Yazar "Yildirim, Musa" seçeneğine göre listele

Listeleniyor 1 - 9 / 9
  • Küçük Resim Yok
    Öğe
    Bacteria-based self-healing of cement mortars loaded at different levels and exposed to high temperature
    (Emerald Group Publishing Ltd, 2022) Yildirim, Musa; Ozhan, Hacer Bilir; Oz, Hilal Girgin
    Structures are exposed to various external effects and loads throughout their service life, which can result in failure at a load lower than the design compressive strength. There are cement-based healing systems for repairing such damage, but it is often insufficient. A more effective autonomous healing system is thus needed, and microbial-induced calcite precipitation (MICP) has been studied for this purpose. In this study, bacterial mortar (BM) samples were produced and loaded at different levels of their ultimate compressive stress. The effects of loading were determined and the effectiveness of bacterial treatments was investigated. Experiments were conducted to determine crack healing, compressive strength, water absorption, ultrasonic pulse velocity and high-temperature effects. In the BM samples, the MICP mechanism repaired cracks about 3.5 times larger than the control samples. While the treatment of cracks and damage observed at 90% and 100% loading levels were highly limited thanks to the autogenous system, some properties of the BMs improved as the loading level increased. The MICP mechanism was especially effective in damaged samples under high load levels. In addition, the BMs demonstrated superior physical, mechanical and durability properties at each loading level.
  • Küçük Resim Yok
    Öğe
    Durability properties of basalt fiber-reinforced mortars with different mineral admixtures exposed to high temperatures
    (Elsevier Sci Ltd, 2023) Yildirim, Musa; Ozhan, Hacer Bilir
    This study investigated the durability properties of mortars containing basalt fiber and various mineral admix-tures against high temperatures. Different types of mortar samples were produced with basalt fiber, metakaolin, silica fume and fly ash. The samples were exposed to temperatures of 400 degrees C, 600 degrees C and 800 degrees C. Residual compressive strength, flexural strength, ultrasonic pulse velocity, mass loss, water absorption, capillary water absorption and microscope analysis tests were carried out. Test results revealed that basalt fiber improved the residual durability properties of the mortars exposed to high temperatures. Basalt fibers exhibited bridging behavior and prevented high temperature-induced cracks. Basalt fibers showed excellent consistency with all three mineral admixtures, and the mineral admixtures increased the contribution of basalt fiber to durability properties. Because of this harmony, basalt fiber-reinforced and mineral admixture-added samples had 86.42% greater residual compressive strength and 144.42% greater flexural strength than the control samples. The void -free internal structure provided by mineral admixtures increased the effect of BF and significantly reduced water absorption, capillary water absorption and mass loss values. UPV tests and microscopic analysis revealed that basalt fiber and mineral admixtures reduced high temperature-induced cracks.
  • Küçük Resim Yok
    Öğe
    Effect of bacterial curing and bacterial additive on concrete properties
    (Josip Juraj Strossmayer Univ Osijek, Fac Civil Engn & Architecture Osijek, 2023) Yildirim, Musa; Ozhan, Hacer Bilir
    In this study, calcium carbonate was formed on the surfaces and inner structure of concrete using the microbially induced carbonate precipitation method. Bacillus megaterium bacteria were supplemented into the curing water and concrete mixtures. Three types of concrete were tested: control concrete, bacteria-containing concrete, and concrete cured in bacterial liquid. Compressive strength, water absorption, capillary water absorption, scanning electron microscopy (SEM), and mapping analyses were conducted to investigate the effects of bacterial additive or bacterial curing to concrete specimens. Bacteria spore added to the concrete mixture and curing in bacterial media increased the compressive strengths of concrete by up to 9,52 % at the end of 28 days of curing. Bacterial curing and the addition of bacteria spores caused a reduction in water absorption rates owing to changes in the concrete structures. Calcite only formed on the surfaces of the samples treated with bacterial curing liquid, thereby limiting its effect on capillary water absorption. In contrast, capillary water absorption in the bacterial concrete decreased by 50 % compared to the control concrete. The crystalline structures of calcium carbonate and bacterial concrete were analysed through SEM imaging. Mapping analysis revealed that the primary elements of calcite were considerably more concentrated on the surface of bacterial concrete than in the control concrete.
