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Öğe Aggressive Environment Performance of Low Energy Cements Containing Fly Ash(Gazi Univ, 2021) Gokce, H. Suleyman; Simsek, OsmanIn this study, compressive strength performance of boron active belite cement containing fly ash at the ratios of 0, 10, 20, and 30% (by weight of cement) is researched against aggressive environments; sea water, 5% sodium sulphate solution, and 5% ammonium nitrate solution in addition to tapping water. Alternative low energy cement i.e., Portland-composite cement was used and its results were compared with those of boron active belite cement. Early strength losses (reaching up to 40%) of the boron active belite cement with incorporation of fly ash up to 30% were found to be less pronounced than those (reaching up to 51%) of Portland-composite cement in tapping water. Although, the losses were highly compensated with the prolonged curing period (90 days), boron active belite cement and Portland-composite cement kept their losses up to 14% and 36%, respectively. Residual mechanical properties (reaching up to 67%) of boron active belite cement against aggressive environments were found almost similar to those of Portland-composite cement in presence of 30% fly ash. In conclusion, the study shows that belite cements with low fly ash contents can be a reasonable alternative for specific applications such as mass concrete, hot weather concreting especially in aggressive environments.Öğe Assessment of Alternative Segregation Test Methods for Self-Consolidating Heavyweight Concrete(Asce-Amer Soc Civil Engineers, 2019) Gokce, H. Suleyman; Aksan, Umut; Andic-Cakir, OzgeThis investigation is focused on the use of alternative segregation test methods on high-performance self-consolidating heavyweight concrete. Many segregation test methods have been developed by researchers up to now; however, the disadvantages of these methods, such as being time-consuming, the requirement of excessive labor, and the lack of precision, cannot ensure their worldwide prevalence. In the study, the segregation limitations stated in various test methods, that is, the column test, density variation method, and 3-compartment sieve test, were evaluated on self-consolidating heavyweight concrete produced with barite aggregate. For this purpose, in total, eight self-consolidating heavyweight concrete mixtures designed in two water/binder ratios were prepared by replacing viscosity modifier, silica fume, and fly ash with ordinary Portland cement in different amounts. The mixtures were constituted in satisfactory segregation grades, allowing researchers to evaluate the relationship between those methods. The segregation coefficient limits of the column test, density variation method, and 3-compartment sieve test are recommended as 7%, 1%, and 6.3% for the self-consolidating heavyweight concrete mixtures tested in the study.Öğe A bio-inspired solution to alleviate anisotropy of 3D printed engineered cementitious composites (3DP-ECC): Knitting/tilting filaments(Elsevier, 2023) Zhou, Wen; Mcgee, Wes; Gokce, H. Suleyman; 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.Öğe DETERMINATION OF ALKALI-SILICA REACTION EFFECTS OF ZEOLITIC TUFF ADDITION ON THE DIFFERENT AGGREGATES(Gazi Univ, Fac Engineering Architecture, 2010) Gokce, H. Suleyman; Taban, Saniye; Simsek, OsmanThe aim of this study is to determine the alkali-silica reaction (ASR) related characteristics of crushed stones that are produced from rocks of perlite, andesite and limestone when zeolitic tuff (ZT) is used in the mortar mix as cement replacement in different ratios. Accelerated mortar bar experiments in accordance with ASTM C 1260 were carried out on crushed stone aggregate samples to determine the ASR. CEM I 42.5 R type cement was replaced by ZT material in the following ratios: 0, 10, 20, 30 and 40%; in order to investigate the effects of replacement on the ASR pertaining to the aggregate types, 45 mortar bar pieces were produced. The length change values of the samples were measured on the 3, 7, 14, 28, 42, 56 days according to the accelerated mortar bar method. Measured length changes for the control samples on 14(th) day were found to be 0.570% at the level of potentially harmful for perlite, 0.101% at the level of critic for andesite and 0.061% at the level of harmless for limestone. Length changes at the harmful levels were taken under control for perlite at 30 and 40%, for andesite at 20, 30 and 40% ZT replacement ratios. Length change values of all samples decrease as ZT replacement increases. As a result, ZT replacement is effective to suppress the ASR of reactive aggregates.Öğe A Dynamic Segregation Test Method for Heavyweight Concrete: Density Variation Method(Amer Soc Testing Materials, 2020) Gokce, H. Suleyman; Andic-Cakir, O.Several segregation evaluation methods have been developed for concrete; however, none of them have been specially focused on heavyweight concrete, which has more of a tendency toward segregation because of differences in density of paste matrix to heavy aggregate. Thus, for heavyweight concrete, the segregation may be determined by measuring the difference density in a vertical direction. In this study, a simple reliable method, i.e., the density variation method, that considers the variation in vertical layers of the concrete is modeled to assess dynamic segregation of heavyweight concrete. In addition, 35 heavyweight concrete mixtures with high consistency were designed with various mixing parameters, and the results were compared with the model findings. The suggested test method was also compared with a conventional method (column segregation test by wet-sieving), and an equivalent segregation limit was determined. A strong linear relation (R-2 : 0.86) was found between the density variation method and column segregation test, and a segregation coefficient limit for segregation of heavyweight concrete is recommended as 1.7 %.