Keleş, Ömer Faruk; Çolak, Muhammed Ali; Demiriz, Ahmet Oğuz; Baş, Fatih İrfan

In this study, the combined effect of waste lubricating oil (WLO) and waste pine branch ash (WPBA) was investigated to improve the low-temperature fracture behavior of asphalt mixtures. To investigate the low-temperature fracture behavior of the mixtures containing 2%–6% WLO and 3%–12% WPBA, the semi-circular bending (SCB) test was conducted at −15 °C, and the experimental results were analyzed using a statistical approach. Fracture toughness (K(IC)), total fracture energy (GF) and its pre-peak and post-peak components, crack resistance index (CRI), flexibility index (FI), and toughness index (TI) were determined. The findings indicate that the optimal combination depends on the fracture parameter under consideration. The best fracture toughness results, K(IC) = 24.96 MPa·mm0.5, indicating increased resistance to crack initiation, was obtained at 4% WLO and 12% WPBA content. On the other hand, the best fracture energy results, GF = 1.202 N/mm, reflecting an increase in energy dissipation during crack propagation, was obtained at 4% WLO and 9% WPBA content. The highest FI, CRI, and TI values were obtained with 6% WLO and 9% WPBA, corresponding to increases of approximately 66%, 69%, and 16%, respectively, compared with the reference mixture. This resulted in greater crack-initiation resistance, improved post-peak deformation capacity, and higher energy-dissipation capacity, although the greater WLO content led to a decrease in structural integrity. When the results are evaluated overall, it is understood that the use of WLO in the mixtures increases deformation capacity, while the use of WPBA controls crack propagation through its hardening and filling effects. In mixtures containing 4% WLO and 9%–12% WPBA, a balanced behavior was achieved in terms of crack initiation, crack propagation, and stiffness under low-temperature conditions.

Polat, Melih Sakir; Turan, Ahmet İhsan; Kucuk, Mesut; Kumbasaroglu, Atila; Yalciner, Hakan; Ayaz, Yasar

The increasing demand for sustainable structural materials in the construction industry has intensified the need to develop high-performance and environmentally efficient reinforced concrete systems. In this context, the incorporation of functional material-enhanced concrete systems, including raw lightweight aggregates such as perlite, offers a promising pathway for reducing environmental impact while maintaining adequate structural performance. This study experimentally investigates the flexural behavior of reinforced concrete (RC) beams incorporating raw perlite aggregates within a functional material-enhanced structural framework. A total of four RC beams with identical geometry and reinforcement details were produced, including perlite aggregate beams (P25 and P40) and conventional aggregate beams (C25 and C40), corresponding to compressive strength classes of 25 MPa and 40 MPa. All specimens were tested under monotonic flexural loading conditions. The structural response was evaluated in terms of load–displacement behavior, stiffness degradation, ductility, energy dissipation capacity, moment–curvature response, and failure modes. The results indicate that perlite aggregate beams exhibit reduced stiffness and energy dissipation capacity compared to conventional counterparts at comparable mixture-average compressive-strength levels. However, the high-strength perlite beam (P40) demonstrated comparable flexural capacity and ductility to the normal-strength conventional beam (C25), highlighting its potential for sustainable structural applications. Furthermore, a building-scale environmental assessment based on a representative three-story reinforced concrete structure demonstrates that the use of raw perlite aggregates significantly reduces energy consumption, CO2-equivalent emissions, and water usage. From a functional materials perspective, the findings provide a basis for the future development of multifunctional load-bearing concrete systems, where lightweight aggregate substrates can be combined with protective or performance-enhancing coating technologies to achieve improved durability, environmental resistance, and structural efficiency. This integration could further enhance durability and long-term structural performance in load-bearing applications.

Çolak, Muhammed Ali; Zorlu, Elif; Çodur, Muhammed Yasin; Baş, Fatih İrfan; Yalçın, Özgen; Kuşkapan, Emre

The rapid growth of the world population and the rapid diversification of consumption habits due to technological advancements have increased waste production. An investigation of the effects of biomass products, such as waste vegetable oil and waste agricultural ash, on bitumen’s physical and chemical properties was conducted in this study. By recycling biomass products, this study aimed to improve the performance and stability of bituminous hot mixtures, optimize the number of additives, and create more economical designs. Using the Taguchi method, 0%, 2%, 4% by weight of waste vegetable oil and 0%, 3%, and 6% by weight of waste agricultural ash were added to 70/100 penetration pure bitumen with an orthogonal array of L9. For 10, 20, and 30 min, modified bitumen samples were prepared at 170 °C, 180 °C, and 190 °C with a constant mixing speed of 3000 RPM. The samples were tested for penetration, softening point, flash point, rolling thin film oven (RTFOT), FTIR, and Marshall Design stability and flow. Based on the obtained performance statistics, 95% confidence levels were assigned to the predictions. The stability and softening point values decreased as the oil content increased, while flash and penetration values increased. With increasing ash content, stability, flash, and softening point values increased, and penetration values decreased. Compared to oil and ash additives, mixing temperature and time had relatively little effect on the modification process. Overall, the optimum parameter levels were 4% for oil, 0% for ash, 170 °C for temperature, and 10 min for time.

Baş, Fatih İrfan; Bayrak, Osman Ünsal; Bayata, Halim Ferit

This study aimed to determine the material properties and the thickness of the layers of an unbonded jointed plain concrete pavement design over a deteriorated flexible pavement that lost its service capability. Maximum principal stresses occurring under the concrete pavement should not exceed the modulus of rupture of the concrete. Three-dimensional finite element analyses using ANSYS (Release 18.1 SAS IP, Inc.) software were carried out with the Taguchi method. The most reliable solution for the pavement design was investigated with whole configuration axle loading that reflects the realistic traffic situation. The stress values under the concrete slab due to the positive temperature gradient neglected in the American Association of State Highway and Transportation Officials (AASHTO) method were also investigated. The concrete slabs are exposed to these stresses for longer than the axle loads. Temperature distributions throughout the thickness of the concrete slab were calculated with the bilinear formulas suggested in the study. Axle loadings were applied on both the pavement edge and corner to reflect the most critical loading condition in the pavement design. The critical axle type was found to be 1.2. It was observed that a 0.15 m concrete thickness was appropriate for the concrete class, joint spacing and hot mix asphalt (HMA) elasticity modulus levels used for the 1.22, 1.122, and 1.2 + 111 axle types, but it was not appropriate for the 1.2 axle types. The slab thicknesses calculated with the AASHTO method, and the finite element method were found to be close to each other. It was determined that the concrete thickness significantly affected the maximum principal stress, with a performance statistic (S/N) value of 1692 for the 1.2 axle type. This was followed by the modulus of elasticity of the concrete with an S/N value of 0.356, the modulus of elasticity of the existing flexible pavement with an S/N value of 0.244, and the concrete joint spacing with an S/N value of 0.105. A practical design guide was recommended to extend the service life of a highly deteriorated flexible pavement with the construction of unbonded jointed plain concrete.