  • Küçük Resim Yok
    Öğe
    Effects of hybrid metallic wastes on the strength and durability properties of cementitious mortars
    (Emerald Group Publishing Ltd, 2023) Yildirim, Musa; Ozhan, Hacer Bilir
    The amount of industrial waste is increasing along with industrial production. Therefore, reusing or recycling these harmful wastes is quite a significant issue for waste management. Concrete, the most widely used material in the world, is a suitable place to use these wastes. This study used grinding swarf, which had not been used in cementitious composites before, and metal shaving from the CNC milling process. The effects of these wastes on the strength and durability of cement mortars were investigated by using them separately and in hybrid forms. Flowability, fresh unit weight, compressive strength, flexural strength, water absorption, and high-temperature effect tests were conducted on mortar samples. Although the wastes contributed when used alone, they yielded the highest contribution when combined. When the waste materials were used in a hybrid form, they increased compressive strength, flexural strength, and high-temperature resistance by 29%, 12.98%, and 49.50%, respectively. Metal shavings showed fiber effects, and grinding swarfs improved the strength and durability properties owing to their physical and chemical composition.
  • Küçük Resim Yok
    Öğe
    Enhancing the high-temperature resistance of self-healing bio-cementitious composites using tea waste as a bacterial carrier
    (Elsevier, 2025) Yildirim, Musa; Ozhan, Hacer Bilir; Oz, Hilal Girgin; Ogut, Hamdi
    Bacterial composites exhibit advanced self-healing capabilities; however, their effectiveness is often constrained by production processes and environmental conditions. To enhance bacterial viability, protective carriers are required, with natural fibers recently utilized for this purpose. Fiber reinforcement has been shown to improve self-healing efficiency by limiting crack propagation. This study investigates the potential of tea waste as a bacterial carrier in cementitious composites. Bacillus megaterium spores were absorbed into tea waste and incorporated into mortar specimens at varying concentrations. The durability of bacterial composites under hightemperature exposure, a critical yet underexplored aspect, was also evaluated. Mortar specimens containing bacterial tea waste were subjected to different high-temperature conditions in both undamaged and pre-cracked states, followed by compressive strength assessments. Post-exposure microstructural changes were analysed via scanning electron microscopy (SEM). The findings demonstrated that tea waste effectively functioned as a bacterial carrier, exhibiting behaviour comparable to natural fibers. Additionally, it contributed to enhanced residual strength by mitigating thermal stress and promoting calcite precipitation, facilitating damage repair. These results highlight the potential of tea waste as a sustainable and effective medium for improving the durability of bacterial composites against high-temperature effects.
  • Küçük Resim Yok
    Öğe
    Production of self-healing mortar using bacterial spores encapsulated with jute fibre
    (Josip Juraj Strossmayer Univ Osijek, Fac Civil Engn & Architecture Osijek, 2023) Yildirim, Musa; Ozhan, Hacer Bilir; Oz, Hilal Girgin
    Cement-based composites have various advantages such as low cost, easy shaping, and high compressive strength. Therefore, they are widely used in the construction industry. However, their brittle structure makes them prone to cracking, which must be repaired promptly to avoid possible loss of strength and durability and ultimate structural failures. Microbially-induced calcite precipitation (MICP) offers an effective method for healing these cracks. Unlike other treatments, MICP method is a natural and environment-friendly option for self-healing of cracks. However, bacteria can be damaged by cement and mechanical impacts; therefore, encapsulation is necessary to protect them. Encapsulation in fibres is a simpler and more cost-effective method than the other techniques. This study tested the effectiveness of encapsulating Bacillus megaterium spores in jute fibres and added them to cement-based mortars. Different nutrient supplements were used, and physical analyses and compressive strength tests were conducted on 28-day cured cube specimens. Present findings revealed that Bacillus megaterium-type bacteria encapsulated in jute fibres improved the compressive strength recovery and healed the loading-induced cracks.
