Advanced Materials Research Vols. 255-260

Abstract: Considering the hot mix asphalt compaction quality is difficult to reach and it can be destroyed easily, the warm mix asphalt is used for thin overlay of airport cement concrete pavement. The mixture proportion of warm mix asphalt was designed, the performance of the base asphalt and the modified emulsify asphalt were measured, and the optimum asphalt quantity was determined, then the performance comparison between warm mix asphalt and hot mix asphalt were analyzed. Results indicate that warm mix asphalt has the same performance with hot mix asphalt, it can also satisfy the requirement of the airport cement concrete pavement thin overlay. Finally, in order to validate the project application effect, the warm mix asphalt was used in a northwest airport cement concrete pavement thin overlay. After four years use, the construction of the pavement is in good condition, and no disease emerging, the performance can meet the using requirements of the airport.

Abstract: Two gradations of asphalt mixtures were conducted to short term and long term aging tests. And then, static creep test was implemented on the samples of mixture. According to creep compliance curves from the stress-strain relations, Burgers viscoelastic model parameters were got to analyze the influences of aging effect on the viscoelastic response of asphalt mixture. The results and analysis indicated that aging is an important reason introducing viscoelasticity changes of asphalt mixture. For aged asphalt mixtures, the stiffness increases, the flexibility declines, the instantaneous elastic and the viscous compliance decrease. But short-term aging and long-term aging have different effects. And the viscoelastic parameters of the asphalt mixture with large voids vary more significantly, so aging process is much faster.

Abstract: Shaking table test is an important method to study seismic performance of geotechnical structures. Processing the similarity relation and deducing the response of original mold correctly are very important. Based on similarity theory, the paper adopts a dimensional analysis method to solve almost all similar constants, and provides a practical method on designing subgrade model of shaking table test. During the model designing process, several basic similar constants are defined at first and other main similar constants are obtained according to the basic similar constants. This method is applied in practical earthquake simulated shaking table test. Partial results are compared with the theoretical calculation result. The experimental result which is in concordance to the theoretical calculation result can reflect the seismic response rules of subgrade correctly. So the practical designing method is feasible.

Abstract: In order to save energy and reduce the pollution of the environment at the same time reduce construction costs, unconfined compression strength of Roadbed-stabilized soil tests are proceed on the base of potential stimulate agent inspired by fly ash and equal quantity replace the cement as the pavement materials use theory of uniform design . Then contrast tests of different level use of exciting agent are proceed. Regression analysis are put down to the results by using SPSS. Optimum mix of cement, fly ash, gravel and aeolianite are obtained when they have same activator. And then the dosage of fly ash are obtained through large number of contrast tests. The results shows that take Cement Fly-ash as the pavement materials is possible in some aeolian soil area where natural sandy gravel lack. It also provides a reference value in the selection of subgrade materials in aeolian soil area.

Abstract: In order to offer theory base for the widely use of Roadbood EN-1 soil firming agent in road base, triaxial shearing tests are performed on road base consolidated with Roadbood EN-1 soil firming agent, cement and lime to analyze its mechanical properties. Stress-straining curve, peak strength, remnant strength, elastic modulus and shearing strength of road base consolidated with Roadbood EN-1 soil firming agent, cement and lime under different ambient pressures are measured through triaxial shearing test. The conclusions are peak strength, remnant strength and peak straining have straight line relationship with ambient pressure. Its destruction procedure can be explained with impairment. The stress-strain relation curve also indicated that Duncan-Chang Model could not be applied to road base consolidated with Roadbood EN-1 soil firming agent, cement and lime, while the modified Saenz Formula could be used to describe the stress-strain relation of it,and good agreement was obtained.

Abstract: Based on the multi-layer elastic system model, a large general used finite element software is used to analysis in the paper. The conclusion of the most distortion lying the wheel load center and the law of the distortion with basal layer rigidity & thickness change are elicited. Above contents show the finite element method possesses extensive using foreground in the pavement structure analyse.

Abstract: Based on the designing scheme of highway widening project, a serial of model tests were conducted to simulate the performance of geogrid reinforced widening embankment influenced by subgrade differential settlement. Totally, 6 models including no-geogrid reinforcement embankment, geogrid reinforcement embankment, differential settlement of 0mm, 20mm, 30mm, and 50mm between existing subgrade and newly widening subgrade were built. The differential settlement distribution of embankment and stress performance of geogrid on each model were tested and analyzed. The test results show that geogrid reinforcement can effectively decrease the vertical deformation of embankment which with load on the top. The heavier the load, the more effective the decrease of vertical settlement. Meanwhile, the geogrid can significantly adjust the distribution of settlement along the cross-section direction of embankment to less differential. The geogrid at the connection area of existing embankment and newly widening embankment receives the biggest tension stress under the subgrade differential settlement. It is suggested that a solid connection between geogrid and the existing embankment is very important for getting a better geogrid reinforcement effect on decreasing the differential settlement between existing embankment and newly widening embankment.

Abstract: In this paper, based on advanced test methods such as laser particle sizer, scanning electron microscope, DSR and BBR,studies on physical properties of fine volcanic ash are carried out and the effect of single and composite modification on asphalt mastics and concrete by fine volcanic ash are also studied. Cost-effective of asphalt concrete modified by fine volcanic ash are analyzed as well. Results indicated fine volcanic ash can be qualified as a filler modifier for asphalt mixture and it significantly improves asphalt pavement performance and reduces project cost. Fine volcanic ash has favorable social and economic benefits and a broad application prospect.

Abstract: The interior prototype rutting test is designed to research the effect of geogrid on reducing rutting. Three models are studied, which include unreinfored, Telegrid JBS20 and Tensar SS30. The change trend of rutting and the influence of differential structure geogrid on rutting are analyzed to evaluate the effect of geogrid on reducing rutting. The results of the tests prove that the geogrid reduce pavement rutting on soft foundation effectively, SS30 with higher node intensity and rigidity obviously exceeds JBS20 with higher tensile strength on the effect of reducing rutting, and the effect on reducing rut is not very good by improving tensile strength of geogrid.

Abstract: The combined effect of moisture and dynamic loading on asphalt mixtures has been recognized as one of the main causes of premature deterioration of flexible pavements. Based on porous medium theory, the asphalt mixture is regard as saturated porous material, and a three-dimensional finite element model is established to investigate dynamic response of two typical asphalt pavement structures, which are the semi-rigid asphalt pavement and the semi-rigid asphalt pavement with flexible base course. Then the spatial and temporal distribution of stress, strain and pore fluid pressure of the two structures are calculated, respectively. Analysis results show the superiority of semi-rigid asphalt pavement structure with flexible base course to the semi-rigid asphalt pavement in aspect of moisture resistance capability.