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Amirhosein Motamedi, Gholam Hossein Hamedi, Fereidoon Moghadas Nejad,
Volume 0, Issue 0 (8-2024)
Volume 0, Issue 0 (8-2024)
Abstract
Moisture damage in asphalt mixtures poses significant challenges to infrastructure durability, necessitating accurate modeling for effective mitigation strategies due to the complex nature of moisture susceptibility. Current tests, such as those utilizing general indicators like the indirect tensile strength ratio, examine moisture susceptibility in asphalt mixtures. However, these tests incur substantial costs and require considerable time. Therefore, this study aims to develop moisture susceptibility prediction models using Multi-Gene Genetic Programming (MGGP). The research utilized four types of aggregates (two limestone and two granite types) and eight different Performance Grade (PG) bitumen types. The modified Lottman test method (AASHTO T283) was employed for moisture susceptibility assessment, with samples subjected to specific conditioning protocols including vacuum saturation (13-67 kPa absolute pressure), freeze-thaw cycles (-18°C for 16 hours), and hot water conditioning (60°C for 24 hours). Indirect tensile strength tests were conducted under controlled loading conditions (2 Hz frequency, 0.1s loading time, 0.4s rest period) at 25°C. The dataset comprised 34 samples and 11 variables to predict two key indicators: Inflection Stripping Point (ISP) and Stripping Slope (SS). The MGGP model demonstrated remarkable performance in predicting both ISP and SS, achieving R2 values of 0.981 and 0.974 for the test data, respectively. Several crucial parameters were analyzed, including the apparent film thickness (AFT) calculated using aggregate specific surface area, permeability measured through falling head test method (ASTM PS 129-01), and surface free energy components. The surface energy analysis incorporated both cohesive free energy (CFE) and adhesive free energy (AFE), with special attention to the acid-base theory components: Lifshitz-van der Waals (LW), Lewis acid (Γ+), and Lewis base (Γ-) components. For ISP prediction, the MGGP model identified key variables including the ratio of base to acid surface free energy (SFE), asphalt-water adhesion (ΓAsphalt-Water), cohesive free energy (CFE), adhesive free energy (AFE), permeability of asphalt mixture (PAM), asphalt film thickness (AFT), and degree of saturation (DS). The model for SS prediction emphasized the importance of ΓAsphalt-Water, aggregate-water adhesion (ΓAggregate-Water), wettability, specific surface area (SSA), PAM, and DS. The study employed various performance metrics to evaluate the MGGP models. For ISP predictions, the model achieved RMSE, MSE, and MAE values of 5.228, 27.337, and 3.843, respectively. For SS predictions, these values were 0.294, 0.086, and 0.231, respectively, indicating high accuracy and low error rates. These results surpass those of previous studies employing traditional Genetic Programming (GP) methods, highlighting the potential of MGGP as a powerful tool in modeling asphalt moisture susceptibility. The practical implications of this research are significant for improving asphalt mixture durability, reducing maintenance costs, and enhancing road safety. Future research could focus on validating the models across a broader range of asphalt mixtures and environmental conditions.
Mohammad Mehdi Dadaei, Pouria Hajikarimi, Mohammad Rahi, Mehdi Dastoori Razaz, Behnoosh Tahmasbi, Fereidoon Moghadas Nejad,
Volume 0, Issue 0 (8-2024)
Volume 0, Issue 0 (8-2024)
Abstract
Accurate analysis of bitumen behavior as a viscoelastic material and its natural phenomena such as aging are important issues in pavement engineering. Therefore, controlling the low and high temperature properties of bitumens is essential to prevent low temperature cracking and common high temperature distress in order to provide proper service throughout the pavement life. In this study, the aging phenomenon and its effects on the mechanical properties of bitumens were simulated using the Superpave method, namely the RTFOT method for short-term aging and the PAV method for long-term aging. In order to investigate the effect of repeated PAV cycles on the properties of bitumens, three types of bitumen with different penetration degrees of 40-50 (PG70-16), 60-70 (PG64-22) and 85-100 (PG58-28) were selected and three samples of each were subjected to one to three PAV aging times. The beam shear rheometer (BBR) test was performed at three temperatures from 0 to -12°C and the dynamic shear rheometer (DSR) at seven temperatures from 46 to 82°C. Based on the results obtained, the high temperature performance of the bitumens increased by a maximum of three grades and their low temperature performance increased by a maximum of two grades. In other words, the grading of the triple bitumens, after three times of PAV, became 82-4, 82-10, and 70-16, respectively. Also, the relationship between the high temperature performance properties of the aged bitumens and their chemical changes at different times of aging was investigated and their changes were examined to show the correlation between these properties. The results showed that the high temperature viscoelastic properties and the chemical aging index of the different bitumens had a strong linear relationship with a coefficient of determination (R2) of more than 0.9.
Ali Zarei, Abolfazl Hassani,
Volume 18, Issue 6 (12-2018)
Volume 18, Issue 6 (12-2018)
Abstract
In this research, 0, 5, 10, 15 and 20 percent of crumb rubber mix was used as a fine grained substitute for concrete pavement. Also, in another state, half percent of the steel fibers recovered from worn tires were added to these samples. The results of this study indicate that the compressive strength of samples with 5, 10, 15 and 20% crumb rubber in comparison with the control sample was reduced by 1.6, 36.9, 49.9% and 63.1%, and samples with 0, 5, 10, 15 and 20% crumb rubber and 0.5% steel fibers, respectively, decreased by 0.3, 11.2, 33.7, 5 / 41% and 44.3% respectively. Therefore, it is observed that the compressive strength of concrete containing crumb rubber and steel fibers is better than specimens with crumb rubber. Also, by replacing 5%, 10%, 15% and 20% of crumb rubber in concrete, its indirect tensile strength would be reduced by 7.5%, 15.3%, 41.4% and 31.2% , and by adding 0.5% of the steel fibers to the concrete by replacing 0, 5, 10, 15 and 20% of crumb rubber in concrete, Indirect tensile strength increased by 67.8%, 46.7%, 32.4%, 17.8% and 3.5%, respectively, and it is concluded that the tensile strength of concrete increases due to the addition of steel fibers.
