فهرست مطالب babak golchin

Although bitumen makes up only a small portion of asphalt mixtures, it significantly impacts their performance. Over the past few decades, bitumen modifier additives, such as nano-silica, have been utilized to enhance asphalt performance. This research aims to investigate the influence of nano-silica on the mechanical properties of asphalt and bitumen mixtures. The study utilized crushed stone materials with grading No. 4 of the Iran Road Pavement code, 70-60 pure bitumen, and nano-silica in varying amounts (2%, 4%, and 6% by weight of bitumen). Marshall and resilient modulus tests were employed to evaluate the mechanical properties of asphalt mixtures, while Marshall's resistance ratio was used to assess moisture sensitivity. Additionally, tests on penetration degree, softening point, and elasticity were conducted to evaluate the effect of nanosilica on bitumen properties. The findings revealed that modification of bitumen with nanosilica led to decreased penetration, increased softening point, and reduced plasticity. Furthermore, the use of nano-silica improved Marshall strength and reduced Marshall's flow in asphalt mixtures, with a 6% addition of nano-silica increasing strength by 41% compared to the control sample. The addition of nano-silica also enhanced the moisture sensitivity of the mixtures and increased the resilient modulus by 95% compared to control asphalt samples.

The use of roller-compacted concrete in construction projects, such as road paving, parking lots, dam construction, and industrial pavement, is attributed to its quick implementation, relatively low cost, and sufficient strength without the need for steel bar. However, the brittle nature of roller-compacted concrete prompted an investigation into how steel fibers could improve its mechanical behavior. This research focused on the effect of steel fibers on fracture strength, compressive strength, and tensile strength of roller-compacted concrete. The study involved testing semicircular samples with edge cracks under three-point bending loading to simulate pure tension, pure shear, and their combination. Additionally, the compressive and tensile strength of roller-compacted concrete samples with steel fibers were evaluated at 7 and 28 days. The laboratory results showed that adding 0.1%, 0.3%, and 0.5% steel fibers improved the 28-day compressive strength by 12%, 15%, and 36%, respectively, and the tensile strength by 14%, 21%, and 39%, respectively. Moreover, the failure load of all samples increased in all loading modes with higher percentages of steel fibers, leading to greater resistance to crack growth. The study identified 0.3% of steel fibers as the most effective amount for improving the fracture resistance of roller-compacted concrete in different loading modes, while the optimal percentage for enhancing the compressive and tensile strength was determined to be 0.5%.

Increasing population and urbanization have been caused many problems such as: increased traffic in cities, travel time, cost, fuel consumption, air pollution and so on. In the mentioned situation, some methods are needed to increase the safety and efficiency of the transportation system. In this regard, one of the programs that can be implemented to improve transportation is the use of Autonomous Vehicles. These vehicles have attracted the attention of researchers and industries, so that many transportation experts are currently working on this field. This system can act as the basis for economic growth and countries development. In the present study, the roles of AVs in transportation system have been discussed. The main structure of this project is neural network as one of the machine learning methods. The task of this section is to learn the system and make decisions based on the current condition.  Accordingly, the combinations of Dense and Convolutional neural networks and Udacity simulator have been used. It showed that the simulator can help to speed up the process and implementation of AVs. The results indicated that there is high similarity between human driving cars and AVs which are implemented by the Udacity simulator.

Porous asphalt (PA) are used to drain water from the surface of the asphalt pavements. It reduces aquaplaning and subsequently decreases splash and spray. Clogging reduces the permeability of PA over the years. The double layer PA are used to mitigate this problem. Different aggregate gradations and binder types can alter the performance of double layer PA. The objective of this research is to evaluate the effects of these parameters on the performance of double layer PA. For this purpose, different samples were fabricated using various aggregate gradations based on Malaysian asphalt mixture standards. Indirect tensile strength, permeability and air voids of the samples were determined. The proposed aggregate gradation for top and bottom layers were mixed with two different asphalt binders. Cantabro and binder drainage tests were later carried out on these samples. The results were then compared with the corresponding results from the Dutch double layer PA gradations. Laboratory test results showed that aggregate gradation significantly affect the indirect tensile strength, permeability and air voids of both top and bottom layer of PA. The design binder content for the bottom layer is also lower than that for the top layer. However, the binder type did not significantly change the design binder content.

