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Öğe Activation of Polypropylene (PP) Fiber Surface with 1-Vinyl-1,2,4-triazole and Vinyl Acetate: Synthesis, Characterization, and Application in Cementitious Systems(Mdpi, 2025) Kaya, Yahya; Balci, Petek; Ozen, Suleyman; Mardani, Ali; Kara, AliRecently, the potential of recycled materials to improve the performance of concrete and other building materials has become an important research topic. It is known that various methods are applied to improve the tensile strength and energy absorption capacity of cementitious systems. One of the most common of these methods is the addition of fibers to the mixture. In this study, the effects of surface-modified polypropylene (PP) fibers obtained from recycled masks on the mechanical properties of mortar mixtures were investigated. In order to improve the matrix-fiber interface performance, 6 mm and 12 mm long recycled PP fibers were chemically coated within the scope of surface modification using 1-Vinyl-1,2,4-Triazole and Vinyl Acetate. With this modification made on the surface of PP fibers, we aimed to increase the surface roughness of the fibers and improve their adhesion to the matrix. Thus, we aimed to increase the mechanical properties of mortar mixtures as a result of the fibers performing more effectively in the concrete matrix. FTIR AND SEM-EDS analyses confirmed the success of the modification and the applicability of 1-Vinyl-1,2,4-Triazole and Vinyl Acetate to the fiber surface and showed that the fibers were successfully modified. It is seen that the fibers modified with Vinyl Acetate exhibit superior performance in terms of both the workability and strength performance of cementitious systems compared to the fibers modified with 1-Vinyl-1,2,4-Triazole. This study provides a significant contribution to sustainable construction materials by revealing the potential of using recycled materials in cementitious systems.Öğe Assessment of Colemanite Waste in Hybrid Fiber-Reinforced Mortars Exposed to Elevated Temperatures(Springer Heidelberg, 2025) Altun, Muhammet Gokhan; Benlioglu, Arif; Ozen, SuleymanThis 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.Öğe Effect of graphene oxide-coated jute fiber on mechanical and durability properties of concrete mixtures(Elsevier Sci Ltd, 2024) Ozen, Suleyman; Benlioglu, Arif; Mardani, Ali; Altin, Yasin; Bedeloglu, AyseVarious methods are applied in order to improve the mechanical properties of concrete and to provide ductility. The most common method is the addition of fiber to cementitious systems. The fibers used in cementitious systems are divided into two categories: artificial and natural. Natural fibers are preferred due to their lower production cost, lower environmental impacts such as lower carbon emissions and fossil fuel consumption, biodegradability, lower density and ease of manufacturing. On the other hand, graphene-derived materials have been proven to improve the mechanical and interface properties between fiber and matrix. In this study, the effect of surface treatment of jute fibers with various chemical treatments and graphene oxide coating on the mechanical and some durability performances of concrete mixtures was investigated. For this purpose, the surface of jute fibers was roughened with graphene oxide coating. Within the scope of the experimental study, different fiber concrete mixtures were prepared by adding jute fibers of 30 and 50 mm length to the mixture at 0.25 and 0.5 % of the total volume in addition to the fiber-free control mixture. The fiber was used in 2 different ways, both without any treatment and by coating the surface with graphene oxide. Slump tests were performed on the concrete mixtures produced. The 28-day hardened concrete specimens were tested for compressive strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity and depth of water penetration under pressure. The resistance of the concrete specimens at 300 and 600 degrees C high temperatures and after 300 cycles of freeze-thaw was determined by examining their compressive strength. In addition, the microstructural properties of the jute fiber specimens were examined using Scanning Electron Microscopy (SEM).Öğe Effect of interlayer cold joint on mechanical properties and permeability of roller compacted concrete(Higher Education Press, 2025) Bayqra, Sultan Husein; Ozen, Suleyman; Mardani, Ali; Ramyar, KambizOne issue with layer application of roller compacted concrete (RCC) is the development of cold joints, which can cause damage to RCC structures. In this study, fly ash was used in place of 0%, 20%, 40%, and 60% of the cement or aggregate to examine the impact of interlayer cold joint formation on RCC mixtures. To promote cold joint formation, the second layer was placed and compacted with a delay of 0, 60, 120, or 180 min after the first layer. Three methods were tried for preventing cold joints from forming: one was to apply a bedding mortar to the interlayer, another was to add a set retarder admixture, and the third was to spray an adhesion-enhancing chemical additive on the surface of the first layer. Based on the 28 d specimens' compressive and splitting-tensile strengths as well as the depth of water penetration under pressure, the most effective method was found to be applying interlayer bedding mortar. Considering 180 min delayed layer castings, the splitting-tensile and compressive strengths of the control samples decreased by 31% and 17%, respectively, while the strengths of mixtures applying interlayer bedding mortar decreased by 9% and 10%. In addition, bedding mortar treatment decreased the water permeability by 59% compared to the control. Interlayer cold joint decreased all mixtures' moduli of elasticity, regardless of the age of the specimens. When the interlayer delay was 60 min, the modulus of elasticity decreased by 1%-4%. It was between 2% and 14%, and between 10% and 24% at 120 and 180 min for the interlayer delay. The longer the delay in placing the second RCC layer, the more detrimental the effect of the cold joint. This effect was most noticeable on mechanical and permeability properties tested with applied load or water pressure parallel to the cold joint, such as flexural and splitting tensile strengths and water penetration depth under pressure.