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Öğe Assessment of geopolymer composites durability at one year age(ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2020) Aygörmez, Yurdakul; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Geopolymers are important alternative materials for use in support of recycling and sustainability, and one of the most important properties is durability. While many studies perform durability tests 28 days after production, we carried out durability tests on a mixture of geopolymers starting 365 days after production. In this case, other conditions that occur until durability conditions are applied are taken into consideration. The geopolymer mixture consisted of metakaolin (90% by wt.) and boron waste colemanite (10% by wt.). The study investigated heat and wet-dry curing methods and polyolefin and polyamide fibre ratios (0.5, 1.0, and 1.5% by vol.) on durability. Durability issues related to concrete, such as long-term exposure to hydrochloric acid, freeze-thaw cycles, and abrasion were recorded. Results show that polyamide fibres provide better results than polyolefin fibres, the optimum polyamide fibre ratio was 1%, and the wet-dry curing method increased geopolymerisation more than heat curing. The Si-O-Al bonds were found to be stronger after wet-dry curing. All durability studies showed that the compact structure of the geopolymers withstood the durability tests performed one year after production. Scanning electron microscopy (SEM) analysis supports these results.Öğe Assessment of strength and abrasion resistance of elasto-plastic fiber reinforced concrete using geopolymer based recycled aggregates(Yıldız Teknik Üniversitesi, 2021) Mohamed, Abdelaziz; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Recycled aggregates and geopolymer binders are green materials contributing to the sustainability of the planet. We investigated the performance of geopolymer concrete using recycled aggregates (fly ash (FA) and ground granulated blast furnace slag (GGBS)) related to their mechanical properties. Geopolymer concrete were prepared by mixing 50% low calcium fly ash, 50% GGBS, sodium hydroxide and sodium silicate solution, Coarse aggregate (Natural coarse aggregate, Recycled coarse aggregate), Fine aggregate (Crushed Sand, Riverbed Sand) and elastoplastic fibers. Recycled aggregate used was obtained locally from Istanbul, Turkey. To explore the efficiency of recycled aggregate, during the production of geopolymer concrete, partial replacement of recycled coarse aggregate with natural aggregate was made in 10, 20, 30, and 40%. To compare the results, geopolymer concrete containing 100% natural aggregates was made. Since concrete gains strength with time after casting, On Day-28 and Day-90, the compressive strength, split tensile strength, and flexural strength of those geopolymer based concrete were examined. Results of the test showed that the compressive strength of 28 and 90 days w.r.t. different ratios was 26.8, 25.3, 24.2, 23.1, 23 MPa, and 30.2, 28.1, 27.0, 25.2, 25.0, 23.0 Mpa respectively, while split tensile strength was 1.9, 1.5, 1.5, 1.4, 1.4 MPa and 2.0, 1.9, 1.9, 1.6, 1.5 MPa respectively, and the ultimate flexural strength of tested beams were in the range of 3.53 to 4.54MPa. Although the general performance of the produced samples was showing a decrement with the increasing ratio of recycle aggregates, the obtained results indicated that using recycled aggregate is up to some extent of 30% is beneficial in terms of strength.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 Effect of various NaOH molarities and various filling materials on the behavior of fly ash based geopolymer composites(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2020) Al-Mashhadani, Mukhallad M.; Canpolat, OrhanAmong the recent research interests in the construction section, Geopolymers, represent a rising trend due to their significant performance in terms of strength and long term properties. In this research, an attempt was conducted to examine the effect of using different filling materials and the effect of different NaOH concentrations on the properties of the resulted composites. Strength properties, physical properties, abrasion resistance, and freezing-thawing behavior were tested along with a microstructural characterization that included scanning electron microscopy (SEM) and X-ray diffraction (XRD). In general, the effect of including crushed limestone and waste foundry sand was beneficial in terms of the general properties of the fabricated specimens. Also, the microstructural analyses showed a compact matrix that could be considered in line with the obtained results from the other tests.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 Evaluation of the 12–24 mm basalt fibers and boron waste on reinforced metakaolin-based geopolymer(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2020) Ali, Nawar; Canpolat, Orhan; Aygörmez, Yurdakul; Al-Mashhadani, Mukhallad M.Concerning sustainability and recycling considerations, geopolymers have recently raised as one of the most active alternatives to the current cement-based composites, in addition to that, the existence of fibers in any binding matrix yields a significant improvement in the behavior of the matrix. On the other hand, using waste materials in the binding matrices fulfills one of the main aims of sustainability, namely reusing wastes. In this concern, the previous research attempts focused on the effect of using fibers and wastes separately and hence using them together in one matrix is not clearly highlighted. The main objective of this study was to examine the engineering properties of metakaolin-based geopolymer mortars in the case of colemanite substitution up to 30% and basalt fiber of different lengths. In the 10 series produced, firstly 7th day and 28th day compressive and flexural strengths, UPV, abrasion resistance test, porosity, unit weight, and water absorption results were examined. As the durability tests, 90 cycles of freezing-thawing between 20 and +20 C, high-temperature tests of 250, 500 and 750 C were applied. Also, geopolymer samples were exposed to 10% Hydrosulfuric Acid (H2SO4) for 3 months. