Browsing by Author "Bayraktar, O.Y."

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A study on sustainable foam concrete with waste polyester and ceramic powder: Properties and durability
(Elsevier Ltd, 2024) Bayraktar, O.Y.; Tunçtan, M.; Benli, A.; Türkel, İ.; Kızılay, G.; Kaplan, G.
The textile and apparel sectors currently produce millions of tons of textile waste annually on a global scale. Textile waste fibers are a viable option for sustainability as they can be utilized to reinforce cement-based composites internally by improving ductility and reducing the development of cracks. The issue of ceramic waste accumulation can be effectively resolved by using ceramic waste as supplementary cementitious materials (SCM), for sustainable construction, which also lowers energy use and CO2 emissions during the cement manufacturing process. This study evaluated the fresh, physico-mechanical, durability, and thermal characteristics of foam concrete (FC) reinforced with waste polyester (WP) incorporating waste ceramic powder (CP) as a replacement of cement in the rates of 0, 10 and 20 %. Twelve mixtures with a 0.3 water/binder (w/b) ratio were fabricated using a sodium lauryl sulfate foaming agent. The WP used in this study have four percentages of 0, 0.2, 0.4 and 0.6 % by volume. Durability performance of the mixtures for dry shrinkage, sulfate attack, high temperatures, alkali silica reaction and freeze-thaw cycles was also carried out. Microstructure of the mixtures was analyzed by SEM. Cost investigation and environmental impact of FC mixtures were also investigated. The findings indicated that the mixture with 10 % CP and 0.6 % WP had the largest 28-day compressive strength of 8.78 MPa, representing a 47 % decrease over the reference mixture (without CP and WP). The same mixture also exhibited the lowest dry shrinkage after the reference mixture. The mixture containing 0%CP and 0.2WP had the lowest thermal conductivity with a reduction of 74.0 % as per the reference mixture. The 0.4 % WP and 0%CP incorporated mixture exhibited the best thermal and F-T performance.
A study on sustainable foam concrete with waste polyester and ceramic powder: Properties and durability
(2024.01.01) Bayraktar, O.Y.; Tunçtan, M.; Benli, A.; Türkel, I.; Kizilay, G.; Kaplan, G.
The textile and apparel sectors currently produce millions of tons of textile waste annually on a global scale. Textile waste fibers are a viable option for sustainability as they can be utilized to reinforce cement-based composites internally by improving ductility and reducing the development of cracks. The issue of ceramic waste accumulation can be effectively resolved by using ceramic waste as supplementary cementitious materials (SCM), for sustainable construction, which also lowers energy use and CO2 emissions during the cement manufacturing process. This study evaluated the fresh, physico-mechanical, durability, and thermal characteristics of foam concrete (FC) reinforced with waste polyester (WP) incorporating waste ceramic powder (CP) as a replacement of cement in the rates of 0, 10 and 20%. Twelve mixtures with a 0.3 water/binder (w/b) ratio were fabricated using a sodium lauryl sulfate foaming agent. The WP used in this study have four percentages of 0, 0.2, 0.4 and 0.6 % by volume. Durability performance of the mixtures for dry shrinkage, sulfate attack, high temperatures, alkali silica reaction and freeze-thaw cycles was also carried out. Microstructure of the mixtures was analyzed by SEM. Cost investigation and environmental impact of FC mixtures were also investigated. The findings indicated that the mixture with 10% CP and 0.6% WP had the largest 28-day compressive strength of 8.78 MPa, representing a 47 % decrease over the reference mixture (without CP and WP). The same mixture also exhibited the lowest dry shrinkage after the reference mixture. The mixture containing 0%CP and 0.2WP had the lowest thermal conductivity with a reduction of 74.0 % as per the reference mixture. The 0.4 % WP and 0%CP incorporated mixture exhibited the best thermal and F-T performance.
Do Picea pungens engelm. organs be a suitable biomonitor of urban atmosphere pollution?
(2023.01.01) Ateya, T.A.A.; Bayraktar, O.Y.; Koc, I.
