Advanced Materials Research Vols. 255-260

Abstract: It’s an effective method for measuring and monitoring of structure response of asphalt pavement with sensor to evaluate materials performance and to verify the validity of mechanical model. In this paper, a real-time system is established with FBG temperature and strain sensors. The strain of pavement structure caused by static test, the temperature fluctuation and the strain caused by air temperature variation are monitored with this system. The analytical results were derived by transfer matrix method based on the measured data and then were compared with the monitoring ones. The agreement of experimental observations and calculative results shows the feasibility of FBG sensors in temperature and strain monitoring of asphalt pavement structures and the validity of mechanical model.

Abstract: It takes on the technical and economic double benefits that fly ash taking the place of cement. However, water/binder of modern concrete is generally low; the research on the concrete performance which is based on large water/binder is no longer suitable for analysis of modern concrete. As to this problem, using different proportions of W/B and FA dosage as influencing factors, specimen is compounded for the compressive strength test. Then, mechanical properties of HPC are studied systematically. Based on this, macro-performance is analyzed from a micro-mechanism point of view through taking the electron micrograph. As the study shows, strength of HPC mixed with fly ash has low characteristics at early period while high ones at later period. At later hydration, fly ash effect plays a significant role, the growth rate of concrete strength increases as the increase of FA dosage. Compressive strength of concrete decreases as the increase of W/B and FA dosage. When the W/B is high, compressive strength is not sensitive to the change of W/B and FA dosage; but when the W/B decreases from 0.30 to 0.25, the concrete strength transition occurs. The influence of W/B on concrete compressive strength is more significant than that of the FA dosage; in the preparation of HPC, fly ash can be added more and cement is added less relatively by decreasing the W/B, displaying the role of micro-aggregate filling and modification, improving the strength and other performance of concrete. The study on micro-mechanism proves well the macro-phenomena above.

Abstract: Waste rubber is a typical black pollution. Producing asphalt rubber with crumb rubber is an effective way of reducing the pollution and resource utilization. The swelling and degradation degree of crumb rubber in the asphalt is a main factor of the performance of asphalt rubber. In order to study the physical and chemical behavior such as swelling and degradation, the influence of crumb rubber on the viscosity of asphalt rubber under different conditions was analyzed. And the microscopic changes of the crumb rubber were discussed by the micrographs. Test results indicate that the viscosities of asphalt rubber are increasing with the increase of the producing temperature and the dose of crumb rubber. And the viscosities are increasing firstly and then decreasing with the size decrease of the crumb rubber. The viscosity of asphalt rubber is the maximum with 60-mesh crumb rubber. The microwave can significantly improve the swelling and degradation degree of crumb rubber in the asphalt. The micrographs show that the microscopic states of crumb rubber are different in the asphalt under different conditions. The crumb rubber may only swell or swell and degrade at the same time.

Abstract: Temperature is one of the most important factors affecting the design and performance of both flexible and rigid pavements. The functional as well as the structural performance of flexible and rigid pavements is highly dependent on the temperature regime to which these pavements are exposed. Temperature variations within pavement structure contribute to distress and possible failure of that structure. According to pavement temperature stress calculation principle, based on general finite element software ANSYS, the paper adopt three-dimensional finite element method analysed temperature stress in concrete overlay on old asphalt pavement,in which discussed influence law of overlay thickness and modulus, equivalent rebound modulus on base course top and overlay structure parameters to temperature stress, providing theoretical principle and basis for old asphalt concrete pavement overlay method base on reliability.

Abstract: The design of asphalt pavements in china is currently based on the multilayered elastic method, which is analytical in nature and yields stresses, strains, and deflections in the pavement system for a particular loading condition and pavement geometry, which are compared with established failure criteria to determine the performance of the given pavement. This design approaches is deterministic. In this paper, typical asphalt pavement structure reliability analysis was performed in which factors that affect pavement reliability regarded as input random , pavement surface deflection, layers of bottom stress and limit state function regarded as output variables , by reliability tool infinite element analysis, base on Monte Carlo’s Latin hypercube sampling method.At last the paper pertinently offered decision basis for improve the reliability of pavement structure and important reference values for drafting and selecting of asphalt pavement design parameters through calculating the reliability of pavement structure, sensitivity analysis of the design parameters is made.