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermogravimetric/Differential Thermal Analysis (TGA-DTA) analyses were performed at the end of the durability tests. The results showed that in the case of 10% colemanite substitution, it increased the compressive strength results and lowered it at higher rates. With a colemanite substitution of 10%, the compressive strength results of 28 days increased by 1.71%, and in the case of 20% and 30% colemanite substitution, there was a decrease in the compressive strength of 13.64% and 26.99%, respectively. The compressive strength results showed that 24 mm long basalt fiber reinforced samples had better results than 12 mm long basalt fiber reinforced samples. It was seen that geopolymer specimens maintain stability in freezing-thawing, elevated temperatures, and sulfuric acid effects.Öğe Fly ash based geopolymer composites partially replaced with silica fume: An experimental investigation(International Committee of the SCMT conferences, 2019) Al-Mashhadani, Mukhallad M.; Canpolat, Orhan; Aygörmez, Yurdakul; Uysal, Mucteba; Sahin, FurkanNowadays, the environmental impact which is caused by the industrial development specially in construction section have led to an increasing interest in geopolymer field and thereby have promoted the research in terms of full replacement of Portland cement binder and feasible utilization of waste materials. In this paper, an attempt was done to fabricate a binding matrix that is totally cement free and based on eco-friendly materials. The effect of adding silica fume on strength properties, physical properties and resistance to abrasion were studied. In general, silica fume was found to enhance the investigated properties due to the fineness of silica fume particles which generally formed geopolymeric composites with more compact matrix. The geopolymeric matrix which is fabricated with the presence of silica fume has shown an obvious improvement in terms of physical properties. Moreover, the compactness of the matrix led to a good performance regarding the abrasion resistance, to be more specific, the abraded surface was more resistant to weight loss after adding silica fume. In addition to that, an acceptable degree of correlation was obtained when the results of the studied properties were linked, results from strength tests and the ones from non-destructive tests were having a good degree of correlation. © 2019 International Committee of the SCMT conferences. All rights reserved.Öğe High-temperature effects on white cement-based slurry infiltrated fiber concrete with metakaolin and fly ash additive(PONTIFICIA UNIV CATOLICA CHILE, ESCUELA CONSTRUCCION CIVIL, AV VICUNA MACKENNA 4860, SANTIAGO 0000, CHILE, 2020) Aygörmez, Yurdakul; Al-Mashhadani, Mukhallad M.; Canpolat, OrhanIn this study, the high flexural parameter properties of Slurry Infiltrated Fiber Concrete (SIFCON) were examined, as was the use of metakaolin and fly ash with PC CEM I 52.5 R (White Cement). 5 series were prepared and metakaolin and fly ash replaced PC CEM I 52.5 R at 25% and 50%. In this study, while researching White Cement in the production of SIFCON samples, metakaolin which is easy to obtain in kaolin-rich soils, and fly ash, which is a waste material, were also evaluated to reduce CO2 emission in cement production. 5% of steel fiber was used in all series and the results of 7 and 28 days flexural and compressive strengths and ultrasonic pulse velocity (UPV) were examined. Given the 28-day test period, a strength increase was observed in metakaolin-added samples, while lower results were obtained in fly ash-added samples since fly ash was not yet completely hydrated. After the 200, 400, and 600 °C high-temperature tests, the results of flexural and compressive strengths, UPV, and weight loss were examined. The increase in strength after 300°C can be caused by drying shrinkage of the matrix, whose C-S-H structure is not yet intact, and compression of the fiber wall. The conversion from Ca(OH)2 to CaO begins at about 400°C, and the C-S-H structure is quickly destroyed as it approaches 600°C. SIFCON samples have the highest mechanical and durability properties by replacing the metakaolin with White Cement by 25%. The lowest results were obtained by replacing the fly ash with White Cement by 50%.