Öğe The effect of various industrial dust particles on the performance of photovoltaic panels in Turkey(Springer Heidelberg, 2023) Gungor, Okan; Kahveci, Hakan; Gokce, H. SuleymanThe 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 (R-2 >= 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 R-TH.Öğe A Functional Bleeding Test Apparatus for Concrete(Amer Soc Testing Materials, 2019) Gokce, H. Suleyman; Andic-Cakir, OzgeBleeding 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.Öğe Investigation of Usability of Basaltic Pumice Aggregate At Prefabricated Structure Light-Weight Concrete Components(Gazi Univ, 2011) Gokce, H. Suleyman; Simsek, OsmanAt prefabrication, concrete which is 30 MPa and more compressive strength is generally used in the production of structure components such as colon, beam etc. In new generation productions, expected property of the components is not only compressive strength, but also tensile splitting strength, bond strength and lightness which provides advantage on movement and molding. In this study, the engineering properties of the concrete prepared by CEM I 42.5 R type cement by using pumice and normal aggregate were investigated On determination of compressive strength 100x200 mm sized cylinder sample, on determination of tensile splitting and bond strength 150x150x150 mm sized cube sample and O12 ribbed steel bar was used. It is found that light-weight concrete (LC) which was prepared with pumice aggregate is 30% lighter than normal concrete (NC) prepared with normal aggregate and at equal strength. According to the NC, the LC was obtained by 48% less tensile splitting strength and 15% less bond strength.Öğe Optimising High Lime Fly Ash Content By Means of Silica Fume Incorporation to Control Alkali-Silica Reaction And Drying Shrinkage of Mortars(Gazi Univ, 2020) Gokce, H. Suleyman; Hosseinnezhad, Hojjat; Uzum, Onur; Hatungimana, Daniel; Ramyar, KambizIn this study, the effect of binary and ternary cementitious systems composed of portland cement, high-lime fly ash and silica fume on the compressive strength, alkali-silica reaction (ASTM C 1567) and drying shrinkage of mortar mixtures was researched. For this purpose, binary and ternary binders were prepared with partial replacement of cement with either fly ash (15wt% and 30wt%) or silica fume (5wt%) or both mineral admixtures (15wt+%5wt% and 30wt%+5wt%). An alkali reactive basalt aggregate was used in this study. It was found that partial replacement of cement with high-lime fly ash reduced the strength of mortar mixtures even up to 28-days. Besides, addition of 5% silica fume had not a significant effect on the early strength of fly ash-bearing mixtures. However, silica fume inclusion improved the 28-day strength of mixtures. In terms of alkali-silica reaction (ASR), the fly ash with lower lime content reduced the 14-day expansion more than that of fly ash with higher lime content. The opposite results were the case in 28-day ASR expansions. The ASR expansions of the fly ash-bearing mixtures were significantly reduced by the introduction of the additional 5% silica fume to these mixtures. However, silica fume incorporation remarkably increased the drying shrinkage values of the mixtures. Finally, fly ash with higher lime content was found to be more satisfactory in terms of compressive strength, alkali-silica reaction and drying shrinkage in the ternary binder system.Öğe RESEARCH OF PESIMUM REACTIVE AGGREGATE RATIO OF THE PERLITE AGGREGATE WITH DIFFERENT METHODS(Gazi Univ, Fac Engineering Architecture, 2010) Gokce, H. Suleyman; Simsek, OsmanIn this study, it is purposed to determine of reactive aggregate ratio of the perlite aggregate for given up the highest length change. For this purpose, properties of relate to alkali-silica reaction (ASR) of the perlite aggregate determined with non-reactive limestone aggregate. For the determination of ASR, according to ASTM C 1260 accelerated mortar bar method, for microstructure; Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis were carried out on the samples which are perlite, limestone and used both of them. Mixtures were prepared by weight at 0, 10, 20, 30, 40, 50 and 100% ratios with usage of perlite aggregate that obtained from Ankara Cubuk region instead of limestone aggregate that obtained from Ankara Hasanoglan region. 21 pieces of mortar bars were produced for 7 different mixtures. The length change values of the samples were measured on the 3, 7, 10, 14, 21 and 28-day according to the accelerated mortar bar method. Morphology and chemical composition of highest length changed samples were determined with SEM and EDX. Increase of fracture density and Ca ratio was observed in parallel with the increase of length change. According to average of 14 days length change, 40% perlite aggregated samples underwent highest length change and these samples were determined as pesimum reactive aggregate ratio of the perlite aggregate.Öğe Time-dependent fresh properties characterization of 3D printing engineered cementitious composites (3DP-ECC): On the evaluation of buildability(Elsevier Sci Ltd, 2022) Zhou, Wen; McGee, Wes; Zhu, He; Gokce, H. Suleyman; 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 strainstress 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.
