Person: MARDANİ, ALİ
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MARDANİ
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ALİ
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Publication How does rheological behaviour affect the interlayer-bonding strength of 3dpc mixtures?(Taylor & Francis Ltd, 2023-10-06) Şahin, Hatice Gizem; Mardani, Ali; MARDANİ, ALİ; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-8915-879X; 0000-0003-0326-5015; C-7860-2015; IAQ-9713-2023; AAE-2420-2022The biggest obstacle to become widespread 3D Printing Concrete (3DPC) is the insufficient interlayer-bonding strength (IBS). The parameters affecting the IBS are classified as physical effects such as cleanliness and roughness, effects caused by the material properties it contains, and printer-induced effects for instance interlayer interval time, nozzle shape and printing speed. However, it was stated that the rheological properties of 3DPC mixtures should also be examined in order to strengthen the IBS. In this article, the relationship between IBS and rheological properties of 3DPC mixtures is discussed. It was stated that the static yield stress and the structural build-up have an optimum value in terms of the effect on IBS of 3DPC mixtures. On the other hand, studies indicating that the IBS of 3DPC mixtures depends on surface moisture of the layers were also encountered.Publication Effect of water-reducing admixtures having hybrid silicon air-entraining surfactants on some properties of concrete mixtures(Asce-Amer Soc Civil Engineers, 2022-09-01) Emin, Ayvaz; Özen, Süleyman; Mardani-Ağhabağlou, Ali; Ünlu, Ayda; Kapti, Tolga; Emin, Ayvaz; MARDANİ, ALİ; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-0326-5015; GNY-1454-2022; C-7860-2015In order to improve the fresh properties and freeze-thaw resistance of cementitious systems, water-reducing and air-entraining admixtures are actively used in concrete mixtures. Generally, these mentioned admixtures are added to concrete mixtures as two separate admixtures. In this case, when the properties/compositions of one of the admixtures change, compatibility problems of admixtures may occur with each other or with the cement, and the fresh/hardened properties of the concrete may be adversely affected. In this study, a modified water-reducing admixture with both fluidity and air-entraining properties was produced. The utilization effect of high-range water-reducing admixtures (HRWR) having different ethylene oxide/propylene oxide (EO/PO)-based air-entraining surfactants (AES) on some properties of concrete mixtures was investigated. For this purpose, firstly, hybrid silicone AESs with a silicon content of 20%, 33%, and 38.5% were supplied. Then, HRWRs containing seven different AES were produced by using substitution and synthesis methods. In HRWRs produced by the substitution method, 3 and 5 wt. % of HRWR were substituted with EO/PO-based hybrid silicon AES. In the other method, EO/PO-based hybrid silicon air-entraining macromonomers were bonded to the HRWR at ratios of 1, 3, and 5 wt. % during its synthesis process. Replacing HRWR with hybrid silicone AESs increased admixture demand to provide the target slump value in concrete mixtures. Utilization of AESs containing 20% and 33% silicon in HRWR by the substitution method positively affected the permeability and compressive strength of concrete mixtures, while the rise of this ratio to 38.5% by using the synthesis method did not affect them significantly. The presence of surfactant with 20% silicon in 3% and 5% of the admixture and with 33% silicon in 5% of the admixture positively affected frost resistance of concrete mixtures. However, the use of surfactants with 33% silicon content in 3% of the admixture and 38.5% silicon in 1%, 3%, and 5% of the admixture showed a negative effect on the frost resistance of the mixtures.Publication Research on modeling the thixotropic properties of cementitious systems using regression methods in machine learning(Elsevier Sci Ltd, 2023-12-28) Şahin, Hatice Gizem; Altun, Öznur Biricik; Eser, Murat; Bilgin, Metin; BİLGİN, METİN; Mardani, Ali; MARDANİ, ALİ; Mühendislik Fakültesi; Bilgisayar Mühendisliği Bölümü; 0000-0002-8915-879X; 0000-0003-0326-5015; C-7860-2015; AAL-2592-2020; JPK-8822-2023; IAQ-9713-2023; AAE-2420-2022; KUD-7264-2024In this study, the rheological properties of cementitious systems were investigated through modeling studies on structural build-up and breakdown area. The area values were calculated using Herschel Bulkley analysis and hysteresis area method. The properties were examined by varying the composition of the cementitious system (cement