Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
Browse
4 results
Search Results
Article Citation - WoS: 9Citation - Scopus: 11Evaluation of Diatomite Substitute With Thermal Power Plant Waste Fly Ash in Sustainable Geopolymer Through Life Cycle Assessment(Springer, 2025-02-28) Ilkentapar, Serhan; Orklemez, Ezgi; Durak, Ugur; Gulcimen, Sedat; Bayram, Savas; Uzal, Nigmet; Atis, Cengiz DuranThis research demonstrates the potential of diatomite as a fly ash replacement to improve mechanical properties and environmental sustainability and presents it as a viable alternative for sustainable construction. Additionally, a life cycle assessment (LCA) was conducted on the produced mortars to quantitatively compare their environmental impacts using a cradle-to-gate approach. In mixtures, it was used by replacing the diatomite in the ratios of 1%, 2%, 3%, 4%, and 5% by weight of the fly ash. Workability, unit weight, flexural and compressive strength, abrasion resistance, elevated temperature resistance and microstructure analysis were carried out. The results indicated that replacing 1%, 2%, and 3% diatomite increased the compressive and flexural strength of mortars due to their higher specific surface area. Two percent replacement of diatomite provided the best results. FESEM results of 3% diatomite inclusion showed more intense and compact microstructure of geopolymer. Diatomite inclusion increased the abrasion resistance of geopolymer. Since 2% diatomite replacement was found to be optimum, the LCA results showed that geopolymer mortar with 2% diatomite has 25% lower impacts in terms of global warming potential and 10% lower impacts in terms of terrestrial ecotoxicity than conventional Portland cement mortar.Article Citation - WoS: 8Citation - Scopus: 10Compatibility and Biomineralization Oriented Optimization of Nutrient Content in Nitrate-Reducing Microbial Self-Healing Concrete(MDPI, 2021-08-11) Kardogan, Beyza; Sekercioglu, Kadir; Ersan, Yusuf CagatayMicrobially induced calcium carbonate precipitation (MICP) can be mentioned among the popular approaches to develop a self-healing concrete. The production of dissolved inorganic carbon through microbial activity is the main precursor for MICP in concrete and it is limited by the bioavailability of the nutrients. When nutrients are added to the mortar as admixtures, their bioavailability becomes more significant for crack repair because nutrients disperse in the mortar and considerable fraction stays far from a single crack. Therefore, the determination of bioavailability of nutrients and its variation with the initial nutrient content and crack age is essential to optimize a recipe for bacteria-based self-healing concrete. This study presents the optimum nutrient content defined for nitrate-reduction-based self-healing bioconcrete. In the tests, calcium nitrate (CN) and calcium formate (CF) were combined with a CF:CN w/w ratio of 2.50. Mortar properties and bioavailability of nutrients were analysed at different nutrient doses. Moreover, the bioavailability of nutrients at different crack ages changing between 3 and 56 days was monitored. Finally, resuscitation, microbial activity and the MICP performance of nitrate reducing biogranules were tested at defined nutrient bioavailabilties. The optimum nutrient content was determined as 7.00% (CF 5.00% and CN 2.00%). The leaching rates of formate ions were twice the leaching rate of the nitrate ions at similar initial concentrations, which led to a bioavailable HCOO-/NO3-N ratio of 23 g/g in cracked mortar. Under optimum nutrient conditions, the CaCO3 precipitation yield of nitrate reducing biogranules was recorded as 1.5 g CaCO3/g HCOO- which corresponded to 68% C precipitation efficiency.Article Citation - WoS: 4Citation - Scopus: 4Characterization of Limestone Calcined Clay Cement Made With Calcium Sulfoaluminate Clinker(Springer int Publ Ag, 2024-07-02) Atasever, Muhammet; Erdogan, Sinan TurhanThis study concentrated on producing limestone calcined clay calcium sulfoaluminate cement by replacing portland cement in limestone calcined clay cement with calcium sulfoaluminate cement, with the goal of increasing the early strength of limestone calcined clay cement. The mineralogy and microstructures of hydrating pastes were investigated using x-ray diffraction and scanning electron microscopy. Heat evolution was studied using isothermal calorimetry. Strength development and workability were assessed on mortar samples. The 1 day strengths of limestone calcined clay calcium sulfoaluminate cement samples exceeded those of limestone calcined clay cement by similar to 30-80%, though its strength gain slows significantly after 1 day due to the lack of calcium silicates, affecting pH and clay dissolution. Despite this, the strength development of limestone calcined clay calcium sulfoaluminate cement, when adjusted for CO2 emissions, is comparable to limestone calcined clay cement. Additionally, limestone calcined clay calcium sulfoaluminate cement provides a 10-15% higher flow and exhibits a lower heat of hydration beyond 12 h, while maintaining a production cost similar to that of limestone calcined clay cement.Article Citation - WoS: 8Citation - Scopus: 9A New Quantitative Welding Degree Classification for Ignimbrites(Springer, 2023-06-28) Akin, Mutluhan; Topal, Tamer; Dincer, Ismail; Akin, Muge K.; Ozvan, Ali; Orhan, Ahmet; Orhan, AyseAs a pyroclastic rock type, ignimbrites may reveal varying degrees of welding depending on the temperature (> 535 celcius) and overburden pressure conditions during its formation. The welding degree of ignimbrites increases as the formation temperature and the thickness of the overburden deposit in the depositional environment escalate, which are the most crucial factors controlling the rate of welding in ignimbrites. With the increasing temperature, plastic deformation is observed in ignimbrites and the glassy minerals are being welded. Furthermore, the thickness of the overburden causes the deformation of the ash matrix in ignimbrites at the lower sections and the pumice grains are flattened at different rates. An increase in the degree of welding of ignimbrites causes an improvement in the physical and mechanical properties of the rock material as well. Within the scope of this research, petrographical, mineralogical, and geochemical studies were carried out on a total of 16 different ignimbrite types, which have different color and texture properties, obtained from three different regions of Turkey (Kayseri, Nevsehir, Ahlat) where ignimbrites extensively crop out, and the physical and mechanical properties of these samples were revealed. Consequently, a new welding classification was developed for ignimbrites considering the uniaxial compressive strength and dry unit weight. The proposed welding classification consists of six classes ranging from non-welded to highly welded. When the welding degrees of the selected ignimbrites are evaluated, Kayseri ignimbrites mostly exhibit moderate welding characteristics. Nevsehir ignimbrites, on the other hand, have a low welding degree whereas the degree of welding in Ahlat ignimbrites may vary from low to high. Additionally, long and short axis lengths of pumice grains in the ignimbrite specimens were determined by measuring under the microscope, and shape ratios were determined by different shape parameter evaluation methods. As a result, it has been concluded that the pumice grains in Kayseri and Ahlat ignimbrites have a more lenticular structure than the pumice grains in Nevsehir ignimbrites. Eventually, the welding degree classes of ignimbrites and the classification developed by using threshold values of the oblateness ratio (OR) values of pumice grains at different welding degrees are quite compatible. The proposed welding degree classification is of great importance in the selection of ignimbrites widely used as dimension stone and in terms of engineering classification of this rock type as well as it will guide to the scientific studies to be performed on ignimbrites with varying physical and mechanical properties.