Dr. Salih Kocak

The use of sustainable materials in road construction has been gaining popularity to provide a better future for the next generations. This study investigates the possible use of two common sustainable road construction materials, recycled asphalt pavement (RAP) and recycled tire rubber (RTR), for pavement maintenance applications. Mixtures were produced either with combined RAP and RTRs or 100% RAP with petroleum-based (RAP-A) and bio-based (RAP-B) rejuvenating oils. Because pavement maintenance applications such as pothole patching have traditionally been performed with cold mixtures (CM), a typical cold patching mixture was also investigated along with six hot asphalt mixtures. RTR mixtures were produced using different rubber modification technologies. They were manufactured using crumb rubber wet (WET), crumb rubber dry (DRY), devulcanized rubber (DEV), and crumb rubber terminal blend (TB) technologies. Each RTR-modified mixture included 40% RAP and approximately 12% rubber content by weight of the binder. The performance of the mixtures was compared using dynamic modus (DM) testing for linear viscoelastic characterization, flow number (FN) testing for rutting potential, and tensile strength ratio (TSR) testing for moisture susceptibility. The cost-effectiveness of different mixtures was performed using the life cycle cost analyses (LCCA) approach for bituminous materials. The results showed that any recycled hot-mix asphalt outperformed the CM. The 100% hot RAP mixture with petroleum-based rejuvenator performed as well as any combined RTR-RAP mixtures, and it became the most cost-effective alternative for pavement maintenance applications.

This paper investigates the viability of using a commercially available liquid polymer (LP) in lieu of ordinary cement to stabilize soil during rammed earth (RE) construction. The scope of this study includes modifying and testing the locally available natural soil with two different LPs at various percentages. Once the optimum moisture content (OMC) of the soil with LPs was determined using the Proctor test, test samples were prepared by chemical and mechanical stabilizations. Following the curing process in an unconfined open-air laboratory environment for 7 days, soil samples were tested to determine the unconfined compressive strength (UCS) and California bearing ratio (CBR) values. The results demonstrate that the lubrication effect of polymers is different than that of water. The first polymer type yields a lower OMC compared to water, while the second polymer achieves a higher OMC. The CBR and UCS values of polymer-stabilized soils are improved for both polymer types at all dosages. The CBR values of polymer-modified soils showed as high as a 10-times improvement compared to Portland cement (PC) stabilization. A similar trend is observed for the UCS results as well. The UCS value of polymer-stabilized soils reached over 1900 psi (13 MPa), which was over 3-times higher than the UCS of PC-stabilized soil.

Recently, scrap tire rubber-modified asphalt binders and pavements have been the preferred choice of state DOTs and parties involved due to the desirable engineering, as well as economic and environmental impacts. Rheological and mechanical properties of rubber modifications have been the main focus of researchers for the last couple of decades. This paper investigates the rutting potential, fatigue cracking resistance, and continuous performance grade (CPG) changes of waste tire rubber-modified, original, and aged asphalt binders. The CPG of asphalt binders is determined at high, intermediate, and low temperatures. A Delta T Critical comparison of the binder was carried out to establish a relationship between measured parameters. Linear amplitude sweep (LAS) tests at equi-stiffness temperatures were conducted to discover the fatigue life of all binders while the multiple stress creep recovery test is performed to assess the high-temperature rutting performance of asphalt binders as per the Superpave performance grading system at accepted regional (58 degrees C) as well as high PG temperatures. In addition, parallel-plate geometry and concentric cylinder geometry were used with the Multiple Stress Creep Recovery (MSCR) test to discover the impact of discrete particles available in crumb/ground tire rubber-modified asphalt binders as per standards. The results show that rubber modifications improved the base binder's rutting resistance and continuous PGs without adversely affecting the fatigue cracking resistance. Based on the mathematical expressions developed, 2.71%, 7.82%, 12.94%, and 18.05% (by weight of binder), GTR modifications improved the high PG of the modified binders one, two, three, and four grade bumps, respectively. Similar linear correlations with R-2 0.872 and 0.6 were established for continuous low and intermediate PGs, respectively. MSCR test results revealed that both 9% and 20% GTR modifications were achieved to enhance the H-grade traffic level of the original binder to E-grade.

