مجله مهندسی زیر ساخت های حمل و نقل
سال نهم شماره 3 (پیاپی 35، پاییز 1402)

Dissemination of polymeric waste in the environment is one of the most important concerns of the world today. Used plastics and worn tires are one of the most important sources of this type of waste. Chemically, these materials are very similar to bitumen as the most used and expensive component of asphalt mixtures. Therefore, using these waste materials as an additive in bitumen while reducing environmental pollution can improve the performance characteristics of the pavement. Investigating the effect of each type of additive on the fatigue performance of asphalt mixture is essential as one of the most important factors in causing pavement damage. Therefore, in this research, in addition to examining the physical properties of bitumen, the fatigue performance of asphalt mixture containing different percentages of waste plastic and rubber powder has been investigated using the four-point bending beam method. The results of this test using the hardness method, Normalized hardness and energy method were analyzed. The results showed that waste plastic reduced the fatigue resistance of the asphalt mixture, which was compensated to a significant extent by adding rubber powder. So that the samples containing rubber powder and waste plastic at the same time had a longer fatigue life than the control sample.

Aging is one of the factors affecting the physical and chemical properties of bitumen. This factor can lead to moisture damage in the asphalt mixture. The objective of this study is to investigate the effect of short- and long-term aging on the moisture damage mechanisms of hot mix asphalt containing Wetfix using the Pull-off method. Two types of bitumen with different performance grades (PG 58-22 and PG 64-16) modified with Wetfix BE additive and two types of aggregate (limestone and granite) were used. First, the rheological properties of bitumens and the physical characteristics of aggregates were determined, and then the chemical compositions of aggregates were obtained through an X-ray fluorescence (XRF) test. After modifying the bitumens with Wetfix, the pull-off test was performed to determine the cohesion strength of bitumen and the adhesion strength of bitumen to aggregate on aged and unaged samples in dry and wet conditions. Short-term aging increased the cohesion strength and long-term aging caused a decrease in cohesion strength in wet conditions. Therefore, long-term aging leads to a decrease in bitumen performance in wet conditions and as a result, a decrease in pavement resistance against moisture damage. However, adding Wetfix increased the cohesion strength between 20-32% and 26-48% in short and long-term aging, respectively, and adhesion strength between 43-26% and 57-38% in short- and long-term aging, respectively. Comparing the effects of aging of base and modified bitumen on the reduction of adhesion and cohesion strengths shows that the addition of Wetfix not only eliminates the negative effects of aging on these parameters, but also improves the resistance of modified bitumen compared to base bitumen against moisture damage.

Every year, huge costs are spent on the maintenance of road pavements due to premature reflective deterioration of the road surface, a large part of which is related to road surface paving. Accordingly, in order to prevent the propagation of reflective cracks in newly coated pavements, various methods have been used and researched. The results have shown that all the adopted reflective crack control methods have only delayed the propagation of this type of crack. However, some methods have caused a greater impact on the appearance of reflective cracks and reducing the intensity of these cracks, and one of the best methods is the use of geosynthetic products and interlayers. In this research, the performance of 2 different types of geocomposite (with tensile strengths of 50 and 100 kN/m) in asphalt pavements in delaying the initiation of reflective cracks compared to control samples at different temperatures and loading frequencies was investigated. Based on the studies, it was observed that the use of type I geocomposite with high tensile strength is the most effective in increasing the fatigue life and among the mentioned factors, the temperature parameter will have the most negative effect on this performance. After the temperature, in order of the type of geocomposite used in terms of tensile strength and then the loading intensity, they will have the greatest effect on the fatigue life changes (about 53,000 cycles of loading difference, between the temperature of 40 and 0 degrees Celsius) on the reinforced asphalt coatings. Based on the results of variance analysis of the fatigue life model obtained in this research, the value of R² and Adjusted R² are equal to 0.987 and 0.981, respectively, which indicates the high accuracy of the presented model.

