فرزین پورحیدری ممقانی

Nanomaterials have indicated a hopeful capacity in improving the behavior of pavement. As hot mix asphalt is a viscoelastic material, several distresses were occurred during their life time. Furthermore, steel slag was used to enhance the properties of mixture because of its outstanding physical properties. This research evaluated the effect of nanoclay and Styrene Butadiene Rubber (SBR) on performance behavior of bitumen and high and intermediate temperature performance of SMA mixtures containing steel slag aggregate. Through this paper, the AC-60/70 and AC-85/100 penetration grade bitumen’s were used as base bitumen. Moreover, SBR (0%, 2%, 4%, 6%, 8% and 10% by weight of binder), and nanoclay (0%, 1%, 2%, 3%, 4%, and 5% by weight of binder) were used as a mixture modifier. For evaluating the performance behavior of bitumen, the rotational viscosity, Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR), Multiple Stress Creep Recovery (MSCR), and linear Amplitude Sweep (LAS) tests were implemented. Moreover, Resilient Modulus (Mr), Indirect Tensile Strength (ITS), dynamic creep, wheel track, and Four Point Beam Fatigue (FPBF) tests were performed to investigate the performance of mixture samples. To analyze the data statistically, two-factor analysis of variance (ANOVA) is evaluated. The rheological behavior test outcomes showed that the utilization of NC/SBR additive results in an enhancement in the rutting and fatigue resistance of binders. The utilization of NC decreases the low-temperature resistance of binders, while SBR improves the bitumen’s low-temperature resistance. Storage stability test outcomes reveal that utilization of NC enhances the storage stability of binders. Also, the application of SBR leads to enhance phase separation. The MSCR test results demonstrate an enhancement in the high-performance temperature of the virgin binder at different stress levels by the addition of NC/SBR. Moreover, the utilization of NS improves the rutting strength of samples. Based on the LAS test outcomes, the utilization of NC/SBR additives improves the fatigue properties of the asphalt binder. The mixture test results reveal that using NC/SBR increases the permanent deformation resistance, MR, ITS, fracture energy, and intermediate temperature properties of specimens.

Composite modification is increasingly used to alleviate the detrimental problems associated with asphalt modifiers and meet the massive demand for asphalt pavement. In this study, nano-Al2O3 composite modifications at three concentrations of 1%, 2%, and 3% by weight of asphalt binder were implemented in neat and modified asphalt binders to improve their performance at high and intermediate temperatures. These binders were evaluated in terms of their physical, rheological, and high-temperature storage stability properties. In addition, nano-Al2O3 composite modified binders were utilized in asphalt concrete and investigated for their resistance to cracking, permanent deformation, and moisture damage. The nano-Al2O3 composite modifications were made using neat, polymer-modified, and crumb-rubber (CR) modified asphalt binders. Adding nano-Al2O3 to the asphalt binders was found to improve stiffness, high-temperature storage stability, permanent deformation resistance, and cracking tolerance. Moreover, the composites of nano-Al2O3 with neat and modified asphalt binders were found to provide improved resistance to permanent deformation, cracking, and moisture damage in hot mix asphalt concrete. The composite of 2% nano-Al2O3 showed the best performance in terms of resistance to permanent deformation, the composite of 3% nano-Al2O3 showed the best performance in terms of resistance to moisture damage, the composites of 2% nano-Al2O3 with polymer and CR-modified asphalt binders both showed the best performance in terms of resistance to cracking, and the composite of 3% nano-Al2O3 with AC20 showed improved resistance to cracking.

Asphalt pavements are one of the most widely constituents utilized to pave highway pavement which experience various failures during their lifetime, such as rutting, fatigue and thermal cracking. Therefore it should be used to improve the bitumen performance by addition of modifiers such as polymers and Nano Clays (NC). Among the various additives used to improve the bitumen performance, Ethylene Vinyl Acetate (EVA) is one of the most useful and effective materials for paving. In this study, the rheological behavior of bitumen and rutting and fatigue behavior of mixture containing EVA/Nanoclay and EVA latex were evaluated. EVA/NC and EVA latex were made and mixed with bitumen. Results of storage stability test shown that EVA/NC-modified bitumen is steadier than EVA-latex-modified bitumen. The results of the fatigue test of the mixtures showed that the asphalt mixtures made of bitumen modified with nanocomposite are more resistant to fatigue than bitumen modified with EVA polymer. The results showed that the addition of 6% EVA/NC and 6% EVA increased the fatigue life by 43% and 20%, respectively. The results of the rutting resistance tests showed that the rutting resistance of the samples increased with the increase of EVA polymer. Also, the addition of montmorillonite increased the resistance of polymer mixtures against rutting.

