Ali Ikbal Tutar

The development of advanced hydraulic lime-based mortars incorporating mineral additives and graphene nanoplatelets offers potential opportunities for improving material performance in the conservation of historic masonry structures. This study investigates the mechanical and microstructural performance of hydraulic lime-based mortars incorporating mechanically milled mineral additives and commercially available graphene nanoplatelets (GNPs). Hydraulic lime, brick powder, repair mortar, injection mortar, slaked construction lime, and gypsum plaster were processed using planetary ball milling under identical conditions, whereas graphene nanoplatelets were incorporated without additional mechanical treatment. The additives were introduced at 1%, 2%, and 3% by mass of the original hydraulic lime binder. Compressive and flexural strengths were evaluated after 28 days of curing, complemented by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results demonstrated that mechanical performance was strongly influenced by additive type and dosage. The mortar containing 3% injection mortar additive (IM-3%) achieved the highest compressive strength of 9.75 MPa, representing a 4.4% increase over the reference mixture, together with a 25.8% improvement in flexural strength. The incorporation of 1% slaked construction lime (SCL-1%) produced the highest mean flexural strength of 3.02 MPa, corresponding to a 28.0% increase, whereas 1% graphene nanoplatelets (GN-1%) enhanced flexural strength by 19.1% despite reducing compressive strength. Most other modified mixtures exhibited lower mechanical strengths than the reference mortar. Microstructural characterization revealed variations in matrix morphology and local elemental distribution, while the principal carbonate- and silicate-related characteristics were largely retained. These findings demonstrate the composition-dependent mechanical response of hydraulic lime-based mortars incorporating mechanically milled mineral additives and graphene nanoplatelets, providing a basis for further investigations into their long-term performance and compatibility with historic masonry materials.

Polymer concrete (PC) is widely recognized for its high strength, rapid curing, and superior durability; however, its inherently brittle behaviour limits its performance under flexural loading. Fiber reinforcement is commonly used to enhance toughness and crack resistance, yet high fiber contents often result in workability loss, fiber agglomeration, and increased material heterogeneity. In this study, the mechanical and microstructural behaviour of polymer concrete incorporating chopped polypropylene fibers at low volume fractions was systematically investigated. A Box Behnken experimental design was employed to evaluate the effects of fiber length (6 mm and 12 mm) and resin content on density, flexural strength, compressive strength, and ultrasonic pulse velocity (UPV). Mechanical tests were complemented by UPV measurements to assess internal integrity and dynamic elastic properties, while fracture surfaces were examined using digital microscopy to identify governing failure mechanisms. The results indicate that low fiber contents do not significantly enhance global mechanical properties, with flexural and compressive strengths remaining within relatively narrow ranges. Statistical analysis shows that resin content governs density, whereas longer fibers and their interaction with resin moderately influence compressive strength. In contrast, flexural strength and UPV are largely insensitive to the investigated parameters. Microstructural observations reveal a matrix dominated behaviour, where fibers contribute locally through crack bridging and pullout without forming an effective reinforcing network. Overall, low fiber reinforcement improves workability and material homogeneity but provides only limited mechanical benefits. The findings emphasize the importance of reaching a critical fiber content to effectively modify load transfer mechanisms in polymer concrete.

Natural and human-induced hazards have caused major disasters in terms of loss of life and property for thousands of years. Coping with these losses will only be possible by creating disaster-resilient infrastructure. Structures such as health facilities, schools, and nuclear facilities, which must be used uninterruptedly, must be resilient during and after hazards. Turkey and its Kocaeli city are in a highly seismically active region and are frequently exposed to severe earthquakes. However, there still exist many infrastructure systems that have not yet been made resilient to earthquakes, and many lives and properties have continued to be lost from earthquake hazards. This was the case of the Kocaeli’s Mw 7.1 earthquake of 17 August 1999 and even the recent Mw 7.8 Kahramanmaraş earthquake of 6 February 2023, in which tens of thousands of people lost their lives and a large amount of financial loss was experienced. To better prepare for a future earthquake disaster for resilient critical infrastructures such as healthcare systems, it is important to study the urban earthquake risk of these facilities. This study proposed a probabilistic approach using the North Anatolian Fault to study the earthquake hazard of Kocaeli’s city and the related risk to healthcare buildings in the region. The seismic hazard for 2% and 10% probability of exceedance in 50 years confirmed the region's high seismicity and related risk to hospital buildings, alerting the local government in developing new plans and implementing earthquake risk mitigation strategies for this first needed health infrastructures.

Polymer-based materials have become increasingly used in concrete production and various engineering applications due to their versatile properties. In particular, polymer concrete (PC) has become a preferred reinforcement material in the construction industry. Various studies have been carried out to evaluate the performance of PC and to improve its mechanical properties by adding different admixtures. This study investigates the effects of fine materials such as iron powder (IP) and blast furnace slag (BFS) on the mechanical performance of PC. Within the scope of the study, samples with 5% and 10% IP, 5% and 10% BFS, 2.5% IP + 2.5% BFS and 5% IP + 5% BFS were prepared. These specimens were cured in the same laboratory environment and subjected to mechanical tests at the end of the 7th day. The results of the mechanical tests were compared to reveal the effect of fine materials on the performance of the PC. The potential of an artificial neural network (ANN) model is investigated to replicate real-world outcomes. The findings provide valuable insights into the potential of iron powder and blast furnace slag as admixtures to improve the mechanical properties of PC.