Background: Heavy metal contamination in the air has been gaining importance from scientists due to increasing industrial activities, population growth, and density in urban areas causing many crucial environmental pollution problems. Heavy metals do not quickly disappear and do not decay in nature; they accumulate in plant organs and indirectly affect human and environmental health. On the other hand, some elements are essential for plant growth, but some have poisonous or carcinogenic consequences, even at small concentrations. Thus, determining and observing heavy metal concentrations in the atmosphere is crucial., Plants are the utmost important indicator of heavy metal concentration changes in the air and are called biomonitors. The current study aims to determine the variation in some elements (K, P, Fe, Zn, Cu, Cd, and Cr) concentration in Picea pungens Engelm. (valued for its bluish or silvery-gray foliage) grown in the Ankara city center (capital of Turkiye and second crowded city), based on the plant needles and the age of the branch. Thus, this study tried to determine the potential of using needle leaves and branches of P. pungens as a biomonitor to determine some heavy metal concentrations. Results: The heavy metal concentrations significantly differed by organ and organ age. The element levels were higher in the branches in some years and the needles in some years. Conclusions: This result indicates that Picea pungens needles and branches are suitable for observing studied heavy metal concentrations. Using branches and needles does not also harm the plant species.
Durability of green rubberized 3D printed lightweight cement composites reinforced with micro attapulgite and micro steel fibers: Printability and environmental perspective
(2024.01.01) Bodur, B.; Isik, M.A.M.; Benli, A.; Bayrak, B.; Öz, A.; Bayraktar, O.Y.; Kaplan, G.; Aydin, A.C.
The increasing amount of tires manufactured annually worldwide has made waste tire management a major environmental concern. The goal of this work is to investigate the potential applications of waste tire aggregates (WTA) in a novel class of affordable, recycled composite materials. This study assesses the material behavior of rubberized 3D printed lightweight cement composites (3DLC) reinforced with raw micro attapulgite (ATP) and micro steel fibers (MSF) using WTA as a 100 % replacement for fine aggregate manufactured through 3D printing. The paper takes advantage of 3D concrete printing's advantages and addresses the environmental issues associated with waste tires. The extrudability and buildability properties of 3DLC are determined in the fresh state. Physical and thermal properties of 3DLC were determined. Mechanical properties of 3DLC including compressive, flexural, shear strength and flexural toughness were assessed. 3D printed samples were exposed to high temperature and sulfate (MgSO4), and their durability properties were determined. The microstructures of the mixes was analyzed. The CO2 emissions and costs of the blends were also assessed. The outcomes revealed that, the 3DLC mixture with 10 % ATP and 2 % MSF showed the greatest compressive strength performance, with increases of 17.82 and 29.51 % at 28 and 90 days, respectively relative to the mixture without ATP. Regardless of MSF level, at 28 and 90 days, all mixes with 10%ATP content showed the largest flexural strengths. The 3DLC mixture with 10 % ATP and 2 % MSF had the highest measured thermal conductivity. The blends with 20 % ATP and 0 % MSF showed the lowest thermal conductivity. The mixture containing 10 % ATP and 2 % MSF demonstrated the greatest high temperature performance, demonstrating strength enhancement of 21.85, 6.72 and 3.36 % at 200,400 and 600 degrees C respectively. Replacing cement with 10 and 20%ATP greatly increased the sulfate resistance of 3DLC mixtures and the mixture with 20%ATP and 2%MSF exhibited the best sulfate performance. The lowest CO2 emission and cost were determined for the mixture containing 20%ATP and 0%MSF (A20S0).
Durability of green rubberized 3D printed lightweight cement composites reinforced with micro attapulgite and micro steel fibers: Printability and environmental perspective
(Elsevier Ltd, 2024) Bodur, B.; Mecit Işık, M.A.; Benli, A.; Bayrak, B.; Öz, A.; Bayraktar, O.Y.; Kaplan, G.; Aydın, A.C.
The increasing amount of tires manufactured annually worldwide has made waste tire management a major environmental concern. The goal of this work is to investigate the potential applications of waste tire aggregates (WTA) in a novel class of affordable, recycled composite materials. This study assesses the material behavior of rubberized 3D printed lightweight cement composites (3DLC) reinforced with raw micro attapulgite (ATP) and micro steel fibers (MSF) using WTA as a 100 % replacement for fine aggregate manufactured through 3D printing. The paper takes advantage of 3D concrete printing's advantages and addresses the environmental issues associated with waste tires. The extrudability and buildability properties of 3DLC are determined in the fresh state. Physical and thermal properties of 3DLC were determined. Mechanical properties of 3DLC including compressive, flexural, shear strength and flexural toughness were assessed. 3D printed samples were exposed to high temperature and sulfate (MgSO4), and their durability properties were determined. The microstructures of the mixes was analyzed. The CO2 emissions and costs of the blends were also assessed. The outcomes revealed that, the 3DLC mixture with 10 % ATP and 2 % MSF showed the greatest compressive strength performance, with increases of 17.82 and 29.51 % at 28 and 90 days, respectively relative to the mixture without ATP. Regardless of MSF level, at 28 and 90 days, all mixes with 10%ATP content showed the largest flexural strengths. The 3DLC mixture with 10 % ATP and 2 % MSF had the highest measured thermal conductivity. The blends with 20 % ATP and 0 % MSF showed the lowest thermal conductivity. The mixture containing 10 % ATP and 2 % MSF demonstrated the greatest high temperature performance, demonstrating strength enhancement of 21.85, 6.72 and 3.36 % at 200,400 and 600°C respectively. Replacing cement with 10 and 20%ATP greatly increased the sulfate resistance of 3DLC mixtures and the mixture with 20%ATP and 2%MSF exhibited the best sulfate performance. The lowest CO2 emission and cost were determined for the mixture containing 20%ATP and 0%MSF (A20S0).
