مجله مهندسی زیر ساخت های حمل و نقل
سال هشتم شماره 1 (پیاپی 29، بهار 1401)

Due to the importance of roads in creating connections between different areas, the issue of road maintenance is always a vital issue for road organizations. One of the most important methods of preventive maintenance of roads is microsurfacing surface treatment. This preventive method reduces energy consumption and long-term maintenance costs. The purpose of this study is to evaluate the feasibility of using waste ceramic fillers in the microsurfacing mixing design to evaluate its performance. In this regard, first, the physical and chemical properties of stone materials and waste ceramic fillers are investigated and then to evaluate the performance of microsurfacing mixture, from 5 different compounds containing zero, 25, 50, 75, and 100% of waste ceramic fillers were used in three different levels of bitumen emulsion Asphalt. Samples were measured by wet adhesion tests at 30 and 60 minutes, loaded wheel, and abrasion in wet conditions according to ASTM D6372 instructions. The results showed that the mixtures containing ceramic fillers meet the requirements of the regulations and improve the microsurfacing performance. Also, among the mixtures, the mixture containing 100% ceramic fillers compared to the control sample increased the adhesion at 30 and 60 minutes by 30.8 and 33.3%, respectively, improved the abrasion resistance by 62%, and reduced the mixture bleeding by 31 Percent. This mixture has 2% more emulsion bitumen than the control sample to achieve proper adhesion in a given time.

Asphalt pavement cracking is an unavoidable phenomenon and the main factor of failure in pavement, which if followed, will lead to high costs and yet, with preventative measures, these costs can be reduced very effectively. Crack sealing is one of the preventive maintenance methods and the simplest and most economical way to repair recently cracked surfaces of asphalt pavement. This study was conducted to investigate the effect of discontinuity dimensions and their repair on the mechanical behavior of asphalt. Therefore, asphalt samples with treated and untreated discontinuities were made. Then dynamic creep, resilient modulus, fatigue, and durability testing were performed by the Lottman method on the samples. The results show that for a layer with finer granulation, sealing of narrow cracks (up to 20 mm wide) improves the corrosion resistance of asphalt concrete. Also, sealing cracks can increase the resistance of asphalt concrete to fatigue, regardless of the dimensions of the cracks. For a coarser-grained layer, sealing cracks deeper than width also reduces the resistance of asphalt concrete to sealing. Sealing cracks with overall width and depth of 20 mm reduces fatigue performance. Regarding resilience modulus for a layer with finer granulation and a layer with coarser granulation, crack sealing increases the modulus of resilience of asphalt concrete by 7.7% and 8.9%, respectively. The findings also indicate a more prominent role of discontinuity width than its depth on rutting behavior and durability. The results of this study are key in deciding the appropriate time to seal the cracks after their formation and improving some pavement properties in parallel with the treatment of cracks. Even though, generally, the desired effects of treatment on rutting, fatigue, and durability of pavements are partial and mostly negligible. However, sealing can be considered as a way to increase the resilient modulus of cracked pavements.

Bitumen modification using additives is one of the ways to improve the performance characteristics of bitumen and asphalt mixture. Nanomaterials are one of the newest technologies, which is rapidly advancing in various sciences. The many advantages of this technology have led researchers in the field of pavement to use it to improve the properties of asphalt mixtures. Heat cracking is one of the most common road failures. Considering the relationship between fatigue failure and grooving in bitumen and asphalt mix at medium and high temperatures and the lack of studies on thermal cracking at low temperatures, it is important to evaluate the relationship between thermal cracking parameters in bitumen and asphalt mix. For this purpose, flexural beam rheometer (BBR) test for bitumen and SCB flexural semicircle test for asphalt were used. The purpose of this study is to investigate the behavior of bitumen and asphalt mixture modified with nano-silica. The results showed that the strength of the asphalt mixture modified with silica nanoxide was cracked and the modulus of resistance was about 1.6 and 1.4 times. The index related to moisture sensitivity of asphalt mixtures also increased by about 7% compared to the control sample. However, bitumen test results indicate a decrease in the performance of nanosilica-modified bitumens at low temperatures. The toughness results in SCB test for asphalt mix are consistent with BBR test results in bitumen. Tensile bonds of FTIR test and increased stiffness in asphalt mixture are effective factors in improving the behavior of nanosilica modified bitumen compared to the control sample.

