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Hamburg wheel tracking (HWT) is prominently used for rutting resistance test. The HWT is a versatile device to determine moisture susceptibility and permanent deformation, which has been widely used in many states and agencies in the United States. However, the standard of the test for the HWT device conducted in water is not related to a primary result of rutting, which is due to repeated traffic loading cycle especially in the dry condition. In this study, the HWT test in different conditions (i.e. dry and wet) was conducted to compare the behavior of hot mix asphalt (HMA) during testing. The objective is to determine the comparison between the dry and wet condition testing in HWT test, and to evaluate relative effect of moisture conditioning in wet HWT on the creep stage. Fitting curve using Francken model was applied to determine the tertiary point of HWT curve. Power law model was used to determine the effect of the moisture conditioning in wet HWT on the creep stage. The moisture damage in the wet HWT test was also verified by the Bitumen Bond Strength (BBS) test. The results indicated that the wet HWT currently specified in the AASHTO 324 can be deployed as a substitute to the dry HWT test in the creep stage (before the stripping inflection point) since the difference in creep slope estimated for both conditions is within the experimental error. The wet HWT results after the creep slope remain useful for detecting the moisture sensitivity with the confirmation by the measured cohesion/adhesion of asphalt mastics from each mixture. The BBS test can also verify the moisture sensitivity occurred in the dry and wet HWT with the creep slope and tertiary/stripping slope well correlated to mastic cohesion change in BBS test. [ABSTRACT FROM AUTHOR]

Rutting is one of the most important failures occurring in hot mix asphalt (HMA) especially in the summer season and slow moving traffic areas. Rutting is a pavement surface failure compromising the safety and ride comfort of traveling and thus needs to be accurately evaluated in a laboratory. Although the flow number (FN) test is commonly used for evaluating the rutting resistance of HMA in a laboratory, there are some shortcomings in using FN test such as the costly and complicated equipment. Another potential test that is likely to be more advantageous than the FN test for evaluating the rutting resistance is the Hamburg Wheel Tracking (HWT) test, however, it is typically conducted in wet condition, and inadequate results in dry condition have been reported. The objective in this study is to optimize the HWT test subject to dry condition to be one potential method in measuring rutting resistance in a laboratory. Two rutting mechanisms (densification and shear failure) of HMA samples conducted in the HWT device were determined by Image Processing and Analysis version 2 (IPAS 2 ). Results indicate that HMA samples under the dry HWT test can exhibit both rutting mechanisms in which typically occur in the field. Also, the dry HWT test shows a very good R 2 for a relation of creep slope with the confined and unconfined FN test. As a result, the dry HWT can be an effective tool of quantifying rutting potential with better simulating to field behavior, lower cost of equipment, and less complicated geometry that can also accommodate field cores. [ABSTRACT FROM AUTHOR]

Abstract: Predicting the permanent deformation in asphalt binders under service load is an important step towards selecting the most appropriate asphalt binder for a flexible pavement. A model to predict the permanent strain in asphalt binders as a function of load duration and stress level at a constant temperature was developed in previous studies. In this approach, total strain was predicted as the summation of permanent and recoverable strain. This paper investigates the effect of temperature as an additional factor in this model. Considering the Arrhenius equation as the governing physicochemical rate process equation of many materials, it was hypothesized that temperature can be considered as an independent correction factor for permanent strain. This was verified by conducting a full factorial design and obtaining the interaction between temperature and other main factors. The significance of the factors was also computed to determine which factors should be incorporated in the prediction model. Analysis of the creep test results at different temperatures showed that the total strain under step loading follows the time–temperature superposition. Therefore, the recoverable strain in asphalt binders under a step loading at any given temperature can be predicted using the time–temperature superposition and Arrhenius equation. The model for prediction of the asphalt binder response was extended to include temperature as an additional factor. The extended model was verified under different loading conditions. This model will help engineers to better understand the rheology of asphalt binder and choose an appropriate asphalt binder based on traffic and environmental conditions. [Copyright &y& Elsevier]

Short-term oven aging (STOA) is used in current practice to simulate typical aging of asphalt mixtures during plant production and field construction. This study compares the volumetrics and performance of laboratory-produced asphalt mixtures and corresponding plant-produced mixtures to examine whether STOA simulates plant short-term aging. Eight plant-produced mixtures with varying levels of binder performance grade, binder content, filler content, and traffic design levels were tested for rutting and cracking resistance using Hamburg wheel-tracking (HWT) and semicircular bending (SCB) tests, respectively. The eight mixtures were duplicated in the laboratory and subjected to 2 h of reheating and 2 h of oven aging before testing. The eight lab-produced mixtures had comparable volumetric properties to the plant-produced mixtures, and the performance results showed a relatively high level of equality between plant- and lab-produced mixtures even when the properties of their extracted and recovered binders at high and intermediate temperatures are found to be significantly different. Based on the findings of this study, the use of the outlined STOA procedure is considered sufficient to represent standard plant production aging. [ABSTRACT FROM AUTHOR]