Australian Journal of Civil Engineering (14488353)20(1)pp. 195-207
More penetration of the prime coat increases the stabilisation thickness of the sub-asphalt layer and makes it more difficult for water to penetrate. Therefore, the purpose of this study is to identify the effective parameters on the penetration of Cationic Emulsion Bitumen (CEB) and investigate their effects. Short and long-term penetration tests are used. For better evaluation, two types of silica and limestone aggregates are selected in dry and wet conditions. To better compare the results of penetration, the penetration of MC250 cutback bitumen was also measured. The results show that among the identified parameters, the maximum penetration increase is influenced by the time of penetration, the material of aggregates, aggregate humidity, type of prime coat, kerosene percentage, and colloid mill speed which is equal to emulsifier percentage and the percentage of pure bitumen. Also, the least effect is observed for increasing soap temperature. Another result is that the CEB penetration in limestone aggregates is inappropriate in all cases. However, the penetration of CEB in silica aggregates in almost all cases provides minimum requirement so that the moisture being most effective to increase it. The value of MC250 penetration in limestone aggregates is only appropriate for wet and long-term conditions. © 2021 University of Isfahan.
Construction and Building Materials (09500618)337
Semi-flexible pavement (SFP) is known as a pavement with a high rutting resistance and a considerable load-bearing capacity. Despite its advantages, it is vulnerable to thermal cracking due to the difference in the stiffness properties of SFP components, including cement mortar and porous asphalt. This study aims at improving the overall performance of SFP, most notably cracking resistance, through approximating the stiffness of its constituent materials to each other. To reduce the stiffness of cement mortar, a cement mortar containing rubber powder was modified with nano-silica. The Ethylene Vinyl Acetate (EVA) modified bitumen was employed to increase the porous asphalt stiffness. Modified rubber mortar was poured into the modified porous asphalt mixture to produce the modified SFP (MSFP). The performance of MSFP was compared to conventional SFP (CSFP) using performance-based test methods of low-temperature bending, four-point bending fatigue, and rutting. The results showed that the low-temperature bending strength and strain improved up to 38 and 43%, respectively, for MSFP compared to CSFP. Moreover, the fatigue life and rutting resistance of MSFP were greatly superior to CSFP. © 2022 Elsevier Ltd
Australian Journal of Civil Engineering (14488353)19(2)pp. 134-147
Glass fibre with high tensile strength and Ethylene Vinyl Acetate (EVA) polymer may change Stone Matrix Asphalt (SMA) performance significantly due to its good performance. Therefore, the study’s main objective is to evaluate these two additives’ performances and their combination on SMA. Thus, modified bitumen’s physical properties with 3, 4 and 5% of EVA and mechanical properties of SMA made by 3, 4 and 5% of EVA and 0.1%, 0.2% and 0.3% of glass fibre are investigated. For this purpose, penetration, softening point, rotational viscosity, dynamic shear rheometer, resilient modulus, dynamic creep, and fatigue tests are performed. The results demonstrate that the performance graded of modified bitumen with an optimum value of 4% EVA is improved as two classes, leading to a significant improvement in the SMA performance. However, the performance of SMA containing 0.2% and 0.3% of glass fibre decreases severely due to the fragility of the fibres. The performance of the mixture in 0.1% of the fibres is slightly improved due to the reinforcement of the bitumen mortar and the lack of effect of the fibres on the overall structure of the mixture. Also, only the combination of 4% EVA with 0.1% glass fibre gives an acceptable result. ©, Engineers Australia.
