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Öğe Combined effect of using steel fibers and demolition waste aggregates on the performance of fly ash/slag based geopolymer concrete(TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2023) Lakew, Asfaw Mekonnen; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.; Uysal, Mücteba; Niş, Anıl; Aygörmez, Yurdakul; Bayati, MohammadDeveloping sustainable construction products has been showing a rising trend recently. Geopolymer composites are remarkable binding materials fabricated based on recycling and sustainability. In this paper, an experimental investigation was conducted to study some mechanical and durability characteristics of steel fiber-reinforced fly ash/slag-based geopolymer concrete (GPC) with different proportions of recycled coarse aggregate. Steel fiber-reinforced geopolymer concrete mixtures incorporating recycled coarse aggregates of up to 40% at the interval of 10% were prepared, and the mixtures without recycled coarse aggregate were used as reference samples. The steel fiber ratio of 0.3% and 0.6% were used and the combined effect of steel fiber and recycled coarse aggregate on the geopolymer composites’ behavior regarding strength properties, sulfate resistance, elevated temperature resistance, abrasion resistance, and freezing-thawing resistance was addressed. A significant improvement in strength properties was observed in steel fiber reinforced recycled aggregate geopolymer concrete with increasing fiber content; however, the strength properties of geopolymer concrete were decreased with the increase of recycled coarse aggregate amount. Also, the properties such as abrasion resistance, resistance to elevated temperature, sulfate resistance, and freeze-thaw resistance were improved with the addition of steel fiber. It indicates that the synergetic effect of steel fiber and recycled aggregate helps to produce ecologically sound geopolymer concrete with good engineering properties and durability characteristics that will bring sustainability to the concrete sector. Generally, the results show that the recycled coarse aggregate ratio of up to 30% and 0.6% of steel fiber can be considered an ideal combination to make geopolymer concrete with better overall properties.Öğe Elevated temperature, freezing-thawing and wetting-drying effects on polypropylene fiber reinforced metakaolin based geopolymer composites(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2020) Aygörmez, Yurdakul; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.; Uysal, MüctebaIn this study, metakaolin-based geopolymer samples produced by substitution of silica fume and colemanite waste up to 20% were subjected to high-temperature effects at 300, 600, 900 C, the wettingdrying effect of 5, 15 and 25 cycles and freezing-thawing effect of 56 and 300 cycles. At the end of the tests, compressive and flexural strengths, ultrasonic pulse velocity and weight changes’ results were examined. In addition to these, micro-computed tomography (CT), XRD and SEM analyses were performed to examine the microstructure properties as well as visual inspection. 5 series produced for high temperature and wetting-drying effects were also produced with polypropylene fiber. It has been observed that samples exposed to 900 C maintained their stability. Polypropylene fiber has been shown to increase the samples’ flexural strength results compared to the non-fiber samples after exposing to high temperatures. For the freezing-thawing effect, air-entraining admixture was added to 5 series. An increase for compressive strength was seen after 56 cycles but a decrease was seen after 300 cycles. The geopolymer samples thus began to suffer the real distortion effect in subsequent cycles after the freezing-thawing effect, which contributed to geopolimerization in a sense occurring in the first 56 cycles. During the wetting-drying cycles, fluctuations were observed in the results and an increase in the compressive strength, UPV and weight changes’ results after 5 cycles, a decrease in the results after 15 cycles and an increase again in the results after 25 cycles were seen.Öğe Evaluation of slag/fly ash based geopolymer concrete with steel, polypropylene and polyamide fibers(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2022) Kuranlı, Ömer Faruk; Uysal, Mücteba; Abbas, Mele Tidjani; Çoşgun, Turgay; Niş, Anıl; Aygörmez, Yurdakul; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Geopolymer composites have become an essential product to reduce CO2 emissions, which is an important problem today and ensures green sustainability. With the increasing concerns with global climate change, studies on geopolymer have also increased. The addition of different fibers also has essential potential for increasing the performances of geopolymer composites. Within the scope of this study, it is aimed to produce a green sustainable product as an alternative to traditional concrete by producing different fiber-reinforced geopolymer concrete. In this study, slag-fly ash-based geopolymer concretes reinforced with three different fiber types (Polypropylene (PP), steel (ST), and polyamide (PA)) were produced and the mechanical properties such as compressive, tensile, drying shrinkage and flexural behavior were investigated. Furthermore, elevated temperature (300, 600 and 900-celsius degrees) and freeze-thaw (250 cycles) tests were carried out within the scope of durability properties. Microstructural analyzes were also carried out to understand the matrix composition. Experimental test results revealed that fiber reinforcement improved some of the strength properties, but was ineffective for some properties. The addition of polypropylene and steel fibers significantly improved the flexural toughness factor value (1469% and 566%, respectively) of geopolymer concretes, while this rate of improvement remained quite low (46%) in the polyamide fiber reinforced geopolymer series. According to shrinkage test values, 50S50FA08ST sample ranged from 264 to 297 microstrains. Also, PP fibers increased the initial crack load from approximately 4500 N to 6750 N and the deflection values significantly improved by reaching the deflection values of 7.5 mm. Moreover, the compressive strength values after 900 ?C was obtained as 11–12 MPa for steel fiber reinforced geopolymer concretes. But the freeze–thaw experiments generally revealed that fiber addition did not contribute to the improvement of strength properties.