Yazar "Ozen, Suleyman" seçeneğine göre listele

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    Assessment of Colemanite Waste in Hybrid Fiber-Reinforced Mortars Exposed to Elevated Temperatures
    (Springer Heidelberg, 2025) Altun, Muhammet Gokhan; Benlioglu, Arif; Ozen, Suleyman
    This study systematically investigates the effects of colemanite waste and hybrid fibers on the high-temperature performance of cementitious mortars, aiming to mitigate the negative impact of colemanite waste on mechanical properties through the use of various fibers, both individually and in hybrid combinations, and thereby providing critical insights for sustainable construction materials. In the study, cement was used as the binder, with colemanite waste substituted at rates of 3, 5, and 7%. Standard sand was used as aggregate, and fibers were incorporated at a volume of 0.4% each of steel fiber, basalt fiber, polypropylene fiber, as well as hybrid fibers (0.2% steel + 0.2% basalt and 0.2% steel + 0.2% polypropylene). The compressive strength, flexural strength, and water absorption rates of the produced mixtures were determined at 7 and 28 days. Additionally, to assess the mechanical performance of the mixtures under high-temperature effects, the 28-day mixtures were exposed to temperatures of 300 and 600 degrees C, and residual compressive and flexural strengths were evaluated. The results indicate that the use of fibers, whether separately or in hybrid forms, enhances the mechanical properties, water absorption capacities, and high-temperature performance of the mixtures, regardless of the substitution ratio of colemanite waste. Among the mortars subjected to high temperatures, the sample containing 7% colemanite waste exhibited the lowest results, whereas the sample, which contained 3% colemanite waste and 0.4% steel fibers, yielded the best results.
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    Influence of sulfonate and phosphate groups in polycarboxylate ethers on properties of fly ash blended cementitious systems
    (Elsevier Sci Ltd, 2025) Altun, Muhammet Gokhan; Karakuzu, Kemal; Ozen, Suleyman; Hatungimana, Daniel; Mardani, Ali; El-Mir, Abdulkader; Assaad, Joseph J.
    This investigation examines the effect of anionic monomer groups in polycarboxylate ether (PCE) superplasticizers on rheology, setting, compressive strength, and water absorption of cementitious systems containing fly ash additions. Five PCEs having the same backbone structure and different anionic groups are synthesized. The carboxylate functional group is replaced with 10 % or 30 % sulfonate or phosphate groups, while the total anionic monomer content, molecular weight, and side chain length are kept constant. Test results showed that the PCEs containing 30 % sulfonate or phosphate functional groups are effective in improving flow and reduce apparent viscosity, particularly in mixtures containing increased fly ash additions. Because of improved adsorption properties, setting times are extended, which consequently reduces the 1-day compressive strength when the carboxylates are gradually replaced by 10 % or 30 % sulfonate or phosphate functional groups. Yet, the late age strengths and water absorption are not affected by such replacements. Data reported in this paper can be of interest to admixture producers and concrete technologists seeking an efficient performance of PCE polymers in fly ash concrete mixtures.
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    Influence of waste aggregate type on the mechanical strength and durability of slag-rice husk ash-based geopolymer composites
    (Taylor & Francis Ltd, 2025) Benlioglu, Arif; Demirel, Mertcan; Altun, Muhammet Gokhan; Ozen, Suleyman
    This study explores the utilization of construction and demolition waste (CDW), ceramic waste (CW), and marble waste (MW) as partial sand replacements in geopolymer mortars produced with granulated blast furnace slag (GBFS) and rice husk ash (RHA). Mortars were prepared with 75% GBFS and 25% RHA, activated using sodium silicate and 12 M sodium hydroxide, and cured at ambient conditions for 28 days. Waste aggregates were substituted at 10%, 20%, and 30%, while mix ratios were kept constant. Hardened properties, drying shrinkage, and high-temperature performance (300 and 600 degrees C) were evaluated, alongside microstructural analyses (X-ray diffraction, scanning electron microscopy, thermogravimetric analysis/derivative thermogravimetric). Results showed MW10 achieved the highest compressive strength with an increase of 27%, while CW20 exhibited the best flexural strength with an increase of 8%. CW and MW reduced drying shrinkage, whereas CDW increased it and caused significant strength loss at elevated temperatures. Combining waste aggregates with industrial by-products boosts sustainability and performance.