Applied Mechanics and Materials Vols. 505-506

Abstract: The gross volume density of mix asphalt material compacted specimen is a crucial indicator in the design of asphalt mixture and quality control of asphalt pavement, and it directly determines the asphalt aggregate ratio and the degree of compaction. It has a great practical significance to distinguish and choose the test method of gross volume density correctly. The specific aspects of the methods to determine gross volume density have been controversial. A new method named brush wax method is put forward for these issues. The density, priority, VMA and compactness of asphalt mixture were measured by different methods in the tests. By comparison of the new method and the other methods, the main technical indexes of asphalt mixture obtained by the brush wax method are the only one which greatly satisfies the technical requirements.

Abstract: In this paper, combine with specific projects of Dahe railway design to study the key technical problems of laying CWR in large temperature difference alpine region, including stress-free temperature design, stability analysis of heavy haul CWR, heavy haul rail design in special sections, etc. The result has vital significance to guide the similar project design.

Abstract: The change of moisture and temperature is the key factor that influences the permafrost roadbed stability. Based on Moisture-Heat control equation and permafrost sub-grade deformation control equation, the permafrost sub-grade model was established. Studies showed that roadside accumulated water had remarkable influences on deformation of sub-grade; Moisture infiltration contributed to the production of longitudinal crack, and the longitudinal cracks were likely to be developed at the roadside where the water was accumulated for the longer time , and the greater changing of longitudinal cracks were developed.

Abstract: Polymer modified bitumens have tended to be the most popular among the various types of modified binders that are available worldwide. Polymer modification significantly alters the rheological characteristics of the binder, thereby requiring the use of fundamental rheological testing methods to provide an indication of the performance of the binder and subsequently the asphalt mixture. In this paper the characterization of bitumen modified with epoxidized natural rubber (ENR) was done with four percentages of ENR content. The effects of the modifier on the conventional properties, storage stability and rheological properties were investigated. The results indicated that storage stability of ENR modified bitumens (ENRMB) were mainly dependent on the ENR content. ENR reduced the temperature susceptibility. The degree of the improvement generally increased with ENR content up to 9%.

Abstract: The most widely used pavement roughness index is the international roughness index (IRI), but it is a poor predictor of ride comfort. In addition, the rider has not yet been included in the vehicle model used to evaluate pavement roughness. In this paper, in order to evaluate the comfort of the rider directly and consider the effects on ride comfort of pitch movement, a five-degree-freedom vibration model was built when a rider was added to a pitch-plane vehicle model. The vertical weighted root-mean-square (RMS) acceleration of the rider was suggested to be pavement roughness indices, which were related to ride comfort, respectively. The new roughness indices were calculated and a new pavement roughness evaluation method was developed.

Abstract: Continuously reinforced concrete pavement (CRCP) does not require any contraction joints which is a high-performance pavement structure type that just need a sufficient number of reinforced pavement longitudinal configuration to constrain sideway random crack width. With continuous basalt fiber as reinforced material and synthetic resin as the matrix material and adding appropriate adjuvants, basalt fiber reinforced polymer (BFRP) bar form a new type of material after pultrusion processing and surface treatment technologies. BFRP on the mechanical properties were studied by two kinds of test methods which are using extensometer strain detection and fiber optic strain sensing and the parameter of homegrown BFRP bars mechanical properties. Because of the lower tensile elastic modulus of BFRP bars compared with rebar, the mechanical properties of basalt fiber-steel wire composite bar has been studied along with the research corrosion and flexural properties of BFRP bar.

Abstract: After thin layer repaired, airport pavement will still appear crack, this situation not only spend a lot of maintenance costs, and seriously affect the use. This paper made flat constraint test for concrete containing poly carboxylic acid by using reinforced constraint plate mold, then the KON-FK(O) crack width tester and KON-FSY crack depth tester has been used in measuring on the surface of a block. Through the measured data analysis, crack effect is best when poly carboxylic acid with percentage of 2% and 2%.

Abstract: Based on the fiber Bragg grating sensing principle, and according to the characteristics of asphalt pavements, two types of FBG sensors are designed. One type is rigid sensor packaged by steel casing which labeled as R-type, and the other one is flexible sensor packaged by rubber which labeled as F-type. Through the tests of sensing performance, high-temperature stability performance and low-temperature stability performance, a comprehensive analysis of the long-term service performance is obtained. Analysis show that both rigid and flexible packaing have sensitizing effect while flexible packaging is better. Both types of sensors have good high temperature stability and low temperature stability, while R-tpe is better than F-type.

Abstract: The current cement concrete pavement design specification considerate the limit state of pavement via using the most adverse combination of maximum load stress and temperature load stress. This method enlarged the effect of temperature stress which lead to the overly conservative results. According to it, the reasonable combination of the ultimate axle load and temperature stress was deeply researched. The proper value of temperature gradient, reliably coefficient, stress reduction coefficient, comprehensive coefficient and the effect of load position in structure calculations were studied respectively. The improved calculation method of cement ultimate axle load of concrete pavement was proposed and verified, rely on the practical construction.

Abstract: Conventional fatigue damage test of asphalt mixture is usually under the condition of constant stress-mode or strain-mode, the specimen is broken when the cyclic load reaches certain number of times. In fact, vehicles on the road are not continuous, traffic volume is different in different time, there is a time interval between neighbouring vehicles. In this paper, time interval was set between two neighbouring cycles, the effect of recovery way, strain size and temperature on cumulative dissipated energy were analyzed. The results show that: in the early stages, recovery methods have little impact on the cumulative dissipated energy, with the increase of cyclic number, the value of trabecular under unconstrained condition will be greater than that of trabecular under constrained one. The bigger the strain size, the greater the value of cumulative dissipated energy; The lower the temperature, the greater the value of cumulative dissipated energy. Under the conditon of low strain size or high temperature , the value of cumulative dissipated energy decreases linearly. For the high strain or low temperature, there is a sharp decrease between the first cycle and second cycle, and then decreases linely in the later cylcles.