  • Küçük Resim Yok
    Öğe
    Repair of Cracks in Concrete with the Microbial-Induced Calcite Precipitation (MICP) Method
    (Sciendo, 2023) Ozhan, Hacer Bilir; Yildirim, Musa; Ogut, Hamdi; Oz, Hilal Girgin
    In this study, the microbiologically-induced calcium carbonate precipitation (MICP) method was employed to examine its potential for repairing cracks in concrete. In addition, specific gravity and porosity values were measured to examine the effect of calcite formations on concrete surfaces and microstructures. Bacteria-supplemented concrete repaired cracks up to 0.4 mm wide by filling them with CaCO3. Furthermore, this study not only examined the healing of the width but also the length of cracks. However, as the width of the treated cracks decreased, their length increased. This indicated that the MICP treatment is more effective in a limited crack range. Specific gravity values increased, and porosity values decreased in concrete supplemented with calcifying bacteria. SEM analyses showed that calcite is a bacterial product that forms a very tight bond with a cement gel and that calcite fills visible cracks and voids and creates more of a void-free and undamaged concrete structure.
  • Küçük Resim Yok
    Öğe
    Residual Durability Performance of Glass Fiber Reinforced Concrete Damaged by Compressive Stress Loads
    (Budapest Univ Technology Economics, 2023) Yildirim, Musa; Ozhan, Hacer Bilir
    Concrete is exposed to a variety of stresses throughout its service life, which can result in cracks and damage. The use of fibers in concrete mixtures is known to improve the mechanical and durability properties of the concrete. In this study, glass fiber-reinforced concrete cube specimens were produced and stressed at 70 and 90 percent of their maximum compressive strength. The effects of stress loading-induced cracks and glass fiber reinforcements on mechanical and durability properties of concrete specimens were investigated using UPV, capillary water absorption, acid effect, and high-temperature effect tests. Glass fibers increased compressive strength and reduced water absorption in specimens that were not stressed. On the other hand, glass fibers increased the durability of stressed specimens at both degrees of compressive load stress. The bridging effects of glass fibers reduced crack creation, resulting in improved UPV test results. Glass fibers did not dissolve in acid solution due to their chemical resistance, resulting in less weight loss and higher compressive strength in concrete specimens. In the high-temperature effect tests, decreasing compressive strength values were observed as the stress load and temperature levels increased. However, such reductions were lower for glass fiber reinforced concrete than for control concrete without glass fiber. As a result of the present findings, glass fiber reinforcements prevent stress -induced cracks, making the concrete more durable and stronger against external forces.
  • Küçük Resim Yok
    Öğe
    Utilization of tea waste as a bacterial carrier in self-healing mortars
    (Springernature, 2025) Yildirim, Musa; Ozhan, Hacer Bilir; Oz, Hilal Girgin; Ogut, Hamdi
    The protection of bacteria in self-healing composites is crucial for an effective healing process. However, materials used for protection often require advanced techniques and incur additional costs. This study investigates the use of tea waste as a bacterial carrier and natural fibre reinforcement in mortar. Tea waste, a fibrous by-product with high water absorption capacity, was used as a bacterial carrier for Bacillus megaterium spores. Mortar samples with different amounts of tea waste containing bacteria were evaluated through crack healing analysis, compressive strength, water absorption, ultrasonic pulse velocity (UPV), capillarity, and microstructural analyses. Additionally, the healing efficiency of the mortars was investigated using pre-cracked specimens. The results showed that tea waste effectively absorbed and protected the bacterial spores. Due to its fibrous nature, tea waste restricted cracks and created a more favourable condition for self-healing. Bacterial mortars with tea waste repaired cracks up to 0.68 mm wide and exhibited a 26.49% increase in compressive strength compared to control samples after 90 days. Moisture from the tea waste improved the bacterial environment and promoted internal curing, leading to denser structures with higher UPV, reduced water absorption, and lower capillarity. Scanning electron microscopy analysis confirmed that tea waste supported bacterial calcite formation. FT-IR analysis demonstrated that tea waste was highly compatible with the bacterial mortar matrix. Consequently, the incorporation of tea waste led to a notable presence of bacterial calcite products within the mortar structure. The findings indicate that tea waste can be effectively utilized to enhance the self-healing capabilities of mortars.