In previous researches, the properties of bitumen and asphalt mixture have been considered for investigation of thermal cracking. In these methods, the roles of different components of the asphalt mixture are not considered. The use of surface free energy and the basic characteristics of asphalt mixture can also be used in the investigation of thermal cracking. In this research, it has been tried to investigate the role of these basic properties of materials in the occurrence of these cracks along with the surface free energy parameters. For this purpose, surface free energy components have been measured for four types of aggregates and eight types of bitumen. Also, the bitumen creep stiffness and m-value were obtained from the bending beam rheometer tests. Asphalt film thickness, aggregate index and the specific surface area of the aggregates have been also determined. For thermal cracking potential, the semicircular bending test was used on 32 different combinations of asphalt mixtures at low temperature. Then, statistical methods have been used for assessing the relationship between the mentioned parameters and the semicircular bending test results. Statistical analysis shows that the basic characteristics of the materials, including the asphalt film thickness, the aggregate index, the free energy of cohesion, the free energy of adhesion, the ratio of basic to acidic components of the surface free energy and the specific surface area of the aggregate have a significant and positive effect on the cracking indices such as semicircular bending fracture energy and fracture toughness.

Today, due to the rapid increase in the bitumen price and environmental problems, the hot mix recycling is taken into consideration in the construction of asphalt pavements. From a technical point of view, fibers are materials that improve a number of behaviors of asphalt mixtures. The aim of this research is to investigate the technical properties of reclaimed asphalt pavement (RAP) in the presence of para-fibers in order to achieve a suitable combination of these parameters. For this purpose, a new approach was utilized to design the experiment, analyze the results and choose the appropriate asphalt mixture. This approach uses a two-level factorial design in the Design Expert software environment based on desirability functions. The results showed that in the mixture containing 50% RAP and 6% bitumen, increasing the fibers from zero to 0.2% increases the Marshall strength value by 17.4% and decreases the Marshal flow value by 3.8%. In the same mixture with 4% bitumen, with the increase of fibers from zero to 0.2%, Marshall's strength and flow increase by 1.8 and 21.5, respectively. The most air voids are related to the mixtures, containing 50% RAP, 4% bitumen and 0.2% fibers. The results for selected materials showed that the suitable combination for the production of reclaimed asphalt mixtures according to the design criteria in Iran Highway Asphalt Paving Code is 6% bitumen, 50% RAP and 0.2% para-fiber.

The use of microsurfacing layer can provide some good preventive characteristics for asphalt pavement surfaces. Various additives can be used to improve the properties of microsurfacing layers. One of these acceptable additives is latex adhesive. It is claimed that latex adhesive as a polymeric material can withstand environmental factors such as alkaline conditions, acidic conditions, the presence of leachate and oil spilled on road surfaces. In this study, the effect of using latex adhesive in different amounts (4 and 5 %) on wet adhesion properties, setting time, compatibility of materials, abrasion resistance in wet track abrasion and sand adhesion of microsurfacings have been investigated. For this purpose, laboratory samples with different amounts of cement (1.5 and 3 %) and bitumen (8, 10 and 12 %) were prepared and tested. The results showed that the use of latex adhesive improves the behavior of microsurfacing in different percentages of bitumen and cement.

Moisture damage in asphalt mixtures generally occurs due to the separation of bitumen from the surface of stone materials and due to the presence of water. This type of failure causes stripping and premature failures. Investigating the effective factors in this type of damage can be useful in improving the process of designing and producing asphalt mixtures. In the past years, significant research and efforts have been made to reduce these types of failures. In this article, the effect of adding Polytec 505, as a new material with complex amines that reduce the acidic nature of bitumen, on the moisture damage of asphalt mixtures has been investigated. For this purpose, two types of granite and lime aggregate and 60-70 bitumen have been used. The modified Lottman test was used to check the moisture damage, and pull-off tests were used to evaluate the cohesion properties of bitumen and the adhesion of bitumen to aggregate. The results show that the use of this additive causes an increase in the indirect tensile strength ratio of samples with granite and limestone aggregate, and as a result, the performance of these samples against moisture damage improves. This improvement increases with the increasing of this additive. The results of the Pull-off test show that the use of this additive improves the adhesion and cohesion of pull-off pull off test.

