Advanced Materials Research Vols. 243-249

Abstract: According to the situation of Shao-Gan expressway slope project, the strategy of expressway slope ecology protection was put forward, including life-span ecology protection, zoology comeback and environment amalgamation, thorough environment protection. Then the slope ecology protection method by using coconut fibre nets and local frutex was brought forward. The validity of the reducing scour ability by using coconut fibre nets and local frutex mix-seminating or herbage and frutex mix-seminating was confirmed by the indoor model test and spot test. The slope ecology protection method which put forward in this paper was applied in the Shao-Gan Expressway and proved effective, which provide a new method and way to the slope ecology protection method of expressway in northern region of Guangdong province.

Abstract: Based on the viscoelasticity theory and the data of creep test, Burgers model was established, which was used to study the viscoelastic property of SBR asphalt mixtures, and the viscoelastic constitutive relation was obtained. Using the finite element method, the temperature stresses field was calculated under the environmental conditions and the thermal stresses of SBR modified asphalt pavement was given at the last part of this paper. The study indicated that SBR modified asphalt mixtures have the advantage over common asphalt mixture in low-temperature performance.

Abstract: Buton rock asphalt (BRA) is possessed of both performance and economic advantages. In order to reveal the modification mechanism, X-ray diffraction experiment (XRD), X-ray fluorescence spectrum analysis and environmental scanning electron microscopy experiment (ESEM) are used to study on microstructure of BRA in this paper. It demonstrates that BRA can extremely adsorb free bitumen due to abundant microscopic pores, which consists of 70~80 percent Buton rock (BR) minerals and 20~30 percent pure rock asphalt (RA). RA with high viscosity is strongly adsorbed internal and outer of the surface of BR, which has high alkaline pH, high crystallization and strong surface activity. Then a special microstructure named “RA~BR” blend with stable property and strong spalling-resistance capability develops. Meanwhile, dynamic stability rheology test (DSR) is employed to study on the rheological mechanics property of BRA modified asphalt mastic. The high temperature performance grade (PG) level of BRA modified asphalt mastic with different mixing content is determined. The reasonable mixing content of BRA in matrix asphalt is 20~30 percent. The research proves that BRA modified asphalt possesses wonderful high temperature stability and has broad prospects for pavement application.

Abstract: This paper studies the optimum proportion of rubber-particles in rubberized concrete for road, tests the impact of 12 modifiers and their modified processes in rubberized concrete and discusses the function mechanism of the modifiers in rubberized concrete. Research indicates: the optimum proportion of rubber-particles in rubberized concrete for road is low mix-proportion (volume ratio<5%); inorganic salt as modifier can markedly enhance the bonding strength between rubber-particles used in road and cement and improve the physical properties of rubberized concrete, among which CaCl₂ produces the most effect; but organic solution, acidic or alkaline solutions are not fit to be used as modifiers in rubberized concrete for road.

Abstract: Due to the heavy traffic and channelization, vehicle often brake and park for a long time at the urban road signal intersection, especially at heavy traffic intersection, for which it is easy to present permanent deformation on asphalt pavement. It can significantly improve the technical characteristics of the road intersection with adding Dolanit fiber into asphalt concrete. Based on BISAR3.0 software of applying layered elastic system theory and combined with the surface layer analysis on indoor mechanical property test to Dolanit fiber rein-forced asphalt concrete pavement, the results show that the allowable tensile stress is 0.61MPa. Even if at the condition of overload 50% and emergency braking, there is no shear failure on the Dolanit fiber rein-forced asphalt concrete pavement.

Abstract: This research mainly uses the image binaryzation to quantify water fog in order to have a better understanding about the water fog degree that drainage pavement reduces and the relationship between drainage pavement thickness and water fog. By observing the water fog that tires splash while raining, the study result shows that the most adequate pavement thickness of drainage pavement is 4cm. The water fog it reduces is double of 2.5cm drainage pavement. The thicker drainage pavement is also considered safer to drivers. About the drainage path, the shorter the faster it can drain off the rainwater and reduces the water fog degree that heavy vehicles splash.

