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In this study, the mutual effect of polyphosphoric acid (PPA) and ethylene bis(stearamide) (EBS) modification was examined on the high and low service temperatures and viscosity of a performance grade (PG) 58-22 asphalt binder as a conventional neat bitumen widely used for paving applications. Three different dosages of PPA, including 0.5%, 1.0%, and 1.5% were used to modify the neat asphalt binder, and 3% of EBS as a selected percentage was added to PPA-modified samples. The dynamic shear rheometer was used to evaluate the high-temperature properties of the neat and modified bitumens based on standard Superpave protocol parameter (G*/sinδ) and multiple stress creep and recovery test. The low service temperatures of the samples were determined using the bending beam rheometer test. Also, the high-temperature ranges viscosities of the samples were evaluated using a series of rotational viscometer tests. The results have shown that increasing the PPA dosage up to 1.5% enhances the high service temperature of the neat asphalt binder 20.4°C and 14.7°C based on Superpave protocol and multiple stress creep and recovery test, respectively. However, it deteriorates the low-temperature performance of modified binders from −24.3°C to −16.9°C. The EBS can significantly compensate for the negative effect of PPA modification on the low-temperature behavior of modified bitumens. The optimum combination was 1% PPA+3% EBS as it provides a similar low-temperature grade to the neat asphalt binder having a significant two grades enhancement of high service temperature. Modifying a PPA-modified asphalt binder with EBS can reduce its viscosity at high temperatures, leading to saving energy of mixing and compaction. [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]

• 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]