مجله مهندسی زیر ساخت های حمل و نقل
سال ششم شماره 3 (پیاپی 23، پاییز 1399)

The use of waste materials, including plastics, to improve the properties of asphalt mixtures, in addition to economic benefits, has environmental benefits. Crumb rubber (CR) is one of these wastes that can improve many of the properties of asphalt mixtures, especially at low temperatures. But this additive also has weaknesses that can be compensated by making a double additive based on CR. In this study the influence of CR and EVA polymer on rheological and physical properties of unmodified bitumen has been studied and evaluated. To this aim, penetration, softening point, rotational viscosity and dynamic shear rheometer tests by using DSR machine were done on control bitumen and modified bitumen with a combination of 10 and 15% CR and EVA polymer based on the weight percentage of base bitumen (control) has been done with different ratios. The results of the dual combination of these additives with control bitumen show that the softening point and rotational viscosity increase and the degree of penetration decreases, which confirms the decrease in thermal sensitivity of the modified bitumen compared to the control bitumen. In addition, the results of the DSR Test also show that all modified bitumen have a larger complex shear modulus (G*) and a smaller phase angle(δ), and as a result have a larger sinusoidal coefficient (sin δ / G*) compared to the control bitumen. Besides, the fatigue coefficient caused by loading in the middle temperatures of all bitumen modified with dual compounds of these additives is smaller recommended. According to the findings of this study, the most appropriate dual combination of EVA additives and CR for improving the physical and rheological properties of base bitumen with a penetration rate of 60/70 is the use of dual combination of 25% EVA and 75% CR by proportion of 15 percent of bitumen.

Some people have been killed due to car accidents every year in the world. Safety is a way to create conditions that make it difficult for users to take risks from harming personal and financial harm. One of the most important steps is to have safe ways to develop a safety rating system for roads. There are several methods in this area that consider each of the specific parameters for road safety rating. As a result, the study attempts to explore the feasibility of using one of the most current methods used in the world in the field of road safety assessment (iRAP) in Iran, in order to use the results for designing and implementing new roads in terms of safety, and also improved the quality of safety of existing roads with appropriate technical and economic solutions. The results of this study show that using the star rating method in order to improve the safety of our country's roads can help in reducing accidents and improving safety. Result in case study part show that 70% of Kermanshah eastern bypass have been maximum 3 stars which is disappropriate in term of safety and only 30% of roads ad 4 or 5 stars.

Rutting is one of the most important failures of flexible pavements, which is dramatically affected by bitumen characteristics. To prevent this failure, it is necessary to use bitumen with good performance characteristics in the construction of asphalt mixtures. Numerous studies have shown that polymer modified bitumen has many advantages. The storage stability of polymer modified bitumen is difficult because the compatibility between bitumen and polymer is low. During storage, it forms two phases of bitumen and polymer, which reduces the performance characteristics of asphalt mixtures such as rutting resistance. For this reason, polymer bitumen modified with nanocomposites have been used. By adding magnesium nano oxide to the polymer bitumen, the compatibility between the polymer and the bitumen and the performance characteristics of the bitumen will be improved, and the possibility of damage such as rutting will be reduced. The present study was conducted to evaluate the effect of magnesium oxide nanoparticles on the rutting performance of polymer bitumen. In this study, pure bitumen 60/70 was modified with SBS polymer and magnesium oxide nanoparticles in 5 different levels. Rotational viscosity and multiple stress creep recovery test (MSCR) have been used to evaluate the effect of nanoparticles on polymer modified bitumen. Research shows that magnesium oxide nanoparticles increase the viscosity of polymer modified bitumen and improve the Jnr and the percentage recovery of bitumen. These results show that magnesium oxide nanoparticles have a significant effect on improving the high temperature performance of nano modified polymer bitumen and increase the rutting resistance. In general, bitumen modified with SBS/MgO nanocomposites have a good potential for improving bitumen performance and can be used in warm areas.

