Semnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Comparison of Induction and Microwave Heating in the Healing Process of Asphalt Mixtures Containing Conductive MaterialsComparison of Induction and Microwave Heating in the Healing Process of Asphalt Mixtures Containing Conductive Materials116873910.22075/jtie.2024.34128.1673FAMahmoudAmeriProfessor, School of Civil Engineering, Iran University of Science and Technology (IUST), Tehran, I. R. Iran.MansourSadeghiavazPhD. Candidate of Raod and Transportation, School of Civil Engineering, Iran University of Science and Technology (IUST), Tehran, I. R. Iran.Journal Article20240515One of the well-known methods regarding the return of asphalt mixture failures and, as a result, increasing its lifespan is self-healing, which has always been of interest to researchers due to its many benefits. Applying thermal energy or heating the asphalt mixture leads to self-healing the asphalt mixture by accelerating the bitumen healing process. Two main methods of induction heating and microwave are used in this field. This article compares these two heating-healing methods and introduces the more appropriate option. For this purpose, both induction and microwave heating methods have been used to apply heat to the components of the asphalt mixture, including bitumen, filler, and aggregates. The research results showed that the microwave heating rate of bituminous mastic containing conductive materials is higher than its induction heating rate, so the microwave heating rate of the mastic sample containing 10% by weight of iron powder (0.100 °C/s) was more than three times its induction heating rate (0.031 °C/s). Additionally, bituminous mastic heated with microwaves exhibits a more consistent thermal distribution, which enhances its self-healing properties. Unlike induction heating, which requires conductive additives and aggregates, the microwave method can heat components with or without conductive materials. However, addition of conductive materials can accelerate the microwave heating process. For instance, adding 10% by weight of iron powder to bitumen could increase its microwave heating rate from 0.083 to 0.100. In contrast, achieving the same results with the induction heating method requires several times more energy than the microwave method. Therefore, it is advisable to use the microwave heating method instead of induction heating for thermal healing of asphalt mixtures.One of the well-known methods regarding the return of asphalt mixture failures and, as a result, increasing its lifespan is self-healing, which has always been of interest to researchers due to its many benefits. Applying thermal energy or heating the asphalt mixture leads to self-healing the asphalt mixture by accelerating the bitumen healing process. Two main methods of induction heating and microwave are used in this field. This article compares these two heating-healing methods and introduces the more appropriate option. For this purpose, both induction and microwave heating methods have been used to apply heat to the components of the asphalt mixture, including bitumen, filler, and aggregates. The research results showed that the microwave heating rate of bituminous mastic containing conductive materials is higher than its induction heating rate, so the microwave heating rate of the mastic sample containing 10% by weight of iron powder (0.100 °C/s) was more than three times its induction heating rate (0.031 °C/s). Additionally, bituminous mastic heated with microwaves exhibits a more consistent thermal distribution, which enhances its self-healing properties. Unlike induction heating, which requires conductive additives and aggregates, the microwave method can heat components with or without conductive materials. However, addition of conductive materials can accelerate the microwave heating process. For instance, adding 10% by weight of iron powder to bitumen could increase its microwave heating rate from 0.083 to 0.100. In contrast, achieving the same results with the induction heating method requires several times more energy than the microwave method. Therefore, it is advisable to use the microwave heating method instead of induction heating for thermal healing of asphalt mixtures.https://jtie.semnan.ac.ir/article_8739_9385d7dc0d70571c3b27e898a3249639.pdfSemnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Experimental and Numerical Micromechanical Modeling of the Viscoelastic Behavior of Asphalt Mastic Containing Limestone FillerExperimental and Numerical Micromechanical Modeling of the Viscoelastic Behavior of Asphalt Mastic Containing Limestone Filler1738876410.22075/jtie.2024.34351.1674FAFereidoonMoghadas NejadDepartment of Civil & Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran0000-0003-3830-4555PouriaHajikarimiDepartment of Civil & Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, IranAliKhodaiiDepartment of Civil & Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, IranJournal Article20240605The volume filling ratio and type of filler significantly influence the rheological and mechanical properties of bituminous composites. This effect can stem from either chemical interactions between the filler and bitumen or simple physical phenomena. Understanding the influence of filler on asphalt mastic performance is crucial for comprehending the behavior of asphalt mixtures. This study employs both experimental and numerical modeling approaches. The rheological properties of asphalt mastic samples made with pure bitumen and limestone filler at various filler contents were determined using frequency sweep tests. The experimental results indicated that increasing the volume filling ratio in asphalt mastic leads to non-linear changes in the values of the complex shear modulus (G*) and phase angle (δ), known as the stiffening phenomenon. Considering the concept of the transitional zone between filler and bitumen, a parameter called the Effective Volume Filling Ratio (EVFR) was introduced to explain this phenomenon. To predict the viscoelastic behavior of asphalt mastic based on the mechanical properties of bitumen and filler, finite element method (FEM) simulations were utilized. The accuracy of these models was evaluated by calculating the relative difference between the experimental complex shear modulus (G*) and the complex shear modulus predicted by the model. The results of this evaluation indicated that incorporating the Effective Volume Filling Ratio (EVFR) into the numerical model can significantly enhance the accuracy of the predictions for the viscoelastic behavior of asphalt mastic samples.The volume filling ratio and type of filler significantly influence the rheological and mechanical properties of bituminous composites. This effect can stem from either chemical interactions between the filler and bitumen or simple physical phenomena. Understanding the influence of filler on asphalt mastic performance is crucial for comprehending the behavior of asphalt mixtures. This study employs both experimental and numerical modeling approaches. The rheological properties of asphalt mastic samples made with pure bitumen and limestone filler at various filler contents were determined using frequency sweep tests. The experimental results indicated that increasing the volume filling ratio in asphalt mastic leads to non-linear changes in the values of the complex shear modulus (G*) and phase angle (δ), known as the stiffening phenomenon. Considering the concept of the transitional zone between filler and bitumen, a parameter called the Effective Volume Filling Ratio (EVFR) was introduced to explain this phenomenon. To predict the viscoelastic behavior of asphalt mastic based on the mechanical properties of bitumen and filler, finite element method (FEM) simulations were utilized. The accuracy of these models was evaluated by calculating the relative difference between the experimental complex shear modulus (G*) and the complex shear modulus predicted by the model. The results of this evaluation indicated that incorporating the Effective Volume Filling Ratio (EVFR) into the numerical model can significantly enhance the accuracy of the predictions for the viscoelastic behavior of asphalt mastic samples.https://jtie.semnan.ac.ir/article_8764_a29d5a1f0aca48fa60bebfb73db785e2.pdfSemnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Investigating the Effect of Using Polyurethane Nanocomposites on Modification of Bitumen PropertiesInvestigating the Effect of Using Polyurethane Nanocomposites on Modification of Bitumen Properties3961862410.22075/jtie.2024.33303.1665FASeyed RezaSajadiPhD Candidate of Raod and Transportation, Faculty of Civil Engineering, Semnan University, Semnan, I.R. IranGholam AliShafabakhshProfessor, Department of Road and Transportation, Faculty of Civil Engineering, Semnan University, Semnan, I. R. Iran.HassanDivandariAssistant Professor, Department of Civil Engineering, Central Tehran Branch, Islamic Azad University, Tehran, I. R. Iran.Journal Article20231217Bitumen, as one of the constituent elements of asphalt, plays an important role in the properties and performance of asphalt as well as its longevity and stability. However, its structure requires modification due to low mechanical properties, limited thermal stability, and susceptibility to cracking under environmental conditions. In this study, in order to increase the strength and flexibility, improving functional and thermal properties, enhance adhesion, and prevent phase separation, a modifier based on NCO-terminated polyurethane/CNT were used. For this purpose, NCO-terminated polyurethane pre-polymer was prepared, and then CNTs were added to it at 0.5%, 1%, and 1.5% wt.