Enhancing foam concrete: A comparative analysis of PLA+ fiber reinforcements with plain, hooked, and corrugated fibers
(Elsevier Ltd, 2024) Yildizel, S.A.; Acik, M.; Kaplan, G.; Bayraktar, O.Y.
This study examined the enhancement of foam concrete by using hooked, plain, and corrugated PLA+ fibers that were made with a 3D printer. The PLA+ fibers were added into the foam concrete mixtures at volumetric ratios of 0.5 %, 1 %, and 1.5 %. The main objective was to evaluate the mechanical and durability characteristics of the composites, such as compressive and flexural strengths, thermal conductivity, water absorption, and freeze-thaw resistance. In addition, the microstructural interactions between the fibers and the concrete matrix were examined using scanning electron microscopy (SEM). The inclusion of hooked fibers greatly improved the flexural strength, resulting in a notable 48.57 % improvement when the fiber usage rate was set at 1 %. Although the samples with stronger fiber reinforcement showed higher water absorption, all recorded values were below the acceptable threshold of 30 % for practical engineering purposes. In addition, the thermal conductivity of the samples dropped when PLA+ fibers were included, reaching its minimum value at a concentration of 1.5 %. After subjecting the samples to 15 and 30 freeze-thaw cycles, it was observed that all samples reinforced with fiber showed good frost resistance, with a mass loss of less than 5 %. The SEM analysis revealed that the fiber-reinforced samples exhibited a denser microstructure compared to the reference mix, resulting in enhanced pore structures. And the thermal conductivity of the samples declined as the amount of PLA+ fiber increased. The fiber-reinforced materials exhibited good frost resistance, determined by a mass reduction of less than 5 % after 15 and 30 freeze-thaw cycles.
Feasibility of foam concrete using recycled brick and roof tile fine aggregates
(2024.01.01) Bayraktar, O.Y.; Ahiskali, A.; Ahiskali, M.; Eksioglu, F.; Kaplan, G.; Assaad, J.
Brick (BR) and roof tile (RT) fine aggregate fractions derived from construction and demolition wastes have a low recycling rate in new construction and building materials. This article assesses their suitability for replacing the limestone aggregate in foam concrete, which helps valorise such fractions and conserve natural limestone resources. Two concrete categories containing or not silica fume (SF) were investigated, while the BR and RT aggregate replacement rates were 10%, 20% and 40%. Tested properties include flow, density, water absorption, porosity, thermal conductivity, mechanical strengths, microscopy, drying shrinkage, resistance to freeze/thaw cycles and elevated temperature. Results showed that the concrete mechanical properties improved when the limestone aggregate was replaced by 10% BR or RT but gradually curtailed at higher addition rates. Such results concorded with the density, water absorption and porosity measurements. Foamed concrete containing BR is more resistant (compared to RT) to drying shrinkage, freeze/thaw cycle, and heat exposure, which was ascribed to the relatively lower BR porosity that improves the concrete mechanical properties and durability.
Impact of rice husk ash on physico-mechanical, durability and microstructural features of rubberized lightweight geopolymer composite
(2024.01.01) Zeyad, A.M.; Bayraktar, O.Y.; Tayeh, B.A.; Öz, A.; Özkan, I.G.M.; Kaplan, G.