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 Investigation of mechanical and durability properties of brick powder-added White Cement composites with three different fibers(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2022) Alcharchafche, Mahmood Anwar Shaker; Al-Mashhadani, Mukhallad M.; Aygörmez, YurdakulTraditional Portland Cement is used extensively in the construction industry today. Portland Cement has a gray color and has been explored with numerous substitutes. With the increasing interest in concrete technology, the interest in composite materials with higher performance and strength has gained more importance. White Cement (WC) is an important cement type in this field. However, studies of substitute materials for White Cement are limited and more research is needed. In this study, while White Cement and clay brick powder (CBP) were substituted at three different rates (5%, 10%, and 15%), three different fibers (copper-coated (CC) steel fiber, crimped (C) steel fiber, and basalt (B) fiber) were used at the ratio of 0.4% to examine the effect of fibers at the same time. The compressive and flexural strengths of the prepared series were investigated for 28 and 90 days. Three different durability tests were applied after 90 days: elevated-temperature test (250, 500, and 750 ?C), freezing-thawing test (90 cycles), and sulfate effect (90 days). Following the durability tests, weight and strength values were compared. In addition, SEM and XRD analyzes were made while making comparisons before and after the durability test of the samples and a visual examination was made in the durability conditions. The use of 5% brick powder increased the strength values due to the formation of C-A-S-H and C-S-H gels due to its higher Al2O3 and SiO2 content, while the use of higher brick powder caused a decrease in strength. While the fibers contributed positively to the strength values, the highest increase was in the longer crimped steel fiber added sample and the lowest increase was in the shorter copper-coated steel fiber added sample. While there was a 13% increase in compressive strength in the crimped steel fiber and 5% brick dust added sample compared to the control sample, there was a 21% increase in flexural strength. As a result of the durability tests, the samples behaved in similar order and maintained their stability despite significant losses.Öğe Mechanical and durability of geopolymer concrete containing fibers and recycled aggregate(Techno-Press, 2022) Mohamed, Abdelaziz Yousuf; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Recently, the interminable ozone depletion and the global warming concerns has led to construction industries to seek for construction materials which are eco-friendly. Regarding this, Geopolymer Concrete (GPC) is getting great interest from researchers and scientists, since it can operate by-product waste to replace cement which can lead to the reduction of greenhouse gas emission through its production. Also, compared to ordinary concrete, geopolymer concrete belongs improved mechanical and durability properties. In spite of its positive properties, the practical use of geopolymer concrete is currently limited. This is primarily owing to the scarce structural, design and application knowledge. This study investigates the Mechanical and Durability of Geopolymer Concrete Containing Fibers and Recycled Aggregate. Mixtures of elastoplastic fiber reinforced geopolymer concrete with partial replacement of recycled coarse aggregate in different proportions of 10, 20, 30, and 40% with natural aggregate were fabricated. On the other hand, geopolymer concrete of 100% natural aggregate was prepared as a control specimen. To consider both strength and durability properties and to evaluate the combined effect of recycled coarse aggregate and elastoplastic fiber, an elastoplastic fiber with the ratio of 0.4% and 0.8% were incorporated. The highest compressive strength achieved was 35 MPa when the incorporation of recycled aggregates was 10% with the inclusion of 0.4% elastoplastic fiber. From the result, it was noticed that incorporation of 10% recycled aggregate with 0.8% of the elastoplastic fiber is the perfect combination that can give a GPC having enhanced tensile strength. When specimens exposed to freezing-thawing condition, the physical appearance, compressive strength, weight loss, and ultrasonic pulse velocity of the samples was investigated. In general, all specimens tested performed resistance to freezing thawing. the obtained results indicated that combination of recycled aggregate and elastoplastic fiber up to some extent could be achieved a geopolymer concrete that can replace conventional concrete.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 of fly ash-GGBS elasto-plastic fiber reinforced geopolymer concrete containing recycled aggregates(American Institute of Physics Inc., 2023) Mohamed, Abdelaziz; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Recycled aggregates and Geopolymer binders are green materials that can contribute to the sustainability of the planet. This study investigated the Performance of recycled Aggregates on mechanical properties of Fly Ash and GGBS Based Geopolymer Concrete. Specimens of Geopolymer concrete were made by mixing low calcium fly ash, GGBS, sodium hydroxide and sodium silicate solution, coarse recycled aggregates, fine aggregates, natural aggregates and fibers. Recycled aggregate used was obtained locally in Istanbul Turkey. Through the mixes of geopolymer concrete the recycled aggregate was partially replaced of natural aggregate in different proportions at 10, 20, 30 and 40% respectively, also geopolymer concrete of 100% natural aggregate was used as a control specimen. compressive strength split tensile strength, and flexural strength of this geopolymers were examined at 28 and 90 days. Results of the test showed that the compressive strength of 28 and 90 days was in the range of 28.9-30.2 MPa while split tensile strength was between 1.9-2.0 MPa and the ultimate flexural strength of tested beams were in the range of 3.53 -4.54 MPa. Although the general performance of the produced samples was showing a decrement with the increasing ratio of recycle aggregates, the obtained results indicated that using recycled aggregate is up to some extent is beneficial in terms of sustainability. © 2023 AIP Publishing LLC.