%. Based on tensile and TGA tests, the sample containing 1.5% nanoparticles was selected as the optimum nanocomposite and subsequently combined with bitumen and then it was mixed with bitumen at 2, 4, 6 and 8 percent. FTIR test confirmed the chemical bonds between the nanocomposite and bitumen. To investigate the properties and performance of the resulting samples, morphological analysis, viscometry (RV) test, and rheological (DSR) tests for fatigue resistance and rutting under environmental conditions were performed. Also, results of multiple stress creep-recovery (MSCR) test was compared with results of rheology analysis and it was shown that the presence of nanocomposite in the structure of bitumen increased the elasticity and cohesion of the modified bitumen structure. It reduces the negative effects caused by the increase in stress and temperature in bitumen properties and the nanocomposite prepared in this research can be used as a suitable option to improve bitumen performance at high and medium temperatures.Bitumen, as one of the constituent elements of asphalt, plays an important role in the properties and performance of asphalt as well as its longevity and stability. However, its structure requires modification due to low mechanical properties, limited thermal stability, and susceptibility to cracking under environmental conditions. In this study, in order to increase the strength and flexibility, improving functional and thermal properties, enhance adhesion, and prevent phase separation, a modifier based on NCO-terminated polyurethane/CNT were used. For this purpose, NCO-terminated polyurethane pre-polymer was prepared, and then CNTs were added to it at 0.5%, 1%, and 1.5% wt.%. Based on tensile and TGA tests, the sample containing 1.5% nanoparticles was selected as the optimum nanocomposite and subsequently combined with bitumen and then it was mixed with bitumen at 2, 4, 6 and 8 percent. FTIR test confirmed the chemical bonds between the nanocomposite and bitumen. To investigate the properties and performance of the resulting samples, morphological analysis, viscometry (RV) test, and rheological (DSR) tests for fatigue resistance and rutting under environmental conditions were performed. Also, results of multiple stress creep-recovery (MSCR) test was compared with results of rheology analysis and it was shown that the presence of nanocomposite in the structure of bitumen increased the elasticity and cohesion of the modified bitumen structure. It reduces the negative effects caused by the increase in stress and temperature in bitumen properties and the nanocomposite prepared in this research can be used as a suitable option to improve bitumen performance at high and medium temperatures.https://jtie.semnan.ac.ir/article_8624_58fcd773d06f52ba45fd79a39616f32b.pdfSemnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Effects of Simultaneous Use of Crumb Tires and Fly Ash on the Shear Behavior of Encased Stone Columns: A Laboratory StudyEffects of Simultaneous Use of Crumb Tires and Fly Ash on the Shear Behavior of Encased Stone Columns: A Laboratory Study6379873510.22075/jtie.2024.34022.1671FASaeedNegariDepartment of Civil Engineering, Yazd University, Yazd, IranMaryamMokhtariDepartment of Civil Engineering, Yazd University, Yazd, IranJournal Article20240505Applying stone columns (SCs) is an economical method to improve loose soil. This laboratory study is conducted on the effects of simultaneous use of crumb tire (CT) and fly ash (FA) on the shear behavior of SCs encased with geotextile and fiber-reinforced polymer (FRP) in soft clay. A large-scale direct shear device was utilized to do the desired tests. The samples were exposed to normal stress values of 20, 40, and 70 kPa. First, optimal percentages of CT and FA were determined to be used with granular materials in the SCs. The impact of installing ordinary reinforced and unreinforced SCs on the shear behavior of the assembly was examined. Installing the SCs in soft clay bed and adding the CT-FA composite to the SC materials increased the shear strength. Supplementing the CT-FA composite to the SC materials increased shear strength of the assembly to 4.6%-10%. The shear strength rose more than twice when the normal stress increased from 20 kPa to 70 kPa and it was mobilized more since CT-FA composite is present. It increased due to a rise in the replacement ratio of the SCs in the assembly. By installing the ordinary composite SCs in clay bed under the normal stresses of 20 