Yazar "Bayer, Ismail Raci" seçeneğine göre listele

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    Eco-hybrid cement-based building insulation materials as a circular economy solution to construction and demolition waste
    (Elsevier Sci Ltd, 2023) Ozcelikci, Emircan; Oskay, Atakan; Bayer, Ismail Raci; Sahmaran, Mustafa
    The primary focus of this study is to develop non-structural ultra-lightweight circular building insulation ma-terials by utilizing a substantial amount of construction and demolition waste (CDW). A unique type of Eco-hybrid cement was formulated as the binder phase, while fine recycled concrete aggregates (FRCA) were used in the aggregate phase. The physical, mechanical, and thermal conductivity properties of the mixtures were assessed by altering the content of Eco-hybrid cement, FRCA, foaming agent, silica-aerogel and water-to-binder ratio. The findings indicated that the fresh properties are primarily influenced by the FRCA and foaming agent ratio, whereas the mechanical properties are predominantly associated with the Eco-hybrid cement and foaming agent content. Microstructural analysis revealed that thermal performance is greatly affected by the pore size distribution and their interconnectivity. Consequently, an ultra-lightweight green foam concrete was successfully developed with a dry density of 0.514 g/cm3 and a thermal conductivity of 0.049 W/mK.
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    Effects of High Temperature and Cooling Regimes on Properties of Marble Powder-Based Cementitious Composites
    (Mdpi, 2023) Bayer, Ismail Raci; Sevim, Ozer; Demir, Ilhami
    The demand for cement is increasing every day worldwide. To meet this demand, natural resources are rapidly being depleted. The excessive consumption of natural resources encourages researchers to conduct studies on the use of waste materials instead of cement. Marble waste is one of the major natural wastes abundantly generated worldwide. It has been evaluated that there is a gap in the literature regarding a study comparing the effects of different cooling regimes on cementitious composites with a marble powder (MP) replacement that has been exposed to high temperatures. In this study, waste marble powder (MP) was used as a replacement for cement at percentages of 5%, 10%, 15%, 20%, and 25% by mass. The water-to-binder ratio was kept constant at 0.5 for all mixture groups. Subsequently, the prepared cementitious composites were exposed to high temperatures (300 degrees C, 600 degrees C, and 800 degrees C) and subjected to air- and water-cooling regimes. Within the scope of this study, unit weight (Uw), ultrasonic pulse velocity (UPV), flexural strength (ffs), compressive strength (fcs), and mass loss tests were conducted. Additionally, a microstructure analysis was carried out using scanning electron microscopy (SEM) to examine the effect of MP replacement and the cooling regime. When examining the results of the samples tested in the laboratory, it was observed that the mortar with 5% MP replacement exhibited better mechanical properties compared with the others. In general, it can be said that the mechanical properties of samples cooled in air after exposure to high temperatures were better than those of samples cooled in water. As a result of this study, it was determined that MP replacement could positively contribute to the resistance of cementitious composites to high temperatures. Additionally, the use of a significant amount of waste MP can lead to savings in cement usage and significant reductions in CO2 emissions.
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    Evaluation of Mechanical and Microstructural Properties of Engineered Geopolymer Composites with Construction and Demolition Waste-Based Matrices
    (Asce-Amer Soc Civil Engineers, 2024) Kul, Anil; Ozcelikci, Emircan; Ozel, Behlul Furkan; Gunal, Muhammed Faruk; Yildirim, Gurkan; Bayer, Ismail Raci; Demir, Ilhami
    The main purpose of this work was to combine the advantages of increased material greenness, waste upcycling, reduced raw material demand, and the superior characteristics of traditional engineered cementitious composites (ECCs). To this end, engineered geopolymer composites (EGCs) with matrices based entirely on components from construction and demolition waste (CDW) as precursors and aggregates were developed. The CDW-based precursors included roof tiles, red clay bricks, hollow bricks, glass, and concrete. Different combinations of sodium hydroxide, sodium silicate, and calcium hydroxide were used as alkaline activators. Hybridized polyethylene and nylon fibers were used as fibers. To investigate the influences of the additional calcium source, slag-substituted versions of the same mixtures were produced. At the fresh state, Marsh cone and mini-slump tests were performed. At the hardened state, mechanical property tests (compressive strength and four-point bending) and microstructural characterization tests (X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy) were conducted. The findings revealed that, regardless of the mixture composition, all EGCs exhibited a deflection-hardening response coupled with multiple microcracking behavior. The 28-day average ranges for compressive strength, flexural strength, and midspan deflection results were 25.2-42.1 MPa, 6.2-9.5 MPa, and 14.1-28.3 mm, respectively. Slag substitution mostly improved the mechanical performance of EGCs. The main geopolymerization products were sodium aluminosilicate hydrate (NASH), calcium aluminosilicate hydrate (CASH), and C-(N)-ASH gels, the formation of which varied depending on the type of precursor and activator.