Construction and Building Materials (09500618)302
Semi-flexible pavement offers a high bearing capacity and resistance to rutting. It comprises a layer of cement mortar and one of porous asphalt and is subject to thermal cracking because of the difference in stiffness of these materials. In this study, rubber powder (RP) was used to approximate the stiffness of the cement mortar relative to porous asphalt concrete in order to reduce thermal cracking. Nano silica (NS) was used to reduce the negative effect of RP on the compressive and flexural strength. The effects of these additives on the behavior of 20 mortar mixtures were investigated by mechanical testing and scanning electron microscopy. The results showed that 0.5% to 1% NS can prevent the fluidity loss and increase the drying shrinkage in the matrix. Three of the best-performing mortars were rated, and the optimum mixture was NS1-RP5 containing 1% NS and 5% RP. With an elastic modulus loss of about 20%, it exhibited the best performance and mechanical properties. © 2021 Elsevier Ltd
Case Studies on Transport Policy (22136258)9(1)pp. 161-171
Modifying travel behavior is a pressing issue in the face of increasing urbanization and the challenges that poses for existing infrastructure and deteriorating environmental conditions. Such challenges are particularly acute in cities which have a rich history and which have seen substantial population growth. One such is Isfahan, the third largest city in Iran, where the current study was conducted. Successful modification of travel behavior relies on an understanding of that behavior, but there are substantial methodological and theoretical barriers to doing so. This study reports a survey (N = 400) of Isfahan residents and visitors, and the modeling of the resulting data using a fuzzy logic approach. Together they illustrate the relative desirability, and potential effectiveness, of different Travel Demand Management strategies that might be employed to address the traffic challenges of Isfahan and other heritage cities worldwide. © 2020 World Conference on Transport Research Society
Road Materials and Pavement Design (14680629)21(1)pp. 156-178
Demolition and repairing of buildings produce large amounts of construction and demolition waste. The produced debris not only takes up space, but also leads to environmental degradation, unpleasant scenery, and above all, waste of construction materials and money. In this regard, recycling is a good solution that has received less attention in the construction section than other sections of industry. In road construction, part of the large amount of aggregates used in pavements can be provided from recycled construction and demolition (C&D) Waste. The aim of this laboratory study was to evaluate feasibility and usability of C&D in base and subbase courses of pavement. For this purpose, usable C&D materials were separated and the proportion of each was determined. Each material was passed through a crusher and a 25 mm sieve. The segregated materials were then mixed and technical specifications of the mixture were controlled against AASHTO standards. Finally, mix proportions were determined so that AASHTO technical specifications were satisfied. For this purpose, different percentages of C&D were mixed with control sample materials and technical specifications of the result were evaluated using compaction, California bearing ratio (CBR), and resilient modulus tests. The results showed the necessity of C&D decomposition, using crusher and sieve to control maximum grain size allowed, and exclusion of materials not complying with technical standards, before performing strength evaluations. Proportions of waste components must be selected so that all technical specifications are satisfied. Sometimes it might be necessary to mix waste materials with additional standard ones to achieve a technically standard final result. In this study, compaction and CBR tests showed that the obtained mixture is suitable for use in base and subbase layers but minimum requirements of resilient modulus for the base course are not met. Alterations in mixture components resulted in a significant reduction in C&D content for the base course. Therefore, it is recommended that C&D is used only in subbase layers of pavements. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.
Transportation Letters (19427867)pp. 1-10
The equations used to calculate horizontal curve radius are presented in geometric design regulations based on the following assumption: the curve is on the flat ground without overlap with longitudinal slope or any vertical curve. The aim of this study is to evaluate the effect of overlapping longitudinal slope and vertical curves on the horizontal curve radius. For this purpose, three different cases are investigated: horizontal curve in a flat road, horizontal curve in a sloping road, and horizontal curve in the presence of a vertical curve. For the above-mentioned cases, different forces are exerted on the vehicle. The direction of their effect is modeled using the point-mass method, and the equations for determining minimum horizontal curve radius are extracted. The results demonstrate that the equations for the overlap of a horizontal curve with a crest vertical curve indicate a need for increasing the horizontal curve radius in some cases. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Australian Journal of Civil Engineering (14488353)pp. 1-11
Even though fillers such as Limestone Powder (LP), Hydrated Lime (HL), cement and ashes improve the performance of pure bitumen, application of Herbal Fillers (HFs) such as oat, wheat and potatoes provides a better mixture in mastic asphalt considering environmental protection problems. Therefore, the aim of this study is to investigate the performance of bitumen modified with HFs. Penetration, softening point, viscosity and dynamic shear rheometer tests are performed using 3 and 5 wt% of fillers in the bitumen. For a better comparison of the results, samples containing LP and HL fillers are also tested. The results show that HFs improves the softening point, viscosity and penetration index. The rutting parameter (Formula presented.) exhibits a significant improvement in dynamic shear rheometer test. However, its effect on the fatigue parameter (Formula presented.) is negative. In addition, the shape of the filler is an effective parameter. It was revealed that the performance of fibre-shaped filler is higher than that of spherical one. Oat is the most effective herbal filler, while potato one shows the worst performance. © 2020, © 2020 Engineers Australia.
Road Materials and Pavement Design (14680629)21(3)pp. 683-700
Fibre is additive to hot mix asphalt that can improve fatigue life, rutting resistance, durability of asphalt concrete mixtures, creep compliance, tensile strength, dynamic modulus, elasticity, viscoelasticity, and reflective cracking. The fibres can be useful in controlling the cracks. Previous studies on various fibres have mostly focused on changing and optimising fibre percentage. No study has been conducted on appropriate fibre length in the mixture. Therefore, the effect of various fibre lengths on mixture properties needs to be clearly determined. The aim of this study was to evaluate the effect of various parafibre lengths on mechanical properties of hot mix asphalt through Marshall strength, indirect tensile strength, and resilient modulus tests. To achieve this, we added 0.5% fibre by weight of the asphalt mixture with lengths of 3, 6, 9, 12, 15, and 18 mm to hot mix asphalt samples and performed the above tests on the samples. The results showed that fibre improves hot mix asphalt mechanical properties; however, fibre percentage needs to be increased as the length increases, so that there are sufficient fibres present in the mixture to act against cracks. Accordingly, in all three tests, 12 mm fibres at 1% fibre content created the highest values. Therefore, the optimal fibre length was 12 mm, and for this length the most affected properties were resilient modulus, indirect tensile strength, and Marshall strength, respectively. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.
