JOURNAL OF TRANSPORTATION INFRASTRUCTURE ENGINEERING (JTIE)
Year:2016 | Volume:2 | Issue:1|Papers Count:7

Warm mix asphalts (WMA) have advantages and disadvantages in comparison with common asphalt mixtures. Most of the advantages of WMA are related to the low temperature of the production, environmental issues, less bitumen aging, reduction in fuel consumption and extension of the possible period for constructing the asphalt during the year. Warm mix asphalts have disadvantages such as weak performance in moisture damage. In this study, the effect of hydrated lime, which is an amendment material in similar cases, in modifying of this property and improving other properties, like rutting, dynamic module and creep resistance, will be analyzed. The cost problem is well-considered in selecting the amendment material, so as to preserve the greatest advantages of WMA, which are reduction in production cost and ease of accessibility. For this purpose, different amount of hydrated lime (0, 1, 2, 3 and 4 percent of aggregates) was added to WMA as filler, and then, the creep, moisture damage, dynamic module and rutting tests were performed. It was concluded from the obtained results that hydrated lime can be used in WMA as an anti-stripping and resistant to moisture damage material. Using hydrated lime for 2% of aggregates as a replacement for part of the filler in WMA is recommended.

In this paper, a computational scheme called half-plane boundary element method (BEM) was proposed for analyzing multi-layered soil media. In this method, it is only required to discretize the interface layers and boundaries of the tunnel. Therefore, one of the important challenges in the previous studies on the full-plane BEM, which considered fictitious limited boundaries and discretizing the smooth ground and underground boundaries' surfaces, was improved as well. After analyzing several examples and verifying the results with existing analytical responses, some parametric studies were presented for a two-layer soil including underground circular tunnel, located in the second layer and subjected to uniform internal pressure. The results showed that the proposed half-plane BEM has great capability in modelling the multi-layered soils. This method can be particularly used for modelling the geological problems in the field of soil mechanics and related sciences vis-a-vis traditional full-plane BEM scheme.

The significant problem with reinforced concrete rigid-framed railway bridges can be insufficient ductility due to shortage of transverse reinforcement in the joint region and also lack of embedded length of the beam reinforcements within this region. The investigations of such structures, based on current standard codes, approve the improper efficiency under severe earthquakes. The objective of this study was to investigate the seismic behavior of deficient reinforced concrete exterior beam-column joints in bridges before and after retrofitting with precast HPFRCC (High performance fiber reinforced Cementitious Composite) panels. In the first part of the study, mechanical properties of HPFRCC panels having different ratios of Polypropylene and hooked end steel fibers have been determined by compression and four-point flexural tests. In the second part of the study, behavior of the HPFRCC panels in retrofitting of beam-column joints of the bridges has been modeled using the results of the first part of the study. After validation, by using a finite element software, the nonlinear behavior of reinforced concrete beam-column joints, which have been designed based on criteria for railway bridges, has been evaluated. In the present resaerch, three types of beam–column joints are modeled and investigated. Results of the first part of the study reveald that adding fibers can significantly increase the tensile strength of the specimens and also the toughness mechanisms, such as bridging of the fibers, can dissipate energy, decrease brittle failure and also cause ductile behavior of the load-deflection curve after the peak load in fiber reinforced composites. Moreover, the analytical results of the second part of the study showed that such high performance materials can enhance bearing capacity and ductility of the joints. Behavior of the exterior beam-column joints, retrofitted with HPFRCC panels, have caused an increase in ductility, lateral strength and drift rather than reference joint specimen which is fully casted with normal concrete nearly 93%, 45% and 102%, respectively.

Drainage conditions of base and sub-base layers are one of the key factors that affect serviceability of asphalt pavement of the roads. The non-destructive testing method of ground penetrating radar (GPR) has been considered as an applicable method in this respect. In this paper, the relationship between obtained data from recorded images by GPR machine and moisture content of asphalt pavement system was investigated. Eighteen cylindrical samples with 80 cm diameter and height were constructed from asphalt, base, sub-base, compacted medium and natural medium in three different moisture percentages, and then were compacted. Then, a GPR machine, with 250 MHz antenna, was conducted over samples for profiling survey and the obtained radar images were analyzed statistically using Labview software. Comparison of the statisticall parameters obtained from the images showed that distribution of kurtosis is similar to a normal distribution and has logical and interpretable variation-trend with moisture percentage. Therefore, by using a linear curve, fitted between kurtosis and moisture content, an equation was extracted which could help to estimate nearly accurate the moisture content of pavement layers, based on the output of GPR test.

Performance of road-marking paints is one of the important parameters in their evaluation. The performance of road marking paints depends on many factors, which the most important ones are type of pavement, preparation of pavement surface and type of road marking paint. In this research, the performance of one of the two-component road-marking paints that is used in the streets of Tehran is evaluated. To perform the test, an adhesion-testing machine was used. In this research, the considered goals included best runtime of the two-component road marking paint on fresh asphalt surface, role of aggregate materials in interaction of road marking paint and pavement surface, modification of the primer used in pavement surface and role of the primer in interaction of two-component road marking materials and pavement surface. Analysis of the results showed that durability of two-component road marking materials in calcic pavements is more than siliceous pavements. Also, the best runtime is 15 days after the implementation of the asphalt. Also, the results revealed that implementation of a layer of primer in concrete surfaces and old road marking paint surfaces increases the adhesion strength (about 10%). On the other hand, implementation of a layer of primer in asphalt surfaces decreases the adhesion strength (about 35%).

Performance of road-marking paints is one of the important parameters in their evaluation. The performance of road marking paints depends on many factors, which the most important ones are type of pavement, preparation of pavement surface and type of road marking paint. In this research, the performance of one of the two-component road-marking paints that is used in the streets of Tehran is evaluated. To perform the test, an adhesion-testing machine was used. In this research, the considered goals included best runtime of the two-component road marking paint on fresh asphalt surface, role of aggregate materials in interaction of road marking paint and pavement surface, modification of the primer used in pavement surface and role of the primer in interaction of two-component road marking materials and pavement surface. Analysis of the results showed that durability of two-component road marking materials in calcic pavements is more than siliceous pavements. Also, the best runtime is 15 days after the implementation of the asphalt. Also, the results revealed that implementation of a layer of primer in concrete surfaces and old road marking paint surfaces increases the adhesion strength (about 10%). On the other hand, implementation of a layer of primer in asphalt surfaces decreases the adhesion strength (about 35%).

Strengthening of poor and improper soils, in order to be utilized in civil engineering projects, for fabricating a soil with ideal engineering properties, is called stabilization and reinforcement. Soil stabilization is used for various purposes such as prevention of surface erosion, improvement of poor subgrades, controlling of shifting soils, rehabilitation of base layers and retrieving of old paths. Today, because of weaknesses such as poor strength and long duration for curing with common stabilizers (lime and cement), the attitude for finding new materials which can improve these deficiencies has increased. In this research, a sandy soil, a petrochemical material called epoxy resin (as stabilizer), and also a fiber (as soil reinforcing agent) were used to evaluate their effects on soil resistance-parameters. The behavior of stabilized soil in compression and shear was determined in this project. Results of the tests revealed that compression and tensile strengths of stabilized soil with epoxy resin were increased significantly; while the strengths of the sandy soil without epoxy were too weak. By addition of fiber to the soil samples, the soil compression strength was not increased; whereas, it has profound effect to promote tensile strength. Also, soil samples containing fiber showed more deformation. This means that they absorb more energy under loading to reach the rupture stage.