Can Chen

Assessment of Composite Pavement Performance by Survival Analysis

AbstractThe main objective of this paper is to identify the most appropriate rehabilitation method for composite pavements and to evaluate the influence of different factors for the reflective crack development in composite pavement by survival analysis. Four composite pavement rehabilitation methods are evaluated: mill and fill, overlay, heater scarification, and rubblization. Survival analysis is used to evaluate the four methods using three pavement performance indicators: reflective cracking, international roughness index (IRI), and pavement condition index (PCI). Rubblization can significantly retard reflective cracking development compared with the other three methods. No significant difference for PCI is seen in the survival analysis for the four rehabilitation methods. Heater scarification shows the lowest survival probability for both reflective cracking and IRI, whereas overlay results in the poorest overall pavement condition based on PCI. Parametric survival models are employed to further anal...

Water flow simulation and analysis in HMA microstructure

Abstract: This paper introduces a new method for reconstructing virtual two-dimensional (2-D) microstructure of hot mix asphalt (HMA). Based on the method, the gradation of coarse aggregates and the film thickness of the asphalt binder can be defined by the user. The HMA microstructure then serves as the input to the computational fluid dynamic (CFD) software (ANSYS-FLUENT) to investigate the water flow pattern through it. It is found that the realistic flow fields can be simulated in the 2-D micro-structure and the flow patterns in some typical air void structures can be identified. These flow patterns can be used to explain the mechanism that could result in moisture damage in HMA pavement. The one-dimensional numerical permeability values are also derived from the flow fields of the 2-D HMA microstructure and compared with the measured values obtained by the Karol-Warner permeameter. Because the interconnected air voids channels in actual HMA samples cannot be fully represented in a 2-D model, some poor agreements need to be improved.

Performance characteristics of epoxy asphalt paving material for thin orthotropic steel plate decks

ABSTRACT Early pavement distress caused by heavy traffic is frequently observed on bridges with relatively thin decks of orthotropic design, particularly in hot climates. This study investigates the possible use of epoxy asphalt to stiffen the thin deck/pavement composite, minimise deflection and ultimately fatigue failure. Three different epoxy asphalt binders were used and two pavement mix designs were employed. The binder and pavement mixture properties were evaluated by direct tensile and pull-off strength test on the binder, Marshall test of the paving mixture and flexural fatigue tests of paving mixture on steel plates. Test results show that a relatively high modulus binder and a relatively stiff pavement can effectively reduce the composite’s deflection and improve fatigue resistance on a relatively thin steel plate. Binder adhesion to the aggregate in the composite seems to play a pivotal role and the strength of this bond may have a close relationship with the stiffness of the pavement.

Examination of the Ignition Oven Method Correction Factor for Hot Mix Asphalt with Granite Aggregates

Ignition oven is a widely-used equipment for determining the asphalt content and gradation in hot mix asphalt. Accurate determination of the asphalt content and post-plant gradation by ignition oven method are the fundamentals of quality control in hot mix asphalt production. However, a correction factor is usually needed, mainly due to the mass loss of the asphalt binder and the aggregates decomposition during the high temperature burn-off process. This study investigated the influences that could affect the correction factors for both asphalt content and aggregate gradation using granite materials. Results show that smaller size aggregates would give a higher asphalt content correction factor than the large size aggregates, and a higher ignition oven temperature would lead to higher asphalt content correction factor. As for the aggregate gradation correction factor, larger size aggregate would lead to more breakdown than the smaller size aggregate, however, for the same type of aggregate, different ignition oven setting temperature does not obviously change the gradation correction factor. The polarized light microscope analysis demonstrates that granite aggregates that subjected to the extremely high temperature in the ignition oven, have minerals being partially decomposed, producing brown fractured chlorite and hornblende altered by chlorite.

Stiffening Thin Orthotropic Deck Structures with Thermoset Epoxy Asphalt for Improved Fatigue Resistance

Early fatigue cracking of the pavement was frequently observed on bridges with relatively thin decks of orthotropic design, particularly in hot climates. This study investigates the possible use of epoxy asphalt to stiffen a thin steel deck and mitigate flexural and fatigue failure. Three different epoxy asphalt binders were used and two pavement mix designs were employed. The binder and pavement mixture properties were evaluated with direct tensile test and pull-off strength test on the binder, Marshall and flexural fatigue tests on paving mixture with steel plates. Test results show that a relatively high modulus binder and a relatively stiff pavement can effectively reduce the composite’s deflection and improve fatigue resistance. Binder adhesion to the aggregate in the composite seems to play a pivotal role and the strength of this bond may have a close relationship with the stiffness of the pavement.