Sürdürülebilir Kalkınma Amaçları
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- MakaleYalnız künye2026Scopus SJRQ1Upcycling marble waste into construction materials and heavy metal adsorbents via hot-pressed geopolymerization technique
Öksüzer, Nurullah; Uslu, Emin; Gökçe, H. Süleyman
This study presents a sustainable approach to utilizing marble dust waste by producing bifunctional metakaolin-based geopolymers via a synchronized hot-pressing technique. In this study, the environmental footprint was minimized by designing mixtures in which marble waste constituted 50% of the total volume. Three stoichiometric series were investigated by varying the activator modulus (SiO2/Na2O = 3 and 4) and the Si/Al ratio (2 and 3) under two curing temperatures (150 and 300 °C) and three compaction stresses (5, 25, and 50 MPa). Thus, a high-volume industrial byproduct was transformed into a functional component. In this context, it investigated the transformation of industrial products into next-generation materials by using them to produce cementless composite geopolymers for civil engineering and to adsorb heavy metal (Cu2+). As a result of the research, an early compressive strength of 58 MPa was obtained through heat treatment and pressing applied at 300 °C and 50 MPa. This optimum strength was achieved in the SiO2/Na2O = 3, Si/Al = 3 series, whereas excess silica (SiO2/Na2O = 4) and excess aluminum (Si/Al = 2) limited the strength to 16.8 and 35.2 MPa, respectively. Microstructural analyses (SEM/EDS and FT-IR) revealed that marble dust was used as a filler material in the microstructure to produce an N-A-S-H-containing matrix. The produced materials were then ground after their service life and used to purify water containing heavy metals. More than 99.75% of Cu2+ was removed through ion exchange between copper ions used as heavy metals. The residual Cu2+ concentration fell below 0.25 mg/L from an initial concentration of 100 mg/L, and the released Na+-to-adsorbed Cu2+ molar ratio of approximately 1.8–2.3 confirmed an ion-exchange-dominated uptake mechanism. This structural and environmental impact demonstrates that marble waste, which is otherwise discarded as waste, is considered inert, offering an alternative model for the circular economy and environmental applications.
- MakaleAçık Erişim2023Scopus SJRQ1The effect of various industrial dust particles on the performance of photovoltaic panels in Turkey
Güngör, Okan; Kahveci, Hakan; Gökçe, H. Süleyman
The accumulation of dust is one of the main causes of power loss in photovoltaic (PV) farms, and the effect of dust particles’ size and chemistry on system performance is often overlooked. This study has focused on a comprehensive analysis of the effect of different dust particles collected from common industrial production facilities in Turkey on the performance of PV panels in the indoor laboratory environment. The collected dust samples were analyzed to determine the dust sample particles’ chemical properties, size, character, and topography. The data for dust samples at different weights with changes in maximum power point (MPP) of PV panel has been collected using the artificial solar irradiation source system. Thus, the mathematical correlations (R2≥0.965) between the PV panel Thevenin resistance (RTH), fill factor (FF), MPP, and pollution rate were obtained using these collected data and particle swarm optimization (PSO). According to the results of the obtained mathematical correlations, marble dust is 2.3, 3.4, and 4.2 times less polluting than cement, fly ash, and silica fume, respectively. Additionally, it was observed that smaller dust particles block more light than larger ones of the same weight and reduce MPP, FF while increasing the RTH.
AtıfScopus19WoS14OpenAlex21
İncele - MakaleAçık Erişim2023Scopus SJRQ1A bio-inspired solution to alleviate anisotropy of 3D printed engineered cementitious composites (3DP-ECC): Knitting/tilting filaments
Zhou, Wen; McGee, Wes; Gökçe, H. Süleyman; Li, Victor C.
Widely reported anisotropy in 3D printed cementitious structures has been a primary concern to structural integrity, especially for fiber-reinforced cementitious material, e.g., engineered cementitious composites (ECC). To alleviate the anisotropy present in 3D printed ECC (3DP-ECC), two innovative printing patterns, “knitting” and “tilting” filaments, were proposed, mimicking the natural crossed-lamellar structure of conch shells. 3D spatial paths were designed to allocate tensile/flexural resistance to multiple directions and to create an interwoven interface system to strengthen the structure. Four-point bending tests loading from three different directions were conducted. It was found that knitted and tilted filaments revealed superior or comparable bending performance to cast ECC in two favorable orientations. Furthermore, flexural performance in the weakest orientation was notably improved by knitting and tilting, with up-to-179% increases in flexural strength compared with that of parallel filaments. This novel approach holds great promise in alleviating anisotropy of 3DP-ECC without introducing additional reinforcement.
