Mitigation strategies for reflection cracking in rehabilitated pavements – A synthesis

The placement of an asphalt overlay on top of an existing pavement is rarely a lasting solution. Due to continuous movement of the existing pavement, existing discontinuities such as cracks and joints propagate through the overlay causing reflection cracking. Reflection cracking is a serious challenge associated with pavement rehabilitation. Practical experience shows that reflection cracking propagates at a rate of 1 in. per year. As the need grows for new rehabilitation methodologies to improve the performance of overlays against reflection cracking, a number of state transportation agencies tasked the authors of this paper to conduct a comprehensive review of treatment methods available to delay or to prevent reflection cracking in rehabilitated pavements and to survey current state of practice in addressing this distress. Based on the results of the literature review and the survey questionnaire, a summarized assessment is presented for each treatment method. Further, a number of treatment methods were identified for further evaluation by the state transportation agencies. For existing HMA pavements, crack sealing and overlay, chip. Keywords: Reflection cracking, Mitigation strategies, Fractured slab approaches, Saw and seal, SAMI, Chip sea

DEVELOPMENT OF AN ARTIFICAL NEURAL NETWORK MODEL TO PREDICT SUBGRADE RESILIENT MODULUS FROM CONTINUOUS DEFLECTION TESTING

The subgrade resilient modulus is an important parameter in pavement analysis and design. However, available non-destructive testing devices such as the falling weight deflectometer (FWD) have limitations that prevent their widespread use at the network level. This study describes the development of a model that utilizes the rolling wheel deflectometer (RWD) measurements to predict the subgrade resilient modulus at the network level for flexible pavements. Measurements of RWD and FWD obtained from a testing program conducted in Louisiana were used to train an artificial neural network (ANN) based model. The ANN model was validated using data from a testing program independently conducted in Minnesota. The ANN model showed acceptable accuracy in both the development and validation phases with coefficients of determination of 0.73 and 0.72, respectively. Furthermore, the limits of agreement methodology showed that 95% of the differences between the subgrade resilient modulus calculated based on FWD and RWD measurements will not exceed the range of ±21 MPa (±3 ksi).The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Field and theoretical evaluation of thermal fatigue cracking in flexible pavements

Thermal cracking in flexible pavement occurs when the tensile stress exceeds the tensile strength of hot-mix asphalt at a given temperature or when fluctuating stresses and strains caused by temperature variation lead to a buildup of irrecoverable deformations over time. The objective of this study was twofold: (a) to quantify the measured strain magnitude associated with thermal fatigue through field measurements and (b) to present a three-dimensional, finite element (FE) model that accurately simulated thermal fatigue in flexible pavement. Results of the experimental program indicated that pavement response to thermal loading was associated with a high strain range, reaching a maximum recorded value of 350 μm/m. This finding confirms the hypothesis that the criticality of thermal fatigue arises from the high stress-strain level exhibited in each cycle rather than its frequency, which is usually the critical factor in load-associated fatigue cracking. Moreover, the developed FE model accurately simulated pavement response to thermal loading by conducting a sequential coupled heat transfer analysis. Results of the developed FE model were in agreement with field measurements and demonstrated the model\u27s capability to simulate both the temperature and stress fields associated with thermal loading. This model may be used to evaluate pavement performance against transverse cracking induced by thermal fatigue

Image-Based Modeling of the Dynamic Complex Modulus Test for Asphalt Concrete

Due to the limitations of the elastic continuum theory, pavement engineers have recently paid considerable attention to the use of advanced modeling techniques for simulating the realistic behavior of asphalt mixtures. The objective of this study is to develop a three-dimensional (3D), heterogeneous model to describe the response of asphalt mixtures in the dynamic complex modulus test using an X-ray computed tomography (CT) image-based FE modeling approach. Experimental testing results for two Superpave mixtures including one conventional hot-mix asphalt (HMA) and one warm-mix asphalt (WMA) mix were used to validate and to calibrate the developed FE models. Adequate agreement between laboratory-measured and model-predicted dynamic modulus test results was achieved. Results of the developed FE models at different temperatures indicated that most of the deformations during the dynamic modulus test are derived from the mastic. In addition, asphalt mastic had more influence than the aggregates on the results of the dynamic complex modulus test