Öğe Influence of wetting-drying curing system on the performance of fiber reinforced metakaolin-based geopolymer composites(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2019) Arslan, Ahmet Ali; Uysal, Mücteba; Yılmaz, Arın; Al-Mashhadani, Mukhallad M.; Canpolat, Orhan; Şahin, Furkan; Aygörmez, YurdakulIn this study, mechanical and durability properties of geopolymer composites prepared using metakaolin and colemanite binding materials with basalt and polyvinyl alcohol fibers were investigated under the influence of curing systems. For the 7 series prepared, two different curing conditions have been applied: wetting-drying and heat curing. The mechanical properties of geopolymer samples were investigated for 7 and 28 days strength and ultrasonic pulse velocity results, water absorption, unit weight and porosity. After the abrasion test, weight loss and length change were examined and after the high temperature tests of 200, 400 and 600 C, the results of strength, ultrasonic pulse velocity and weight loss were found. The results showed that the residual strength values were high after high temperature tests. As a result of SEM, FT-IR and TGA-DTA analyzes, it was observed that high temperature post-geopolymer samples retained their stable structure. When the wetting-drying curing was applied, it was observed that the SiAOAAl bonds were higher in the FT-IR results. This showed a higher rate of geopolymerization and increased strength values. Similar behaviors were observed according to TGA-DTA results, and weight loss with temperature was found to be lower in samples applied to wetting-drying curing. Also, there was a positive effect on the strength results with the increase in basalt and polyvinyl alcohol fibers ratio. The main reason for this situation is the formation of a resistant layer with the effect of basalt and polyvinyl alcohol fibers. The compact structure of the geopolymeric matrix brings along a good degree of adhesion. This allows geopolymer samples to resist freezing-thawing. In geopolymer samples, despite the 90 cycles, the residual strength were high and the decrease in the ultrasonic pulse velocity rate results were limited.Öğe Mechanical and durability properties of steel, polypropylene and polyamide fiber reinforced slag-based alkali-activated concrete(TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2023) Kuranlı, Ömer Faruk; Uysal, Mücteba; Abbas, Mele Tidjani; Çoşgun, Turgay; Niş, Anıl; Aygörmez, Yurdakul; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Alkali-activated composites are significant materials in reducing CO2 emissions and ensuring sustainability. With the increasing concerns about climate change globally, the interest in alkali-activated materials has also increased. Researching different fibers has very important potential in this area. This study aims to make alkali-activated concretes widespread in the concrete sector by using the materials common in conventional concretes and ensuring that alkali-activated concretes are an alternative in terms of sustainability. Experimental studies were conducted to examine the mechanical, durability, and microstructural properties (SEM) of slag-based alkaliactivated concrete (AASC) reinforced with three various fibers. The fibers, polypropylene (PP), polyamide (PA), and steel (ST), were used with two ratios (%0.4 and %0.8 by vol.). Compressive, splitting tensile, and flexural strength tests were carried out at 28 and 90 days. In terms of durability properties, the samples were exposed to high temperatures (300–600–900 C) and freeze-thaw test (250 cycles). The results showed that the addition of fibers improved the strength and durability properties; for instance, the existence of steel and polypropylene fibers increased the flexural toughness factor values by 430% and 260%, respectively. Moreover, the compressive strength of the fibrous samples exposed to 900 C was obtained in the range of 6-23 MPa.Öğe Mechanical Performance Enhancement of AlkaliActivated Composites Using Synthetic Fibers with Metazeolite and Aluminum Sludge-Based Recycled Concrete Aggregates(İstanbul Gelişim Üniversitesi Yayınları / Istanbul Gelisim University Press, 2024) Aygün, Beyza Fahriye; Uysal, Mücteba; Çingi, RamazanThis study examines the substantial enhancement in the performance of alkali-activated composites (AACs) produced from a distinctive combination of metazeolite (MZ) and slag (S), reinforced with synthetic fibers, and augmented with aluminum sludge (AS) and recycled concrete aggregate (RCA). The composites were subjected to activation through the use of a specific sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) blend in a 2:1 ratio, with an activator-to-binder ratio of 0.95. Through a process of experimentation, the research team identified an optimal mix by varying the molarities of sodium hydroxide (NaOH) between 8M and 14M and the ratios of metazeolite to slag between 25% and 100%. The aforementioned mixture, comprising 50% MZ and 50% S, was activated with 12M NaOH and enhanced with 30% aluminum sludge, exhibiting remarkable strength characteristics. Furthermore, the incorporation of synthetic fibres, including polyethylene (PEF), polyamide (PAF), and basalt fibers (BF), resulted in a notable enhancement of the material's performance. It is noteworthy that the addition of basalt fibers at a concentration of 0.5% resulted in a 7% increase in compressive strength and a 24% improvement in flexural strength. This pioneering research illuminates the transformative potential of MZ-S-based AACs, particularly when combined with AS and BF, paving the way for the development of sustainable construction materials that meet contemporary performance and environmental standards.