This study investigates the effects of incorporating rice husk ash (RHA) on the characteristics of lightweight geopolymer concrete (LWGC), which includes waste tire aggregate (WTA). This study utilized RHA to replace 15 % of ground blast furnace slag (GBFS) in LWGC. The LWGC also included WTA as a partial substitute for pumice aggregate, with varying rates of 10 %, 25 %, and 50 % by volume. In addition, curing temperatures of 75 degrees C and 100 degrees C were utilized for 3 h following the casting process. 16 LWGC blends were created, each with a dry density below 1800 kg/m 3 . To study the features of hardened LWGC, various tests included apparent porosity, water absorption, capillary water absorption, dry density, compressive and flexural strength. In addition, freezing and thawing cycles (20, 40, and 60 cycles) and elevated temperatures of 250 and 500 degrees C affect compressive strength and density loss in addition to examining the thermal conductivity coefficient and morphological imaging by SEM on microscopic structure. The results showed that adding 15 % RHA as a partial replacement for GBSF led to a decrease in the density of hardened concrete to about 1561 kg/m 3 . At the same time, the compressive strength decreased to 24 and 21 MPa for the samples subjected to 75 and 100 degrees C heat treatments, respectively. Including 15 % RHA also reduced the thermal conductivity coefficient to 0.978 W/mK. Regarding the inclusion of WTA as a substitute for pumice aggregate, it led to a decrease in density and compressive strength as the replacement rate increased. In addition, the thermal conductivity coefficient decreases to its lowest level when WTA replaces 50 % of the pumice.
Impact of rice husk ash on physico-mechanical, durability and microstructural features of rubberized lightweight geopolymer composite
(Elsevier Ltd, 2024) Zeyad, A.M.; Bayraktar, O.Y.; Tayeh, B.A.; Öz, A.; Özkan, İ.G.M.; Kaplan, G.
This study investigates the effects of incorporating rice husk ash (RHA) on the characteristics of lightweight geopolymer concrete (LWGC), which includes waste tire aggregate (WTA). This study utilized RHA to replace 15 % of ground blast furnace slag (GBFS) in LWGC. The LWGC also included WTA as a partial substitute for pumice aggregate, with varying rates of 10 %, 25 %, and 50 % by volume. In addition, curing temperatures of 75 °C and 100 °C were utilized for 3 h following the casting process. 16 LWGC blends were created, each with a dry density below 1800 kg/m3. To study the features of hardened LWGC, various tests included apparent porosity, water absorption, capillary water absorption, dry density, compressive and flexural strength. In addition, freezing and thawing cycles (20, 40, and 60 cycles) and elevated temperatures of 250 and 500 °C affect compressive strength and density loss in addition to examining the thermal conductivity coefficient and morphological imaging by SEM on microscopic structure. The results showed that adding 15 % RHA as a partial replacement for GBSF led to a decrease in the density of hardened concrete to about 1561 kg/m3. At the same time, the compressive strength decreased to 24 and 21 MPa for the samples subjected to 75 and 100 °C heat treatments, respectively. Including 15 % RHA also reduced the thermal conductivity coefficient to 0.978 W/mK. Regarding the inclusion of WTA as a substitute for pumice aggregate, it led to a decrease in density and compressive strength as the replacement rate increased. In addition, the thermal conductivity coefficient decreases to its lowest level when WTA replaces 50 % of the pumice.
Investigation on the sustainable use of different sizes of sawdust aggregates in eco-friendly foam concretes: Physico-mechanical, thermal insulation and durability characteristics
(2024) Özkan, İ.G.M.; Aldemir, K.; Alhasan, O.; Benli, A.; Bayraktar, O.Y.; Yılmazoğlu, M.U.; Kaplan, G.
The extensive mining of natural resources, such as sand, for the construction industry, poses a hazard to the environment. To preserve the environment, the researcher must thus take into account the use of industrial byproducts rather than natural materials. The use of sawdust (SD) produced by the wood industry in foam concretes (FC) has been investigated in this study. This study examined the physical, mechanical, thermal, microstructural and durability characteristics of FC containing SD as a replacement of silica sand (SS) in the rates of 0, 25, 50 and 100 %. Two different SD sizes of 0–4 mm (SD4) and 0–1 mm (SD1) were used in the fabrication of FC mixtures. Protein-based foam agent was used to create FC mixtures. Fourteen mixtures with a 0.6 water/binder (w/b) ratio were produced at two different cement contents of 400 kg/m3 and 500 kg/m3. The fresh, mechanical, physical, and sorptivity characteristics of the FC mixtures were investigated in relation to the impacts of cement dosage, SD size, and SD replacement levels of SS. Durability of FC against high temperature, sulfate attack and freeze-thaw cycles was assessed. Costs and CO2 emissions from the blends were also assessed. The outcomes revealed that a 25 %SD1 integrated FC mixture with a cement content of 500 kg/m3 generated the highest 28-day compressive strength of 3.56 MPa with a 20 % strength loss as per the Ref.500 mixture. 17 % lower thermal conductivity was gained with the inclusion of 100 %SD4 as per the Ref.400 mixture. The mixture with 50 %SD4 and 400 kg/m3 cement dosage exhibited the best resistance to high temperature. The mixture with 25 %SD1 and 400 kg/m3 cement dosage showed the best frost resistance. SD incorporated mixtures showed better durability performance than the reference mixtures.