Abstract: The asphalt pavements which are designed for 15-years usage are often highly damaged in the early period. In order to eliminate this phenomenon, researches have been carried out in many aspects, but the situation of asphalt pavement damage cannot be essentially changed. In the view of reliability, the frequent early stage damage phenomenon of asphalt pavements means that nowadays process of asphalt pavements must have not sufficient reliability, and just it leads the asphalt pavements can not reach the design purpose. Based on the basic engineering reliability theory, the reliability of the asphalt pavement design, from the determination of effect actions to selection of material parameters and the calculative model about pavement, has been analyzed; meanwhile the reliability of construction process has been analyzed too. The analysis on the reliability of asphalt pavement shows that the determination of design parameters makes the actual material is weaker than design; the construction process of the asphalt pavement makes the asphalt mixture greatly different anticipations and makes the layer condition deviated the ideal bonding condition. It is just these various uncertainties in design and construction that causes the asphalt pavement damage in early stage. So in order to change the situation of early damage in asphalt pavement, the effective measures are to focus on the reliability of design and constructions.

Abstract: Four combinations of frequency and amplitude induced vibrations and six start vibrated ages which ensured that the concrete would be exposed to vibration in each of the following age ranges: before initial set, during the setting process, and after final set are designed in the test. The purpose of the test is to testify whether the induced vibrations would affect the attainable tensile strength of concrete at cure ages of 1, 3 and 28 days. The splitting tensile tests are performed and 76 splitting tensile strength results are acquired. There are 29 groups splitting tensile strength weaker than the control group. Of the 29 results, they are all less than 10% compared to control ones, and the ones those less than 7% account for 76% of the weaken results. The test results have shown that, the induced vibrations designed in the test have a slight negative effect on the attainable the splitting tensile strength of concrete.

Abstract: Taiwan's climate is marine tropical. The northern part of the island has a rainy season that lasts from January through late March during the northeast monsoon, and experiences hot, humid weather from June through September. Thus, road’s maintenance is a difficult issue due to its long-season rains as well as high groundwater levels. In the mean time, the current roads are generally weaker in most suburban areas due to those soft soil bases uncompacted in construction. Those aspects explain the low performance of suburban roads in northern Taiwan. Therefore, this research takes the Yilan county, located in the northeast part of the island and well-known as a rainy county, as a study area where major suburban roads are selected to take asphalt concrete specimens for testing. The major purpose is to investigate the time effect of asphalt pavements for those of specimens with a period time of three years. A total number of 329 asphalt concrete specimens are characterized as Class I specimens, 305 of which were taken in 2007, as well as Class II of 24 taken in 2010. First, as for the Class I specimens, the Indirect Tensile Strength test (ITS) is conducted, together with the Control Chart as a filter, and then the remaining 253 specimens come to the average ITS value of 15.55 kgf/cm². Secondly, as for the Class II specimens of 24, the Film Stripping (FS) tests are conducted to obtain the Index of Retained Strength (IRS) values, from which the basis of ITS comparisons is found. Thus, the different average ITS value, 19.16% in three years, is obtained. The result also indicates that the annual reduction of ITS value for an area similar to the study area may be taken as approximately 11% (33.14/3 %) and 4.7% (13.98/3 %) for the conditions of high traffic flow and low traffic flow, respectively. It may also address the common effect of traffic and environment on moisture damage in asphalt pavements.

Abstract: Because of the special capillary and water-sensitive characters, the moisture content of silt subgrade in Alluvial Plain of the Yellow River is generally higher than the optimum value, which will lead to bad support conditions of subgrade. In order to analyze the water-absorbent property of silt subgrade, both the rainfall seepage and the capillary phenomenon were simulated in laboratory, which reveals that both factors have distinct effects on the moisture content of compacted silt soil. Triaxial tests of compacted silt soil reveal that the cohesive force reduces obviously with the increasing of moisture content. What’s more, the internal friction angle also reduces rapidly arriving at saturation state. By adopting Geo-slope code, the rainfall infiltration mode of silt subgrade was simulated under different rain type and rain duration. Results show that the subgrade slope is easy to lose stability because of much rainfall infiltration. In addition, the minimum safety coefficient happens at the time of rainfall ending. And the slope safety can be threatened seriously by the repetitious rainfall.