Papers by Author: Hong Wang

Abstract: The waterproof-adhesive layer plays an important role in cement concrete bridge pavement. The adhesive strength of the layer between the cement concrete deck and the asphalt pavement may affect the bridge’s service performance directly. In the study, the direct shearing-strength experiment between the asphalt pavement, waterproof adhesive layer and the cement concrete deck was done in a laboratory. Some testing parameters were considered, including different loading speed, surface processing mode of the cement concrete deck and adhesive materials. The result shows that the coarser the surface of the cement concrete deck is, the larger the shearing strength of the adhesive material is at the same temperature. The loading speed of the shearing test has important effect on the shearing strength. The rapid loading speed can cause high shearing strength. Especially, the experiment datum indicates that the relationship between the loading speed of the test and the shearing strength can be described using the power exponent. Ultimately, the study is aimed at providing bridge engineers with an efficient testing method that attempts to increase the prediction accuracy of adhesive strength for more reliable design.

Abstract: Flexible pavement-asphalt mixture plays an important role in structures of the primary road and bridge at present. However, the mixture is a type of viscoelstic material and is sensitive to environment temperature, especially a high temperature. The permanent deformation due to high temperature and the material’s viscoelastic shorten the service life of the road and even lead to traffic accident. Therefore it is necessary to analyze the pavement’s mechanical performance. In the study, the viscoelastic constitutive equation of the mixture is transformed to Prony Series. The objective of this study is to characterize the stability of asphalt pavement at high temperatures with a three-dimensional finite element and accurately predict the pavement’s strain and stress in vehicle load.

Abstract: One micro-powder rubber (styrene butadiene rubber-SBR) at three concentration levels are used for manufacturing polymer modified asphalt with a mixing technique. The effects of concentration of modifiers and mixing temperature on the mechanical properties of the compounds are investigated. Based on a limited study, test results indicate that micro-powder rubbers have positive effect on the performance of asphalt in low temperature. Soft point, penetration and ductility show that the ideal percentage of rubber additive (7 wt. %) and preparing temperature (210°C) are brought forward. The fluorescence microscopy test indicates that rubbers are homogeneous dispersed in asphalt and have a little dissolving at the surface of the ultra-fine rubbers. The difference between soft point values in the high temperature storage stability test is only 0.2~0.5°C, which proves that modified asphalts have good storage stability. Complex modulus master curves are drawn to analyze and compare the rheological properties of various modified asphalts. Results indicate that modified asphalt binders have more excellent properties at both high and low temperatures, compared with original asphalt.

Abstract: Construction of the pavement has consumed a huge amount of high grade aggregates, such as basalt, limestone etc. In some region, these aggregates are very scarce and have to be produced and transported from far aggregate quarries which would cause the waste of energy and resources as well as the increase of cost. Large quantities of gneiss exist in China, the use of gneiss as aggregates might help meet the highway constructing demands and save. In this paper, the feasibility is analyzed with respect to different aspects. Physical properties of gneiss aggregate were evaluated using Los Angeles abrasion, specific gravity and flakiness index. Mixture properties were characterized in terms of Marshall stability, moisture susceptibility, soak wheel track and low temperature cracking resistance property. Experiment results indicate that the physical properties of gneiss aggregates can satisfy the related specifications and these gneiss materials as aggregates can be used in asphalt pavement. Results also show that the optimal gradation component of the mixture consists of the gneiss as coarse aggregate and the limestone as fine aggregate. The use of hydrated lime can improve the moisture susceptibility of the mixtures containing gneiss aggregates.

Abstract: Flexible pavement plays an important role in the primary concrete bridges at present. However, climate environment, to which pavement is exposed, significantly impact pavement stability and long-term performance. Especially, low temperature cracking of asphalt pavement in cold region is a common existing problem. In order to improve the pavement’s crack resistance it is necessary to predict the temperature stress distribution within the asphalt layers. A two-dimensional finite element model of a concrete bridge in thermal and thermal-structural couple analysis is developed to predict temperature and temperature stress variation of asphalt layers in cold region. The temperature stress variation is analyzed at seasonal temperature, different cooling rate and the different thickness of asphalt layers. The model considers a set of primary thermal environmental conditions. Ultimately, the model is aimed at providing pavement engineers with an efficient computational tool that attempts to increase the prediction accuracy of temperature in asphaltic pavement of cold region for more reliable pavement design.

Abstract: Asphalt pavement serving as solar collector has been developed for the heating and cooling of adjacent buildings as well as to keep the pavement ice-free directly. Material parameters such as thermal conductivity and heat capacity are some of the critical parameters related to the efficiency of the asphalt collector. Graphite powders were utilized as thermal conductive fillers to make asphalt collector conductive so as to improve the efficiency of the asphalt collector. The material parameters change with the addition of graphite consequently. In order to access the solar energy absorbability of conductive asphalt collector, it is necessary to predict the temperature distribution within the asphalt layers. A transient, two-dimensional finite element model is developed to predict temperature distributions in conductive asphalt solar collector due to material parameters. The ability of accurately predict asphalt pavement temperature at different depths will greatly help pavement engineers in determining the solar energy potential of conductive asphalt collector. The results from the prediction model show that the surface temperature of pavement decreases slightly with addition of graphite. The differential maximum asphalt temperature variation at a depth of 10cm is significantly more than that at the surface. Higher temperature and lower temperature gradient can also be observed at the depth of 10cm because the heat conduction is accelerated by the addition of graphite.