One of the most common damages in asphalt mixtures is due to the destructive effects of moisture on the cohesion of asphalt binder and adhesion of asphalt binder-aggregate which is called moisture damage (Xiao et al, 2010). Moisture damage can be divided into two mechanisms, adhesion and cohesion. They are related to the strength loss of asphalt mixtures (Tan and Guo, 2013). Water can penetrate between the surface of asphalt binders and the aggregates. It reduces adhesion between binders and aggregates. Also, water can be absorbed in the asphalt binder. It decreases the cohesion properties of asphalt binders. When the cohesion and adhesion properties of asphalt binder reduce, stiffness of asphalt mixtures reduces. There are several different approaches for improving adhesion and reducing moisture sensitivity in asphalt mixtures. One convenient approach is modifying the asphalt binder with a suitable agent. Most of road and transportation agencies have tried to use anti striping additives to increase adhesion at the aggregate-asphalt interface (Kakar et al, 2015). Liquid anti strip additives are chemical surfactants that decrease the aggregate’s surface tension and improve the surface coverage of aggregates. In contrast in this research, the potential of two types of metallic nano materials in two different percentages (nano AL2O3 and Fe2O3) were evaluated.

In this study, the strength of hot and warm asphalt mixtures containing 3% Sasobite in cold regions has been investigated using the principles of fracture mechanics. The effect of temperature and loading modes (tensile and shear) on the fracture toughness of the mixture was investigated using a semicircular samples with an edge crack under three-point bending. The coefficient of critical stress intensity was determined from the results of the fracture test and the shape coefficients were determined from finite element analysis in ABACUS software. In hot and warm asphalt mixtures containing 3% Sasobite, with decreasing temperature, the critical stress intensity coefficient increased in tensile and shear modes. The results showed that the hot asphalt mixture at temperatures of 0, -10 and -20 °C presents significant fracture resistance compared to the warm asphalt mixture in all loading modes. As the temperature decreases, the fracture toughness of both types of both asphalt mixtures increases.

One of the conventional recycling methods of asphalt mixture is the reuse of reclaimed asphalt with cement as a method for treatment of the base layer and its replacement in pavement layers. In this research, cold recycled asphalt mixture with using emulsified asphalt binder has been investigated through response surface method. In this regard, the technical and economical aspects of fabricated samples of recycled cold asphalt mixtures using crushed asphalt materials, cationic emulsified binder and Portland cement (type II) were investigated. Marshal strength and flow, bulk specific gravity and air voids of mixture were determined by experiments. By performing analysis of variance on the proposed models and determining the effective parameters, mathematical equations between independent and dependent parameters were developed and the effect of the parameters was investigated. Finally, an optimum mix design, which has 60% desirability, was suggested for cold recycled asphalt. Results showed that emulsified binder and cement content have significant effect on the marshal strength. Also, water exhibit a significant effect on the flow of asphalt mixtures.

In previous studies, the effect of different types of polyethylene on the performance of asphalt mixtures has been investigated. In this research, the mixing design of asphalt mixtures containing high density polyethylene has been analyzed and modeled based on the conventional and the response surface methods for limestone and granite aggregates. For this purpose, the volumetric and strength behavior of laboratory-made samples have been measured and statistically analyzed. In the optimization process,, the optimal amount of binder and polyethylene has been extracted according to the criteria of the asphalt pavement regulations for Iranian roads and with the desirability approach. Experimental results show that the optimal conditions for limestone aggregate are 6.1% binder and 4% polyethylene with a desirability of 0.909. However, these values for granite aggregate are 5.9% binder, 4% polyethylene with a desirability of 0.962. The polyethylene additive increases the Marshall strength and specific weight of the samples for both materials. The higher percentage of additive has the greater effect on these parameters. Analysis of variance shows that polyethylene percentage has a significant effect on Marshall flow. By increasing the amount of additive from zero to four percent, the flow value decreases.