Amin Khajehdezfuly, Abdolghaour Khademalrasoul, Mojtaba Labibzadeh,
Volume 19, Issue 2 (7-2019)
Volume 19, Issue 2 (7-2019)
Abstract
Nowday, slab track is widely used in the world as railway supresturture because its advantages in comprison with conventioanl ballasted railway superstureure. So, design and analysis process of railway slab track is one the main issues in recent researches. One of the main factor in the design and analysis of slab track is distrubtion of vertical load on longitudinal direction of the track (load distribution factor). In this paper, a 2D numerical model is developed in FORTRAN to investigate the effect of slab track properties on the load distribution factor. In this model, the slab track is comprised of rail, fastening system, concrete slab, elastic layer, concrete base and subgrade. Rail, concrete slab and concrete base are modeled as two nodeded beam element and fastening system, elastic layer and subgrade are simulated as spring element. According to the elements stiffness matrices, slab track stiffness matrix is developed. A wheel load is applied on the rail (in the middle of the model). Based on the two noded beam element shape functions, load vector of the model is developed. The equlibrium equation of the model is solved and load distribution factor is derived. To investigate the validity of the results obtained from the model, a comparsion is made between results obtained from the model and those of ABAQUS as a commercial finite element software. Rail displacement, concrete slab displacement, concrete base displacement and load disribution factor obtained from the ABAQUS are compared with those of the model developed in this paper and a very good agreement was illustrated between results. A parametric study was performed to investigate the effects of rail flexural rigidity, fastening system stiffness, concrete slab flexural rigidity, elastic layer stiffness, concrete base flexural rigidity and subgrade stiffness on the load distribtion factor. The results obtaine from the parametric study indicate that as the slab track element stiffness or flexural rigidity is decreased, the load distribution factor is decreased and vertical load is distributed widely in the longitudinal direction of the track. Rail pad stiffness has the maximum effect on the load distribution factor reletive to the other parameters. As the rail pad stiffness is changed from lowest to highest magnitude, the load distribution factor is varied from 0.3 to 0.7. The results obtained in this research indicate that propeties of lower slab track elements have lower effects on the load distribution factor compared to the upper slab track elements. So when the flexural rigidity of the concrete slab is changed from low to high, load distribution factor is changed from 0.52 to 0.54. Moreover, when the elastic layer stiffness, concrete base flexural rigidity and subgrade stiffness are changed from low to high, the load distibution factor are almost unchanged and is roughly 0.54. This shows that elastic layer stiffness, concrete base flexural rigidity and subgrade stiffness do not have any significant effects on the load distribution factor. So when a model is developed to calculate the load distribution factor and dcrease of analysis computation cost, elastic layer stiffness, concrete base flexural rigidity and subgrade stiffness could be ignored in the model.
Abolfazl Mohammadi Janaki, Abolfazl Hassani,
Volume 19, Issue 4 (11-2019)
Volume 19, Issue 4 (11-2019)
Abstract
Roads are one of the most important and valuable assets of countries, and remarkable amounts are spent annually to repair and restructure them. The pavements are divided into two main groups of flexible pavements (asphalt pavements) and rigid pavements (concrete pavements). In Iran, mainly used asphalt pavements, which were formerly about 90 years old. Therefore, there are many reasons why the most important of them, according to most experts, is the use of the country from abundant oil resources and low initial costs in the construction of this type of pavement. In recent years, with the entry of bitumen as one of the main components of the asphalt composition of the commodity exchange and consequently the increase in the cost of manufacturing and manufacturing asphalt, as well as the development of cement production plants in the country and the creation of carbon dioxide (CO2), a suitable platform for the development of geo-polymeric concrete pavements in competition with asphalt pavements and concrete cement has been provided.
In addition to abbility of bearing and reducing the pressure caused by the vehicle wheels, the pavement layers should be durable against atmospheric and physical factors, including the natural elements of the freeze-thaw cycles, acids and sulfates. Th pavement must be able to withstand the durability and durability of the pavement and maintain its service over the lifetime specified.
These destructive effects led to more attention to the optimal use of resources, pozzolanic materials, and waste. In this regard, the use of ground granulated blast furnace slag and Silica fume in various industries such as road construction and building have been considered as a solution, however, practical, accurate and effective steps have not been taken yet. This research tried to present the materials and experiments carried out and to summarize them in order to eliminate the obstacles and obtain the necessary results for the use of alkaline concrete (geo-polymeric) in the manufacture of durable concrete veneers in the pavement.
The use of alkali-activated slag concrete with the replacement of Silica fume instead of silica in sodium silicate, in addition to the use of waste materials, enables the strength and durability of concrete pavement to be increased under freezing and thawing cycles, acid attacks and being sulfate.
In this study, alkali-activated slag concrete with different percentages of Silica fume was studied using The experiments of compressive and bending strength, durability under freeze-thaw cycles, sulfuric acid, and magnesium sulfate attacks. The results showed that the replacement of 30% silica fume instead of silica in sodium silicate, increasing the compressive strength to 43.8%, increasing the bending strength by 58.9%, increased the durability under freezing and thawing cycles by 78.2%, increasing durability against sodium sulfate to The rate of 57.1%, increase the durability against magnesium sulfate by 54.1%, and the reduction of pavement slab thickness by 20.8% compared with concrete cement.
In addition to abbility of bearing and reducing the pressure caused by the vehicle wheels, the pavement layers should be durable against atmospheric and physical factors, including the natural elements of the freeze-thaw cycles, acids and sulfates. Th pavement must be able to withstand the durability and durability of the pavement and maintain its service over the lifetime specified.
These destructive effects led to more attention to the optimal use of resources, pozzolanic materials, and waste. In this regard, the use of ground granulated blast furnace slag and Silica fume in various industries such as road construction and building have been considered as a solution, however, practical, accurate and effective steps have not been taken yet. This research tried to present the materials and experiments carried out and to summarize them in order to eliminate the obstacles and obtain the necessary results for the use of alkaline concrete (geo-polymeric) in the manufacture of durable concrete veneers in the pavement.
