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    Application of ECC as a Repair/Retrofit and Pavement/Bridge Deck Material for Sustainable Structures: A Review
    (Mdpi, 2022) Yucel, Hasan Erhan; Dutkiewicz, Maciej; Yildizhan, Fatih
    Concrete structures cannot efficiently perform their functions over time due to chemical and physical external effects. Thus, enhancing the relationship between repair and aged structures, and also improving the durability properties of concrete is crucial in terms of sustainability. However, high costs, negative environmental effects, and incompatibility problems occur in repair/retrofit applications. Furthermore, three-quarters of the failures in the repaired/retrofitted structures are caused by a lack of repair durability. The need for repair in pavement/bridge decks is also frequently encountered, and early-age performance problems with repair materials cause pavement/bridge decks to be unavailable for certain periods of time. Engineered Cementitious Composite (ECC) can be effectively used as repair/retrofit and pavement/bridge deck material. It also has a minimal need for repair/retrofit thanks to its high durability properties. This article presents state-of-the-art research regarding the application of ECC as a repair/retrofit and pavement/bridge deck material. Studies in the literature show that the repair/retrofit properties of ECC outperform conventional concrete and steel fiber-reinforced concrete. ECC can be a solution to high early strength and drying shrinkage problems frequently encountered in the use of repair materials. It could also be used for different repair applications such as cast, sprayed, and trenchless rehabilitation. Moreover, ECC might fulfill specific requirements for pavement, pavement overlay, tunnel pavement, airfield pavement, and bridge deck. These superior performances are attributed to ECC's kink-crack trapping mechanism, uniquely large inelastic strain capacity, strain hardening, high tensile strain capacity, and multiple microcracking and ductile behaviors, especially bonding behavior and self-healing.
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    Comparison of Glass Powder and Fly Ash Effect on the Fresh Properties of Self-Compacting Mortars
    (Iop Publishing Ltd, 2017) Oz, Hatice Oznur; Yucel, Hasan Erhan; Gunes, Muhammet
    This study is aimed to determine effects of glass powder on fresh properties of self-compacting mortars. Self-compacting mortars incorporating glass powder (SCMGPs) were designed with a water/binder ratio of 0.40 and a total binder content of 550 kg/m(3). At first, the control mixture was produced with 20% fly ash and % 80 cement of the total binder content without using the glass powder. Then, glass powder was used in the proportions 5%, 10%, 15% and 20% instead of fly ash in the mortars. Mini-slump flow and mini-v funnel tests experimentally investigated on SCMGPs to compare the effect of fly ash and glass powder. With increasing the amount of glass powder used in SCMGPs increased the amount of superplasticizer used to obtain the desired mini-slump flow diameter. So, the use of glass powder reduced the flow ability of SCMGPs in comparison to fly ash. Additionally, the compressive strength and flexural strength of the mortar mixtures were determined at the 28th day. The test results indicated that the mechanical characteristics of SCMGPs improved when the fly ash was replaced with glass powder in SCMGPs.
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    Evaluation of the Performance of Different Types of Fibrous Concretes Produced by Using Wollastonite
    (Mdpi, 2022) Dutkiewicz, Maciej; Yucel, Hasan Erhan; Yildizhan, Fatih
    Production of cement and aggregate used in cement-based composites causes many environmental and energy problems. Decreasing the usage of cement and aggregate is a crucial and currently relevant challenge to provide sustainability. Inert materials can also be used instead of cement and aggregates, similar to pozzolanic materials, and they have positive effects on cement-based composites. One of the inert materials used in cement-based composites is wollastonite (calcium metasilicate-CaSiO3), which has been investigated and attracted attention of many researchers. This article presents state-of-the-art research regarding fibrous concretes produced with wollastonite, such as mortars, conventional concrete, engineered cementitious composites, geopolymer concrete, self-compacting concrete, ultra-high-performance concrete and pavement concrete. The use of synthetic wollastonite, which is a novel issue, its high aspect ratio and allowing the use of waste material are also evaluated. Studies in the literature show that the use of wollastonite in different types of concrete improves performance properties, such as mechanical/durability properties, and provides environmental-economic efficiency. It has been proven by studies that wollastonite is a material with an inert structure, and, therefore, its behavior is similar to that of a fiber in cementitious composites due to its acicular particle structure.