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    Experimental Evaluation of New Geopolymer Composite with Inclusion of Slag and Construction Waste Firebrick at Elevated Temperatures
    (Mdpi, 2023) Sevim, Ozer; Demir, Ilhami; Alakara, Erdinc Halis; Bayer, Ismail Raci
    This study investigates the effect of elevated temperatures on slag-based geopolymer composites (SGC) with the inclusion of firebrick powder (FBP). There is a limited understanding of the properties of SGC with the inclusion of FBP when exposed to elevated temperatures and the effects of cooling processes in air and water. In this regard, in the preliminary trials performed, optimum molarity, curing temperature, and curing time conditions were determined as 16 molarity, 100 degrees C, and 24 h, respectively, for SGCs. Then, FBP from construction and demolition waste (CDW) was substituted in different replacement ratios (10%, 20%, 30%, and 40% by slag weight) into the SGC, with optimum molarity, curing temperature, and curing time. The produced SGC samples were exposed to elevated temperature effects at 300, 600, and 800 degrees C and then subjected to air- and water-cooling regimes. The ultrasonic pulse velocity, flexural strength, compressive strength, and mass loss of the SGCs with the inclusion of FBP were determined. In addition, scanning electron microscopy (SEM) analyses were carried out for control (without FBP) and 20% FBP-based SGC cooled in air and water after elevated temperatures of 300 degrees C and 600 degrees C. The results show that the compressive and flexural strength of the SGC samples are higher than the control samples when the FBP replacement ratio is used of up to 30% for the samples after the elevated temperatures of 300 degrees C and 600 degrees C. The lowest compressive and flexural strength results were obtained for the control samples after a temperature of 800 degrees C. As a result, the elevated temperature resistance can be significantly improved if FBP is used in SGC by up to 30%.
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    The Effect of Magnetized Water on the Fresh and Hardened Properties of Slag/Fly Ash-Based Cementitious Composites
    (Mdpi, 2023) Sevim, Ozer; Demir, Ilhami; Alakara, Erdinc H.; Guzelkucuk, Selahattin; Bayer, Ismail Raci
    The physicochemical structure of the mixing water used in concrete has a significant effect on the physical and mechanical properties of cementitious composites. The studies on the effect of magnetized water (MW) on the properties of FA/BFS-based cementitious composites are still in their infancy. This study explores the effect of MW on the fresh and hardened properties of fly ash (FA)/blast furnace slag (BFS)-based cementitious composites. A total of 22 different mixture groups having FA/BFS (0, 5, 10, 15, 20, and 25%) by weight of cement were produced using tap water (TW) and MW. The fresh-state properties (the initial and final setting times and the consistency) and hardened-state properties (the compressive strength, water absorption properties, and rapid chloride ion permeability test) of produced cementitious composites were investigated. The development of hydration products was analyzed using scanning electron microscopy (SEM) and the mercury intrusion porosimetry (MIP) test. The results reveal that the fresh- and hardened-state properties of cementitious composite samples produced with MW are significantly improved. The properties of the samples utilizing MW showed that FA and BFS could be used at a higher rate for the same target properties in cementitious composites by using MW as mixing water. Using up to 25% FA/BFS in cementitious composites prepared with MW is recommended.