kPa and 70 kPa, the shear strength increased to 34% and 41.7% and it would rise in the encased mode more than in the ordinary mode. Furthermore, the FRP-based reinforcement enhanced the shear strength more than the geotextile reinforcement did.Applying stone columns (SCs) is an economical method to improve loose soil. This laboratory study is conducted on the effects of simultaneous use of crumb tire (CT) and fly ash (FA) on the shear behavior of SCs encased with geotextile and fiber-reinforced polymer (FRP) in soft clay. A large-scale direct shear device was utilized to do the desired tests. The samples were exposed to normal stress values of 20, 40, and 70 kPa. First, optimal percentages of CT and FA were determined to be used with granular materials in the SCs. The impact of installing ordinary reinforced and unreinforced SCs on the shear behavior of the assembly was examined. Installing the SCs in soft clay bed and adding the CT-FA composite to the SC materials increased the shear strength. Supplementing the CT-FA composite to the SC materials increased shear strength of the assembly to 4.6%-10%. The shear strength rose more than twice when the normal stress increased from 20 kPa to 70 kPa and it was mobilized more since CT-FA composite is present. It increased due to a rise in the replacement ratio of the SCs in the assembly. By installing the ordinary composite SCs in clay bed under the normal stresses of 20 kPa and 70 kPa, the shear strength increased to 34% and 41.7% and it would rise in the encased mode more than in the ordinary mode. Furthermore, the FRP-based reinforcement enhanced the shear strength more than the geotextile reinforcement did.https://jtie.semnan.ac.ir/article_8735_da39518781d0bb0b635cb382e55b4443.pdfSemnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Modelling and Analysis of Flexural Behavior of Composite Sleepers Reinforced by Multi-Directional Glass FabricsModelling and Analysis of Flexural Behavior of Composite Sleepers Reinforced by Multi-Directional Glass Fabrics81102876210.22075/jtie.2024.34443.1676FAAmir ArdalanTabatabaieDepartment of Railway Engineering and Transportation Planning, Faculty of Civil Engineering and Transportation, University of Isfahan (UI), Isfahan, IranHamedNorouziAssistant Professor, Department of Railway Engineering and Transportation Planning, Faculty of Civil Engineering and Transportation, University of Isfahan, Isfahan, Iran.Sayyed MahdiHejaziAssociate Professor, Department of Textile Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran.Journal Article20240614Over the past decade, glass fabrics have gained significant attention for use in the construction of concrete railway sleepers. Advances in composite technology have spurred extensive research into glass-based composite materials, suggesting their potential as replacements for traditional sleepers. However, the impact of three-dimensional (3D) glass fabrics on reinforcing concrete sleepers and the optimal application of these fabrics has not been sufficiently explored. Additionally, there has been no comparative analysis of the flexural strength between concrete sleepers reinforced with glass fabrics and those reinforced with steel rebars. This study investigates the potential of Glass Fiber Reinforced Concrete (GFRC) fabrics as an alternative for concrete railway sleepers. Laboratory-scale concrete sleeper samples were prepared and reinforced with two-dimensional (2D) and three-dimensional (3D) glass fabrics, covering 50% and 70% of the surface area. Flexural strength tests were conducted on these samples, and their validity was confirmed through finite element analysis using Abaqus software. The empirical results from small-scale tests were extrapolated to estimate the performance of full-sized sleepers. The findings indicate that the use of 3D fabrics can increase flexural strength and crack resistance by up to 20% and 30%, respectively. Moreover, 3D fabrics with 70% surface coverage can further enhance flexural strength by 15%. GFRC sleepers meet all standards and performance requirements for commercialization, showing up to 25% higher flexural strength and up to 40% improved crack resistance compared to conventional concrete sleepers.Over the past decade, glass fabrics have gained significant attention for use in the construction of concrete railway sleepers. Advances in composite technology have spurred extensive research into glass-based composite materials, suggesting their potential as replacements for traditional sleepers. However, the impact of three-dimensional (3D) glass fabrics on reinforcing concrete sleepers and the optimal application of these fabrics has not been sufficiently explored. Additionally, there has been no comparative analysis