Eyad Masad

Bio: Eyad Masad is an academic researcher from Texas A&M University at Qatar. The author has contributed to research in topics: Asphalt & Aggregate (composite). The author has an hindex of 61, co-authored 324 publications receiving 11773 citations. Previous affiliations of Eyad Masad include Texas A&M Transportation Institute & University of Texas at El Paso.

Internal Structure Characterization of Asphalt Concrete Using Image Analysis

Abstract: The performance of asphalt concrete (AC) mixtures is influenced by the arrangement of aggregates and their associated air voids. Parameters to measure aggregate orientation, aggregate gradation, and air void distribution in AC mixes are proposed. Computer automated image analysis procedures were used to measure these parameters. The air void distribution was characterized using X-ray tomography images. The new parameters were used to study the evolution of the internal structure of AC mixes during laboratory compaction by the Superpave Gyratory Compactor and in the field. The preferred orientation of the aggregate structure in the laboratory was found to increase with compaction up to a certain compaction effort. Thereafter, the aggregate structure tended to have more random orientation. Percent voids measured on X-ray tomography images compared well with percent voids measured in the laboratory. The void distribution in the specimens was found to be nonuniform. More internal voids were concentrated at the top and the bottom portions of the gyratory compacted specimen. The gyratory compacted specimens reached the initial aggregate orientation of the field cores at a higher number of gyrations whereas they reached the percent air voids in cores at a lower number of gyrations. Coarse aggregate gradation of gyratory compacted specimens was well captured using the image analysis techniques. There was no change in gradation with compaction.

Moisture susceptibility of asphalt mixtures, Part 1: mechanisms

Abstract: The detrimental effects of water in asphalt mixtures and its manifestation as distresses in asphalt pavements were first recognised in the 1930s and have been studied extensively during the last 35 years. This deterioration process, referred to as moisture damage, is generally defined as the degradation of the mechanical properties of the material due to the presence of moisture in its microstructure. Moisture damage is a complex phenomenon that involves thermodynamic, chemical, physical and mechanical processes. This paper describes the processes by which moisture damage affects asphalt mixtures. A critique of various moisture damage mechanisms is presented, followed by a review of recent work on modes of moisture transport (i.e. water permeability, capillary rise and vapour diffusion) and their relationship to moisture damage. Special attention is given to the characterisation of void structures of asphalt mixtures, which is an important factor that influences moisture transport. Finally, the paper pres...

Characterization of air void distribution in asphalt mixes using x-ray computed tomography

Abstract: This study describes experimental and analytical methods to quantify the structure of air voids in asphalt mixes. An x-ray computed tomography system along with image analysis techniques were used to measure air void sizes at different depths within asphalt mix specimens. The statistical analyses performed validated the applicability of the Weibull model for describing the air void distribution. Consequently, the Weibull model was used to quantify the effect of the compaction effort, method of compaction, and aggregate size distribution on air voids. The air void size distribution in Superpave gyratory compacted specimens was found to exhibit a “bathtub” shape, whereby larger voids were present at the top and bottom parts of a specimen. This shape was more pronounced at higher compaction efforts. The method of compaction was significant in influencing the air void size distribution. Specimens prepared using the Superpave gyratory compactor with different aggregate sizes were found to have noticeably diffe...

Engineering properties of tire/soil mixtures as a lightweight fill material

Abstract: The United States Environmental Protection Agency (USEPA) estimates that over 279 million discarded tires are being added annually to the already existing stockpile of two billion tires. Current disposal and stacking methods of waste tires are not acceptable due to the possibility of fire and health hazards. Several states and the federal government have issued legislation that encourages or mandates the recycling of discarded tires. One application where shredded tires can be used is as a lightweight fill material behind retaining walls or in highway embankments over weak or compressible soils. This paper presents the engineering properties of shredded tires, Ottawa sand, and a mixture of 50% Ottawa sand and 50% shredded tires by volume (70% Ottawa sand and 30% shredded tires by weight). The maximum size of the tire chips used was 4.75 mm. Gradation, specific gravity, void ratio, density, permeability, and consolidated-drained (CD) triaxial tests were performed as part of the testing program. Although the data obtained were limited to the above three mixes, the results indicate that the use of shredded tires/Ottawa sand mixes as a lightweight fill material is very promising. However, long-term impact of leachates from tires on groundwater quality should be investigated.

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Quantitative X-ray tomography

Abstract: X-ray computer tomography (CT) is fast becoming an accepted tool within the materials science community for the acquisition of 3D images. Here the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one. Our review considers first the image acquisition process, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight (e.g. fast and high resolution imaging, crystallite (grain) imaging) than conventional attenuation based tomography. Methods and shortcomings of CT are examined for the quantification of 3D volumetric data to extract key topological parameters such as phase fractions, phase contiguity, and damage levels as well as density variations. As a non-destructive technique, CT is an ideal means of following structural development over time via time lapse sequences of 3D images (sometimes called 3D movies or 4D imaging). This includes information nee...

Flow in porous media — pore-network models and multiphase flow

Abstract: In the last 3 years there has been a huge increase in the use of pore-scale modeling to study multiphase flow and transport in porous media. Starting from single pore models of fluid arrangements, computations of relative permeability, interfacial area, dissolution rate and many other physical properties have been made. Combined with a realistic description of the pore space, predictive modeling of a variety of processes, including waterflood relative permeability and mass transfer coefficients, is now possible. This review highlights some of the major advances, with an emphasis on models of wettability and three-phase flow.