The use of alkali-activated slag concrete with the replacement of Silica fume instead of silica in sodium silicate, in addition to the use of waste materials, enables the strength and durability of concrete pavement to be increased under freezing and thawing cycles, acid attacks and being sulfate.
In this study, alkali-activated slag concrete with different percentages of Silica fume was studied using The experiments of compressive and bending strength, durability under freeze-thaw cycles, sulfuric acid, and magnesium sulfate attacks. The results showed that the replacement of 30% silica fume instead of silica in sodium silicate, increasing the compressive strength to 43.8%, increasing the bending strength by 58.9%, increased the durability under freezing and thawing cycles by 78.2%, increasing durability against sodium sulfate to The rate of 57.1%, increase the durability against magnesium sulfate by 54.1%, and the reduction of pavement slab thickness by 20.8% compared with concrete cement.
Seyed Farzin Faezi, Mehrdad Mirshekarian,
Volume 19, Issue 6 (12-2019)
Volume 19, Issue 6 (12-2019)
Abstract
Recycled asphalt chips after shaving are considered to be a waste material that has an adverse environmental impact on the environment. On the other hand, the heavy cost of constructing new ways and damages caused by the destruction of existing roads will cause many problems. Therefore, the aim of this study was to investigate the effect of mixed bitumen with filler change on mechanical and functional properties of asphalt foam mixtures of recycled materials. Research method is field study. All experiments were carried out at the Technical and Mechanical Laboratory of the Ministry of Construction in Tehran. In this project, aggregates consumed from asphalt tracks of the 29th straight Shahid Dastgheib International Airport in Shiraz were prepared. The bitumen used in this research was selected as bitumen from Tehran refinery in Tehran. Also, Portland cement fillers of type 425-1, lime and cement and lime mixture as active filler were used and the amount of active filler added in all designs was considered the same. Samples were made by adding cement fillers, lime with different bitumen content and under dry and saturated treatment conditions. Samples were made with filler cement (1.5%), lime (1.5%) and cement, lime (0.75% and 0.75%) and a control sample. Then, the experiments were performed on the modulus of resilience, the strength of the marshall and the indirect pull resistance. To increase the number of observations and increase the accuracy of the mathematical model, samples with cement filler with a ratio of 1 and 2 percent with bitumen 1, 2 and 3 were constructed using Marshall Hammer. Marshall Strength tests, modulus of resistivity and indirect pull resistance were carried out in dry and saturated conditions. Using the results of the modulus of resilience test, the finite element modeling was performed using ABAQUS and KenLayer software, and the effect of changing the modulus on the number of load repetitions that resulted in fatigue failure was evaluated. Finally, a mathematical model was presented. The results of this study, using SPSS and Statisca software, show that in Marshall's strength test, in all plans, increasing the bitumen from 1 to 2 percent, the Marshall Strength increases and then decreases with increasing bitumen by 2 to 3 percent. Marshall Strength ratio (obtained by dividing the Marshall strength of saturated samples to the Marshall strength of dry specimens) revealed that these types of mixtures are sensitive to moisture conditions and at best (2% bitumen and with cement lime filler) this amount reaches 0.46. Also, results of indirect resistance test show that, with increasing bitumen from 1 to 3%, in all designs, indirect resistance is increased during drying, saturation is continuously increased. The cement filler with lime in all treatment modes has the greatest effect on increasing the indirect pull resistance, and the effect of increasing the strength of the filler-containing specimens is more than dry in terms of saturation processing. The results of three-dimensional modeling of Abacus showed that increasing the modulus of the base layer, the number of repetitions leads to fatigue failure greatly increases. Also, half-life parameters, expansion ratio and index of bitumen were measured and the parameters of these parameters were plotted against water percent.
Seyed Farzin Faezi, Seyed Reza Sharifi, ,
Volume 20, Issue 2 (5-2020)
Volume 20, Issue 2 (5-2020)
Abstract
Clay soils often cause problems in construction projects. In cold regions, freezing and thawing of clay soils can cause significant changes in the geotechnical characteristics of the soil. Frozen and thawed soils have shown changes in volume, strength, compressibility, frozen moisture content, bearing capacity and microstructural changes. In road construction projects in cold regions, freezing and melting is one of the factors affecting the unstability of soil engineering behavior, including the durability and performance of pavement and pavement layers. Therefore, the purpose of this research is to evaluate the effect of freezing and melting cycles on the parameters of the durability of calcareous stabilized clay bed based on compressive strength test results. 400 kg of soil samples were collected from the subgrade of the RAZ-PASIN rural road. In the first stage, granulation experiments, Atterberg and ... on 20 soil samples were performed. The second stage was the dry maximum dry matter and optimum moisture content of the soil-cement mixture. The third step was to determine the percentage of suitable cement for mixing, soil-cement mixed density with different percentages (6%, 8%, 10%, 12% and 14%) with limestone cement type 1 and type 2. In the fourth stage, 24 cylindrical specimens were added to the soil sample by adding (8%, 10%, 12%) of type 1 and type 2 calcareous cement and tested for compressive strength. In the fifth step, the indirect tensile strength and the stress-strain modulus of the mixed soil-cement were determined. The results indicated that the maximum dry matter density of the soil-cement mixture was obtained by adding 10% of type 1 and type 2 calcareous cement. The results also showed an increase in the compressive strength of the composite made with type 1 lime Portland cement compared to Type 2 lime Portland cement, and all specimens containing 8% calcareous cement additive exhibit more than 35 kg / cm2 after 7 days of resistance treatment. This means that samples made with Portland cement have a sufficient durability against atmospheric agents. If the use of calcareous Portland cement is used only for bed consolidation as a layer of pavement layers and the appropriate weight percentage of Portland Type II cement is selected to be 8% for the consolidation of the studied soil, the cost of the Rural Road Project will be compared. The Late Valley showed a 13% reduction in the cost of supplying calcareous Portland cement compared to Type II Portland cement (Table 10). This is due to a 15% reduction in energy costs (gas and electricity consumed) in the manufacture of calcareous Portland cement compared to Type II Portland cement. By comparing the results of compressive strength of soil-mixture of type 1 calcareous Portland cement and type 2 cement, it can be concluded that the effect of type 1 calcareous Portland cement in obtaining compressive strength is better than type 2 calcareous Portland cement due to increasing Lime is made of cement composition. This increased resistance is due to the ion exchange reaction and the agglomeration-compaction reaction between lime and soil and is achieved by lime contact with most fine-grained soils. Thus, the calcium ions in the lime are replaced by the lower-capacity positive ions in the soil. This results in the accumulation of calcium ions around the clay particles.