of the flexural strength between concrete sleepers reinforced with glass fabrics and those reinforced with steel rebars. This study investigates the potential of Glass Fiber Reinforced Concrete (GFRC) fabrics as an alternative for concrete railway sleepers. Laboratory-scale concrete sleeper samples were prepared and reinforced with two-dimensional (2D) and three-dimensional (3D) glass fabrics, covering 50% and 70% of the surface area. Flexural strength tests were conducted on these samples, and their validity was confirmed through finite element analysis using Abaqus software. The empirical results from small-scale tests were extrapolated to estimate the performance of full-sized sleepers. The findings indicate that the use of 3D fabrics can increase flexural strength and crack resistance by up to 20% and 30%, respectively. Moreover, 3D fabrics with 70% surface coverage can further enhance flexural strength by 15%. GFRC sleepers meet all standards and performance requirements for commercialization, showing up to 25% higher flexural strength and up to 40% improved crack resistance compared to conventional concrete sleepers.https://jtie.semnan.ac.ir/article_8762_5b8f150873f9ad6cb1ee029b676b1138.pdfSemnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Estimation of Strength Parameters of Saline Subgrade Stabilized by Cement and Industrial Waste Using Finite Element MethodEstimation of Strength Parameters of Saline Subgrade Stabilized by Cement and Industrial Waste Using Finite Element Method103125875410.22075/jtie.2024.33426.1667FAAminFalamakiDepartment of Civil Engineering, Payame Noor University (PNU), P.O. Box 19395-3697, Tehran, IranMahmoudRezaKeymaneshDepartment of Civil Engineering, Payame Noor University (PNU), P.O. Box 19395-3697, Tehran, IranHadiGhodratDepartment of Civil Engineering, Payame Noor University (PNU), P.O. Box 19395-3697, Tehran, IranJournal Article20240302Saline soils are one of the types of problematic soils which are very vulnerable to dissolution and swelling phenomena. This type of soil has been observed in many parts of Iran and has been used as road subgrade. To enhance the resistance properties of salt beds, various methods are usually used, including chemical stabilization, and the geotechnical properties of stabilized salt beds are evaluated with field and laboratory tests. However, estimation of some main parametersو required for road design, such as modulus of resilience, is dependent on the use of three-dimensional cyclic tests, which requires spending considerable time and cost. This article’s aim is to investigate the traffic loads effect on saline soil subgrade stabilized with cement and carbonated waste, by modeling the modulus of resilience parameter via finite elements method. The natural saline soil of this research was stabilized with different percentages of type 2 Portland cement and a type of carbonated waste, without treatment or treated with two different stabilization methods. Then, several resistance tests such as direct shear test, unconfined uniaxial compressive strength and California bearing ratio (CBR) were done on the samples. The obtained shear strength parameters were used in the modeling of the modulus of resilience. Considering the inherence of traffic loading and the type of test, after examining various soil constitutive models, the small strain hardening soil constitutive model was chosen for this analysis. After performing the modeling steps, including determining the model parameters, developing and running the model, analysis of the results showed that modulus of resilience has exponential relationship with the sum of the main axial and confining stresses. The model coefficients’ relationship was determined and shown using multiple regression analyses. Also, the correlation between modulus of resilience and California bearing ration (CBR) are presented.Saline soils are one of the types of problematic soils which are very vulnerable to dissolution and swelling phenomena. This type of soil has been observed in many parts of Iran and has been used as road subgrade. To enhance the resistance properties of salt beds, various methods are usually used, including chemical stabilization, and the geotechnical properties of stabilized salt beds are evaluated with field and laboratory tests. However, estimation of some main parametersو required for road design, such as modulus of resilience, is dependent on the use of three-dimensional cyclic tests, which requires spending considerable time and cost. This article’s aim is to investigate the traffic loads effect on saline soil subgrade stabilized with cement and carbonated waste, by modeling the modulus of resilience parameter via finite elements method. The natural