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    A comparative examination of the conventional and rheological characteristics of crumb rubber modification produced in both laboratory and industrial settings
    (Springer, 2025) Kok, Baha Vural; Yetkin, Zulfu; Ozdemir, Ahmet Munir
    In asphalt production facilities, CR modification is executed through various techniques, which may involve either single or multiple passes utilizing mixing equipment and mills. Laboratory-based CR modification employs different mixing apparatus, varying speeds, durations, and temperatures, and is conducted on a smaller scale than plant operations. The degree to which laboratory mixing replicates the processes used in plant is crucial for the design of effective pavement solutions. This research aimed to evaluate the utilization of CR additive in both laboratory and plant. Enhanced binder performance was achieved in the laboratory by increasing both the mixing speed and duration. Specifically, mixing conditions of 4000 rpm for 60-90 min resulted in a binder exhibiting improved elastic properties due to effective CR-bitumen interaction. Notable differences in rheological characteristics were observed between the CR-modified binders produced in the laboratory and those generated in the plant. It was concluded that the performance of the binder produced in the plant could be replicated in the laboratory at lower speeds of 1000-2000 rpm with a mixing duration of approximately 30 min. Furthermore, to enhance the performance of the plant-produced binder, it is essential to maintain a high number of passes through the mill.
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    Determination of operating conditions of box culverts with different technical specifications
    (Pamukkale Univ, 2026) Kok, Baha Vural; Yetkin, Zulfu; Yalcin, Erkut; Ozdemir, Ahmet Munir
    As a result of improper planning of culvert structures constructed for the passage of water flowing in stream beds to the other side of the road body, the road may become unserviceable and access to the areas that need to be reached, especially in disaster situations, is interrupted, causing significant material and moral damages. In this study, the performance of the most commonly used box culverts on highways is analyzed within the framework of technical parameters. The effects of culvert slope, roughness, length and different culvert inlet types on inlet water height and outlet water velocity were investigated. It was found that outlet-controlled conditions prevail when the culvert slope is low and roughness is increased, slope, roughness and length have a significant effect on the outlet water velocity, and the best performance is obtained when the culvert inlet is inclined at33.7 degrees, the culvert inlet is tapered by 50% and the wing wall is 27 degrees.
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    Dynamic-Mechanic Analysis and Rheological Modelling of Waste Face Mask Modified Bitumen
    (Turkish Chamber Civil Engineers, 2024) Ozdemir, Ahmet Munir; Yalcin, Erkut; Yilmaz, Mehmet; Kok, Baha Vural
    Due to the Covid-19 global pandemic, the use of face masks has increased considerably in recent years. Used face masks are released into our environment and become a severe environmental threat. Therefore, researchers have focused on the recycling of waste face masks. Recently, studies have been carried out on the use of waste face masks as additives in bituminous materials, but a detailed rheological characterization has not been made. In this study, modified bitumens were obtained by adding 1%, 1.5%, 2%, 2.5%, and 3% waste face mask (WFM). Subsequently, frequency sweep test was performed on modified bitumen samples through a Dynamic Shear Rheometer (DSR). Thus, the viscoelastic behavior of WFM modified bitumen was investigated at different temperatures and loading rates. Performance analysis was conducted with rheological master curves, which were characterized according to analytical and mechanistic models. In this study, rheological evaluations were performed according to the Christensen-Anderson (CA) Model, Christensen-Anderson-Marasteanu (CAM) Model, Sigmoidal Model (SM), and finally, the mechanistic Huet-Sayegh Model (HSM). According to the results, it was determined that WFM significantly increased the rutting resistance of bitumen and performed better at low and high loading rates than the pure bitumen at each WFM ratio.
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    Effect of microencapsulated phase change material on the rheological and thermal properties of asphalt binder
    (Elsevier, 2025) Ozdemir, Ahmet Munir; Kok, Baha Vural; Yildirim, Furkan; Aydogmus, Ercan
    Asphalt binders are known for their pronounced sensitivity to temperature fluctuations, often leading to rutting under high temperatures and thermal cracking in colder conditions. While phase change materials (PCMs) have potential to regulate these thermal effects, their direct incorporation into binder poses challenges such as leakage and a lack of structural integrity. In this study, the effects of microencapsulated PCM additives on the rheological and thermal characteristics of asphalt binder was investigated. The results of Rotational Viscosity (RV), Temperature Sweep, Frequency Sweep and Bending Beam Rheometer (BBR) tests showed that PCM additions improve high-temperature performance by boosting viscosity and stiffness, and also help reduce brittleness at low temperatures. Supporting chemical analyses such as FTIR, TGA-DSC, and SEM confirmed both the successful integration and thermal stability of the microencapsulated PCM within the binder matrix. Further evaluation using master curves and the Cross Model highlighted a notable increase in zero-shear viscosity, particularly with an 8 % PCM content, along with improved flow consistency across varying temperatures. Additionally, thermal behavior assessments using a custom-designed experimental setup showed that PCM incorporation had a significant effect on the binder's temperature-time response. The duration to achieve peak temperature was extended, while both the heating rate and cooling slope were reduced, leading to a decrease in the overall thermal load in samples containing PCM. The area under the curve and thermal lag times indicated that PCM effectively absorbs heat during phase transitions, thereby dampening temperature fluctuations and ensuring a more stable thermal response of the binder.
