مجله مهندسی زیر ساخت های حمل و نقل
سال نهم شماره 1 (پیاپی 33، بهار 1402)

In recent decades, due to the high cost of road construction and environmental considerations, different waste materials have been used in asphalt mixtures. Therefore, using waste materials as an additive to improve the performance of bitumen and asphalt is important. Due to its angularity, high porosity, and surface roughness, the use of ferrite as a filler or bitumen additive is expected to increase the friction of aggregate materials and the penetration and adhesion of bitumen, thereby enhancing the physical characteristics of the asphalt mixture. This study investigates the mechanical performance of asphalt mixtures during dry and wet ferrite mixing design and its effect as an additive on bitumen performance. In order to determine the bitumen parameters, ferrite was added to the bitumen as an additive, and then DSR, FTIR, and SEM were conducted. As a next step, asphalt samples were made using modified bitumen (wet mix) and modified filler (dry mix), and Marshall, fatigue, creep, indirect tension, moisture sensitivity, Cantabro, and resilience modulus tests were conducted in two loading conditions, half-sine, and square. Adding 100% ferrite to the asphalt mixture only increased its fatigue factor to the highest value. However, compared to the control sample, the asphalt mix containing 70% ferrite and 30% cement improved the other performance factors by 48%, 90%, 38%, 17.7%, 39%, 67%, and 80%, respectively. In addition, when the percentage of ferrite added to bitumen was increased, the parameters of fatigue and rutting improved, with the seven percent sample showing the best performance.

This article compares the characteristics of the improved bogie used in the long-edge mineral freight car to bear the axial load of 22.5 tons with the original H665 bogie. The H665 bogie is being used in the Middle East and specifically in the cargo fleet of Iran. Static and vibration analysis of individual parts and the infrastructure of railway vehicles is an integral part of designing and improving the performance of railway vehicles. Therefore, static and vibration analysis of the bogie frame was performed in our model using the finite element method. The Abaqus software package performed numerical calculations based on the FEM approach. In this research, theoretical results related to structural stress values , natural frequencies, and shape of vibration modes of the improved bogie and the original bogie were extracted. While comparing the results, the amount of structural stress reduction and the feasibility of increasing this axial load were investigated.

Thermal cracking and moisture sensitivity are two of the most important failures that face asphalt pavement with serious threats during the operation period. In this research, the effect of nano CaO and nano CaCO3 additives to HMA has been evaluated in order to improve their performance against cracking and moisture sensitivity. In order to achieve the goals of this research, bitumen was mixed with 0.9% of nano CaCO3 and 1.5% of nano CaO, and to evaluate the functional characteristics of HMA samples containing nano additives, semicircular bending (SCB) tests were performed in three The temperature was -5, -10 and -15 °C, and modified Latman was performed at two temperatures of 10 and 20°C. According to the SCB and ITS test results, the best performance and the highest resistance is related to the sample containing 1.5% Nano CaO, which is about 22% more resistant to thermal cracks and about 6% less sensitive to moisture than the control sample. Based on the SCB test results, it can be seen that with the increase of Me from zero to about 0.4-0.6 when the loading is a tensile-shear combination, the fracture toughness will decrease and then increase when the loading goes to pure tension. Such that the greatest resistance to cracking occurs in pure tension.

The use of recycled materials in engineering applications brings economic and environmental benefits. Disposal of these materials in landfills is costly and creates potential environmental problems. Recycling and reuse of construction and demolition materials, in cases such as pavement structures and non-structural elements of the building, leads to the preservation of natural resources and reduction of environmental pollution. In recent years, these materials are mainly used in the construction of new road construction projects and therefore gradually show their impact on the environment. In this research, we investigated the uniaxial compression strength (UCS) and California Bearing Ratio (CBR) of clay soil stabilized with concrete waste (CW) and blast furnace slag (BFS). Clay samples were stabilized with 25 and 50% CW and 2 and 4% BFS content. Curing times of 7, 14 and 28 days were used. The obtained results showed that the addition of CW and BFS to clay soil increases the CBR value of the mixture and the curing time also has a positive effect on the CBR results. Also, the BFS content has a significant impact on the UCS of clay and clay-CW mixture (especially clay with 50% CW) and the combination of 50% CW and 4% BFS in 28 days curing time can increase the value of uniaxial compressive strength up to 5 times.

Considering the importance of roads and highways as vital elements of the economy of countries which are used for transport and movement of passengers and goods, the issue of maintenance and management of them is among the most important and fundamental infrastructure of the countries. Use of the surface treatments as a preventive measure in repair and maintenance of pavements in Iran and the world is a common and worldwide practice. In the present age, one of the greatest environmental issues is considerable production of construction wastes (CW). The use of recyclable CW in pavements could help with conservation of non-renewable materials and at the same time reducing environmental problems. The main goal of this study is investigation of implementing recycled waste concrete powder (RWCP) in the mix design of the thin layer surface treatment (slurry seal) in comparison to the mineral filler (MF). For this purpose the wet cohesion test, wet track abrasion test, loaded wheel-displacement test and loaded wheel-sand adhesion test were performed in five different combinations: RWCP0+MF100, RWCP25+MF75, RWCP50+MF50, RWCP75+MF25 and RWCP100+MF0 based on the total weight of filler and then, using artificial neural networks (ANNs), the correlation and accuracy of laboratory results of thin layer surface treatment mixtures containing RWCP were investigated. The results showed that the mixture of RWCP100+MF0 with 9% residual bitumen improved sample, in terms of abrasion, wet cohesion, and vertical and lateral displacements by about 27, 24, 28 and 20%, respectively. One of the most important reasons for replacing RWCP filler is having irregular shapes and uneven and rougher surfaces and a high percentage of CaO and SiO2, which improves the performance of thin layer protective asphalt.

Due to the importance of environmental issues and reducing energy consumption, the use of waste materials to improve the engineering properties of soils has been widely noticed by researchers in recent years. This research investigates the effect of carpet waste fibers on the compaction, hydraulic, and consolidation properties of kaolinite clay. Standard compaction, falling head permeability, and one-dimensional consolidation tests were performed on soil samples containing 0.5, 1, and 2 percent of fibers (relative to the dry weight of the soil). In order to investigate the effect of the fiber length on the results, the length of the fibers was changed from 6 to 30 mm. The results showed that the presence of carpet waste fibers decreases the maximum dry density and increases the optimal moisture content of the samples. Also, the carpet fibers increased the hydraulic conductivity of the samples and reduced the settlement of clay soil and its swelling index. So that the compression index and swelling index for the sample with 2% fibers with a length of 30 mm decreased by 35 and 64%, respectively. The presence of carpet fibers in the soil increases the speed of clay consolidation. From the obtained results, it was found that the changes in the consolidation properties of clay are more significant with the content of fibers compared to the length of the fibers.

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.