Ali Yarahmadi, Mohsen Fallah Zavareh, Majid Zabihi Tari,
Volume 20, Issue 2 (5-2020)
Volume 20, Issue 2 (5-2020)
Abstract
Speeding contributes to increased frequency and severity of road crashes. Strengthening deterrence of speeding requires imposing effective penalties for non-compliance with speed limits, as well as effective enforcement of the legislation. Yet, different monetary and non-monetary penalties have been proposed for offensive drivers. The literature, however, lacks evidence on relative deterrence of existing penalties and the way the drivers respond to new forms of penalty systems. This study is among the first that investigated relative deterrence of different speeding penalties including “monetary fines”, “demerit point”, “car detention”, and “social deprivation”. Questionnaire was designed based on choice experiment method (CEM) with considerations of balance and orthogonality. Convenience sampling method was used to collect data in campuses of Kharazmi University in Karaj, College of Engineering in University of Tehran, and East Tehran Branch of Islamic Azad University, which all are among the largest university campuses in the country. A total of 550 questionnaires including 2004 choices were conducted (response rate: 91.1%). Using an indirect approach, we conducted a mixed logit (ML) model to estimate the drivers’ willingness to pay (WTP) for non-monetary speeding penalties. Results indicated that “social deprivation” would offer stronger deterrence compared to other penalties. Deterrence effect of “monetary fines” and “demerit point” increases with increase in drivers’ age. Findings emphasized that further development of non-monetary penalties in the future would increase deterrence of speeding violations.
Saeed Amani, A .kavussi, Mohammad M.karimi,
Volume 20, Issue 3 (10-2020)
Volume 20, Issue 3 (10-2020)
Abstract
Aging in asphalt pavements results in reduced serviceability and flexibility of pavements. Aging is not commonly considered as distress, but it substantially effects the rate of evolution of various distresses. One of the common distress observed in aged asphalt pavements is cracking. If cracks/micro-cracks are healed during their initial formation, the service life of the pavement will be increased. Otherwise, there will be the risk of crack propagation that results in more cracking and loss of pavement strength. It is well known that asphalt mixes have capability of self-healing their cracks/micro-cracks when they are exposed to high temperatures. Cracks/micro-cracks in asphalt mixes can be healed through an induced healing process. Induced healing of asphalt mixes by applying external electromagnetic radiation is an innovative technique to repair cracks/micro-cracks. Applying external energy through electromagnetic radiation increases the temperature of the asphalt binder in mixes, allowing it to move and fill the cracks/micro-cracks. Flowing and crack filling of asphalt binder play a significant role in induced healing characteristics of mixes. As temperature of the asphalt binder is increased, its viscosity will be decreased drastically. When asphalt binder gets to Newtonian fluid temperature or higher, the melted binder moves inside the cracks and micro-cracks and subsequently, the cracks will be healed. The aim of this research was to evaluate the effects of different aging levels on induced heating-healing of asphalt mixes. In order to impose different aging levels, asphalt mixes were aged in oven for 3, 5, 7 and 9 days at 85 ºC. Activated carbon was added to mixes so that to enhance electromagnetic sensitivity of mixes. In addition, effects of activated carbon on mechanical properties and microwave heating rate of mixes were determined. Results indicated that activated carbon, as a powder-based additive, improves electrical conductivity, induced heating-healing rate of asphalt mixes. In addition, it was shown that aging phenomenon in asphalt mixes decreases their heating rate, which was more pronounced in higher aging level. Lower heating rate of asphalt mixes resulting in lower efficiency of induced healing of mixes. For evaluating healing capability of mixes that were subjected to different aging levels, Semicircular Bending tests (SCB) was conducted at intermediate and low temperatures. It presented that induced healing efficiency of mixes decreased as the aging level and the notch length in SCB testing were increased. The adverse effects of aging on induced healing process can be attributed to increased viscosity of the asphalt binder in mixes, which limits moving capability of melted asphalt binders to move through damages and properly heal the cracks. Moreover, it resulted that, lower heating rate of aged mixes can be considered as another reason of reduction in induced healing efficiency. The results indicated that increased notch lengths not only affects load at fracture and fracture energy of mixes, but also it plays a significant role in induced healing efficiency of mixes. For further evaluation of the healing ability of asphalt mixes, combination effects of aging, notch lengths and testing temperature parameters were also investigated. Notch length and testing temperature was found to have significant effects on induced healing efficiency of mixes. In addition, the results indicated that induced healing efficiency of low temperature cracked asphalt mixes were more than that of asphalt mixes that were cracked at intermediate temperatures. The results suggest that the necessity of considering aging level in analyzing induced heating-healing process of asphalt mixes.
Mohsen Ahmadi, Ghshafabakhsh Ghshafabakhsh, Abolfazl Hasasni,
Volume 21, Issue 2 (5-2021)
Volume 21, Issue 2 (5-2021)
Abstract
In order to expand the application of roller Compacted concrete (RCC) in high speed roads, casting a thin layer of concrete with high skid resistance immediately the after implementation and compaction of RCC has been suggested. In the present study, the mechanical and fracture properties of this kind of two lift concrete pavement (2LCP) evaluated and compared with common single lift concrete pavements. Therefore, a thin layer of plain concrete and polypropylene fiber reinforced concrete with relative thickness of 30% of total pavement thickness has been casted of RCC pavement.. Compressive strength and mode I fracture tests were performed on samples after 28 days curing.
Result showed that the addition of polypropylene fibers to plain concrete reduces the compressive strength of concrete slightly. Also, replacement of normal concrete or fiber reinforced concrete with roller concrete in the upper layer of 2LCP did not have a significant negative effect on flexural strength and fracture of the specimens compared to single lift RCC pavement with equivalent thickness.