Liquid polymers (LP) have become an important structural material used in the construction industry in the last decade. This paper investigates the viability of using commercially available LPs as a coating material to improve the flexural strength of fiber-modified concrete beams. The scope included preparing rectangular prism concrete beams with a concrete mixture including fly ash and fiber and coating them with four different liquid polymers at a uniform thickness following the curing process while one set of samples was maintained under the same conditions as a control group without coating. In addition, cylindrical samples were prepared to determine the compressive strength of the concrete mixture. Following the curing process in an unconfined open-air laboratory environment for another 28 days, concrete samples were tested to determine the flexural strength and deflection characteristics under center point loading equipment. The results revealed that all four coating types enhanced both the flexural strength and the average maximum deflection of the beams compared to the control group. While the enhancement in the flexural strength changed approximately between 5% and 36% depending on the coating type, the improvements in average maximum deflections varied between 3.7% and 28.4%. 

Fixing the potholes using bituminous patching mixtures is a critical and costly pavement maintenance activity.

The patching mixture’s quality significantly affects patch durability and performance; always using the best

material available is advisable. This study investigated the feasibility of using 100% hot recycled asphalt

pavements (RAP) as a possible patching material by comparing the performance results with cold patching

mixtures (CPM) as well as Superpave hot mix asphalt (SHMA) mixtures. Four different RAP mixtures, two fine-graded and two coarse-graded, from two distinct sources, are obtained. RAP mixtures were handled in a laboratory environment to obtain the hot recycled patching materials. Three different rejuvenators were incorporated into hot-recycled pavement material (HRPM) at manufacturer-recommended dosages to determine the best rejuvenator type. Performances of the mixtures are evaluated in terms of linear viscoelastic characterization, permanent deformation, and low-temperature thermal cracking potentials using dynamic modulus, flow number, and indirect tensile strength tests, respectively. The results show that RAP mixtures with any RAP source, gradation, and rejuvenator type outperformed CPM in performance tests and behaved similarly to SHMA mixtures.

Research was conducted on the mechanical and anisotropic properties of 3-D printed plastics (PLA and ABS), and the prevailing orientation and deposition of additive layers. Samples were tested in accordance with ASTM D638 - Standard Test Method for Tensile Properties of Plastics. Five print orientations were tested, including 0°, 30°, 45°, 60°, and 90°. Six samples were tested in each orientation, with a total of 30 samples being tested in each iteration of the experiment. An initial, “proof of concept” iteration was conducted with PLA plastic, followed by a second iteration which tested both PLA and ABS.
Testing was conducted and based on the hypothesis that the material printed in the 0° orientation (parallel to the direction of applied tension) would be stronger, and that the strength of test specimens would be largely dependent on orientation of the material. In contrast, it was believed that the strength of 90° samples (perpendicular to the direction of applied tension) would be largely dependent on the strength of the bonds formed during the layer by layer deposition of heated material, and comparatively weaker. This was largely proven during testing. Samples printed in the 0° orientation exhibited statistically higher properties of both stress and strain. Conversely, plastics printed in the 90° orientation exhibited statistically weaker properties. It was noted that samples printed in the 30°, 45°, and 60° orientations exhibited some measure of improved ductility, although this was not the focus of the study.
•Anisotropic properties of 3-D printed plastic.•Stress-strain curves of 3-D printed plastic samples.•Correlations between orientation, stress, and strain.•Broader impacts of materials quality.