Öğe Effects of Colemanite and Fiber Types on Strength and Water Absorption of Mortar Mixtures Containing Air-Entraining Admixture(Mdpi, 2025) Ozansoy, Ayse Irem; Ozen, SuleymanThe global construction industry heavily relies on cementitious systems, which are a major contributor to carbon dioxide emissions due to the energy-intensive nature of cement production. These emissions account for approximately 8% of global CO2 output, exacerbating climate change and environmental degradation. The global reliance on cementitious systems has led to substantial carbon dioxide emissions during cement production, intensifying the need for environmentally sustainable alternatives. Turkey, which holds 73% of the world's boron reserves, offers a unique opportunity to explore boron-based minerals like colemanite as potential replacements for cement. In this study, the effects of colemanite (a boron mineral) and four fiber types-steel, basalt, carbon, and polypropylene-on the compressive strength, flexural strength, and water absorption of mortar mixtures incorporating air-entraining admixtures were investigated. All mixtures contained 0.1% air-entraining admixture (by cement weight), with fixed parameters: a water/binder ratio of 0.485, a sand/binder ratio of 2.75, and slump-flow values of 190 +/- 20 mm. Cement was partially replaced with colemanite at 3% and 5%, while fibers were added at 0.5% by volume. Fresh-state properties (slump-flow and admixture requirements) and hardened-state properties (28-day compressive/flexural strength and water absorption) were evaluated. Selected samples underwent SEM analysis for microstructural assessment. Key findings revealed that both colemanite and fibers increased admixture demand to achieve target slump flow. While colemanite and fibers collectively enhanced compressive strength, their interactions varied: basalt and carbon fibers exhibited superior performance in mixtures without colemanite, whereas steel fibers showed greater efficacy in colemanite-containing mixtures. The strength increase was less pronounced when colemanite was introduced to mixtures containing carbon, polypropylene fibers, and basalt. The trend of flexural strengths was comparable to that of compressive strengths. SEM images revealed that the void distribution in the samples, influenced by the effects of colemanite and fibers, had a more dominant effect on compressive and flexural strengths. Water absorption inversely correlated with mechanical performance. This study not only contributes to reducing the carbon footprint of cementitious systems by partially replacing cement with colemanite but also provides practical insights to optimize the use of fibers to increase strength performance and reduce water absorption properties from durability parameters. These findings support the development of more sustainable and durable materials.Öğe High-temperature and drying shrinkage behavior of mortars containing colemanite and different fiber types with air-entraining admixture(Taylor & Francis Ltd, 2025) Benlioglu, Arif; Ozansoy, Ayse Irem; Ozen, SuleymanIn recent years, the construction industry has become a major source of global greenhouse gas emissions, primarily because of the energy-intensive process of cement production. Turkey holds about 73% of the world's boron reserves, providing a significant opportunity to use boron-containing minerals such as colemanite as alternative binders. In this study, mortar mixtures were developed incorporating colemanite, air-entraining admixtures (AEAs), and various fiber types (steel, basalt, carbon and polypropylene). The AEA was used at 0.1% of cement weight, while colemanite replaced 3% and 5% of the cement, and each fiber type was added at 0.5%. The results indicated that mixtures containing 3% and 5% colemanite with steel fibers exhibited the highest performance after thermal exposure, showing up to 130% higher residual compressive strength and 60% higher flexural strength compared to the reference mixture. Moreover, the inclusion of colemanite and fibers generally reduced drying shrinkage, while their combined use significantly enhanced the high-temperature and shrinkage resistance of cement-based mortars. In contrast to previous studies, this work emphasizes the eco-friendly use of colemanite as a partial cement replacement and its synergy with fibers and an AEA, offering practical potential for sustainable and heat-resistant construction materials.Öğe 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.Öğe 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, SuleymanThis 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.Öğe Modification of Polypropylene Fibers with Sodium Silicate: Enhancement of Pozzolanic Properties in Cement-Based Systems(Mdpi, 2025) Kaya, Yahya; Balci, Petek; Ozen, Suleyman; Mardani, Ali; Kara, AliThis study investigates the effect of sodium-silicate-based chemical surface modification of polypropylene (PP) fibers on the mechanical and fresh-state properties of cementitious composites. The proposed method introduces silanol and siloxane groups onto the PP surface through a radical-assisted chlorination route, aiming to enhance fiber-matrix interfacial bonding. Modified fibers increased the polycarboxylate ether (PCE) demand by 100% compared to the control mixture, while unmodified PP fibers caused a 58% increase at equivalent workability. The incorporation of PP fibers resulted in limited changes in compressive strength (1-7%), whereas silicate-modified fibers led to notable late-age flexural strength gains of 10% (28 days) and 17% (56 days). Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed successful surface functionalization, while the heterogeneous silicate deposition still contributed positively to interfacial transition zone (ITZ) performance. Overall, sodium-silicate-modified PP fibers improve flexural behavior and interfacial bonding in cement-based systems, offering a promising approach for enhanced mechanical performance and sustainability.