Mohammad Mahdi Dibaee, Amir Kavussi,
Volume 21, Issue 3 (5-2021)
Volume 21, Issue 3 (5-2021)
Abstract
Asphalt binder has an important role in asphalt mixture behavior. Therefore binder fatigue characterization has been widely investigated. Significant research efforts were focused on developing reliable fatigue prediction models. Those efforts in the beginning were concentrated on relating initial responses, such as strain or stress levels of asphalt mixtures to their fatigue life. Such phenomenological relationships were usually developed by means of testing samples under different loading conditions and generating regression models. Considering different combinations of loading conditions, and the long time duration needed for a single fatigue test, the phenomenological approach requires extensive time and funding. Therefore, the mechanistic approaches which substitute excessive testing with analytic equations, have become more common in the field of fatigue behavior characterization. Viscoelastic continuum damage (VECD) mechanics is one of the well-studied mechanistic approaches to characterize the fatigue life of viscoelastic materials. In this approach an internal state variable (ISV), called damage, is defined to stand as a representative of material structural state. Then the state of the modulus is determined as a function of damage, namely damage function. Determination of damage function can facilitate asphalt fatigue prediction under different loading patterns. However, VECD analysis has its own complications. The damage parameter needs to be calculated in each cycle during the test, while its calculation needs damage function trend to be known. Thus, damage parameter can only be determined using a procedure of try and error. In this research an inventive method has been introduced that can simplify efforts to yield damage function, requiring less time and fewer samples. A formulation framework has been presented here which is based on an analytical solution of the governing differential equation of damage evolution power-law. The solution is made assuming the ruling conditions of this study. These assumptions which are clarified in the paper could be reconsidered to form new formulations through a similar approach. Using the formulation, developed in this study, damage function can be found, using the data obtained from two constant-strain, or a single incremental-strain tests. According to this method Time Sweep Test can be performed at two different strain amplitudes and the developed models could be fit to the initial responses data of the material to yield VECD parameters needed to constitute the fatigue prediction model. This approach uses a nonlinear regression analysis to determine VECD parameters, even without calculating the values of damage during test. Afterward, the proposed procedure was validated by experimental tests. Time Sweep tests were performed on binder samples modified with SBS polymer. The binder samples were modified using SBS Polymer, due to its popularity among asphalt researchers. Such modification transforms a simple binder to a complex one. Results showed that the try and error procedure can be substituted by regression model to yield damage function in less time. The discrepancies between the data obtained from the two above-mentioned methods were negligible. It was concluded that the similar results are due to the same mechanism, used in try and error and regression methods which is performed through different approaches.
Mohammad Sedighian-Fard, Nader Solatifar,
Volume 21, Issue 3 (5-2021)
Volume 21, Issue 3 (5-2021)
Abstract
One of the critical environmental factors that affect the deformation of flexible pavements is the depth temperature of asphalt layers. This is due to the viscoelastic behavior of the asphalt mixtures. The stiffness of the asphalt layers has a significant effect on the structural capacity of flexible pavements. This property is a function of the asphalt layer temperature and changes daily and seasonally. As the temperature increases, the stiffness of the asphalt layer decreases, which increases the stress in the base and subbase layers of the pavement. Therefore, the pavement response to the applied loads is affected by the depth temperature. Hence, the depth temperature of asphalt layers is one of the most important and main factors in the analysis, design, and rehabilitation process of flexible pavements. Some predictive models have been developed to determine the depth temperature of asphalt layers in pavement maintenance and rehabilitation activities. These models, as an alternative to field and laboratory measurements of this factor, are low-cost, rapid, and simple methods to determine the depth temperature of asphalt layers. It should be noted that these models are based on the limited field and laboratory data, therefore, there is a need for developing new models for prediction of the depth temperature of asphalt layers in different traffic and climatic conditions. The objective of this study is to develop a model for predicting the depth temperature of asphalt layers based on climatic data. In recent years, Artificial Neural Networks (ANNs) have shown good performance as a useful tool for modeling physical events. The modeling method used in this study is a Back-Propagation Neural Network (BPNN) model that predicts the average hourly depth temperature of asphalt layers based on several variables, including the time of the day, desired depth from the pavement surface, average hourly air temperature, average speed and direction of the wind, minimum air humidity and total solar radiation. Data was extracted from the Long-Term Pavement Performance (LTPP) database. After extracting and preparing raw data, all the needed data were acquired from different data tables and linked to each other in a database. As a case study, data points collected from pavements in Ohio, USA, has been used for modeling. Also, to ascertain the presence or absence of multicollinearity between independent variables, the Pearson correlation test has been conducted. For this reason, the maximum speed and direction of the wind and maximum air humidity parameters were removed from the data set. According to the results of the Pearson correlation test, the average hourly air temperature has the most powerful impact on the average hourly temperature of the asphalt layer depth (correlation=95.2%). After training and testing the neural network, the performance of the developed model has been evaluated, and results were compared with a non-linear quadratic regression model. The results show that the developed model is more accurate than the regression-based model. In addition, the ability of the developed model in predicting the depth temperature of asphalt layers based on existing climatic data with a very good prediction accuracy (R2=0.96) and very low bias and error has been shown. Furthermore, the performance of the developed model has some restrictions for the prediction of depth temperature of asphalt layers. Other factors such as material characteristics can be scrutinized and applied to enhance the performance and applicability of the model.
مهردخت Doosti, Amir Kavussi, Mehdi Azarnia,
Volume 21, Issue 4 (10-2021)
Volume 21, Issue 4 (10-2021)
Abstract
Over the past decades, pavement researchers have taken different approaches to enhance rheological properties of bitumen and performance of asphalt mixtures. Application of additives such as Crumb Rubber is one of the most economic approaches.
The use of Crumb Rubber not only improves performance of asphalt mixtures by increasing fatigue life and rutting resistance of mixes but it reduces moisture susceptibility of mixes and bring about several environmental benefits. Despite the above mentioned advantages, mixing Crumb Rubber with bitumen in conventional dry and wet processing results in problems such as increased production cost, initial aging, and coagulation of rubber modified bitumen, as well as phase separation of the modified binder.