Abstract: The internal mechanical response of asphalt pavement structure is difficult to be obtained because of the limitations of theoretical calculation and present testing methods. In order to get practical information of instructure layers, this paper analyzed the cumulative and instantaneous strains of layers’ bottom of semi-rigid base asphalt pavement based on Accelerated Pavement Testing and Fiber Bragg Grating sensors, as well as got the spatial distribution and time-variation law of longitudinal, lateral and vertical strain responses under controlled loading condition. The research result shows that under the moving vehicle loads, there is an obvious alternative property of tension-compression as the strain response of the pavement structure, and different variation shapes of instantaneous stain are in different layers from top to down. Also the measured instantaneous three-direction strain of the bottom of each surface are higher than the calculated values with BISAR, while they anatomizes well in base. This paper can be regarded as useful and tentative research and application on future correlative study.

Abstract: This paper systematically elaborates the impact upon performance of emulsion asphalt cold reclaimed asphalt mixture by different RAP contents, through a series of testing on six cold reclaimed asphalt mixtures with various RAP contents, such as single axle compression test, 15°C indirect tensile strength (ITS) test, 40°C rutting test and -10°C low-temperature bending beam test. Testing results indicate that 15°C ITS decreases from around 0.75 MPa to 0.58 MPa with the RAP content of mixture increasing from 0% to 100%. 40°C dynamic stabilities reduce considerably from around 19,000 time/mm of 0% RAP mixture to 3,600 time/mm of 100% RAP mixture. -10°C failure strains only change from 1500με to 2000με.

Abstract: During the construction of Heda expressway, the Ermi landslide, which occurred on section K377, has interrupted the construction of the expressway. Additional engineering geological investigation became necessary. The direct economic losses are over 3 million US dollars. This paper analyzed the Ermi landslide from the aspects of formation process, engineering geological conditions, the structural characteristics and stability analysis of the landslide. The results show that the formation of the Ermi landslide is mainly due to geological conditions in project area. Because the structure of the sliding body is loose and some weak interlayer exists in the slope, the shear strength of the sliding surface and sliding body is low. As cut-slope excavating, the resistant of the slope body reduced. Eventually the slope lost its stability and a landslide formed. In the stability analysis of the slope, the shear strength parameters of the sliding surface was determined by anti-analysis. Therefore, the result of the evaluation is closer to the actual conditions. Analyzing the stability of the three sliding surfaces respectively, the stability factors for initial slope are between 1.211 and 1.468, and the stability factors for current slope are between 0.958 and 1.076. Hence, the cut-slope excavation is the direct cause of the landslide.

Abstract: The Semi-Circular Bending (SCB) test, which is chosen as the best inspecting method for pavement cores, is of great significance. Based on the SCB test and flexure beam test, this paper presents the findings of a laboratory study that aimed to evaluate the effects of recycled tire rubber on the fatigue properties of asphalt mixtures. Three mix types, a conventional hot-mix asphalt concrete, a dry process rubber modified asphalt concrete, and a wet process asphalt-rubber concrete, were included in the investigation. It is found that the asphalt mixtures produced by the wet and dry process showed better fatigue performance, which is the same conclusion from the SCB test and flexure beam test. The SCB test can be an effective evaluation means for the pavement service performance of asphalt rubber mixtures.

Abstract: Maintenance and protection of road pavements are one of important tasks of highway agencies. Many studies are done about specifying suitable time for pavement preventive maintenance. The probability distribution isn't used in this study, although the significant factor in decision making is relevant to probability function. In present paper, the suitable time between two preventive repairs is determined by Erlangen probability distribution function method. Economical factors are one of important parameters in this method, so, maintenance and repairing process cost, the useful life of maintenance process and the cutting of traffic flow are applied in calculation of suggested method.