AtıfScopus45WoS39OpenAlex42İncele - MakaleYayıncıda açık erişim2022Scopus SJRQ1Time-dependent fresh properties characterization of 3D printing engineered cementitious composites (3DP-ECC): On the evaluation of buildability
Zhou, Wen; McGee, Wes; Zhu, He; Gökçe, H. Süleyman; Li, Victor C.
Failure of the structure due to poor buildability is a major concern in 3D printing of cementitious materials. Evaluation of buildability based on fresh material properties and print parameters is of significance. In this paper, the buildability of printable engineered cementitious composites was investigated and quantified at the material and the structural scale. Fresh ECC material showed excellent load capacity and deformation resistance at the material scale, therefore preventing material failure of the bottom layers, as confirmed by constant shear rate tests and incremental loading tests. To predict vertical deformation of a 3DP structure, a time-dependent strain-stress model of printable ECC was proposed and validated based on the green strength evolution of the material and the buildup rate of the designed structure. At the structural scale, the approach of predicting critical height at self-buckling failure based on stiffness evolution was validated by printing a straight wall and a cylinder structure.
AtıfScopus56WoS46OpenAlex52İncele - MakaleAçık Erişim2019Scopus SJRQ3A functional bleeding test apparatus for concrete
Gökçe, H. Süleyman; Andiç-Çakır, Özge
Bleeding is one important indicator that is related to the physical and mechanical properties of fresh and hardened concrete. Standards generally prefer methodologies that are similar to one another to measure the bleeding of fresh concrete. The preferred test apparatus used in the standards is troublesome because it requires a manual test procedure and repeated measurements until final setting of the fresh concrete. The functional bleeding test apparatus presented in this study will ease test performance and eliminate the faults caused by the test procedure and the experimenter.
AtıfScopus2WoS1OpenAlex3İncele - MakaleAçık Erişim2019Scopus SJRQ1Effect of fly ash and silica fume on hardened properties of foam concrete
Gökçe, H. Süleyman; Hatungimana, Daniel; Ramyar, Kambiz
In this study, the effects of foam content as well as fly ash and silica fume inclusion on some physical and mechanical properties of foam concrete, subjected to various curing regimes, were researched. Totally, forty-five series of foam concrete mixtures were prepared at three replacement levels of fly ash and silica fume (0, 10 and 20%, by weight of cement), at three foam contents (0, 31 and 47%, by volume) and at three curing regimes (7- and 28-day standard water curing and autoclave curing). Density, water absorption, compressive strength and thermal conductivity values of the mixtures were determined on prismatic specimens with dimensions of 40 × 40 × 160 mm. The density (oven dry), water absorption, compressive strength and thermal conductivity results of the foam concrete were found to be between 873–1998 kg/m3, 3.5–35.9%, 1.5–88.1 MPa and, 0.239–0.942 W/m.K, respectively. A balanced benefit with regard to both compressive strength and water absorption of foam concrete was found in the mix with density of 1320 kg/m3. Particularly in the mixtures having high foam content, silica fume introduction resulted in superior compressive strength values and greater compressive strength/thermal conductivity ratios than fly ash introduction.
AtıfScopus271WoS237OpenAlex276İncele - MakaleYalnız künye2019Scopus SJRQ1Bleeding characteristics of high consistency heavyweight concrete mixtures
Gökçe, H. Süleyman; Andiç-Çakır, Özge
Bleeding, a type of static segregation derives from density difference of concrete ingredients in fresh state. Due to having this difference higher than normal weight counterparts, heavyweight concrete is more susceptible to bleeding, thus, this type of concrete is commonly produced in low slump values. In order to give a response to advances and demands in concrete technology, heavyweight concrete mixtures with high slump values were designed at various mixture characteristics, and their bleeding characteristics were researched in the study. For this purpose, totally, thirty-five concrete mixtures with ≥150 mm slump values were produced by using common cement replacement materials (silica fume and fly ash), viscosity modifier, and various water/binder ratios at two binder dosages. The mixtures showed excessive bleeding capacities ranged from 0 to 11.7% and bleeding rates ranged from 0 to 5.1 kg/m2/h. Silica fume was found as the most effective admixture for reducing or elimination of the bleeding. Bleeding time generally shorten at high binder content and at high water/binder ratio. It was observed that the bleeding adversely affects the hardened characteristics of heavyweight concrete mixtures.