Due to the high permeability of pervious concrete, its using as an upper layer in road and airport pavement could help to guide heavy rainfall, surface water management and its collection. Studies show that despite this important advantage, due to the lower mechanical properties of this type of concrete compared to conventional, its using is not widespread. In order to improve the mechanical properties of pervious concrete, in this study, the effect of adding polypropylene fiber and SBR latex separately and simultaneously on the porosity, permeability, compressive, flexural, and tensile strength of pervious concrete has been evaluated.The results of this study show that by increasing the amount of SBR latex and polypropylene fibers each individually, the mechanical properties of pervious concrete are improved in the composition of control sample, but the percentage of porosity is reduced.The reduction is much greater for the addition of polypropylene fibers than for the addition of SBR latex.With the simultaneous addition of SBR latex and polypropylene fibers, the mechanical properties of pervious concrete are further improved, but the percentage of porosity is also reduced.By controlling the amount of polypropylene fibers used in terms of the necessary restrictions to comply with a minimum of 15% porosity, the optimal combination of latex SBR and polypropylene fibers can be achieved. In this research, this optimal combination has been obtained by adding 35 kg of SBR latex and 0.7 kg of polypropylene fibers, in which the percentage of concrete porosity with 24% reduction compared to the control sample is 15.65%.Compressive strength values increased by 37% (27.6 MPa),tensile strength increased by 36% (3.61 MPa), flexural strength increased by 41% (4.51 MPa) and fracture toughness increased by 24% (MPa.m0.5537). 0) has shown a significant improvement in the mechanical properties of pervious concrete by applying this optimal combination in the present study

This study aimed to investigate the effects of crumb rubber and recycled steel fibre on the durability properties of concrete. The effects of crumb rubber (0–20%) and recycled steel fibre (0–0.5%) on the compressive strength, as well as abrasion and freezing-thawing resistance of concrete were investigated. The results indicated partial replacement of the fine aggregate with crumb rubber in concrete had contradicting results based on the test module. By implementing Response Surface Methodology on the results, it was concluded that adding crumb rubber decreases abrasion resistance in the dressing wheel test but increases abrasion resistance in the wide wheel test. During the wide wheel abrasion test, the crumb rubber particles in the rubberized concrete projected beyond the smooth surface of the concrete, confined the surface rubbing of the concrete, and led to more abrasion resistance compared to the control mix. On the contrary, the most abrasive surfaces in the dressing wheel abrasion test were those with the highest crumb rubber contents due to a weak bond between cement paste and crumb rubber. Adding recycled steel fibre did not have any result on abrasion resistance. While replacing fine aggregate with crumb rubber leads to more mass loss in the presence of 3% saline solution, there is a synergic effect between crumb rubber and recycled steel fibre on freezing-thawing resistance. The combination of 12.5% crumb rubber and 0.34% fibre is the optimum mixture to achieve the maximum synergic effect in freezing-thawing resistance.

In this study, the effect of fine aggregate angularity was evaluated using Marshall strength ratio and indirect tensile strength tests on moisture sensitivity, sample failure and cracking capability of hot asphalt mixtures. Two types of Qubit crusher (Mix design-1) and hydro-cone (Mix design-2) were used to prepare fine-grained stone materials for the production of hot asphalt. By comparing the parameters of both designs, the results of this study showed that although the grain size of both sands was the same the angulation coefficient of sand produced in Qubit crusher has decreased by 7% compared to sand produced in hydro-cone crusher, which increases by 1.2% the optimal amount of asphalt mixture. Despite this increase in the optimal amount of bitumen in the asphalt mix of mix design-1, the amount of effective bitumen in this asphalt mix decreased by 1%. The reduction of effective bitumen in the asphalt mixture weakened the bond between the bitumen and the aggregate, and accordingly, the moisture durability and resistance in all failure modes of the asphalt mixture of mix design-1was less than that of the asphalt mixture of mix design-2.

In this laboratory study, Ultrasonic Pulse Velocity (UPV) was investigated in high-temperature slag slag concrete used in pavement at high temperature at 90-day curing age, followed by scanning electron microscopy (SEM) imaging test in concrete. The overlap of the results was analyzed and investigated. In this regard, one mixing design was made of control concrete and three mixing designs were made of low-slag slag concrete containing 0, 4 and 8% nanosilica. Then, the optimal design obtained from the test results was selected from three designs of alkaline slag concrete and 1 and 2% of polyolefin fibers were added to it, and two other designs were made of alkaline slag concrete, new samples under room temperature and High temperatures were subjected to UPV, SEM and analysis. The results showed an 11% improvement (Scheme 3 compared to Scheme 2) in the passage of ultrasonic waves by adding nanosilica to alkaline slag concrete at room temperature, but the presence of polyolefin fibers reduced the UPV by 12% (Scheme 6 compared to Scheme 3). High heat application in concrete had harmful effects on the results of UPV and SEM test, so that the lowest and highest rate of decrease in ultrasonic wave velocity in concrete samples of 37 and 46%, respectively, belong to plan 1 (containing ordinary concrete) and plan 2. (Alkaline slag concrete without nanosilica) was obtained. Microstructural studies of SEM showed the coordination and overlap of the results obtained in this study.