2013 Session: 826

• Thermomechanical Model to Study Impact of Internal Void Structure on Mechanical Performance of Asphalt Mixtures
  Abstract: This paper evaluates the impact of the internal air void structure of asphalt mixtures on the thermo-mechanical response of asphalt courses. A random field technique was used to stochastically generate probable air void distributions, replicating those observed in actual field cores. These spatial void distributions were later used to assign different thermal diffusion properties throughout the asphalt layer, and a thermal-diffusion process was simulated after implementing the model in finite elements. The pavement is also subjected to mechanical loading, and the viscoelastic material properties of the asphalt course change in space during the simulations according to both the air void content and the temperature throughout the layer. The main result from this study is that the quality of the compaction process, which is represented by the internal dispersion of the air voids, strongly impacts the uncertainty of the mechanical response of asphalt courses.
  Authors: Castillo, Daniel; Caro, Silvia
  Authors: Castillo, Daniel; Caro, Silvia
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 826
  Paper Number: 13-1420
• Determination of Bulk Volume of Asphalt Specimens with Image-Based Modeling
  Abstract: An approach is explored for modernizing the determination of bulk density of compacted asphalt specimens. It is based on calculating the bulk volume of the specimen in a three-dimensional model reconstructed from its images. The paper presents the basics of image-based modeling, founded upon the science of photogrammetry and computer vision. Next, a demonstrative application is described, in which a field core is photographed from many viewpoints with a consumer grade camera, and the images are combined into a sparse point cloud. This cloud is subsequently ‘meshed’ with planar polygons into a closed 3D shape and its volume calculated. It was found that the model-core volume was very close to that measured with a traditional liquid-displacement approach. It was also found that while the volume was relatively insensitive to the quantity and quality of the images used for the reconstruction, the computational time varied significantly from minutes to hours. Based on the favorable findings of this limited application, the approach is deemed promising and viable, worthy of more in-depth examination.
  Authors: Levenberg, Eyal; Manevich, Alex
  Authors: Levenberg, Eyal; Manevich, Alex
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 826
  Paper Number: 13-1758
• Local Practice of Assessing Dynamic Modulus Properties for Washington State Mixtures
  Abstract: Dynamic Modulus (|E*|) is one of the key elements of a mechanistic-empirical based flexible pavement design procedure. It is used to characterize the material properties of asphalt mixtures and determine the stress-strain responses of a pavement at different loading conditions. Dynamic modulus is also a direct input parameter in several pavement performance models to estimate the field fatigue cracking and rutting performance. To provide a better understanding of the local materials, this study aims to test the typical asphalt mixtures used by Washington State Department of Transportation (WSDOT) and establish a material catalog for dynamic modulus. In this study, seven plant produced mixtures from five regions of Washington State were sampled and tested. These mixtures represent the typical asphalt binder, gradation, and mix designs of the state. One warm mix asphalt (WMA) project was also included in the analysis. Based on the experimental results, it was found that mix properties including air voids and binder properties had an important impact on the dynamic modulus. Due to the limited aggregate gradations, the effect of aggregate gradation on dynamic modulus was inconclusive. The measured dynamic modulus data were compared to the prediction results using the traditional Witczak E* model, the new Witczak E* model, and the Hirsch model. The Hirsch model was found to be the most promising and was further modified by including mastic property into the model. The modified Hirsch model greatly improved prediction quality and can be used as both a design tool and a screening tool to estimate the dynamic modulus of a mixture at early stages of the mix design process.
  Authors: Shen, Shihui; Yu, Huanan; Willoughby, Kim A.; DeVol, Joseph R.; Uhlmeyer, Jeffrey S.
  Authors: Shen, Shihui; Yu, Huanan; Willoughby, Kim A.; DeVol, Joseph R.; Uhlmeyer, Jeffrey S.
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 826
  Paper Number: 13-4181
• Development of Predictive Model for Laboratory Compaction of Asphalt Mixtures
  Abstract: Compaction significantly influences the performance of asphalt mixtures. Insufficient compaction often leads to excessive premature permanent deformation, excessive aging, and/or moisture damage. This study aimed to develop a prediction model for laboratory compaction of asphalt mixtures. This predictive model was developed based on parameters that describe aggregate shape characteristics, aggregate gradation, binder content, and binder properties as a function of compaction temperature. Results from intensive laboratory experiments that were used to quantify the effect of these parameters on the compaction of asphalt mixture in the laboratory are reported. Analysis of these test results show that the asphalt mixture type, aggregate type, and binder content have a significant and substantial effect on the slope and intercept values of the laboratory compaction curves. Two models that describe both slope and intercept of the laboratory compaction curves of asphalt mixtures are presented. These models show strong correlations between the predicted values and the measured ones. The models provide essential inputs that can be used to quantify the compaction effort needed to compact HMA in the laboratory.
  Authors: Awed, Ahmed; Kassem, Emad; Masad, Eyad A.; Little, Dallas N.
  Authors: Awed, Ahmed; Kassem, Emad; Masad, Eyad A.; Little, Dallas N.
  Year: 2013
  Document Type: Paper
  Subject: Materials
  Session: 826
  Paper Number: 13-5250
• Thermomechanical Model to Study Impact of Internal Void Structure on Mechanical Performance of Asphalt Mixtures
  Authors: Castillo, Daniel
  Authors: Castillo, Daniel
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 826
  Paper Number: 13-1420
• Thermomechanical Model to Study Impact of Internal Void Structure on Mechanical Performance of Asphalt Mixtures
  Authors: Caro, Silvia
  Authors: Caro, Silvia
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 826
  Paper Number: 13-1420
• Local Practice of Assessing Dynamic Modulus Properties for Washington State Mixtures
  Authors: Shen, Shihui
  Authors: Shen, Shihui
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 826
  Paper Number: 13-4181
• Development of Predictive Model for Laboratory Compaction of Asphalt Mixtures
  Authors: Kassem, Emad
  Authors: Kassem, Emad
  Year: 2013
  Document Type: Presentation
  Subject: Materials
  Session: 826
  Paper Number: 13-5250