Mechanical and durability properties of polymer fiber reinforced one-part foam geopolymer concrete: A sustainable strategy for the recycling of waste steel slag aggregate and fly ash
(Elsevier Ltd, 2024) Ahıskalı, A.; Ahıskalı, M.; Bayraktar, O.Y.; Kaplan, G.; Assaad, J.
This paper assesses the feasibility of geopolymers (GPs) for use as lightweight foamed concrete, a crucial step towards reducing the carbon footprint and conserving natural resources. A powder activator (i.e., sodium metasilicate) less harmful to the environment was used to activate the fly ash-based GPs, while the limestone aggregates were gradually replaced by up to 100 % waste slag materials to conserve natural resources. Polypropylene fibers were incorporated at high dosage rates of 1 % or 2 %, by volume, to reduce the concrete density and improve its durability properties. Tested properties include flow, density, water absorption, porosity, thermal conductivity, mechanical strengths, drying shrinkage, and resistance to sulfate attack, freeze/thaw cycles, and elevated temperature. Results showed that the concrete mechanical properties improved when the limestone aggregate was replaced by slag materials, but the density and thermal conductivity were slightly curtailed at higher addition rates. The use of polypropylene fibers proved efficient to improve the resistance to freeze/thaw cycles, drying shrinkage, and expansion due to sulphate attack. Such data can help sustain the green building industry development by reducing the carbon footprint and conserving natural resources in foamed concrete applications.
Mechanical and durability properties of polymer fiber reinforced one-part foam geopolymer concrete: A sustainable strategy for the recycling of waste steel slag aggregate and fly ash
(2024.01.01) Ahiskali, A.; Ahiskali, M.; Bayraktar, O.Y.; Kaplan, G.; Assaad, J.
This paper assesses the feasibility of geopolymers (GPs) for use as lightweight foamed concrete, a crucial step towards reducing the carbon footprint and conserving natural resources. A powder activator (i.e., sodium metasilicate) less harmful to the environment was used to activate the fly ash-based GPs, while the limestone aggregates were gradually replaced by up to 100 % waste slag materials to conserve natural resources. Polypropylene fibers were incorporated at high dosage rates of 1 % or 2 %, by volume, to reduce the concrete density and improve its durability properties. Tested properties include flow, density, water absorption, porosity, thermal conductivity, mechanical strengths, drying shrinkage, and resistance to sulfate attack, freeze/thaw cycles, and elevated temperature. Results showed that the concrete mechanical properties improved when the limestone aggregate was replaced by slag materials, but the density and thermal conductivity were slightly curtailed at higher addition rates. The use of polypropylene fibers proved efficient to improve the resistance to freeze/thaw cycles, drying shrinkage, and expansion due to sulphate attack. Such data can help sustain the green building industry development by reducing the carbon footprint and conserving natural resources in foamed concrete applications.
Performance assessment and cost analysis of slag/metakaolin based rubberized semi-lightweight geopolymers with perlite aggregate: Sustainable reuse of waste tires
(Elsevier Ltd, 2024) Bayraktar, O.Y.; Benli, A.; Bodur, B.; Öz, A.; Kaplan, G.
Low-carbon binders or industrial waste can reduce or even eliminate the demand for Portland cement and other natural resources, which reduces environmental pollution in accordance with the principles of sustainable development. The assessment of the mechanical, durability and microstructural properties of slag/metakaolin based rubberized semi-lightweight geopolymer composites (LWGC) with perlite aggregate (PA) is the main objective of this study. Waste tires aggregates (WTA) was produced from discarded waste tires, another environmental pollutant, and used in LWGC mixtures as substitution for the fine perlite aggregate by 0%, 20%, 45%, and 60% replacement. Metakaolin (MK) and ground granulated blast furnace slag (GBFS) were used as precursors in the synthesis of LWGC. Sodium hydroxide and sodium silicate solution was used as activators. Eight mixtures were created; four of them had 100% GBFS, while the other four contained 90% GBFS slag and 10% MK. All eight mixtures were then cured for 5 h at 60 °C and 100 °C. The effects of curing temperature, WTA, and MK on the compressive, flexural strength, physical properties, and sorptivity of the LWGC were examined as well as flowability. The performance of the blends at high temperatures, freeze thaw cycles and sulfate attack was also evaluated. Microstructure analyses of the mixtures were also done using SEM. CO2 emissions and costs of the mixtures were also evaluated. The results showed that inclusion of WTA instead of PA and MK instead of GBFS decreased the flow diameter. Thermal conductivity and dry density of the mixtures also decreased considerably with the addition of WTA. The findings showed that 10%MK incorporated mixture with 60%WTA produced a compressive strength of 25.10 MPa at curing temperatures of 100 °C. The results indicated compressive strength of MK incorporated mixture with 60%WTA increased by 48.10% and 31.20% at heat curing of 60 °C and 100 °C, respectively. The mixture WT60MK0 cured at 100 °C exhibited the best high temperature resistance and the same mixture also presented the best F-T performance regardless of curing temperature. The mixture WT40MK0 cured at 60 °C and the mixture WT60MK10 cured at 100 °C performed the best sulfate resistance.