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    Efficient use of waste photopolymer plates in bitumen modification and an alternative styrene-butadiene-styrene modification method
    (Springer, 2024) Kok, Baha Vural; Yetkin, Zulfu; Yalcin, Erkut; Ozdemir, Ahmet Munir
    Photopolymers, which are composed of monomer, oligomer polymer, and their combinations and exhibit photochemical reactions when exposed to light, are now commonly employed in 3D printers, particularly in the flexographic printing industry, and are becoming waste. The utilization of waste solid sheet Photopolymer Plates (PhP) for bitumen modification is an efficient way of disposing of post-consumer items and an alternate method of obtaining new, high-quality modifiers. The consequences of using waste PhP in bitumen modification, both independently and in conjunction with Styrene-Butadiene-Styrene (SBS) were explored. By combining PhP and SBS, it is hoped that savings can be made without sacrificing performance due to the high rate of single SBS modification. The modified binders prepared using PhP and SBS both separately and together were subjected to conventional and rheological tests. The performance of 5% SBS modification could not be achieved at the highest rate that PhP can be used alone without creating a workability problem. The use of 5-7% PhP in combination with 2% SBS outperformed the single 5% SBS modification. This combined binder did not cause workability problems and showed good low and high-temperature behavior and was found to be an economical alternative to SBS modification.
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    Investigation on the rheological behaviour and ageing characteristics of crumb rubber and polyurethane blends under dynamic shear conditions
    (Taylor & Francis Ltd, 2025) Kok, Baha Vural; Yalcin, Erkut; Ozdemir, Ahmet Munir; Ozdemir, Nisanur Gurcay
    This study aims to investigate the effects of the use of crumb rubber (CR) with polyurethane (PU) in bitumen modification on rheological and ageing properties. A novel modified palm-oil-based polyol was reacted with 4,40-diphenylmethane diisocyanate (MDI) to synthesise a polyurethane-derived polymer. Multiple stress creep recovery (MSCR), single point and frequency sweep tests were carried out. The analysis of the binders' viscoelastic behaviour was conducted using the Christensen-Anderson (CA) model. The complex viscosity was modelled using the Cross model. The low-temperature behaviour of the binders was determined by the bending beam rheometer (BBR) test, and the mixing-compaction temperatures were determined by the steady shear flow (SSF) method. Compared to single CR modification, the use of 4% PU in combination with 8% CR (8C + 4P) was found to broaden the relaxation spectrum, increase stiffness, improve shear-thinning resistance, and lead to a notable increase in resistance against ageing. Due to the polymeric networks developed in the 8C + 4P binder, it was determined that it exhibits superior elastic properties at high temperatures and also offers improved durability against low-temperature cracks. It was ascertained that the 8C + 4P binder demonstrated superior performance in both low- and high-temperature conditions compared to the 4% SBS modification, while there was no significant difference in terms of production temperatures.
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    Rheological investigation and optimization of crumb rubber-modified bitumen production conditions in the plant and laboratory
    (De Gruyter Poland Sp Z O O, 2025) Kok, Baha Vural; Ozdemir, Ahmet Munir
    Among the various bitumen additives, crumb rubber (CR) derived from waste tires stands out due to its economic and environmental advantages. The effectiveness of CR modification is influenced by several factors, including temperature, mixing speed, duration, and particle size. Excessive mixing speed and prolonged mixing in laboratory conditions can lead to the depolymerization of CR, which may adversely affect the elastic properties of the bitumen. In contrast, plant-scale production typically follows a more rapid and simplified process. In this study, bitumen containing 8% CR, modified under plant and laboratory conditions with varying mixing speeds and durations, was rheologically analyzed. Temperature and frequency sweep tests were conducted using a dynamic shear rheometer, and master curves were generated to evaluate the bitumen's viscoelastic behavior through various rheological models. The findings indicate that higher mixing speeds and extended mixing durations in laboratory conditions increase bitumen stiffness; however, excessive mixing leads to depolymerization, thereby reducing its elastic properties. The laboratory-produced CR modification demonstrates significantly superior performance compared to that generated in the plant. Furthermore, response surface methodology optimization analysis results indicate that the ideal conditions for mixing are a speed range of 3,000-4,000 rpm and a duration of 45-60 min.
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    Self-Healing and Mechanical Properties of Aged Hot Mix Asphalt Containing Waste Oil Capsules
    (Springer Heidelberg, 2025) Erdogan Yamac, Ozge; Yilmaz, Mehmet; Yalcin, Erkut; Ozdemir, Ahmet Munir; Garcia-Hernandez, Alvaro; Kok, Baha Vural
    Hot mix asphalts are known to have a self-healing property and microcracks in the pavement can close to some extent after they occur if they are not subjected to load and if sufficient time is allowed. However, this healing period is prolonged, and the healing rate is not very high. In this study, calcium alginate capsules containing waste vegetable oil and waste mineral oil as rejuvenating agents were produced, and used in asphalt mixtures at four different rates (0.25%, 0.50%, 0.75%, and 1.0%) by weight. The study aims to develop an environmentally friendly and economically viable repair method by using waste oils. Marshall stability and flow and tensile strength ratio tests were conducted on cylindrical specimens. Additionally, three-point bending test was performed on aged asphalt mixtures to determine the self-healing rates of cracks formed in the specimens. Fourier transform infrared spectroscopy was conducted on bitumen specimens taken before crack formation and after the healing period to determine the percentage of ruptured capsules in the mixture. The results showed that the addition of capsules containing waste mineral oil and vegetable oil reduced stability values and increased flow values. However, according to the results of the retained Marshall stability test, it was determined that the addition of capsules, especially at a 0.5% ratio, increased resistance to moisture damage. Regarding crack-healing results, it was found that temperature and curing time increased healing rates, and capsules containing waste mineral oil provided higher healing rates compared to those containing waste vegetable oil.