In this study, an attempt has been made to investigate how the rheological behaviors of bitumen are affected by the use of lignin and soybean oil. In the current research, lignin (3%, 5%, 7% by weight of bitumen) and soybean oil (5% by weight of bitumen) were added to modify two main types of bitumen (AC 60-70 and AC 85/100). The performance evaluation of different bitumen was evaluated by examining their physical and rheological behavior by penetration tests, ductility, linear range sweep, multiple stress creep recovery, dynamic shear remoter, rotational viscosity and softening point tests. The results of rheological behaviors showed that the use of lignin additive increases the softening point and decreases the degree of penetration. The use of lignin reduces the low-temperature strength of the bitumen, while oil improves the low-temperature strength of the bitumen. The results of the multiple stress creep recovery (MSCR) test with the addition of lignin showed an increase in the high yield temperature of virgin bitumen at different stress levels. While the use of oil reduces the creasing strength of the sample. According to the results of the linear range sweep (LAS) test, the use of lignin additive reduces the fatigue properties of bitumen. While soybean oil strengthened it.

As a new way of modifying asphalt or asphalt mixture, composite modification has obvious effects. In order to improve the perfor- mance of asphalt pavement in a simple, fast and efficient way, a new kind of composite reinforcing material (CRM) is used in this study. The Marshall Immersion test, the freeze–thaw splitting test and low-temperature bending test were conducted to evaluate the pavement performance of the asphalt mixture with different CRM contents. Test results show that the pavement performance of modified asphalt mixtures is better than unmodified asphalt mixture. When the CRM content increases, resistance to rutting at a high temperature increases significantly, low temperature cracking resistance and moisture damage resistance first rise and then fall. In consideration of other pavement performance, such as dynamic stability (DS), indirect tensile strength ratio (TSR) and maximum tensile strain, the sug- gested optimal CRM dosage is 5.9‰ to 7.9‰.

In this study, the effect of the use of two WMA additive sasobit and rheofalt additives on the fatigue properties of the asphalt mixes was evaluated. For this purpose, laboratory samples containing 100 % RAP and a hot mixture were constructed using RAP material, which is separated from the bitumen. The recycled mixtures include a hot recycling sample and three warm (1 non - additive sample, 1 sample containing sasobit additive, 1 containing rheofalt additive). In this research, different experiments such as indirect tensile strength, resilient modulus and fatigue are investigated. Fatigue test was performed on four - point bending test with constant strain level at three levels 600, 800 and 1000 micro - strain with sinusoidal loading. The fatigue life of specimens was evaluated based on a 50 % reduction in the initial hardness modulus. The results showed that sasobit and rheofalt additives had a positive effect on the compression and functional properties of the blends. In the performance of fatigue and low - temperature cracks, the hot mixture was better in spite of the positive effects of additives.

The purpose of this paper is to investigate the effect of rubber powder and Gilsonite powder on the rheological properties of bitumen. In this study, the gilsonite powder was used as additive in percentages (0 %, 10 %, 20 %, 30 % and 40 %)in bitumen. Also, in order to limit the degree of penetration to 30 - deci mm at 25 C, the Gilsonite percentage is considered to be 30 % fixed and the percentages of rubber powder are considered to be 30 %, 10 %, 15 %, 20 %). In order to investigate the performance characteristics of bitumen, the penetration, softening point, ductility, dynamic shear rheometer, bending beam rheometer, rotational viscosity, multiple stress creep recovery (MSCR) tests were performed. Results showed that the G */ Sind parameter increases with addition to gilsonite. Also, rubber powder causes an increase in the value of G * / Sind parameter and the rutting parameter increases by addition of crumb rubber percentage. The addition of gilsonite powder causes an increase in values of G *. Sind and adding crumb rubber powder cause a decrease in values of G *Sin d. it is found that the parameter (Jnr) decreases with addition of gilsonite and rubber powder. The lower values (Jnr) indicates the further resistance of the mixture made with the bitumen or less rutting sensitivity. The results show better values for rubber powder additive compared to Gilsonite.

In this research, the duration and appropriate time of walking to reach the routine destinations and meet the needs of individuals based on the different criteria of city districts and neighborhoods including individual, social, economic, and physical ones as well as land uses. The results can evaluate challenges and deficiencies based on the affecting indicators in different regions, and finally, they can lead to the adoption of measures and propositions so that people can fulfill their purposes and needs by walking over a proper time. The analysis method performed here was to by using statistical regression modelling. To reach the goal of this study, first, the city of Gorgan, Golestan province, Iran, was introduced, then, the land use map and land use distribution diagram by neighborhood were given, and next, the demography of the respondents to the questionnaire was investigated. Finally, four modelling types were addressed to measure the walking time for different purposes; 1) occupational, 2) educational, 3) shopping, and 4) recreational. By investigating the results of walking time models in different districts of Gorgan and by considering the t-test coefficients and Watson coefficient, being 1.5-2.5 for all the models which is acceptable, the independent variables of the area and concentration of office land uses, age, and car ownership (to measure the walking time of occupational travels), the independent variables of the area of educational land uses, income, and age (to measure the walking time of educational travels), the independent variables of the area and concentration of service land uses, age, and car ownership (to measure the walking time of shopping travels), the area of greenbelts and parks, and different variables of the area of sporting  land uses, car ownership, and age (to measure the walking time of recreational travels) were determined to be significant. At last, tables showing the coefficients of independent variables and the constant of the prediction model for the walking time of each type of travel were presented.