In order to overcome the above problems, an innovative technique was developed to produce CRM mixtures in TMU Road Research Centre. This method, named Processed Crumb Rubber Modifier (PCRM), was consisted of incorporating surface activate materials in rubber-bitumen blends and produce rubber type granules.
Since this material is new, extensive experimental research works are required to evaluate properties of the P-CRM modified bitumen and performance of asphalt mixtures prepared with that. In this research, with producing reacted and activated rubber bitumen, the moisture susceptibility and fatigue resistance of asphalt mixtures, prepared with P-CRM and CRM were investigated. This was with testing mixes under Indirect Tensile Strength (ITS) and Indirect Tensile Fatigue Test (ITFT). In addition, properties of the P-CRM content specimens were compared with those of the wet-processed rubber modified bitumen.
Moisture susceptibility testing results showed that the application of Crumb Rubber in modifying bitumen with wet processing as well as with P-CRM method increased indirect tensile strength of the specimens in both dry and saturated conditions. However, specimens prepared using P-CRM material had better performance in saturated conditions. On the other hand, results of mixes tested under ITFT indicated that fatigue resistance of specimens containing P-CRM was greater (compared with the control specimens and those modified using CRM).
Mohsen Rostamkhani, Neda Kamboozia, Mahmoud Ameri,
Volume 21, Issue 4 (10-2021)
Volume 21, Issue 4 (10-2021)
Abstract
Because of having amazing mechanical physical properties including noise pollution reduction, quiet, reliability, most cost-effective, sustainable and lasting life, asphalt pavement system has been utilized for parking lots, roadways, airstrips by the most state and federal governments highly prefer asphalt pavement by many civil engineers. Generally, asphalt pavement is made up of sand, stone (aggregate), liquid (petroleum) asphalt and additives. In the present study, the thermo-dynamic behavior of porous viscoelastic asphalt pavement system under a moving harmonic load based on the classical plate theory is analyzed. The asphalt pavement system is modeled as a rectangular sandwich plate structure. Three states of porosity distribution pattern, i.e., uniform porosity, non-uniform symmetric porosity, non-uniform asymmetric porosity distributions are considered for porous asphalt layer which are supposed to vary along the in-plane and thickness directions. The equations of motion are extracted in accordance with Hamilton’s variational principle and then solved using the expanded Fourier series. The accuracy and correctness of the extracted formulation are firmly demonstrated by comparing the data accessible in the literature and finite element simulation COMSOL Multiphysics®. In this study, the dynamic response of the asphalt pavement system was evaluated analytically and numerically by considering the porous asphalt layer under the harmonic load at various velocities in a thermal environment. The classical theory of plates was used for the analytical modeling of the system. The dynamic equations were derived in view of the relations for porosity and thermal strain in the stress-strain matrices in combination with Hamilton’s principle. With the aid of Fourier series expansions, and given the considered boundary conditions, the partial dynamic equations were transformed into differential dynamic equations. Furthermore, the dynamic response of the system was obtained using Laplace transform, which was then evaluated in terms of effective parameters. A finite element simulation software was also used to validate the results against the published articles. In this study, three case of uniform porosity, non-uniform symmetric porosity, non-uniform asymmetric porosity distributions are considered for modeling porous asphalt layer. Parameter studies reveal the impacts of the velocity and the excitation frequency of the harmonic moving load, porosity distributions, and temperature changes on the dynamic response of the pavement system. According to the conducted studies thus far, the dynamic behavior of asphalt pavement system is inevitably affected by such outcomes. Furthermore, the results demonstrated that non-uniform symmetric porosity case is more suitable than the other two types of porosity, The temperature changes lead to a softer asphalt pavement system, With increasing porosity, the dynamic response of the system rises in all the cases of porosity distributions and The amplitude of nondimensional dynamic deflection is directly proportional to the frequency of excitation up to the resonance.
Behnam Abdi, Saber Naseralavi,
Volume 21, Issue 6 (12-2021)
Volume 21, Issue 6 (12-2021)
Abstract
The Driving Anger Scale (DAS) is one of the most reliable and practical tools for measuring drivers' anger. Therefore, this study intends to evaluate the validity and reliability of this scale among Iranian drivers using appropriate statistical tools. To assess the validity of this tool, two methods of exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were used. The results of EFA showed the 6-factor structure is suitable for this scale. Then, the 6-factor structure obtained from the EFA, was compared as three type of models. The results of this method showed that the one-factor structure of this tool is not suitable in comparison with the other two structures, especially the bi-factor one. According to the results of ANOVA test, in terms of gender and age, there are significant differences in driving anger among Iranian participants, which young and men get relatively higher scores. In addition, the results of correlation analysis indicated that there are significant relationships between DAS subscales with Depression-Anxiety-Stress Scale (DASS) and Buss-Perry Aggression (BPAQ) scores. Also, there are significant relationship between the number of major accidents with traffic jams, overall DASS and BPAQ scores. On the other hand, the relationships between the number of minor accidents with the slow driving subscale and the overall BPAQ score were statistically significant. Finally, this study showed that the DAS questionnaire is a valid and reliable criterion for assessing the anger of Iranian drivers.