Cold recycling is one of the methods of pavement rehabilitation, which has become popular in recent years. One of the advantages of cold recycling is that its operations are performed at ambient temperature. However, there are still some concerns regarding the use of emulsified cold recycled mixtures. These pavements are susceptible to problems such as raveling, stripping, low initial strength, and long curing time, which are often countered by the use of additives. In this study, the mechanical behavior of the mixture recycled with emulsion bitumen containing cement kiln dust as a waste from the cement production process and steel slag as a pozzolanic waste were compared with the non-additive mixture and the mixtures with 1% and 2% cement content (as a conventional emulsified cold recycled mixture additive). To evaluate the mechanical properties, Marshal stability, indirect tensile strength, resilient modulus and fatigue test were performed on the samples of different ages at different temperatures. The results showed that the combined use of cement kiln dust and steel slag improves the mechanical properties, especially after prolonged curing periods. In some cases, this improvement was even greater than the improvement resulting from the addition of cement. The fatigue test results showed that the mixture containing the new additive had a better fatigue behavior than the non-additive mixture and a comparable behavior with the cement-containing mixture specially at lower strain levels.

Bridges are very important components of transportation networks.Considering the very vital role of the technical infrastructure especially the bridges, it became necessary to examine the condition of the bridges of the road arteries of Alborz province. In this survey, the first, important and influential technical buildings were identified in the Tehran-Karaj-Qazvin axis, the special Karaj-Qazvin axis, the Kandavan axis, the Taleghan axis, and the Eshtehard axis. Then, technical inspection groups were sent to the area and functional inspection of the structure and identification of vulnerability factors were carried out based on pre-prepared checklists. After extensive field observations, defects in the structures were prepared along with all the items related to their current physical and functional condition. All the parameters taken in the structures were weighted based on the importance and type of impact of the damage, and according to all the taken parameters as well as the importance coefficient of each, a kind of management classification was made based on the levels of vulnerability in the buildings of the province into four groups. According to the results obtained in Eshtehard axis: 2 bridges with the degree of vulnerability A and one bridge with the degree of vulnerability B, in the Taleghan axis: 2 bridges with the degree of vulnerability A and 3 bridges with the degree of vulnerability B and 1 bridge with Vulnerability level C and 2 bridges with vulnerability level D, in the Karaj-Qazvin axis: 10 bridges with vulnerability level A, 12 bridges with vulnerability level B, 16 bridges with vulnerability level C and 3 bridges with damage level D vulnerability and in Kandavan axis: 11 bridges with vulnerability level A, 10 bridges with vulnerability level B, 9 bridges with vulnerability level C and 2 bridges with vulnerability level D were identified.

Considering the exorbitant costs that are paid annually for the repair and improvement of asphalt pavements and also considering the increasing use of heuristic and meta-heuristic algorithms, the main goal of this article is to determine the most appropriate time for field surveys in pavement management by using the genetics algorithm to prevent more expenses and have better planning for pavement maintenance and repair so that the roads always have an acceptable level of service. However, the indexes affecting different costs should also be determined and these costs should be optimized at the same time as determining the best time to conduct the inspection. For this purpose, according to the factors affecting the optimal time of field surveys and with the help of genetic algorithm, the required program was implemented in MATLAB software and tested for different samples from Khuzestan province that the results of which are very impressive and reasonable. According to the obtained results, it can be seen that by using this method and determining the most appropriate time for field survey of a road, it is possible to avoid excessive and irreparable expenses; With the help of this method and having the basic information of the road, it is possible to determine the best time for field survey in order to prevent excessive damage to the road as well as high costs, and while maintaining the service level of the rosd in the desired state, the satisfaction of the users also attracted

It is necessary to stabilize the road bed in the areas that have fine-grained sand soil or the so-called dune sand. On the other hand, there is no justification for using traditional methods to do this, considering the advancement of technology and the emergence of new materials that are environmentally friendly. In the past years, the concern of researchers in the field of geotechnics has been to choose the best stabilizing material by testing different materials to determined the possible suitability for this purpose.Today, geopolymer materials are considered as one of the best environmentally friendly materials due to their availability, reduced consumption of energy resources, and reduced production of greenhouse gases, and on the other hand, with the development of nanotechnology and researchers' understanding of their properties, nanomaterials can also be used in the preparation of geopolymers. be placed In the past, researchers have conducted studies on the stabilization of some types of soils using geopolymeric materials, but the use of geopolymeric materials based on iron slag and in combination with nano silica to stabilize fine sand soil is a subject that has not been studied in the past. This research has been addressed.This research studies the effect of adding 0-3% of nano-silica to the mixture of sandy soil with 5-20% of geopolymer based on industrial pozzolan obtained from iron smelting furnace slag. In order to achieve the best percentage of preparation of geopolymer mixture, 5-20% alkaline solution with a concentration range of 4-12 M has been used, and the samples have been examined in the processing time of 1-28 days. In this regard, according to the increase of the investigated factors, Taguchi test design optimization method has been used to reduce the number of tests.