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    Fly-ash-based geopolymer composites incorporating cold-bonded lightweight fly ash aggregates
    (Elsevier Sci Ltd, 2021) Oz, Hatice Oznur; Yucel, Hasan Erhan; Gunes, Muhammet; Koker, Turan Sevki
    In this study, effects of cold-bonded lightweight fine aggregate (LWFA) on the geopolymer composites (GCs) were investigated in terms of fresh, physical, mechanical and durability properties. LWFA and different diameters quartz aggregates were used in the production of fly-ash-based GCs. However, LWFA was only replaced with the quartz aggregate of 1.2-2.5 mm. A mixture of 12 M NaOH and Na2SiO3 solution was prepared as 1/2.5. Unit weight, specific gravity, water absorption, apparent porosity, compressive and flexural strengths, ultrasonic pulse velocity and water sorptivity coefficient of GCs were determined. According to the test results, workability of GCs improved as the usage rate of LWFA increased. Due to the surface characteristics of LWFA, the mechanical properties of GC were enhanced by the geopolymerization reaction conducted between LWFA with alkali activators. Thus, the compressive strength of GC with 25% LWFA was 39.6% higher than that of the control GC at 28th day. This conclusion supported by TGA/DTA and FTIR analysis indicated that N-A-S-H gel of GC incorporating 25% LWFA was higher compared to control mixture. Also, GCs incorporating 40% and higher LWFA showed lower performance than control GC. (C) 2020 Elsevier Ltd. All rights reserved.
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    Life cycle assessment and shrinkage properties of high performance mortars incorporating synthetic wollastonite microfibers
    (Emerald Group Publishing Ltd, 2023) Oz, Hatice Oznur; Gunes, Muhammet; Yucel, Hasan Erhan; Ersoy, Orkun; Sever, Yunus; Demirel, Sevgi
    In this study, the use of an alternative material as supplementary cementitious material was researched for the design of high-performance mortars (HPMs). Synthetic wollastonite microfibres (SWMs) were produced from calcite and quartz sand. The SWMs were then replaced at ratios of 0, 3, 6, 9 and 12% by cement weight to investigate the fresh, mechanical and shrinkage properties of HPMs. Test results showed that the mechanical and shrinkage properties of HPMs improved up to 9% inclusion of SWMs. The compressive strength, flexural strength, modulus of elasticity, fracture toughness and fracture energy of HPM incorporating 9% SWM was higher than that of the control mixture by 8.8-9.1%, 7.5-9.9%, 4.7-6.7%, 8.9-4.6% and 13.2-2.5% at 28-90 days, respectively. Similarly, the ratios for maximum drying shrinkage and average crack width were determined as 10.5% and 58.3%, respectively, at the end of 60 days. These findings were also supported by microstructural analysis. Moreover, the potential environmental impacts resulting from the production of 1 kg SWM and HPM incorporating 9% SWM were evaluated using the life cycle analysis software (LCA) SimaPro 8.5.0.0. Based on the LCA results, SWMs can be used as an alternative material to develop sustainable concrete structures.
