Advanced Materials Research Vols. 1065-1069

Abstract: The combustion performance of adding different metal hydroxide flame retardants in asphalt was investigated by the limit oxygen index test, and the flame retardant process of hydroxide flame retardant was studied by thermogravimetric analysis. The results showed that calcium hydroxide, magnesium hydroxide, aluminum hydroxide all play positive roles on flame retardancy of asphalt. Aluminum hydroxide has the best effect on flame retardation; calcium hydroxide and magnesium hydroxide show similar flame retardation. The temperature range of the decomposition of different metal hydroxide was different. Aluminum hydroxide has the lowest decomposition temperature, while calcium hydroxide has the highest decomposition temperature. Barrier layer composed of metal oxides is formed after the decomposition of flame retardant , which can prevent the further burning of asphalt.

Abstract: Existing highway vertical curves may be grouped into two categories: symmetrical vertical curves and unsymmetrical vertical curves. In the past vertical curves design, parabolic arc was used as the vertical curve. This paper presents the new single-arc unsymmetrical vertical curve which is include only one cubic parabola. This curve has the gradual change of the rates of change in grade so that it can provide more comfort to the driver. This paper mainly presents the method by which to find the minimum length for a new single-arc unsymmetrical crest vertical curve based on the minimum sight distance . The discussion will be divided into two situations: the sight distance is longer than the curve length and the sight distance is not longer than the curve length.

Abstract: Cold asphalt mixture can be handled at ambient air temperature and thus is regarded as energy saving, convenient for storage, transportation and construction, and can extend the construction season. However, it is commonly used in preventative maintenance of pavement as slurry seal and Micro-surfacing, not as structural layer due to its inferior performance to Hot Asphalt Mixture (HAM). Therefore, it will produce great economic and social benefit if a new cold mix and cold laid mixture can be developed for newly built road pavement application. Proportion design of AC-13 asphalt mixture using specially developed polymer modified emulsified is carried out and the performance of high temperature, moisture susceptibility, and low-temperature crack resistance are evaluated according to HAM technical specification. The results show that each performance of the AC-13 modified emulsified asphalt mixture can meet the specification requirements, and especially perform very well in rutting resistance performance.

Abstract: According to the mechanism and influencing factors of subgrade frost heaving , subgrade with berms structure was proposed based on typical highway to prevent the frost heaving.The solid model of subgrade was established. Numerical calculation model of subgrade was established by applying the finite difference software FLAC 3D, boundary conditions and parameters of numerical model were determined, models of subgrade with berms of different widths were analysed and calculated. The results show that subgrade with berms can effectively reduce the freezing depth of subgrade, and decrease the stress and deformation of subgrade frost heaving, berm that is 3m wide in given simulation conditions has the most significant effects on preventing and controlling frost heaving .

Abstract: The reclaimed asphalt pavement (RAP) materials with aged SBS bitumen were limited to applied in unmodified asphalt mixture for low level pavement structure by conventional recycling technology. To overcome this, a new recycling procedure was developed to recover the aged SBS RAP as modified asphalt mixture by warm mixing technology. The Marshall method was applied to design Warm Recycled SBS modified Asphalt Mixture (WRMA) with different RAP content (0, 20%, 30%, 40% and 50%). the performance properties of WRMA and hot recycled SBS modified asphalt mixture (HRMA), such as the high temperature stability, water stability and low temperature performance, were evaluated by the rutting test, low-temperature creep test, beam bending test and water immersion Marshall test, respectively. From the testing results, the properties of WRMA was more than HRMA significantly, and the warm recycling technology could effectively increase the RAP content applied in recycled pavement materials.

Abstract: In view of the dynamic compaction method to reinforce the miscellaneous fill subgrade plate load test, the consolidation of the miscellaneous fill characteristic value of subgrade bearing capacity is between 160~326 KPa, and foundation coefficient K₃₀ value is between 122~229 MPa/m. The degree of miscellaneous fill reinforced roadbed compaction is located in between 94.8%~ 99.0%,which is detected through the sand filling method . Plate load test can be used as one of the evaluation index of highway roadbed performance.

Abstract: Research on frost heaving of high speed railway subgrade filling in seasonal frozen soil area is developed indoor. Through freezing and thawing strength and frost heaving amount test, the research analyzes factors affecting frost heaving of subgrade filling, points out that water content, fine stuff admixing amount and plasticity of fine-grained soil have relatively large influence on frost heaving, while freezing temperature and freezing and thawing cycle index have relatively small influence. Water content is main factor to have effect on frost heaving of subgrade filling. When the water content reaches to some certain value, even coarse-grained soil can produce considerable frost heaving amount. Therefore, taking effective waterproof and drainage measures is of great importance in subgrade frost heaving prevention and treatment.

Abstract: The paper seeks to analyze the necessity of setting functional layer between base and surface course of cement concrete pavement. Based on laboratory test, test device is developed to test accumulated deformation of the functional layer mixture. Use common mixture AC-16, AC-13, and AC-10 to analyze the increasing law of cumulative deformation of mixture. According to the results, 3.5mm is set as the maximum limits of accumulated deformation for function layer under specified test condition in this article, which provides theoretical reference for the pavement layer design of cement concretes.

Abstract: With the increase of our construction in the mountainous area, rockfall hazard also increasing seriously. In this paper, the rockfall prone section is determined through understand the engineering geological conditions cause falling rock; then to predict the impact of the range of rockfall movement, the motion characteristics of rockfall is studied, and the calculation methods of rockfall impact is given; Finally, combine with a practical engineering, the rockfall collision impact theoretically and the practically are compared. The result shows that this study may provide a useful approach for protection engineering design.

Abstract: In order to study the influence of ultraviolet aging on the performance of different asphalt, we select two kinds of matrix asphalts of the same symbol and two kinds of modified asphalts of the same brand which are used widely in our country. After ultraviolet aging in different time, we use the samples to do the experiments of three indicators and DSR. The results show that the data of the modified asphalts after ultraviolet aging is more stable. Under the irradiation of ultraviolet light,the performance of modified asphalt is more stable.