Advanced Materials Research Vols. 255-260

Abstract: Water stability of bituminous mixture, whose sediment concentration of coarse and fine aggregate are respectively in 1%, 2%, 3%, 4%, is tested and analyzed; meanwhile, under the condition of vacuum saturation, the water uptake and the residual water of bituminous mixture, whose sediment concentration of coarse and fine aggregate are respectively in 0%, 2%, 4%, are also tested. Based on the test, the tensile splitting strengths are analyzed, in correspondence to different water rates. Results show that the water stability of bituminous mixture reduces as the aggregate sediment concentration increases, and its influence on the cleanness to the fine aggregate is more sensitive than on the coarse aggregate; the ability of water uptake increases as the aggregate sediment concentration increases; residual water approaches to stability with the extension of time. However, the higher the sediment concentration is, the higher residual water ratio will be as it approaching to stability. For clean aggregate, when the ratio of the residual water reaches 50%, its splitting strength appears to be the lowest; but for the unclean aggregate, when its splitting strength is in the lowest, the rate of residual water would rise to above 75%.

Abstract: According to the stage filling theory and particle interfering theory, a new parameter “q” was put forward. The “q” was come from other 3 parameters of Bailey method, which are CA, Fac and FAf, it is used to represent the internal composition of coarse aggregate. Focus on the tropical climate condition of Xishuangbanna which is located in Yunnan Province China, the gradation design and performance of asphalt mixture were in-depth studied. It is concluded that the “q” has an significant effect on the volumetric properties and pavement performances. When the “q”of AC-25 asphalt mixture ranges from2~5, the coarse aggregate is more easier to formed into skeleton, its resistance capability of high-temperature rutting and water damage are very good, and this kind of asphalt mixture can meet the challenge in tropical climate region.

Abstract: Associating with highway widening project of Zhangzhou coastal main artery, the numerical analysis is carried out to analyze the lateral displacement, settlement and soil stress distribution of high fill embankment using geogrid. The results show that using geogrid can reduce the settlement and uneven displacement of high fill embankment. The maximum displacement occurs at the intersection position between old and new embankments, especially the geogrid embedding position. After the geogrid is used, vertical settlement significantly reduced while lateral displacement is in the highest flight. The lateral displacement is nearly 6cm and the total displacement is nearly 7cm, and both values are acceptable in filling construction. Meanwhile, the numerical analysis result manifests that the stress distribution of high fill embankment tends to uniform and then the whole stability of embankment increases. These conclusions may be useful to the design and analysis of reinforced-embankment of high fill and interface between new and old embankments in widened embankment.

Abstract: Inverted asphalt pavement has been widely used in practical application. Anisotropy of granular material has been proved by experiment, but the current design specifications are also based on isotropic theory. Based on linear-anisotropic model, on the condition of the high, medium and low strength of soil subgrade, 4 different thickness of asphalt layer and 3 different thickness of granular sandwich are been systematically studied, the results show that, the strength of the soil subgrade has bigger effect on the pavement deflection, the deflection difference of the low to the high subgrade is about 14~23%, with the increase of granular material anisotropy, the deflection correction factor is bigger, with the granular sandwich anisotropic rates from 0.1 to 0.5, the deflection correction factor is within 1.04, the thin asphalt layer and the thick granular sandwich have bigger effect on the deflection correction factor, for the common inverted asphalt pavement structure, the proposed deflection correction factor is 1.02~1.04, it can be used directly in asphalt pavement design.

Abstract: The chord modulus method mostly used in the layer-wise summation method to evaluate the total settlement of subgrade at present. In order to analyze the deformation field, it is necessary that one of key problem should be considered and solved how to use the chord modulus to implement the computation of the finite element method. Firstly, this paper reviews the characteristics of chord modulus theory. Secondly, the solution how the chord modulus is introduced into the finite element method is discussed, and subsequently the corresponding nonlinear finite element codes are developed. The computational results show that the nonlinear finite element method based on the chord modulus should be recommended owing to its potential application that it may consider the deformation field of the whole subgrade.

Abstract: The effect of short-term aging on rheological properties of asphalts was studied. In this paper, asphalt was aged by rolling thin film oven, which was carried out for 300 minutes and were analyzed at an interval of 75 minutes. The paper gives a description of the most commonly used conventional tests, such as Penetration and Softening Point, and a more detailed description of the viscoelastic behavior and dynamic testing of asphalts by way of Brookfield viscometer and Dynamic Shear Rheometer (DSR). It is found that there are a decrease in penetration and an increase in softening point with aging. The viscosity of aged asphalts was observed to increase with time. The DSR results show that short-term aging significantly increases the complex modulus at low temperature, but complex modulus at high temperature was just lightly affected. The four tests results were also incorporated to evaluate the temperature susceptibility and the rheological characteristics of asphalt binders.

Abstract: In order to evaluate and improve the performance of asphalt mixture at low temperature, low-temperature bending test of asphalt mixture was done at first. It was shown that flexural-tensile strength and flexural-tensile strain of different oil-stone ratios reduced under freeze-thaw condition compared to no freeze-thaw condition. The maximum decay rate of flexural-tensile strength is about 18.97% and the maximum decay rate of flexural-tensile strain is about 6.59%. Then six types of polyester fiber were added to asphalt mixture and bending test at low temperature was done. Through the experiment results comparison of fiber asphalt mixtures, it is found that ultimate flexural strain of Good Road II fiber asphalt mixture increases the largest which is up to 12.95%. Ultimate flexural strain of Dolanit AS fiber asphalt mixture increases 8.67% and other fiber asphalt mixtures increase from 3% to 6%. Fiber bridging and fiber micro-reinforced role in the mixture improves the performance of asphalt mixture at low temperature.

Abstract: Flexible pavements, as one of engineering subject, its stresses field is foundation and take play an important role to its mechanics analysis, life prediction, damage evaluation, and performance estimation. Simple expression of stresses filed in flexible pavement at special conditions (configurations of pavement, material properties, and traffic loading) is given in this research. The work is done by use of numerical analytical methods what 3D finite-element method and function fitting technology. The applicability of the proposed approach is verified using Boussinesq’s solution of semi-infinite elastic solid.

Abstract: Construction formwork is a new type of building material, bringing innovation to building technology aspects such as design theory and construction technology. A summary has been made by combining the research results of the author, the analysis and utilization progress of construction formwork in the aspects of product types, mechanisms of action, construction technology, combined with designing, insulation properties, mechanics and durability, analyzing the key problems that exist during research and application. The comparison of construction formwork walls and traditional walls has shown the application prospects of construction formwork.

Abstract: For complex pavements, there are circular, elliptic and rectangular shape vehicle loads under different conditions. Treatment way of vehicle loads is studied with conformal mapping method in this paper. Approach for transformation them to uniform circular shape is also researched. Terminal goal is enable the road engineers to accommodate changes of vehicle loads in their used way to pavement design which using static loads with uniform vertical pressure distribution without any more attached difficult.