Sürdürülebilir Kalkınma Amaçları
Yayınlar
- Derleme MakaleYalnız künye2023Scopus SJRQ1Nanomaterial and fiber-reinforced sustainable geopolymers: A systematic critical review
Ünal, M. T.; Gökçe, H. S.; Ayough, P.; Alnahhal, A. M.; Simsek, O.; Nehdi, M. L.
Global cement production is associated with a colossal environmental footprint due to its considerable carbon emissions, energy consumption, depletion of natural resources, and waste accumulation. Geopolymer based concretes (GCs) have emerged as revolutionary alternatives to ordinary Portland cement concrete with enormous potential ecological benefits. However, they suffer from deficiencies, such as their brittle behavior under flexural and tensile loads. Using different types of fiber reinforcement and nanomaterial additions in geopolymer composites (GCs) has recently gained considerable attention to enhance various engineering properties, improve crack resistance, toughness, and ductility of the geopolymer matrices. This systematic and critical review analyses the effects of different reinforcing fibers and nanomaterials on the compressive and tensile strengths, modulus of elasticity, and impact resistance of GCs, and highlights the associated microstructural features. It is shown that carbon, basalt, and steel fibers can impart considerable improvement in mechanical strength, modulus of elasticity, and impact resistance of GCs. Furthermore, the introduction of polyethylene fibers has been shown to induce complex cracking behaviors, thereby contributing to the strain-hardening capability of geopolymer matrices. The integration of nanomaterials into GCs has emerged as a powerful strategy for achieving substantial enhancements in mechanical performance. Optimal nanomaterial dosages, typically around 2%, have been identified, with the specific surface area of nanoparticles proving to be a crucial determinant of the resulting mechanical properties. Notably, nano-silica has exhibited pronounced macro-scale reinforcement effects, whereas nano-titanium has displayed the potential to significantly enhance gel micromechanical characteristics. Additionally, synergistic combinations of nanomaterials and fiber reinforcements have led to the development of novel and distinctive mechanical properties within GCs. The synthesis of these findings underscores current best practices, highlights areas requiring further investigation, and emphasizes the need for concerted research efforts to advance the knowledge and implementation of sustainable geopolymers. This review offers a comprehensive analysis of the effects of fiber reinforcements and nanomaterials on geopolymer composites, providing valuable insights for researchers and practitioners.
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İncele - MakaleYalnız künye2021Scopus SJRQ2An online software to simulate the shielding properties of materials for neutrons and photons: NGCal
Gökçe, H. S.; Güngör, O.; Yilmaz, H.
NGCal, a free online computation software (http://ngcal.com), has been developed for narrow beam transmission properties of photons (for energies of X rays and gamma rays between 0.002 MeV and 20 MeV), thermal (25.4 meV) and fast neutrons (4 MeV), in this regard it theoretically calculates the mass and linear attenuation coefficient/factor, mean free path, half- and tenth-value layers of materials formed by elements, compounds and composites. Its calculation assumptions, user guide as well as a comparative example of its results to those of other online computation platforms (XCOM, NCNR, WinXCOM, MCNPX, and Phy-X/PSD) are presented in this study. The developed software allows for more data input consisting of elements/oxides/compound and their fractions, and presents a number of shielding results required by researchers and scientists working on radiation shielding properties of multi-component materials.
AtıfWoS85OpenAlex93İncele - MakaleYalnız künye2021Scopus SJRQ1Enhancing Burnability Characteristics of Low-Temperature Burnt-Cement Clinker by Recycling Phosphogypsum Wastes
Aksan, U.; Köseoglu, K.; Gökçe, H. S.
In the present study, the effect of phosphogypsum, a byproduct from the phosphoric acid production industry, on the clinkerization process was researched in order to improve the burnability of clinkers at lower burning temperatures. Raw meal samples containing phosphogypsum at 0%, 1%, 3%, and 5% by weight were burned at 1,350 degrees C, 1,400 degrees C, 1,450 degrees C, and 1,500 degrees C. The introduction of phosphogypsum reduced the presence of unbounded (free) CaO relatively up to 43%. Thus, the mineralization effect of phosphogypsum promotes lower burning temperatures. The free CaO content of the 5% phosphogypsum containing clinker decreased to 0.94% at 1,400 degrees C after 120 min of burning time. The free CaO content was found to be almost identical (0.75%) to that of industrial clinker burned in a rotary kiln at 1,500 degrees C. Due to the low free CaO content (<1%) and the burnability index (73), the recycling of phosphogypsum wastes was found to be suitable for the production of eco-efficient clinkers. The reduced energy consumption and energy-related CO2 emissions in such modified clinkers can contribute to the economic and ecological goals of the cement industry. (C) 2021 American Society of Civil Engineers.
