Halil Ceylan

Impact of Bio-fuel Co-Product Modified Subgrade on Flexible Pavement Performance

This study explored the feasibility of lignin based biofuel co-product (BCP) for subgrade soil stabilization, and more specifically, its impact on Hot-Mix Asphalt (HMA) pavement performance using the Mechanistic-Empirical Pavement Design Guide (MEPDG). The HMA pavement systems with BCP stabilized subgrade under different traffic and climate conditions were modeled using mechanistic based damage analysis system. The performances of BCP stabilized subgrade and natural soil subgrade sections were compared in terms of fatigue (alligator) cracking and rutting predictions on HMA pavements. The results of this study indicate that BCP stabilization of subgrade soil could achieve more sustainable HMA pavements under different traffic volumes and climate conditions.

Influence of Deicing Salts on the Water-Repellency of Portland Cement Concrete Coated with Polytetrafluoroethylene and Polyetheretherketone

Sustainable super water/ice-repellent pavements are gaining attention as a smart solution for mitigating problems associated with winter pavement maintenance of roadways and airfields. Such smart pavements can facilitate surface drainage and prevent or curb ice formation or snow accumulation. While a conventional method for melting ice and snow is the use of deicing chemicals, such materials can transfer to the surface of nanotechnology-based pavements and influence their water/icerepellency by changing the chemistry of water or ice. This study focused on characterizing the degree of hydrophobicity of Portland cement concrete (PCC) nanocoated with polytetrafluoroethylene/polyetheretherketone (PTFE/PEEK). A layer-bylayer (LBL) spray deposition technique was used for spraying the binding agent and water-repellent materials. The liquidrepellency was characterized by measuring the static liquid contact angles (LCAs) and calculating the works of adhesion (WA). The liquid types used included distilled water and two types of deicing chemicals prepared by dissolving salts in distilled water. Data analysis results revealed that salt contamination improves the waterrepellency of nano-coated surfaces.

Characterization of Asphalt Materials using X-Ray High-Resolution Computed Tomography Imaging Techniques

X-ray Computerized Technology (CT) has emerged as a powerful nondestructive tool to study and quantify the three-dimensional internal structure of HMA. Studies, in conjunction with modeling and computational techniques, have focused on characterization of HMA internal air-void distribution, internal structure evolution during laboratory compaction, damage evolution in specimens during laboratory tests, segregation analysis, forensic investigation of pavements using cores, and the quantification of HMA microstructural properties. The Center for Nondestructive Evaluation (CNDE) at Iowa State University (ISU) has an in-house built high-resolution CT system with customized software for data acquisition, volumetric file reconstruction, and visualization. Preliminary studies were conducted at the CNDE to investigate the capabilities and resolution levels of the imaging systems in studying asphalt materials. Researchers at both ISU and Iowa Department of Transportation are currently using the advanced imaging facilities available at the CNDE and the latest developments in image analysis techniques to develop a deeper understanding of the HMA internal structure, develop and optimize the various parameters that describe the internal structure and relate thm to the performance of pavements in a scientific way. This will provide the foundations to building more durable and long-lasting pavements.

Construction Techniques for Electrically Conductive Heated Pavement Systems

Ice and snow accumulation on airport paved surfaces has the potential to cause fatal accidents and monetary loss due to flight delays and cancellations. Traditional de-icing methods involving the application of chemicals or salt and employing large machines can create negative environmental and structural impact on airport infrastructure systems. These methods are also considered to be labor intensive and a safety hazard, especially in congested areas such as aprons. Heated pavement systems using electrically conductive concrete (ECON) have been proposed as a promising alternative technology for preventing ice accumulation and mitigating the adverse effects of using traditional snow removal methods. The objective of this study is to present information and experience about the design, construction procedures, and performance of heated pavement systems using jointed plain concrete pavements for the construction of large-scale heated airport pavements. It is based on detailed field demonstration of the electrically conductive concrete (ECON) heated pavement system (HPS) at the north general aviation (GA) apron of the Des Moines International Airport (DSM) in Iowa, in collaboration with contractors, and airport staff representatives. The expected outcome of this study will help the construction industry to better understand optimal ECON construction methods.

Mechanistic-Based Characterization of Non-Linear Pavement Mechanical Properties with Evolving Intelligent Information Processing Systems

The backcalculation methodology is an inverse process to determine in-situ materials stiffness of pavement layer from Non-Destructive Test (NDT) surface deflections using iterative optimization or more recently, computational intelligence techniques. Intelligent Information Systems (IIS) have been developed with the idea of dealing with information in a way a human expert would by incorporating abilities to learn fast from a large amount of data, dynamically create new modules, connections and neurons, accommodate imprecise or uncertain knowledge, etc. Evolving Connectionist Systems (ECOS) are IIS created with such requirements in mind. This paper explores the feasibility of applying an ECOS methodology, namely Dynamic Evolving Neuro-Fuzzy Inference System (DENFIS), to backcalculation of non-linear pavement mechanical properties and real-time non-destructive condition evaluation of flexible pavements.

Comparative Performance of Concrete Pavements with Recycled Concrete Aggregate (RCA) and Virgin Aggregate Subbases

Using recycled concrete aggregate (RCA) as base/subbase for road construction is alternative way to manage construction waste and reduces the need for virgin aggregates. This paper discusses the long-term performance of concrete pavements on RCA granular layer in comparison to concrete pavements on virgin aggregate granular layer. 18 representative RCA pavement sections across Iowa were primary selected considering state wide location and pavement age. Detailed visual distress surveys were conducted to identify the current pavement surface condition information and the primary distress on RCA granular layer pavement. The pavement information data for the surveyed RCA subbase sections and the corresponding virgin aggregate subbase sections in similar condition were extracted from the Iowa DOTs Pavement Management Information System (PMIS). The performance of the RCA and the virgin aggregate sections was investigated and compared in terms of the pavement condition index (PCI) and the International Roughness Index (IRI). The results indicate that RCA granular layer provides performance compared to the virgin aggregate granular layer in Iowa pavements and are performing adequately.