The recent increase in bitumen prices and environmental considerations has expanded the use of recycled asphalt mixtures. These mixtures are prepared with different percentages of recycled and new materials including bitumen and aggregate. Sometimes it is necessary to examine the effect of different laboratory parameters quickly and with a smaller number of samples. In this paper, the Taguchi method with 3 effective factors including the percentage of recycled materials (in three levels of 0, 25 and 50%), type of recycled materials (in two levels of two different sources) and the percentage of bitumen (in 3 levels of 4, 5 and 6%) was used to design experiments for rapid analysis of laboratory samples. The strength and volumetric characteristics of asphalt mixtures were determined and analyzed using Minitab software in L18 orthogonal array. The effect of each of the input parameters on the obtained results was determined by signal-to-noise ratio and analysis of variance. The results showed that the percentage of recycled materials significantly affects the strength and volumetric behavior of recycled mixtures. Contrary to expectations, the effect of the source of recycled materials is less than other input parameters.

Abstract
Warm mix asphalt (WMA) is a sustainable clean product that can be fabricated at lower temperatures.  This is an environmentally friendly mixture due to its lower emission and energy consumption in asphalt production plants. Moisture conditioning and aging process are two environmental factors that can adversely affect the stiffness properties of this product. In the field, WMAs are subjected to both moisture damage and aging. In this paper, a new laboratory method was used for evaluating the combined effects of aging and moisture conditioning of WMA samples. WMA specimens were fabricated at various compaction temperatures with different amounts of a surfactant-wax warm additive. Stiffness properties of asphalt mixtures were quantified from the resilient modulus and dynamic creep test. The results showed that moisture conditioning and aging are competing to affect the stiffness properties of mixtures. Polymer modified asphalt mixtures were found to be less susceptible to moisture damage when compared to mixtures fabricated with unmodified binder. Compaction temperature was the most significant factor that affected the resilient modulus of WMA. In the dynamic creep test, the combined effects of aging and moisture conditioning reduced the cumulative micro strain of samples regardless of binder type, additive content and compaction temperature.

Pavement performance prediction is a mounting task due to the many varied influencing factors particularly aging which varies with time, weather, production, type of pavement and etc. This paper presents a conventional mathematical model named Superpave model, Artificial Neural Network (ANN), and Supporting Vector Machine (SVM) techniques to predict the effects of extended aging on asphalt mixture performance measured in terms of rutting properties determined from the dynamic creep test. The accuracy of each method was compared to select the most reliable technique that can be used to forecast the rutting behavior of asphalt mixtures subjected to different aging conditions. The results indicated that the Superpave model was only reliable at lower temperatures, while ANN and SVM techniques showed the capability of precise prediction under all conditions. The overall results showed that the ANN was the most promising technique that can be adopted to satisfactorily forecast the effects of aging on rutting properties of all mixtures. The developed model can be embraced by the pavement management sector for more precise estimation of the pavement life cycle subjected to different aging conditions which can be used to design efficient pavement maintenance and rehabilitation plans.

Due to the sudden increase in the price of binder in recent years and the cracking of asphalt pavements, especially in cold areas, major problems with the implementation and operation of asphalt pavement in some parts of the country can be solved with the use of roller compacted concrete pavements. Therefore, the main objective of this research is to investigate the effect of synthetic fibers on fracture resistance of roller compacted concrete pavement in different loading modes (pure mode I, pure mode II and mixed mode). For this purpose, fracture toughness of roller compacted concretes containing 0.1, 0.2 and 0.3% of a synthetic fiber named Forta was evaluated using linear elastic fracture mechanics. The results show that the effects of the fiber percentages on the mixed mode fracture toughness is very significant and adding this fiber more than 0.3% by weight of the mixture does not lead to a significant improvement of the fracture resistance. Also, by transferring from the pure mode I to pure mode II, the resistance of roller compacted concrete pavement modified with synthetic and without fibers is reduced.

Now days, reclaimed asphalt pavements are used in the production of asphalt mixtures. The use of this material has too many economic and environmental benefits. Beside, warm mix additives are materials that they reduce production temperature of asphalt mixtures and improve their workability in the constructed pavements. There is always a question that “what are the effects of reclaimed asphalt pavement and warm additive on the mix design parameters of asphalt mixtures?” In this research, the simultaneous effects of reclaimed asphalt pavement and a warm additive named Sasobit on the technical properties of asphalt mixtures were evaluated.  For this purpose, an experimental plan was designed based on the response surface method for reclaimed asphalt pavement (from 0 to 50%), asphalt binder content (from 4 to 6%) and Sasobit content (from 0 to 3%). Then, the volumetric and strength properties of these mixtures were determined and compared with the Iranian pavement code criteria. Obtained laboratory results showed that an optimum point for fabrication of asphalt mixtures containing reclaimed asphalt pavement is a mixture with 4.6% asphalt binder, 12% reclaimed asphalt pavement and 3% Sasobit additive. Also, increasing the amount of the Sasobit showed that it increases the value of the Marshal strength, asphalt unit weight of mixtures and it reduces its air voids.

