Three cutting sizes, including 3.35, 2.36, and 1.7 mm were selected based on the previous experimental study of Khodadadi et al. (2021) to generate the mortar model and find the best length scale of the matrix. In addition, the numerical results were compared with the results of the generalized self-consistent scheme model as an analytical approach. Both numerical and the generalized self-consistent scheme models yield adequate results; nevertheless, the numerical solution has more accuracy than the analytical model. The cutting size of the mortar scale had a considerable effect on the LVE properties of the mixture. The result showed that a cutting size of 3.35 mm is more suitable for a mixture with a nominal maximum aggregate size of 19 mm. These findings were consistent with the experimental results. [ABSTRACT FROM AUTHOR]