Peyman Mirzababaei, Fereidoon Moghadas Nejad, Pouria Hajikarimi,
Volume 22, Issue 4 (7-2022)
Volume 22, Issue 4 (7-2022)
Abstract
Road pavements are one of the most important assets of any country, and tremendous amounts of budgets are allocated for their maintenance every year. Unexpected distresses in asphalt pavement cause many financial losses. Winter maintenance of roads and infrastructures and the study of the effects of anti-icers and deicers on the asphalt pavements have always been of interest to researchers, departments, and agencies in the field of roads and transportation. As a contribution to this task, the present study was conducted to evaluate the effect of Zycotherm on the fracture behavior of asphalt mixtures in the presence of moisture and deicers. In order to achieve the research objectives, PG58-22 bitumen and siliceous materials were used to prepare the asphalt mixture and also Zycotherm was used to modify the asphalt binder. Data were collected by testing on laboratory samples. The asphalt mixture samples were conditioned in the presence of distilled water and solutions of brine, calcium magnesium acetate, and potassium acetate in their normal concentration for 96 hours at 60°C. Then, the fracture toughness of the specimens at low temperatures (K1c) and the critical strain energy release rate (Jc) at intermediate temperatures were measured by performing a semi-circular bending test (SCB). The results showed that simulation of low-temperature environmental conditions in the vicinity of distilled water and all deicers reduces the fracture toughness of asphalt mixtures compared to the dry sample. Brine solution has the most negative effect among all the deicers and reduces the K1c parameter by approximately 30%. On the other hand, Zycotherm maintains the fracture toughness of the asphalt mixture at low temperatures in the vicinity of distilled water and deicers at an almost constant level and recovers about 70% of the lost fracture strength of the sample conditioned in the brine solution. The effect of Zycotherm at intermediate temperature is different and causes the softening of bitumen and the reduction of the critical fracture force and the reduction of the critical strain energy release rate. This reduction is 34% and 32% for the dry sample and the specimen in the presence of brine solution, and 23% and 12% for the samples in the presence of calcium magnesium acetate and potassium acetate, respectively, compared to the sample made of neat bitumen. Also, samples in the vicinity of distilled water and potassium acetate solution showed no significant change in their critical strain energy release rate compared to samples in dry conditions. Visual inspection also revealed that calcium magnesium acetate causes additional stress and cracking in the samples. In a general summary and based on the obtained results, Zycotherm has a positive effect on the fracture toughness of the asphalt mixture at low temperatures but reduces the Jc parameter at intermediate temperatures. All specimens have the minimum critical strain energy release rate recommended by ASTM D-8044 at intermediate temperatures. Potassium acetate has no effect on the fracture toughness of asphalt mixtures at low and medium temperatures and can be an appropriate alternative in comparison with other deicers in winter road maintenance.
R. Jalalkamali, P. Kamali Sarvestani,
Volume 22, Issue 5 (12-2022)
Volume 22, Issue 5 (12-2022)
Abstract
In smart cities, with using lots of new technologies, while creating appropriate facilities in routine urban life, infrastructure problems are investigated and the necessary measures are taken in a targeted and systematic manner to solve these problems. One of the most important technologies for managing infrastructure in smart cities is IT technology. GPS and smartphone sensors are other technologies that can be widely used in these cities. Streets, roads, and pavements are important infrastructures in any city and the future smart cities. Proper supervision, repair, and improvement of pavements, streets, and urban pathways are the main factor in reducing the cost of depreciation of vehicles and providing comfort and safety for citizens. On the other hand, if timely action is taken to restore and improve the pavement, huge costs of repair and reconstruction will be avoided, and this can significantly reduce the costs of urban management. The first step to achieving this goal is to identify the location of the roughness and distortion of the surface of the streets and urban pathways and the severity of these failures in the shortest possible time. In this paper, road surface roughnesses and failures have been studied using accelerometer sensors and GPS smartphone devices. Location and vertical acceleration data have been entered into GIS software and a quantitative index based on the values of vertical acceleration has been introduced to determine the quality of each section of urban road pavement. In this research, Androsensor software, which is a useful application for using smartphone sensors, has been used. This software is installed on two smartphones, Huawei, P30 Lite, and BlackBerry, Priv STV100. To collect the data, the smartphones were placed in a fixed position on the right and left sides of the car, on the dashboard. The collected data for analysis is transferred to the computer in Excel files. This research has been done in Kerman city and to collect data, different routes with specific failures have been selected. Data collection was performed in 81 pieces with a length of 500 meters and 24 pieces with a length of 200 meters (105 pieces, 45300 meters in total). By analyzing the vertical acceleration data and calculating some proposed indexes and comparing them, the best index has been selected. This index is classified into different ranges according to the field inspection of the pavement condition in the routes in this study, that each of which indicates the quality status of the pavement. Each of these intervals is introduced with a specific color, and by examining the index obtained in each route and the corresponding interval, the studied routes are marked with different colors on the map. Finally, it was found that the accelerometer sensors and GPS of smartphones can be used with low cost, high speed, and appropriate accuracy to check the surface of pavement of urban roads and grading the quality of the pavement. It also seems that in the smart cities of the future, which are based on IT technology, the use of user data, high accuracy in locating, and speed of action in prevention, the proposed method in this research can be used more favorably.
M. Asadi, A. Hasasni, M. M.karimi,
Volume 22, Issue 5 (12-2022)
Volume 22, Issue 5 (12-2022)
Abstract
Proper and timely maintenance of concrete pavement plays a decisive role in increasing the life of these pavements. Joint plain concrete pavement is a type of concrete pavement used for roads. One of the important parts of this type of pavement is the joints created in it. The use of joints to provide conditions for expansion and contraction in concrete pavements and thus reduce stresses due to changes in weather conditions (temperature and humidity), friction, and facilitate the manufacturing process. Due to the fact that the joint in the joint plain concrete pavements is a weakened area for the conduction of cracks from unforeseen areas of the concrete slab to it, the entry of water and other materials into it causes penetration into the underlying layers of the slab to prevent penetration. Joint Sealants are used in these areas. Hot applied bitumen sealant is one of the most common sealants used in joints, which is based on bitumen. One of the key factors in the longevity of concrete pavement is the proper functioning of the joint and joint sealant. The adhesion and cohesion failures are two main damage types in the hot-applied bituminous joint sealants in concrete pavement joints. The mentioned failures are caused by the contraction of concrete pavement under the temperature drop and fluctuation as well as vertical displacement due to passing traffic load. The failure in joint sealant causes elimination of water proofing feature in joints leading to penetration of water into the sublayers. Subsequently, the presence of water in sublayers results in pumping of water under the concrete slab, which leads to other failures types, such as faulting, blow up, corner break. The resealing of joint sealant is the commonly used approach to repair the joints, which takes considerable costs, times and environmental consequences. In recent years, induction heating has attracted substantial attentions among the pavement engineers for innovative applications, specifically for induced healing. The researchers used this method in asphalt mixtures to heal cracks and microcracks. To make the electromagnetic radiations more effective, they used bipolar additives such as activated carbon and carbon black to raise the temperature of the asphalt mixture and cover the cracks and microcracks. In this study, the induction heating and induced healing of asphalt binder was carried out in reaping the joint sealant and to recover the cohesion-adhesion failures. To this end, a new testing setup and frame were designed to conduct the tensile test on hot-applied bituminous joint sealant. First, the sealant bitumen was placed between two concrete blocks, and then the specimens were conditioned at low temperatures (i.e. -10 °C, -20 °C, and -30 °C). After conditioning, the tensile under a displacement controlled loading test was carried out until failure point of joint sealant. Subsequently, the broken joint sealants were exposed to the electromagnetic radiation in a microwave machine to heat and heal the joint sealant. Then, the tensile test was again conducted on the specimen until failure point. The results showed that induced healing can recover and heal the joint sealant experienced cohesion-adhesion under contraction loading. This observation indicates that the induced heating is a potential technique to repair the joint sealants in jointed concrete pavements.