Heavy cost and growing losses, injury and objects destruction, deep psychological, cultural and social costs of traffic accidents are an important issue for officials, managers, politicians, as well as for the traffic police of the country. The needed to calculate the cost of traffic accidents and to find scientific, logistic and systematic ways to solve this problem is felt more quickly. In addition, determining the cost of traffic accidents highlights the imposing heavy burdens on the community, contribution of the sectors involved in the accidents. Assessing the cost of traffic accidents as a benchmark for comparing and deciding and determining the effectiveness of actions have been taken reduce disasters. Main idea in this research is estimation cost of road accidents in Iran based on latest accident statistics of 1395. Accordingly, the approximate cost of all road accidents occurred in 1395, and hence the cost of each accident in terms of damages and morality was obtained.

There are several methods to investigate the behavior of hot mix asphalt (HMA) at low temperatures. One of these methods is the use of principles of linear elastic fracture mechanics (LEFM). In this paper, the LEFM principles is used to investigate the effects of different loading modes and temperatures on the fracture resistance of HMA incorporating carbon fibers at subzero temperatures. Three-point fracture tests were successfully performed on the semi-circular bend (SCB) specimen containing an asymmetric vertical edge crack under different modes of loading including pure mode I (pure tensile), pure mode II (pure shear) and mixed-mode I/II (tensile-shear). Critical stress intensity factors were then computed using the critical load obtained from the fracture experiments and the geometry factors were determined from the finite element analyses. Results revealed that at all loading modes, modified HMA has higher resistance against crack growth than the unmodified HMA, particularly at low temperatures. Also, fracture resistance of tested HMA was improved by 30-43 percent in the pure tensile mode, 13.2-41 percent in the mixed mode (Me=0.5), 10.5-40 percent in the mixed mode (Me=0.2) and 2-12.5 percent in the pure shear mode.

In the present paper, the effects of a carbon nanotube on the moisture sensitivity of asphalt mixtures were investigated. Moisture sensitivity of asphalt mixtures is related to a phenomenon named stripping. The breaking of the bond between aggregate and asphalt binder is known as stripping (Xiao et al, 2010). Stripping reduces the strength of the material over the years which will manifest itself as rutting, corrugation, shoving, raveling, cracking, etc (Kodaii et al, 2012). Previous researches have introduced some additives for improving the moisture sensitivity of asphalt mixtures. Hydrated lime, Portland cement, polymeric material, and some other liquid anti stripping additives reduce the rate of moisture damage in asphalt mixtures. Recently, the use of nano materials in modifying different materials has become widespread (Alsaffar et al, 2014). In this study, a nano material named carbon nanotube with the quantity of 1, 2 and 3% was used for modification of asphalt binder. Moisture sensitivity of modified samples was investigated using indirect tensile strength test. In addition, the strength of modified samples was evaluated through marshal test.

This paper presents the effects of different amounts of reclaimed asphalt on fatigue life of asphalt mixtures. Central composite method was used to design of experiments based on response surface method (RSM). Binder type (Pen 60/70 and Pen 85/100), reclaimed asphalt pavement (RAP) content (25, 50 and 75%) and loading strain (150, 250 and 350 micro strain) were selected as independent variables, while 50% of initial stiffness, fatigue life and final stiffness of asphalt mixtures were chosen as dependent variables. In this research study, fatigue properties of asphalt mixtures were measured by using the four-point bending beam. The RSM analyses showed that all independent variables were significant factors for prediction of 50% of initial stiffness and fatigue life. In addition, analysis of the tests results showed that the mixtures containing higher amount of RAP at lower strains, had higher final stiffness. Furthermore, the fatigue life of specimens increased, when the level of test strains decreased. Also at the lower level of loading strain, by increasing the RAP content, the fatigue life was not decreased.