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• 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]

[Display omitted] Introducing waste plastics in bituminous composites can increase the composites' durability, provided that the waste plastics are compatibilized with bitumen to avoid phase separation. To enhance the compatibility of plastic particles with bitumen, various treatment methods were used to alter their physical and chemical characteristics. Considering the complex nature of bitumen, knowing the properties of isolated particles is not sufficient to indicate their performance in a bituminous composite. Therefore, there is a need to quantify the efficacy of each treatment method directly. While the plastic-bitumen interface can be examined via advanced characterization instruments such as atomic force microscopy, those methods are often relatively complicated and time consuming for formulators and designers. Here, we use a heterogeneous micromechanical model to calculate compatibility indicators; the model is tailored for viscoelastic bituminous composites containing waste-plastic particles. With experiments using a dynamic shear rheometer and a bending beam rheometer, data were generated on the bitumen with and without waste plastics having various surface treatments. The model was then used to calculate the Effective Volume Filling (EVF) ratio to indicate the interaction between plastics and bitumen as a measure of compatibility. A higher EVF ratio indicates greater compatibility. The corresponding EVF ratio was found to be higher for the oil-treated plastics compared to non-treated plastics, demonstrating higher compatibility of the oil-treated plastics with bitumen. This study promotes sustainability in construction by facilitating the use of waste plastics and enhancing the cracking resistance of bitumen. [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]

• Using a multi-scale approach to find viscoelastic properties of three scales: mastic, mortar, and mixture. • Threshold stress is evaluated to characterize linear viscoelastic properties of the mortar scale. • Mortar with the cutting size of 3.35 mm has the closest behavior to the asphalt mixture with an NMAS of 19 mm. The mortar component plays an essential role in forming different asphalt mixture distresses. The fine aggregate size affects the viscoelastic behavior of mortar. In this study, three cutting sizes of 3.35, 2.36, and 1.7 mm, on the aggregate grading curve were considered to construct the mortar scales, namely mortar (I), (II), and (III), respectively. With a unique loading mode, a frequency sweep test was performed on four different length scales, including bitumen, asphalt mastic, mortar, and asphalt mixture, to make a direct comparison through a multi-scale approach. Also, a stress sweep test was conducted to find the mortar scale's linear viscoelastic domain. The results indicate that different mortar types have variable linear viscoelastic domains. The master curves of dynamic modulus (E*) and phase angle (δ) show that adding filler to bitumen has more effect on the E* than the δ. Although scaling up from the mastic to mortar (II) causes a significant difference between the viscoelastic parameters, the results remained approximately the same. The main gap between the mixture and mentioned sub-scales is filled with mortar (I). While the Cole-Cole diagrams demonstrate that the bitumen to mortar (II) scales have the same behavior, the closest scale to the mixture is the mortar (I). Therefore, using a cutting size of 3.35 mm is recommended to fabricate mortar (for asphalt mixture with a nominal maximum aggregate size of 19 mm) instead of 2.36 mm, which was suggested in previous studies. [ABSTRACT FROM AUTHOR]