Performance assessment and cost analysis of slag/metakaolin based rubberized semi-lightweight geopolymers with perlite aggregate: Sustainable reuse of waste tires
(2024.01.01) Bayraktar, O.Y.; Benli, A.; Bodur, B.; Öz, A.; Kaplan, G.
Low-carbon binders or industrial waste can reduce or even eliminate the demand for Portland cement and other natural resources, which reduces environmental pollution in accordance with the principles of sustainable development. The assessment of the mechanical, durability and microstructural properties of slag/metakaolin based rubberized semi-lightweight geopolymer composites (LWGC) with perlite aggregate (PA) is the main objective of this study. Waste tires aggregates (WTA) was produced from discarded waste tires, another envi-ronmental pollutant, and used in LWGC mixtures as substitution for the fine perlite aggregate by 0%, 20%, 45%, and 60% replacement. Metakaolin (MK) and ground granulated blast furnace slag (GBFS) were used as pre-cursors in the synthesis of LWGC. Sodium hydroxide and sodium silicate solution was used as activators. Eight mixtures were created; four of them had 100% GBFS, while the other four contained 90% GBFS slag and 10% MK. All eight mixtures were then cured for 5 h at 60 degrees C and 100 degrees C. The effects of curing temperature, WTA, and MK on the compressive, flexural strength, physical properties, and sorptivity of the LWGC were examined as well as flowability. The performance of the blends at high temperatures, freeze thaw cycles and sulfate attack was also evaluated. Microstructure analyses of the mixtures were also done using SEM. CO2 emissions and costs of the mixtures were also evaluated. The results showed that inclusion of WTA instead of PA and MK instead of GBFS decreased the flow diameter. Thermal conductivity and dry density of the mixtures also decreased considerably with the addition of WTA. The findings showed that 10%MK incorporated mixture with 60%WTA produced a compressive strength of 25.10 MPa at curing temperatures of 100 degrees C. The results indicated compressive strength of MK incorporated mixture with 60%WTA increased by 48.10% and 31.20% at heat curing of 60 degrees C and 100 degrees C, respectively. The mixture WT60MK0 cured at 100 degrees C exhibited the best high temperature resistance and the same mixture also presented the best F-T performance regardless of curing temperature. The mixture WT40MK0 cured at 60 degrees C and the mixture WT60MK10 cured at 100 degrees C performed the best sulfate resistance.
Performance assessment of fiber-reinforced coral aggregate-based lightweight foam concrete for sustainable marine construction
(2024.01.01) Bayraktar, O.Y.; Danish, A.; Bodur, B.; Kaplan, G.; Aydin, A.C.; Ozbakkaloglu, T.
Based on the storage of raw materials and the high energy consumption associated with marine transportation, using coral aggregates to produce cementitious composites is the most promising candidate to counter these challenges. This research evaluates the suitability of coral aggregate and polypropylene fibers (PPF) to produce lightweight foam concrete. Quartz aggregate was replaced with coral aggregate in percentages of 25, 50, and 100 % along with 0-3 % incorporation of PPF. The performance assessment (through physical, mechanical, and durability tests) and economic and ecological analysis were conducted on the concrete mixtures. Based on the properties assessed, the optimal percentages of coral aggregate in specimens containing 0 %, 1.5 %, and 3 % PPF are 50 %, 50 %, and 100 %, respectively. This research may serve as a guide for future studies, focusing on coral aggregates as an effective alternative to conventional aggregates in cementitious composite production, with the goal of promoting their commercial applications for resource conservation.
Physical, mechanical and microstructural properties of one-part semi-lightweight geopolymers based on metakaolin modified with gypsum and lime
(Elsevier Ltd, 2024) Shi, J.; Bayraktar, O.Y.; Bayrak, B.; Bodur, B.; Oz, A.; Kaplan, G.; Aydin, A.C.
