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    Effects of sulfate on cement mortar with hybrid pozzolan substitution
    (Elsevier - Division Reed Elsevier India Pvt Ltd, 2018) Demir, Ilhami; Guzelkucuk, Selahattin; Sevim, Ozer
    Sulfate is one of the most important chemical risks which affect the durability of concrete and reinforced concrete structures. Therefore, this study investigates the effects of sulfate on blended cement mortars. In this paper, cement mortar specimens were prepared with the substitution of CEM I 42.5 R cement with Fly ash + Bottom ash + Blast-furnace Slag at the ratios of 5%, 10%, 15%, and 20% along with a control specimen without additives. These prepared cement mortar specimens were then cured for 2, 7, 28, 90, 180, and 360 days either in potable water or 10% sodium sulfate (Na2SO4) solution. Cement paste specimens were subjected to the initial setting, final setting, and volumetric expansion tests in accordance with the TS EN 196-3 standard. Cured for 2, 7, 28, 90, 180, and 360 days, cement mortars were subjected to compressive strength tests as per the TS EN 196-1 standard while length change tests were conducted as per the ASTM C 1012 standard. It was found that the compressive strength of cement mortars blended with 5% Fly ash + Bottom ash + Blast-furnace Slag cured in sodium sulfate for 360 days was approximately 2% higher than that of the cement mortar without additives. The length change of specimens obtained from cured in sodium sulfate solution shows best results in higher additive ratio. These all length changes ratio are greater than 0.087% ratio which is maximum length change expansion in potable water. This study suggests that 15% and 20% additive ratios are effective in reducing unfavorable effects of sulfate. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.
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    Fresh and Hardened Properties of Cementitious Composites Incorporating Firebrick Powder from Construction and Demolition Waste
    (Mdpi, 2023) Sevim, Ozer; Alakara, Erdinc H.; Guzelkucuk, Selahattin
    Firebricks are generally used in furnace basins where glass, ceramics, and cement are produced. Firebricks have an important place in construction and demolition waste (CDW). However, there is a limited understanding of the effects on fresh and hardened state properties of cementitious composites. This study investigates the mechanical, physical, and microstructural properties of cementitious composites incorporating firebrick powder (FBP) from CDW. In this regard, the FBP was used at 5, 10, 15, 20, and 25% replacement ratio by weight of cement to produce cementitious composites. The consistency, setting characteristics, and 3, 7, and 28 days compressive and flexural strength tests of produced cementitious composites were performed. In addition, ultrasonic pulse velocity, water absorption, porosity, unit weight, and microstructure analysis of cementitious composites were conducted. As a result, the 28-day compressive strength of the cementitious composite mortars containing up to 10% firebrick powder remained above 42.5 MPa. The flow diameters increased significantly with the increase of the FBP. Therefore, it has been determined that the FBP can be used up to 10% in cementitious composites that require load-bearing properties. However, FBP might be used up to 25% in some cases. Using waste FBP instead of cement would reduce the amount of cement used and lower the cost of producing cementitious composites.
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    Investigation of thermal and mechanical properties of perlite-based lightweight geopolymer composites
    (Springernature, 2023) Demir, Ilhami; Guzelkucuk, Selahattin; Sevim, Ozer; Simsek, Osman
    The objectives of this study include minimizing the thermal conductivity of the produced materials, reducing dead loads of structures through lightweight composite material production, and increasing perlite use in areas close to material deposits. To this end, lightweight geopolymer composites were produced using ground raw perlite as a precursor, expanded perlite as an aggregate, and sodium hydroxide (NaOH) as an activator. The produced samples were cured in an oven at 110 degrees C for 24 h. Within the scope of this study, unit weight, compressive strength, and thermal conductivity coefficient tests were conducted. Additionally, microstructure analysis was carried out using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). As a result, it has been shown that ground raw perlite can be used as a precursor in geopolymer composites, while expanded perlite demonstrates suitability as a lightweight and porous aggregate for heat insulation applications.
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    Mechanical properties and microstructure of cement multicomponent systems containing pozzolan materials under sulfate attack
    (STOWARZYSZENIE PRODUCENTOW CEMENTU, 2020) Guzelkucuk, Selahattin; Demir, Ilhami; Sevim, Ozer; Kalkan, Ilker
    Sulfates are a significant chemical components that may lead to failures of cement concrete composites. The present study is dedicated to analyzing the effects of sulfate on the microstructure of cement composite mortars. For this purpose, cementing composite specimens were prepared with 20% pozzolan mixture [fly ash + granulated blastfurnace slag + bottom ash] by mass of cement, together with the reference additive-free specimen of cement concrete, without any mineral admixtures. These cementing composite mortar specimens were then treated for 2, 7, 28, 90, and 360 days in tap water and 10% sodium sulfate solution. The microstructure of the additive-free mortar and composite cement mortar, partially replaced with 20% pozzolan, was then investigated using a scanning electron microscope. The results showed that increasing curing time also increases the formation of C-S-H [calcium silicate hydrate] gel in the cement mortar, when the microstructural changes in the cement are explored in detail. Ettringite formation [3CaO center dot Al2O3 center dot 3CaSO(4)center dot 32H(2)O] in the specimens cured in 10% Na2SO4 was also noticed, in the present experiments.
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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.
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    Thermal and Compressive Strength Properties of Sepiolite Substituted Autoclaved Aerated Concrete
    (Gazi Univ, 2014) Savas, Musa; Demir, Ilhami; Guzelkucuk, Selahattin; Sengul, Cagri Goktug; Yaprak, Hasbi
    Aerated concrete is a lightweight concrete which has porous structure. In this study, effects of usage of sepioliteas a raw material instead of quartzite on the thermal and compressive strength properties of aerated concrete were investigated.G2/04 class aerated concrete, which has been commercially produced as a wall component, has been focused. Aerated concrete samples have been prepared by substitution of sepiolite instead of quartzite in %5, %10, %15, %20 and %25. Sepiolite has been provided from Eskisehir mine field. After 4 hours cure at 60 degrees C, samples moved to treat in autoklave in the temperature of 180 degrees C and pressure at 11 bar for 6.5 hours. Thermal conductivity and compressive strength properties of samples were determined. As a result, increasing the rate of sepiolite in aerated concrete decreases the compressive strength and increases the thermal conductivity.