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    Rheological and microstructural properties of FA+GGBFS-based engineered geopolymer composites (EGCs) capable of comparing with M45-ECC as mechanical performance
    (Elsevier, 2023) Oz, Hatice Oznur; Gunes, Muhammet; Yucel, Hasan Erhan
    In this study, it has been aimed to obtain the fly ash + ground granulated blast furnace slag (FA GGBFS)-based engineered geopolymer composites (EGCs) having similar bearing strength and deformation capacity with the engineered cementitious composite (M45-ECC) known as M45. EGCs incorporating 70% FA and 30% GGBFS as binder were developed under three different groups in which the different ratios of alkali liquids/binder (AL/Bi) with the different content of AL + Bi. All of eight FA + GGBFS-based EGCs designed with 2.5 ratio of Na2SiO3/NaOH. FA GGBFS-based EGCs, which were kept in the mold under laboratory conditions for 24 h imme-diately after production, were kept in water at 60 degrees C until the test age. The fresh, rheogical, mechanical and microstructural properties of FA + GGBFS-based EGCs were determined. Test results indicated that FA + GGBFS-based EGCs can be developed with similar or higher compressive strength and ductility than that of M45-ECC. However, the flexural strength of M45-ECC was higher than those of all other composites. In addition, TGA/DTA and FTIR analysis supported that the excessive amount of AL + Bi content would not improve the characteristics of FA + GGBFS-based EGCs after the optimal production of C-S-H and N-A-S-H gels which acquired in geopolymerization. However, ductility continued to improve significantly as the AL + Bi content increased. Moreover, reduction of AL/Bi ratio increased the total gel content and thus, the compressive strength of composites developed.
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    Rheological properties, strength characteristics and flexural performances of engineered cementitious composites incorporating synthetic wollastonite microfibers with two different high aspect ratios
    (Elsevier Sci Ltd, 2021) Yucel, Hasan Erhan; Oz, Hatice Oznur; Gunes, Muhammet; Kaya, Yasin
    In this study, synthetic wollastonite microfiber (SWM) with high aspect ratio (44:1/SWM-I) developed with a special technique was used in different proportions instead of cement (C), fly ash (FA) and cement + FA (C-FA) in Engineered Cementitious Composites (ECC). SWM-I decreased the workability as a result of interlocking during flow due to its acicular particle structure. When SWM-I was used instead of C, it was determined that the compressive strength decreased and the ductility improved significantly due to the increased SWM-I content. The use of SWM-I instead of FA improved the mechanical performance up to 6% in terms of compressive strength and flexural performance. However, the mixtures prepared by using SWM-I instead of C-FA provided optimum data, considering both ''increasing deformation capacity'' and ''maintaining the bearing strength by fiber bridging after crack''. Therefore, the effect of SWM-II (30:1) was tested by using instead of C-FA. SWM-I with a higher aspect ratio has been improved the mechanical properties of ECC and reduced the workability of ECC more than that of SWM-II. Increasing FA content in ECC has been provided higher ductility but decreased significantly the compressive strength. The bearing strength and deformation capacity of the ECC designed with finer aggregate has been achieved the higher levels compared to larger aggregate size. As a result of all obtained findings, the data of the optimum mixture has been determined as follows: the compressive strength, flexural strength and ductility of ECC incorporating 6% SWM-I instead of C-FA have been reached higher levels than that of 19.0%12.5%, 12.0%-8.2% and 56.2%-25.5% at 7-28 days, respectively.
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    The Effect of Waste Ballast Aggregates on Mechanical and Durability Properties of Standard Concrete
    (Mdpi, 2023) Yucel, Hasan Erhan; Dutkiewicz, Maciej; Yildizhan, Fatih
    The acquisition and transportation of aggregate exacerbate the negative impact of concrete on the environment, and waste materials are considered an effective solution to this crucial problem. One of these waste materials is waste ballast (WB), which is needed for new infrastructure along with increasing rail track technology. In this study, the effect of WB aggregate (which is basalt-based) on the mechanical and durability properties of standard concrete was examined. Coarse aggregate was replaced with WB aggregate at the rates of 50%, 75% and 100%. The slump, compressive strength, flexural strength, capillary water absorption, rapid chloride permeability and water penetration tests on the mixtures were performed. According to the results of this study, the utilization of WB improved the compressive strength and flexural strength of the mixtures by about 15% and 7%, respectively. Moreover, the capillary water absorption, rapid chloride permeability and water penetration values of all the concrete mixtures with WB were lower than the control mixture. In addition, the correlation relations between the mechanical and durability properties indicated that they have a strong relationship with each other. All the results of this study demonstrated that the utilization of WB instead of coarse aggregate improved the mechanical and durability properties of concrete. WB can also provide a more sustainable material formation by minimizing the negative environmental effects of concrete production.