The elemental composition of precursors is crucial for the performance development of geopolymers. Metakaolin (MK) was used to produce one-part geopolymers (OPG), and the influence of calcium-based components (lime and gypsum) on their properties was investigated. The experimental results show that the use of lime instead of MK increases the fluidity of the mixture, while the addition of gypsum decreases the fluidity. Meanhwlie, the use of lime to replace a small amount of MK increases the concentration of activator by consuming water and the dissolution of calcium ions also participates in the geopolymerization reaction, which enhances the mechanical properties and durability of OPG. When 10 % lime is applied, the 7-d and 28-d compressive strengths of OPG are increased by 210 % and 157.14 % compared with the plain sample, respectively. The addition of gypsum generates AFt in OPG, which reduces the compactness of the microstructure, which is not conducive to the development of the strength and durability of OPG. When 10 % gypsum is applied, the 28-d compressive and flexural strengths of OPG are decreased by 32.14 % and 26.67 % compared with plain samples, respectively. As the lime content increases, further addition of gypsum to OPG has a more negative effect on OPG due to the plundering of calcium ions in the lime. The 28-d dry density of OPG is between 1585 and 1729 kg/m3, which makes it have a lower thermal conductivity (0.87–0.94 W/m·K).
Physical, mechanical and microstructural properties of one-part semi-lightweight geopolymers based on metakaolin modified with gypsum and lime
(2024.01.01) Shi, JY.; Bayraktar, O.Y.; Bayrak, B.; Bodur, B.; Oz, A.; Kaplan, G.; Aydin, A.C.
The elemental composition of precursors is crucial for the performance development of geopolymers. Metakaolin (MK) was used to produce one-part geopolymers (OPG), and the influence of calcium-based components (lime and gypsum) on their properties was investigated. The experimental results show that the use of lime instead of MK increases the fluidity of the mixture, while the addition of gypsum decreases the fluidity. Meanhwlie, the use of lime to replace a small amount of MK increases the concentration of activator by consuming water and the dissolution of calcium ions also participates in the geopolymerization reaction, which enhances the mechanical properties and durability of OPG. When 10 % lime is applied, the 7-d and 28-d compressive strengths of OPG are increased by 210 % and 157.14 % compared with the plain sample, respectively. The addition of gypsum generates AFt in OPG, which reduces the compactness of the microstructure, which is not conducive to the development of the strength and durability of OPG. When 10 % gypsum is applied, the 28-d compressive and flexural strengths of OPG are decreased by 32.14 % and 26.67 % compared with plain samples, respectively. As the lime content increases, further addition of gypsum to OPG has a more negative effect on OPG due to the plundering of calcium ions in the lime. The 28-d dry density of OPG is between 1585 and 1729 kg/m3, which makes it have a lower thermal conductivity (0.87-0.94 W/m & sdot;K).
Sustainable one-part alkali activated slag/fly ash Geo-SIFCOM containing recycled sands: Mechanical, flexural, durability and microstructural properties
(2023.01.01) Bayraktar, O.Y.; Bozkurt, T.H.; Benli, A.; Koksal, F.; Tuerkoglu, M.; Kaplan, G.
Slurry Infiltrated Fiber Concrete or Composite (SIFCOM) is a unique form of steel-fiber-reinforced cement composite that possesses exceptional toughness and superior mechanical properties like compressive, shear, tensile, and flexural strengths. New supplies of fine aggregate are required since the construction industry is experiencing natural sand shortage. By thoroughly evaluating workability, mechanical properties, flexural toughness, durability and microstructure, this study demonstrates the potential of various recycled sands from different sources in the manufacture of sustainable slag/fly ash one-part alkali activated SIFCOM (Geo-SIFCOM). Recycled concrete, brick and ceramic sands were used as a substitute of 10, 25 and 50% by volume of silica sand. Steel fiber ratios of 5%, 10%, and 15% were used and exposed to heat curing for 6, 24 and 48 h at 80 degrees C. Taguchi method was used to investigate the optimum mixture. The results showed that 24 h heat-cured mixture containing 25% recycled concrete sand and 15% fiber (C25F15) had the largest compressive strengths of 68.49 MPa, 74.53 MPa and 80 MPa at 7, 28, and 91 days, respectively. All 6 h - cured mixtures containing 100% slag exhibited the best resistance to freeze-thaw and the mixtures heat cured for 6 h demonstrated the best compressive strength resistance to elevated temperature and F-T cycles regardless of FA content. The largest flexural toughness was also assessed for the mixture with 50% brick sand and 15% fiber (B50F15) heat-cured for 6 h. The mixture with 50% FA and 50%slag (50% ceramic sand and 15% fiber) exhibited the best high temperature resistance.