saline soil of this research was stabilized with different percentages of type 2 Portland cement and a type of carbonated waste, without treatment or treated with two different stabilization methods. Then, several resistance tests such as direct shear test, unconfined uniaxial compressive strength and California bearing ratio (CBR) were done on the samples. The obtained shear strength parameters were used in the modeling of the modulus of resilience. Considering the inherence of traffic loading and the type of test, after examining various soil constitutive models, the small strain hardening soil constitutive model was chosen for this analysis. After performing the modeling steps, including determining the model parameters, developing and running the model, analysis of the results showed that modulus of resilience has exponential relationship with the sum of the main axial and confining stresses. The model coefficients’ relationship was determined and shown using multiple regression analyses. Also, the correlation between modulus of resilience and California bearing ration (CBR) are presented.https://jtie.semnan.ac.ir/article_8754_3679eff8296e4feeed3d79455ced4e4d.pdfSemnan University PressJournal of Transportation Infrastructure Engineering2423-535010120240521Numerical modeling of the use of geosynthetics in improving the behavior of subgrade soilNumerical modeling of the use of geosynthetics in improving the behavior of subgrade soil127140875510.22075/jtie.2024.33951.1672FASeyed HosseinKhatamiGraduated Msc, Highway Engineering, Tehran Branch, Islamic Azad University, Tehran, I.R. Iran.ImanGolpazirDepartment of Civil Engineering, Damavand Branch, Islamic Azad University, Damavand, IranMohammad JavadMalekpourGraduated Msc, Civil engineering, Tehran Branch, Islamic Azad University, Tehran, I.R. Iran.Journal Article20240505In this research, numerical simulation using the finite element method and PLAXIS numerical software (version 8.2) were used. Also, the calculation point of the road settlement, which is the criterion for comparing different models, is selected in the loading center on the road, which is considered as the representative of the road settlement in the output results of the vertical displacement. The results of the numerical investigation of the effect of the tensile strength of geosynthetics on the road settlement show that this parameter did not have a significant effect on the road settlement. Also, from the numerical modeling of the effect of the length of geosynthetics on the road body, it is determined that the settlement of the road in modeling with geogrid is the same size as the width of the road (which is equal to 7 meters in this model) equal to 3.65 mm and with geogrid 9 meters wide. It is equal to 3.5 mm. The results showed that if the amount of friction between the geosynthetic element and the soil is considered equal to the internal friction angle of the soil, the settlement of the road at the loading center of the model has decreased by 12%. Finally, the investigation of the effect of geosynthetic element placement on the road settlement shows that by moving the geosynthetic layer from the sub-base-substrate boundary to the top-base boundary, the road settlement decreased by 0.9 mm.In this research, numerical simulation using the finite element method and PLAXIS numerical software (version 8.2) were used. Also, the calculation point of the road settlement, which is the criterion for comparing different models, is selected in the loading center on the road, which is considered as the representative of the road settlement in the output results of the vertical displacement. The results of the numerical investigation of the effect of the tensile strength of geosynthetics on the road settlement show that this parameter did not have a significant effect on the road settlement. Also, from the numerical modeling of the effect of the length of geosynthetics on the road body, it is determined that the settlement of the road in modeling with geogrid is the same size as the width of the road (which is equal to 7 meters in this model) equal to 3.65 mm and with geogrid 9 meters wide. It is equal to 3.5 mm. The results showed that if the amount of friction between the geosynthetic element and the soil is considered equal to the internal friction angle of the soil, the settlement of the road at the loading center of the model has decreased by 12%. Finally, the investigation of the effect of geosynthetic element placement on the road settlement shows that by moving the geosynthetic layer from the sub-base-substrate boundary to the top-base boundary, the road settlement decreased by 0.9 mm.https://jtie.semnan.ac.ir/article_8755_61a98f373138dae42b88f730a3fa6a81.pdf