Ramez Hajj

Ramez Hajj
University of Illinois, Urbana-Champaign | UIUC · Department of Civil and Environmental Engineering

Doctor of Philosophy

About

31
Publications
2,732
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161
Citations
Introduction
I am currently an Assistant Professor in the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign. My research interests and publications involve characterization of asphalt materials, computational modeling of viscoelastic materials, fatigue and fracture, and solving problems in the world of flexible pavements.

Publications

Publications (31)
Chapter
A number of different factors influence the overall performance of asphalt binder and consequently asphalt mixtures. These include intrinsic factors such as the use of modifiers, additives, reclaimed asphalt pavement (RAP) and other extenders. In particular, the fracture resistance of the asphalt binder is of importance because of the role of aspha...
Article
Full-text available
Patching of flexible pavements is one of the most important functions of pavement maintenance. Although finite element modeling has become commonplace in the world of pavement engineering, modeling has not yet been significantly leveraged for maintenance applications which improve safety, ride quality, and pavement service life. The objective of th...
Article
A procedure based on the linear amplitude sweep (LAS) test has been developed to determine the optimum rejuvenator content for restoring the properties of aged asphalt binders. The LAS test was employed to assess the damage tolerance, fatigue resistance, and fracture behavior of rejuvenated aged binders. In case of fracture analysis, a crack-based...
Article
This investigation employed an interrupted torsion fatigue test using the linear amplitude sweep procedure to assess the intrinsic self-healing potential of unaged, aged, rejuvenated, and re-aged asphalt binders. Continuous oscillatory shear strain loading at different damage levels were interrupted with a single rest period of different durations....
Article
Several laboratory and field studies from the last five decades, predominantly from the 1970s and 80s, have demonstrated that elemental sulfur is a viable binding material that can be used to partially or fully replace conventional asphalt binder in pavement construction applications. The main goal of this study was to determine and demonstrate the...
Preprint
Full-text available
Patching of flexible pavements is one of the most important functions of pavement maintenance. Although finite element modeling has become commonplace in the world of pavement engineering, modeling has not yet been significantly leveraged for maintenance applications which improve safety, ride quality, and pavement service life. The objective of th...
Article
Using reclaimed asphalt pavement (RAP) material in pavement construction is typically an environmentally friendly practice. However, the asphalt available in RAP is already oxidized and stiffened due to various environmental processes. To compensate these problems, rejuvenators can be mixed with aged binder with the aim of restoring its original pr...
Article
Since the adoption of the Performance Grading criteria, researchers and agencies have dedicated efforts toward supplementing the existing parameters with better indicators of asphalt binder cracking susceptibility. This study seeks to evaluate the relationship between ΔTc and the Glover-Rowe parameter, two such parameters. This study contains three...
Article
This study investigates the chemical characteristics of rejuvenators and the effect of different rejuvenators on the morphology and fundamental behavior of rejuvenated asphalt binders. Gas chromatography-mass spectroscopy (GC-MS) and atomic force microscopy (AFM) were conducted to determine the chemical composition of rejuvenators and asphalt surfa...
Article
Current procedures to extract and recover asphalt binders require a large amount of material and consequently a large volume of toxic solvents. To reduce exposure and consumption of such solvents, a micro-extraction method for extracting and recovering asphalt binder from small amounts of asphalt mix or reclaimed asphalt pavement (RAP) is presented...
Article
Determining the permissible amount of reclaimed asphalt pavement (RAP) in new pavement mixes is a design challenge for pavement practitioners due to the limited understanding regarding the interaction between the aged and unaged binders in these mixtures. In this study, the solubility related molecular interactions of blended binders comprising of...
Article
The chemical composition of a bitumen dictates its rheological properties as well as its performance in an asphalt mixture. Any bitumen comprises a wide variety of complex hydrocarbons, and its chemical composition can be characterized by many different parameters. Similarly, the mechanical properties of any given bitumen are typically characterize...
Article
Over the last few years, several researchers have employed computational methods to model and investigate the overall behaviour of asphalt mixture composites and different factors that influence this behaviour. Two-dimensional models, particularly those with computationally generated geometries, are commonly used in lieu of three-dimensional models...
Article
We observed and analysed the early stages of formation and growth of instabilities in binders that lead to crack formation. A monotonic mechanical strain was applied to a thin, confined film of binder between two transparent plates; meanwhile, the bulk of the binder was observed using dark field microscopy to capture its behaviour as the strain inc...
Article
The low-temperature properties of asphalt binder have attracted attention in recent years thanks to an increase in the use of reclaimed asphalt pavements (RAP). Traditional methods to evaluate the low-temperature properties of the binder require a large amount of binder that needs to be recovered from RAP samples for testing with a Bending Beam Rhe...
Article
Asphalt binders in bituminous mixtures with reclaimed asphalt pavement (RAP) comprise fractions of both aged and unaged binders, existing as a single entity. The degree of blending between the aged and virgin binders dictates the extent of homogeneity of the binder in the mix and consequently its mixture performance. However, their mechanism of int...
Article
Friction loss is one of the most critical issues faced by agencies responsible for maintaining and preserving pavement structures. Various methods are used for surface treatments, including seal coats, slurry seals, and ultrathin asphalt concrete overlays. Ultrathin overlays have increased in popularity due to their lack of noise and improved ride...
Article
Several studies have investigated the use of nanomaterials to modify asphalt binders and achieve improved properties. It is possible that in some cases nanomaterials do not disperse and agglomerate within the asphalt binder. In such cases, the benefits from the addition of these nanoscale modifiers are limited and are likely driven by mechanisms th...
Article
Fatigue cracking is a common form of pavement failure and is strongly tied to the properties of the asphalt binder used in the mix. The Superpave grading procedure is currently used in the United States and in other parts of the world to classify and select asphalt binders for the design of asphalt mixtures. The parameter, , in the Superpave gradi...
Article
The search for a test and parameter that can effectively describe the fatigue cracking resistance of an asphalt binder has led to many approaches. Of these, researchers have used stiffness, strength, and ductility-based criteria to screen binders on the basis of inherent resistance to cracking. In this study, poker chip testing on thin films of asp...
Conference Paper
Full-text available
Carbon fiber reinforced polymer composites (CFRPs) are renowned for their superior in-plane mechanical properties. However, they lack sufficient out-of-plane performance. Integrating carbon nanotubes (CNTs) into structures of CFRPs can enhance their poor out-of-plane properties. The present work investigates the effect of adding CNTs, grown on carb...

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Project (1)
Project
Determine the fundamental mechanism by which damage, cracking, ductility, and large deformations occur in asphalt binders and mixtures due to mechanical loading.