AtıfWoS2OpenAlex3İncele - Derleme MakaleAçık Erişim2021Scopus SJRQ1A review on developments of environmentally friendly geopolymer technology
Krishna, R. S.; Mishra, Jyotirmoy; Zribi, Marwa; Adeniyi, Funmilayo; Saha, Suman; Baklouti, Samir; Shaikh, Faiz Uddin Ahmed; Gökçe, H. S.
This study aims to present an overview of the progress of geopolymer composites with regards to the latest developments on its constituents (binders, activators, and aggregates) and manufacturing techniques. Some ecological, economic, and industrial limitations of the traditional aluminosilicate binders yield to the pursuit of alternative ones over the period. Some of these latest binders e.g. ferrochrome ash, mine tailings, rice husk ash, red mud, have been highlighted in this paper. Current advances on replacement of natural fine and coarse aggregates such as mine tailings (iron ore tailings), recycled/lightweight aggregates for geopolymer preparation have been reviewed from the past literature. The paper also focuses on developments regarding the new class of green alkaline and acidic activators, which is traditionally considered to be the binding agent in the preparation of geopolymer composites. Different geopolymer production methods have been briefly discussed to study their effectiveness in achieving a strong and durable composite. This paper may serve to encourage further experimental research works for achieving more sustainable, cost-effective geopolymer composites with enhanced mechanical properties.
AtıfScopus89WoS77OpenAlex88İncele - MakaleAçık Erişim2020Scopus SJRQ1Physical and mechanical properties of cement containing regional hazelnut shell ash wastes
Baran, Y.; Gökçe, H. S.; Durmaz, M.
Turkey is ranked in the first place with two-thirds of the world hazelnut production. As the amount of shell obtained from shelled-hazelnut is almost equal to that of hazelnut by weight, the shell is a regionally important waste. The biomass is consumed as a fuel in some homes, workplaces, and public buildings with the help of specific caldrons. In the study, the use of ash was researched in the production of blended cement. For this purpose, blended cement mixtures containing hazelnut shell ash at the ratios of 0, 5, 10, 15, 20, 25 and 30% by weight of CEM I 42.5R ordinary Portland cement were prepared. The binary cementitious systems were assessed in terms of chemical, physical and mechanical properties. Hazelnut shell ash introduction increased the water demand up to 59% for standard consistency and reduced setting time up to 96% according to the ordinary Portland cement. Compressive strength results were remarkably reduced by an increase in the amount of ash. With over 5% of hazelnut shell ash introduction, the 28-d compressive strength value was found unsatisfactory (<42.5 MPa). The insufficient total amount of SiO2+Fe2O3+Al2O3 reduced the usage amount of the biomass ash in cementitious products due to having no pozzolanic characteristic. Hazelnut shell ash can be used as an alkaline set accelerator in concrete products as it is not steel-reinforced due to its high chlorine ion content. (C) 2020 Elsevier Ltd. All rights reserved.
AtıfWoS35OpenAlex41İncele - MakaleAçık Erişim2020Scopus SJRQ1Development of Eco-Efficient Fly Ash-Based Alkali-Activated and Geopolymer Composites with Reduced Alkaline Activator Dosage
Gökçe, H. S.; Tuyan, M.; Ramyar, K.; Nehdi, M. L.
The eco-efficiency and economy of geopolymer composites largely depend on their alkaline activator dosage. In this study, the effect of applying a pre-setting pressure and variation of the aggregate-to-fly ash ratio on the alkaline solution dosage and mechanical strength of fly ash-based geopolymer composites was explored. It is shown that through control of the aggregate-to-ash ratio and application of pre-setting pressure, compressive strength could be increased by 102% and 86% for Class F fly ash-based geopolymer and alkali-activated Class C fly ash-based mixture, respectively. The total alkaline solution consumption could be reduced from 718 to 188 kg/m(3) and from 769 to 262 kg/m3 for Class F fly ash-based geopolymer and alkali-activated Class C fly ash-based mixture, respectively. The proposed method reduced the alkaline solution consumption per compressive strength (6.2 kg.m(-3).MPa-1) by up to 85% compared to that of the reference manually consolidated control geopolymer. The findings demonstrate that fly ash-based geopolymers could be made more sustainable and eco-efficient through tailored production techniques. (C) 2019 American Society of Civil Engineers.
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