Sustainable use of recycled fine aggregates in steel fiber-reinforced concrete: Fresh, flexural, mechanical and durability characteristics
(Elsevier Ltd, 2024) Benli, A.; Bayraktar, O.Y.; Koksal, F.; Kaplan, G.
Recycling construction waste is a viable tactic for advancing environmentally friendly building methods. With regard to concrete applications, the purpose of this research is to determine whether it is feasible to use recycled fine concrete aggregates (RFA) in lieu of natural fine aggregates (NFA) and to lessen the environmental impact of natural resource depletion and landfill space. A sustainable steel fiber-reinforced concrete was created by replacing NFA with RFA at the replacement ratio of 0 %, 50 %, and 100 %. Steel fibers (SF) were also included to mixes at three different contents of 0, 25 and 50 kg/m3 in order to further improve the qualities of the concretes. Thus, the aim of this paper is to appraise how the addition of FRA affects the mechanical, freeze-thaw, fresh, and non-destructive qualities of concrete. Nine concrete mixtures were cast, and tests were made to evaluate the following properties: flowability, fresh concrete unit weight, tensile and compressive strengths, elastic modulus, surface hardness, crack mouth opening displacement (CMOD), freeze and thaw performance, sulfate resistance and abrasion. Moreover, microstructure properties of concrete were also analyzed. The outcomes revealed that the mechanical, flexural, and durability performances of the concrete mixtures were enhanced by substituting RFA for NFA. The mixture with 50%RFA and 50 kg/m3 SF gained maximum compressive strength of 44.82 MPa which was 20.7 % greater than the reference mixture (RFA0F0). The mixture containing 100 % RFA and 25 kg/m3 SF had the highest elastic modulus and showed an approximately 33 % augmentation in elastic modulus as per the reference mixture. The mixture with 100%RFA and 50 kg/m3 SF exhibited the largest tensile strength indicating 60 % tensile strength enhancement as per the reference mixture. Combined use of RFA and 50 kg/m3 SF in concrete mixtures had the best abrasion and freeze-thaw resistance. SF incorporated concrete mixtures with RFA exhibited worse sulfate resistance. This study contributed significantly to global resource efficiency and environmental preservation by shedding light on the sustainable use of RFA and SF in the making of concrete. The results made important contributions to global research and promote environmentally friendly building methods all throughout the world.
Sustainable use of recycled fine aggregates in steel fiber-reinforced concrete: Fresh, flexural, mechanical and durability characteristics
(2024.01.01) Benli, A.; Bayraktar, O.Y.; Koksal, F.; Kaplan, G.
Recycling construction waste is a viable tactic for advancing environmentally friendly building methods. With regard to concrete applications, the purpose of this research is to determine whether it is feasible to use recycled fine concrete aggregates (RFA) in lieu of natural fine aggregates (NFA) and to lessen the environmental impact of natural resource depletion and landfill space. A sustainable steel fiber-reinforced concrete was created by replacing NFA with RFA at the replacement ratio of 0 %, 50 %, and 100 %. Steel fibers (SF) were also included to mixes at three different contents of 0, 25 and 50 kg/m(3) in order to further improve the qualities of the concretes. Thus, the aim of this paper is to appraise how the addition of FRA affects the mechanical, freeze-thaw, fresh, and non-destructive qualities of concrete. Nine concrete mixtures were cast, and tests were made to evaluate the following properties: flowability, fresh concrete unit weight, tensile and compressive strengths, elastic modulus, surface hardness, crack mouth opening displacement (CMOD), freeze and thaw performance, sulfate resistance and abrasion. Moreover, microstructure properties of concrete were also analyzed. The outcomes revealed that the mechanical, flexural, and durability performances of the concrete mixtures were enhanced by substituting RFA for NFA. The mixture with 50%RFA and 50 kg/m(3) SF gained maximum compressive strength of 44.82 MPa which was 20.7 % greater than the reference mixture (RFA0F0). The mixture containing 100 % RFA and 25 kg/m(3) SF had the highest elastic modulus and showed an approximately 33 % augmentation in elastic modulus as per the reference mixture. The mixture with 100%RFA and 50 kg/m(3) SF exhibited the largest tensile strength indicating 60 % tensile strength enhancement as per the reference mixture. Combined use of RFA and 50 kg/m(3) SF in concrete mixtures had the best abrasion and freeze-thaw resistance. SF incorporated concrete mixtures with RFA exhibited worse sulfate resistance. This study contributed significantly to global resource efficiency and environmental preservation by shedding light on the sustainable use of RFA and SF in the making of concrete. The results made important contributions to global research and promote environmentally friendly building methods all throughout the world.