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A fast and convenient technique for Asphalt Binders was proposed in this paper, which was based on air-jet pressurized and laser to detect the transient deformation and creep recovery of asphalt. Taking five kinds of asphalt and modified asphalt commonly used in China as the research objects, the performance of asphalt were tested and analyzed by adopting the Penetration Test, Dynamic Shear Rheological (DSR) Test, Multiple Stress Creep and Recovery (MSCR) Test and the proposed test technology. The results verified the feasibility of the proposed test technology and the correlation between the traditional tests and the proposed test technology. The results demonstrated that the proposed test technology had good discrimination ability for different kinds of asphalt and could effectively reflect the performance differences. The new test protocol was similar to the Penetration Test. There was a significant correlation between the maximum deformation index and penetration index. The correlation coefficient was above 0.8, and the p value was much less than 0.01. It could be used as a possible alternative to the Penetration Test. The proposed new test was relatively convenient and fast compared with the dynamic shear test. There was a linear correlation between the maximum deflection index and the complex shear modulus G*, and the correlation coefficient between the recovery index and the phase angle is above 0.8, which indicated that the proposed new test and the DSR test had a significant correlation. There was also a good correlation between the creep recovery index of MSCR test and the recovery data of the proposed new test method. The research results provided a new solution for the performance test and evaluation of asphalt in China.

Recently, the modification of bituminous binders is an ongoing trend. However, most current analytical methods are insufficient to characterize bitumen. Generally, standardized laboratory techniques are often time and cost consuming. Moreover, they use one-purpose devices requiring a considerable amount of samples and solvents. Therefore, we investigated three special instrumental analytical techniques to find out bitumen properties. Our main objective was to obtain some additional parameters of bituminous binders to allow their more accurate description. The first studied method, thermogravimetric analysis operated especially in a high-resolution mode that can be used as a fingerprint area in spectrometry to determine the bitumen quality. The second one modulated differential scanning calorimetry provided many various important parameters, including temperature of glass transition, cold crystallization and serviceability limit state. The third one, the thermomechanical analysis also measured the value of glass-transition temperature for comparison with the method mentioned above. We have found correlations between the results from thermal instrumental techniques and standardized laboratory tests.

In laboratory conditions, neglecting time and temperature as two effective parameters on the mechanical properties of asphalt mixtures may affect the results of experimental tests and mislead researchers in analyzing the results. Therefore, it seems necessary that some of the less considered laboratory conditions in past studies need to be perceived more to minimize the error of results obtained by laboratory tests. Hence, in this study, after examining the research on warm mix asphalt and factors affecting laboratory test results, three parameters of short-term aging (asphalt binder storage in oven), curing time (from construction to placement in the test chamber), and thermal equilibrium time (from placement in the test chamber to test onset) were selected to combine different levels for evaluating their effect on the rutting potential by performing dynamic creep test. Based on the results, by increasing the time of aging, the viscosity of asphalt binder increased, thus increasing the mixture’s stiffness and reducing the slippage of materials over each other and decreasing the final strain. Also, increasing the curing time improved the adhesion between the asphalt binder and aggregate and reduced the rutting potential of the sample. However, by increasing the thermal equilibrium time, the viscosity and power of the asphalt binder’s cohesion were reduced, thus loosening the asphalt binder and aggregates, creating shear strain, and increasing the rutting potential of the warm mix asphalt (WMA). Based on the results of statistical analyses, the parameters considered in laboratory conditions affected the rutting potential of WMAs at a 95% confidence level.

The present paper focuses on the behavior of Stone Mastic Asphalt (SMA) mixes incorporating rejuvenated Reclaimed Asphalt Pavement (RAP) materials. The RAP materials were tested for its physical properties and later were rejuvenated using various rejuvenators such as waste cooking oil, waste engine oil and shredded plastics. The rejuvenated RAP materials were incorporated in the SMA mixes at various replacement levels i.e. 0%, 30%, 50% and 70% (by weight). Various binder properties such as viscosity, rheological properties and chemical composition were evaluated for the aged and rejuvenated material. The rejuvenators were incorporated at different dosage levels i.e. 2%, 4% and 6% (by weight of binder). The optimal rejuvenation dosage for each type of rejuvenator was identified and mix design for the SMA was optimized for evaluating its physical and mechanical properties. Based on the results, the optimum rejuvenator dosage was identified at 6% for waste cooking oil and waste engine oil, while 2% for shredded plastics. It was observed that the addition of rejuvenators improved the performance of RAP based SMA mixes.

To improve the improvement effect of rice straw fiber on asphalt mixes, a surface response experimental design method was used to study and the optimal blending method of rice straw fiber asphalt mixture was obtained. The fiber asphalt mixes were prepared according to the optimized scheme and analyzed by rutting test, direct tensile test, water immersion Marshall test, freeze–thaw splitting test, and four-point bending fatigue test for related road performance. The results showed that the optimal solution for the fiber ratio of rice straw fiber asphalt mixture was that the fiber length was 9 mm, the fiber content was 4%, and the oil-to-stone ratio was 5.16%. Rice straw fiber can improve the high-temperature performance and water damage resistance of the asphalt mixture. The stability of the mixing material, the stability of the residual stability and the frozen split intensity of the mixing material were 130.6%, 114.1%, and 116.9% of the matrix asphalt mixture, respectively. At the same time, the fiber can enhance the low-temperature performance of asphalt mixes and extend the fatigue life of asphalt mixes. However, when the fiber and dosage were too large, it would weaken the effect of improving the high- and low-temperature performance and water stability of asphalt mixes.

The performance of sulfur as alternative binder additive in asphalt mixtures was presented in this study. The effect of different sulfur contents was investigated to evaluate the rutting and cracking performances of sulfur modified asphalt mixtures. First, the engineering properties and morphologies of the sulfur modified asphalt binder were investigated using traditional binder tests and the Scanning Electron Microscopy (SEM). Second, further testing was conducted such as the Marshall stability (MS) test, wheel tracking (WT) test, indirect tensile (IDT) test, and indirect tensile fatigue (IDTF) test, to evaluate the performance resistance of sulfur modified asphalt mixtures. It was found that the sulfur modified binder can improve not only the mechanical properties of asphalt binder but also the rutting performance as well as cracking resistance of asphalt pavement significantly. Finally, the performance of sulfur modified asphalt mixtures was evaluated using the mechanistic empirical pavement design guide (MEPDG) program. Based on the results of the study, it can be concluded that the addition of sulfur can enhance the performance of asphalt mixtures significantly.

International Roughness Index (IRI) is the performance index of pavements that exhibits the efficiency of pavement smoothness. Road roughness is a fundamental element used for determining the performance of pavements and the ride quality of road users, therefore, this research aims to develop the precise IRI prediction model for flexible pavements using advanced machine learning algorithms including supervised methods. This research is directed toward accessing the functional performance of the pavements through long-term pavement performance (LTPP) databases. For developing the model, the incorporated dataset includes a set of functional attributes from general pavement studies (GPS-1, GPS-2 and GPS-6) and specific pavement studies (SPS-1, SPS-3 and SPS-5). The developed algorithms showed that the machine learning algorithms are more precise and accurate in predicting the IRI than the traditional regression approaches. The machine learning algorithms use the shapely additive explanation (SHAP) values to access the feature significance for each independent element on the predictive performance. The analysis showed that CatBooster Regression outperformed the random forest regression, artificial neural network (ANN), and the simple regression models in terms of mean square error and prediction quality with a coefficient of determination up to 0.99. The study depicted that it is possible to correlate the roughness index with pavement and structural, climatic and distress parameters that can be utilized for pavement maintenance.