M. Ghodratabadi, M. Yekrangnia,
Volume 22, Issue 5 (12-2022)
Volume 22, Issue 5 (12-2022)
Abstract
In this research, the adequacy of the method recommended by the Iran highway asphalt pavement code (Code 234) for pavement design is investigated. Pavement design in Iran highway asphalt pavement code is in accordance with the ASHTO method. Design variables in this Code are considered as Deterministic and without probability distribution; while the Average Daily Traffic (ADT), the annual growth rate (r), and the variables related to resistance such as modulus of elasticity and thickness of each layer, despite the segmentation, have many changes along a route. As a result, pavements designed on this basis may have a shorter useful life than expected and be destroyed in less traffic or age than the initial design. Iran highway asphalt pavement code uses a method similar to First Order Second Moment (FOSM) to consider the reliability in pavement design. FOSM is an old and simple method. This method has low accuracy in calculating the confidence level, especially for nonlinear functions. There are more accurate methods such as First Order Reliability Method (FORM) and Sampling for reliability analysis that eliminate the disadvantages of the FOSM method and perform reliability analysis more accurately for nonlinear functions. Therefore, it is better to consider the uncertainty of the variables and use accurate reliability methods to calculate the level of pavement reliability. A reliability-based method is proposed to improve the pavement design based on the Iran highway asphalt pavement code. To compare the two methods, traffic data and pavement condition of the Qom-Salafchegan route were collected. At first, the variables were considered Deterministic and without probability distribution, and the overlay thickness was calculated at a confidence level of 80% based on code 234. Then the most appropriate probability distribution of variables was determined by the Anderson-Darling test. According to the thickness of the overlay obtained from the Iran highway asphalt pavement code, the confidence probability of each section was determined by the FORM and Sampling methods of reliability in the Rtx software and Monte Carlo simulation in the R programming language. Based on Code 234, the pavement reliability was approximately 20% higher than that of the proposed method. Furthermore, based on this code, the required overlay thickness was about half of that determined according to the proposed method with an equal reliability level, which leads to was destroyed less traffic and lifetime than the design value and needed repair again. In the following different reliability, methods are compared with each other. According to the sampling method with a higher probability of failure than the FORM method, the required overlay thickness is determined and therefore, leads to a more conservative overlay thickness. To evaluate the accuracy of Rtx software, a Monte Carlo simulation is performed in the R programming language. It was concluded that Rtx results in the overlay design at a lower reliability level than the R programming language. In the ASHTO method, the logarithm probability distribution of wt18 and w18 variables is considered normal. This hypothesis was rejected by performing the Anderson-Darling test on the collected data and these variables do not have a normal distribution.
M. Gholami, P. Hajikarimi, A. Khodaii,
Volume 23, Issue 2 (5-2023)
Volume 23, Issue 2 (5-2023)
Abstract
Asphalt mixtures and bitumens are faced with different traffic loading and thermal stresses during their lifetime. Due to their viscoelastic behavior, these materials exhibit different mechanical properties at different temperatures and traffic loading. Viscoelastic properties of bitumens are commonly expressed using the master curves of complex shear modulus (G*) and phase angle (δ) generally created by the horizontal shifting of the frequency sweep test results using shift factors. There are several methods for evaluating temperature shift factors, such as Williams, Landel, and Ferry (WLF) equation, modified Kaelble method, Log-Linear approach, and LCPC method. The LCPC method, developed using the Kramers-Kronig relationship, can be used to accurately evaluate the shift factor of bitumens, mastics, and asphalt mixtures. This study investigated the possibility of generating the master curves of bitumen based on temperature sweep test results rather than frequency sweep test results. Two types of bitumens were investigated in this study, neat bitumen with an 85-100 penetration grade (PG 58-22 performance grade) and SEPS modified asphalt binder with SEPS polymer content of 2, 4, and 6% by weight of the total binder. Temperature sweep tests were performed on all types of bitumens in a range of temperatures between 30 and 90 °C and the frequency of 1.59 Hz. Also, frequency sweep tests were performed on all kinds of bitumens in a range of temperature between 10 and 60 °C and a range of frequency between 0.1 and 100 Hz. The LCPC method was also investigated to calculate the shift factors for the master curves of complex shear modulus and phase angle, and the master curves of viscoelastic properties for all bitumen types are made based on temperature sweep and frequency sweep test results. The results indicated that the SEPS polymer could effectively increase the complex shear modulus and reduce the magnitude of phase angle. So, this polymer improved the rutting resistance of SEPS polymer-modified binders and led to better high-temperature performance of binders. In addition, the LCPC method effectively produced a valid and accurate form of the master curve using temperature sweep test results similar to the master curve using frequency sweep test results. Furthermore, the master curves of complex shear modulus (G*) and phase angle (δ) derived from temperature and frequency sweep test results exhibited comparable patterns and values. By plotting the value of complex shear modulus and phase angle obtained from the temperature sweep master curves versus the complex shear modulus and phase angle obtained from the frequency sweep master curves at the same reduced frequency, it was observed that all points were scattered in the vicinity of the y=x line. It was indicated that the master curves created based on temperature sweep test results have an acceptable approximation and accuracy with the master curves created based on frequency sweep test results. As a consequence, it may be preferable to generate the master curve of viscoelastic characteristics of bitumens using the results of the temperature sweep test, which is faster and more accurate in some conditions, compared to the results of the frequency sweep test.