Cement asphalt emulsion mortar (CEAM) as a critical and complex engineering material for slab ballastless track is widely used in high speed railways and road pavements. Damping and cracking characteristics of CEAM are very important to resist vibration and the deformation caused by repeating loads. Furthermore, Cement is the fundamental constituent of CEAM, which is notorious for the environmental pollutant. Accordingly, reducing cement consumption has been a significant concern. This study evaluated the effects of using two types of supplementary cementitious materials (SCM), i.e. fly ash (FA) and granulated blast furnace slag (BFS) in corporating with cement kiln dust (CKD) as cement replacement, on the mechanical properties and cracking characteristics of cement emulsified asphalt mortar. To reach the objectives of the study, different experimental tests (i.e. Uniaxial Compressive strength (UCS), indirect tensile (IDT) strength, Moisture susceptibility and semicircular bending (SCB)) were conducted. The results showed that the replacement of 30 percent of cement by fly ash leads to significantly improve the compressive strength and indirect tensile strength of prepared CEAM. Furthermore, all the proposed CEAM containing different percentages of SCMs had ITSR more than 0.8 which pass the standard requirement. The consequences of CEAM cracking resistance indicated that the 30 percentage replacement of cement by BFS considerably enhanced the J-integral of CEAM which results the better cracking resistance of prepared mixture. Moreover, the replacement of 50 percent of cement in CEAM by supplementary cementitious materials revealed that the proposed CEAMs had proper unconfined compressive strength, capability to resistance against crack initiation and propagation and also sufficient endurance against moisture failure. Finally, it can be concluded that the examined CEAMs in this study can be presented as eco-friendly CEAM which had enough resistance against the repeated train and varying environmental loadings.

An appropriate solution for dealing with low-resistance and problematic soils is stabilization of the soil. Also, exploitation and use of mineral resources generates a lot of mine tailings. Increasing the production of these tailings has created a significant concern for the mining authorities, regarding to achieve more depot space and environmental issues caused by waste deposits. The purpose of this research is to stabilize red clay with hydrated lime and iron ore mine tailings. For this purpose, samples with 0, 2, 4 and 6% lime and 0, 10, 20 and 30% of iron ore tailings dense and prepared in three percent moisture content (optimum, wet side and dry side). In order to perform unconfined compression strength (UCS), the specimens were treated for 7, 28 and 56 days. Unconfined compressive strength test showed that by increasing lime content up to a specific value, the UCS increases, and increasing the amount of lime content to more than it will reduce the UCS of samples when the content of iron ore mine tailing remains constant. In addition, the UCS and elastic modules decrease with increasing moisture content and vice versa. The UCS of the 7-day, 28-day and 56-day samples increses 84 to 259%, 97 to 290% and 110 to 342%, respectively, in terms of lime percentage, Iron ore mine tailing percentage and moisture content. Also, the freezing and thawing test showed that by increasing the iron ore mine tailing up to a specific value (2 to 4%), reduces the weight and volume loss of samples, and after that the weight and volume loss increase. Results of this study confirms that the optimum percentage of hydrated lime is 2 and 4%, regrading to 20 and 10 percentage of tailing, respectively by considering both UCS and freezing and thawing criteria.

Pervious concrete with high cavity volume serves as pre-treatment of runoff, as well as groundwater feeder and runoff reducer. Generally, this concrete has low resistance. In this research, we have tried to improve the resistance properties of pervious concrete using magnetic water. To this end, four mixing designs were selected and, based on each mixing design, 28 samples were made with tap water and 28 samples with magnetic water; 14 cubic samples for 7 and28-day compressive strength test and 14 cylindrical specimens for 7 and 28-day tensile strength and permeability tests. The results show that the of the 7-day compressive strength has increased by 36 to 43% using magnetic water. However, 28 day compressive strengths increase only 9 to 16 percent. 7-day compressive strength tap water samples obtained about 44-48 percent of 28-day strength, while in samples made with magnetic water at 7-day compressive strength achieved 56-61% of their 28-day strength. Permeability of Magnetic water samples have been reduced by about 8-34 percent relative to those made with tap water. Samples made with magnetic water have a more uniform appearance and physical properties.

In the present study, the effect of geogrid layers and soil density were investigated in the sand slope model reinforced with geogrid layers. The soil slope did not have stability in normal condition and was unusable for embankment operations. But it reached to the appropriate bearing capacity for embankment operation with improvement made by reinforcing and compacting the desired soil. The main purpose was to compare the footing bearing capacity and soil swelling of the reinforced with the non-reinforced states and also to evaluate the impact of the two soil compacted states with various thicknesses. 19 different states were investigated. The main parameters studied were soil density, the number of geogrid layers, and the distance from the slope edge. The results indicated that the soil slope, which had no stability in the non-compacted -unreinforced state, achieved high bearing capacity using geogrid layers and soil compaction. So that the maximum bearing capacity in compacted reinforced state and when footing was located 30 cm from the slope edge was 433 percent higher than the only reinforced state and 325 percent higher than only compacted state. Also, swelling of first layer of slope was significantly lower relative to the tolerance amount of bearing capacity and more uniformity was observed in all slope locations.The results also indicated that, in the compacted-unreinforced state, an increase in the number of compaction layers did not affect the bearing capacity of footing in the vicinity of the slope. But by moving the footing from the slope edge to 30 cm, the increasing the number of compaction layers from 5 to 7 layers caused increasing the bearing capacity by 34%.s.