Öğe Strength and abrasion performance of recycled aggregate based geopolymer concrete(Yıldız Teknik Üniversitesi, 2022) Lakew, Asfaw Mekonnen; Al-Mashhadani, Mukhallad M.; Canpolat, OrhanThis experimental work evaluated geopolymer concrete containing fly ash and slag by partial replacement of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) to manufacture environmental-friendly concrete. The proportion of recycled aggregates considered consists of 10%, 20%, 30%, and 40% of the total coarse aggregate amount. Also, a steel fiber ratio of 0.3% was utilized. The mechanical properties and abrasion resistance of fly ash/slag-based geopolymer concrete were then assessed. Majorly, the mechanical strength of the concrete samples decreased by the increase of RCA content. The geopolymer concrete with 40% RCA gave 28.3% lesser compressive strength and 24% lower splitting tensile strength than NCA concrete at one year. Also, the flexural strength of concrete specimens was reduced by 35% (from 5.34MPa to 3.5MPa) with the incorporation of 40% RCA. The incorporation of 30% RCA caused 23% and 22.6% reduction in compressive strength at 56 days and one year, respectively. The flexural and splitting tensile strength of the specimens was not significantly reduced (less than 10%) with the inclusion of a recycled coarse aggregate ratio of up to 30%. Furthermore, the abrasion wear thickness of every concrete sample was less than 1 mm. RCA inclusion of 20% produced either insignificant reduction or better strength results compared to reference mixtures. As a result, it was considered that the combination of 0.3% steel fiber and 20% recycled coarse aggregate in fly ash/slag-based geopolymer concrete leads to an ecofriendly concrete mix with acceptable short and long-term engineering properties that would lead to sustainability in concrete production and utilization sector.Öğe A survey on one year strength performance of reinforced geopolymer composites(ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND, 2020) Aygörmez, Yurdakul; Canpolat, Orhan; Al-Mashhadani, Mukhallad M.Heat curing is a widely used method in geopolymer mortar production. While the heat curing shows an increase in strength values, the effect of this situation in the long term has not been examined sufficiently. In this study, the short-term and long-term effects of the curing conditions were examined together and a geopolymer sample with 90% metakaolin and 10% colemanite waste (by weight) was used. Also, polyolefin and polyamide fibers were used as 0.5%, 1.0%, and 1.5%, by volume. A wetting-drying method was applied for curing with heat curing. The Si-O-Al bonds were established to be stronger with wetting-drying curing. 14, 56, 90, and 365 days' flexural and compressive strengths results were determined. Also, the high-temperature test was applied after 365 days. SEM, TGA-DTA, and FTIR analyses were carried out pre and post the high-temperature test. When a comparison was done between the 14-day and the 90-day results, the 90-day results showed a reduction of strength according to 14-days. At the end of 365 days, these reductions fell and results were obtained close to 90 days of strength. The use of high-temperatures for curing was thought to contribute to the development of early-age strength by supporting the dissolution of solid binding materials and the formation of reaction products. On the other hand, due to the adverse effects on the quality and microstructure of the rapidly developing reaction products, strength decreases have been observed. Despite all these effects, the structure of the geopolymer has been preserved.Öğe Using different types of aggregates including waste concrete in the production of geopolymer mortars(International Committee of the SCMT conferences, 2019) Canpolat, Orhan; Şahin, Furkan; Uysal, Mucteba; Al-Mashhadani, Mukhallad M.; Aygörmez, YurdakulIn developed and developing countries, the need for industrial and residential buildings is constantly increasing. The old buildings are either demolished or replaced by new buildings in order to maintain environmental awareness and due to limited usage areas. In this construction process, traditional Portland cement is used and also a serious solid waste problem arises due to the demolished buildings. Because of using Portland cement, a significant amount of greenhouse gas production is generated, as well as high levels of environmental pollution due to the accumulation of concrete solid wastes. New laws have been enacted in many countries to reduce greenhouse gas emissions due to Portland cement and for solid waste management, and even the establishment of recycling facilities for waste concrete has been encouraged. The reduction of greenhouse gas emissions and recycling of construction wastes have gained great importance both because of the protection of the natural environment and its contribution to the economy.In this study, more environmentally friendly geopolymer additives were used instead of traditional Portland cement for the recycling of construction waste, as well as geopolymer mortars were produced with different types of aggregates. The 0.4% basalt fiber additive series of the obtained samples were similarly produced. The geopolymer samples produced by using different aggregate types including the waste concrete aggregate were compared in terms of 28 days compressive strengths, ultrasound velocities, unit weight, voids ratio and water absorption results. © 2019 International Committee of the SCMT conferences. All rights reserved.