Modification of asphalt binders has been one of the common techniques to overcome the climatic and traffic-related distresses that develop in bituminous materials. Over the past decade, many new methods of incorporating recycled tire rubber as a modifier have been developed and evaluated by states and county road departments. This study focuses on the use of the so-called devulcanized recycled tire rubber modifier and its effects on the performance grade, fatigue cracking resistance, and rutting resistance of asphalt binder. Devulcanized rubber was incorporated into hot liquid asphalt at various percentages using high and low shear blending, consecutively. First, the effect of modifications on continuous performance grades (PG) at low, intermediate, and high temperatures was investigated. Second, equistiffness temperatures of the binder-rubber mixes were established, and the fatigue cracking resistances of the rubber-binder blends were measured by using the linear amplitude sweep (LAS) test at different strain levels. Last, the multiple stress creep and recovery test (MSCR) was conducted on the modified asphalt samples to characterize the high-temperature performance. Although there was a significant improvement on high PG as the modifier amount increased, the improvement for intermediate and low PGs was minimal. The same trend observed for high PG of the modified asphalt binders was also obtained for fatigue cracking resistance and rutting resistance. The results showed that the use of devulcanized rubber modification could successfully extend the life of bituminous materials.

In this study, we aimed to identify spatial clusters of countries with high rates of cyber attacks directed at other countries. The cyber attack dataset was obtained from Canadian Institute for Cybersecurity , with over 110,000 Uniform Resource Locators (URLs), which were classified into one of 5 categories: benign, phishing, malware, spam, or defacement. The disease surveillance software SaTScanTM was used to perform a spatial analysis of the country of origin for each cyber attack. It allowed the identification of spatial and space-time clusters of locations with unusually high counts or rates of cyber attacks. Number of internet users per country obtained from the 2016 CIAWorld Factbook was used as the population baseline for computing rates and Poisson analysis in SaTScanTM. The clusters were tested for significance with a Monte Carlo study within SaTScanTM, where any cluster with p < 0.05 was designated as a significant cyber attack cluster. Results using the rate of the different types of malicious URL cyber attacks are presented in this paper. This novel approach of studying cyber attacks from a spatial perspective provides an invaluable relative risk assessment for each type of cyber attack that originated from a particular country.

The disease surveillance software SaTScan™ is used to identify spatial and space-time clusters of counties with unusually high counts or rates of SD bridges. Initially, a descriptive data analysis of over 600,000 bridges, on which data were available for 2017, identified the kind of material and design of all bridges. This was followed by analyzing data on SD bridges for the 3108 counties. The clusters were tested for significance with Monte Carlo study to designate significant SD clusters. While the purely spatial analysis was based on data for 2017, the spacetime analysis used data for the years 2006–2017. A Negative Binomial regression model was used in addition to a cluster analysis. Regression analysis was performed to adjust SD counts for several covariates or risk factors. This study identified counties with high rates of SD bridges as rural counties with old bridges where there is cold weather and low daily traffic.

Improving fatigue cracking resistance of asphalt mixtures is an important issue that concerns roadway agencies, public and industry. There are various, well-established methods for improving the material characteristics, such as polymer modification methods. Recycling/reusing scrap tire rubber in asphalt pavements has also been an interest of engineers. As such, many different methods of scrap tire rubber (herein called crumb rubber) modification alternatives are being developed. This study focused on a comparative evaluation of the fatigue cracking resistance of various base and recycled tire rubber modified asphalt mixtures, including the relatively new and innovative devulcanized rubber (DVR), crumb rubber terminally blend (CRTB), crumb rubber wet process (CRWET), original/base PG58-28 and softer PG58-34 binders, by using Push-Pull Viscoelastic Continuum Damage (PP-VECD) analysis and AASHTOWare Pavement Mechanistic Empirical Design (Pavement ME) software. The results of the study revealed that rubberized asphalt mixtures provided better fatigue lives than the base and softer binders did. Especially, DVR mixtures outperformed at high strain levels, implying they can be used for heavy traffic roads to
enhance the fatigue life of asphalt pavements. Both PP-VECD and Pavement ME produced results that showed similar trends.