Construction and Building Materials (09500618)234
One of the parameters to have a durable asphalt mixture is the existence of high strength materials such as basalt and sandstone. Some experiments indicated that these aggregates should not be used due to their moisture sensitivity and the weakness in the adhesion of bitumen. However, some real world experiences demonstrated that these materials, together with limestone, leads to satisfactory results. Therefore, the aim was to identify the cause of satisfactory results in the used compounds, by examining physical and mechanical properties of the aggregates through microscopic and mineralogical investigations and chemical analyses of the aggregates (petrographic analysis). Asphalt mixture samples are made using different aggregate combinations and are tested using Marshall stability, indirect tensile strength and resilient modulus. The results revealed that petrographic analysis can well describe and predict the behavior of materials. In addition, high stiffness minerals such as quartz, plagioclase, pyroxene, and olivine enhance durability and frictional resistance of the asphalt mixture. Also, the fine aggregates containing sufficient amount of calcite micro-particles prevent the penetration of water by adequately covering hydrophilic aggregates and creating a continuous network of high-adhesive materials. © 2019 Elsevier Ltd
Journal of Materials in Civil Engineering (19435533)31(7)
Additives such as Sasobit, polyethylene, and paraffin can enhance the durability of pavement and prevent further environmental pollution by changing the functional behavior of bitumen. Combining Sasobit with two other low-priced waxes and achieving a satisfactory performance can help moderate the price of Sasobit, making its use pervasive. Therefore, this study aimed to investigate the mechanical and rheological properties of bitumen modified with Sasobit, polyethylene, and paraffin additives, separately and simultaneously. Accordingly, penetration, softening point, ductility, rotational viscometer, dynamic shear rheometer, and bending beam rheometer tests were performed on 10 mixtures in both aged and unaged states. The results of rheology tests indicated an improvement in the phase angle and high-temperature performance of bitumen modified with Sasobit and polyethylene waxes. The results of the rotational viscometer test indicated that the viscosity of bitumen modified with the Sasobit, polyethylene, and paraffin waxes and their mixture was reduced at high temperatures. Sasobit, polyethylene, and paraffin and their mixtures worsened the medium- and low-temperature performances; however, these negative impacts were lower in the combination of Sasobit and polyethylene. © 2019 American Society of Civil Engineers.
Road Materials and Pavement Design (14680629)20(2)pp. 475-489
Application of slag instead of aggregates is of importance in different civil construction works and especially in roller-compacted concrete pavement (RCCP) considering its abrasion resistance, shear strength as well as the cost. The aim of this study was to examine the effect of ground-granulated blast furnace slag (GGBFS) and basic oxygen furnace slag (BOFS) on the mechanical properties of RCCP, using the tests of compressive strength and indirect tensile strength. Mix proportioning was made to introduce BOFS as coarse aggregate and GGBFS as fine aggregate. The results of the study showed that none of the BOFS mix designs could achieve a higher strength than the control sample. Also, the GGBFS mix design proved to have the least compressive strength and tensile strength. It should be mentioned that all samples acquired the minimum strength required for RCCP. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.
Road Materials and Pavement Design (14680629)9(4)pp. 651-664
Porous asphalt mixture or Open Graded Friction Course (OGFC) has many benefits that resulted in its extensive use and development. OGFC improves the friction of a wet pavement, surface reflection, traffic noise, wet weather driving conditions by allowing the water to drain through its porous structure and reduces the hydroplaning, the splashing and spraying of water in the air (acts as spray reducing surfaces). For achieving the advantages mentioned above, this mixture must have big Voids in Total Mix (VTM). The big VTM reduces durability of the paving mixtures and prone them to raveling. The use of hydrated lime in porous asphalt is an accepted practice for many highway agencies in order to increase mixture strength as well as to improve durability of asphalt pavements. The goal of this study is to evaluate the mechanical properties of lime treated OGFC before and after multiple cycles of freeze-thaw moisture conditioning and also to show that hydrated lime improves stability and durability of the mixture more than limestone powder. © 2008 Lavoisier.