AtıfScopus62WoS54OpenAlex59İncele - MakaleAçık Erişim2018Scopus SJRQ1Optimization of reactive powder concrete by means of barite aggregate for both neutrons and gamma rays
Gökçe, H. Süleyman; Yalçınkaya, Çağlar; Tuyan, Murat
High performance concrete has been often preferred in special engineering structures and in challenging composites products. Researchers have recently focused on the radiation shielding characteristics of these type concrete mixtures due to rising nuclear industry in the developing world. In the study, performance of reactive powder concrete was researched with regard to gamma-ray and neutron attenuation when its normal weight aggregate replaced with heavyweight aggregate (barite). For this purpose, reactive powder concrete mixtures were prepared 100% quartz aggregate, 100% barite aggregate and their blending 50–50%, by volume. Some physical and mechanical characteristics such as density, compressive strength, fracture energy, flexural strength and modulus of elasticity of the mixtures were determined. Gamma-ray attenuation coefficients and transmission thickness values were theoretically established for commonly known gamma energies (661.7, 1173.2 and 1332.5 keV). Optimization of the reactive powder mixtures was performed for both neutron and gamma-ray attenuation at 8 MeV. As a result, barite significantly increased the gamma-ray attenuation coefficients of reactive powder concrete. The mechanical performance of reactive powder concrete, however, was markedly reduced as a result of barite substitution. Replacement of quartz by barite aggregate has a more adverse impact on flexural strength than that of compressive strength. A mix that contains 40% barite aggregate of total aggregate volume was found as an optimum RPC mixture for simultaneously shielding neutrons and gamma rays.
AtıfScopus138WoS126OpenAlex141İncele - MakaleYalnız künye2018Scopus SJRQ1A new method for determination of dynamic stability of self-consolidating concrete: 3-Compartment sieve test
Gökçe, H. Süleyman; Andiç-Çakır, Özge
There are many standard test methods and applications to determine or estimate the workability of fresh concrete mixtures, most of them are focused on highly flowable concrete mixtures. Due to its high flowability, self-consolidating concrete (SCC) is much more vulnerable to segregation compared to conventional concrete mixtures. Thus, researchers have been working on adopting dynamic and static test methods for determination and improvement of segregation stability of those mixtures. In this study, the different segregation test methods presented in the literature were assessed and a novel method, i.e. 3-compartment sieve test, was introduced. The dynamic stability of fresh self-consolidating concrete mixtures was evaluated by the suggested test method after slump-flow and J-Ring tests. In conclusion, the developed new method is recommended for determination of segregation in SCC due to satisfactory concurrency of results with those of visual stability index test (0.67 ≤ R2 ≤ 0.90) and sieve segregation resistance test (0.83 ≤ R2 ≤ 0.90), respectively.
AtıfScopus23WoS19OpenAlex23İncele - MakaleYalnız künye2010Ham perlit agregalı hafif beton özelliklerine alternatif genleştirilmiş perlit kullanımının etkisi
Simsek, Osman; Durmuş, Gökhan; Demir, İlhami; Gökçe, H. Süleyman
Perlit, ısı yalıtım ve hafiflik özelliğinden dolayı beton agregası olarak inşaat sektöründe kullanımı ile ülke ekonomisine ve küresel ısınmaya olumlu yönde katkıda bulunan doğal yapı malzemesidir. Yapılan araştırmalar sonucunda dünya perlit rezervinin yaklaşık % 74' ünün Türkiye'de olduğu belirlenmiştir. Bu doğal kaynakların etkin kullanımı ile oldukça zor elde edilen enerjinin daha etkin kullanımının sağlanacağı düşünülmektedir. Enerji kullanımındaki bu tür yaklaşımlar çevre kirliliğinin azalmasına katkı sağlayacaktır. Bu çalışmada, farklı özellikteki genleştirilmiş perlit agregalarının ham perlit agregalı hafif betonlar içinde kullanılabilirliği araştırılmıştır. Ham perlit agregası yerine hacimce %10 oranında üç farklı özellikte genleştirilmiş perlit agregası kullanılarak 7 ayrı karışım oluşturulmuştur. Hazırlanan hafif beton karışımları ile 100x100x100 mm ebatlı küp numuneler elde edilmiştir. Bu numunelerin 28 günlük basınç dayanımı, birim hacim ağırlık ve su emme oranları test edilmiştir. Sonuç olarak, uygun özellikteki genleştirilmiş perlit agregası kullanımının perlit agregalı hafif betonların mekanik ve fiziksel özellikleri üzerinde etkili olduğu anlaşılmıştır.
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