fineness, C4AF, C3S, C2S, C3A, equivalent alkali and metakaolin ratio) and changes made in the rheological measurement processes (applied shear rate, maximum shear rate and duration). For this purpose, cement paste mixtures were prepared by substituting metakaolin at four different ratios (3%, 6%, 9%, and 12%) into cements with varying C3A content (2.13, 3.60, 6.82, 9.05%). The modeling study of the obtained results was conducted using three different learning methods: Linear Regression Analysis (LR), AdaBoost, and K Nearest Neighbor (KNN), encompassing machine learning and ensemble learning techniques. It was determined that the most dominant parameter affecting the rheology and thixotropic properties of the mixtures is the metakaolin usage ratio. The pre-shear rate was dominant over the duration and maximum shear rate parameters. Effect of the C3A content on dynamic yield stress and viscosity becomes more pronounced with an increase in the applied shear rate. The KNN method has yielded the best results in all experimental modeling studies. Euclidean distance criterion was used in the KNN method. Although the AdaBoost method obtained results close to the KNN method, the opposite situation was observed depending on the number of data. Logcosh, MAE and RMSE metrics were used to evaluate the experimental results. When the results for 3 different metrics in all modeling studies were examined, the success order of the metrics was found to be Logcosh, MAE and RMSE.Publication Review of research on designing methods and properties of roller compacted concrete mixtures(Pamukkale Üniversitesi, 2020-01-01) Mardani-Ağhabağlou, Ali; Bayqra, Sultan Hüsein; Özen, Süleyman; Altun, Muhammet Gökhan; Faqiri, Zia Ahmad; Ramyar, Kambiz; MARDANİ, ALİ; Bayqra, Sultan Hüsein; Altun, Muhammet Gökhan; Faqiri, Zia Ahmad; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-0326-5015; 0000-0003-2200-2691; AAJ-6415-2021; C-7860-2015; CDR-7456-2022; CBF-4437-2022; COI-3623-2022Roller compacted concrete (RCC) has been widely preferred in the world recently due to its rapid production rate, low cost and good durability compared to those of the traditional concrete. Having different production techniques from conventional concrete, RCC is used in many areas such as factories, oil stations, airports, industrial floor coverings, roads and dams. There are several methods for the proportioning of RCC mixtures, among which maximum density method is the most preferred one. In this study, the methods of designing of RCC mixtures are explained with an emphasis on the maximum density method. In addition, the previous studies on the RCC mixtures designed with the maximum density method are reviewed and suggestions are made for the future researches.Publication Flowability, strength, and water absorption of mortars containing fly ash and wra having varying main chain lengths(Asce-amer Soc Civil Engineers, 2023-04-01) Altun, Muhammet Gökhan; Özen, Süleyman; Ramyar, Kambiz; Mardani, Ali; MARDANİ, ALİ; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-0326-5015; C-7860-2015Within the scope of this study, the effect of the main chain length of polycarboxylate-based water-reducing admixture (WRA) on the fresh properties, compressive strength, and water absorption of mortar mixtures containing fly ash was investigated. Three WRAs with the same structure but different main chain lengths and resultantly different molecular weights were used. Effects of the admixtures on the properties of cementitious systems with 0, 15, 30, and 45 wt.% fly ash were investigated. Irrespective of the fly ash substitution level, the fluidity of the mixtures was improved when the admixture main chain length was increased up to a certain level. Possibly beyond a certain main chain length, the entanglement of too large main chains of the polymer to each other reduced the electrostatic effect of the polymer. Thus, the flow properties of the mixtures were affected negatively. The side chain molecular weight (length) of the admixtures was fixed (2,400 g/mol). However, the molecular weight of the admixtures was adjusted as 24, 48, and 71 kg/mol by changing the main chain length of the polymer. The admixture with 48 kg/mol molecular weight showed the best performance in terms of mortar fresh properties. However, the change in the length of the main chain of admixture did not have a considerable effect on the compressive strength and water absorption of the mortar. In addition, apart from the WRA admixture property, time-dependent flow and permeation properties of the mixtures were affected negatively by the increase in fly ash substitution level.Publication Effect of chain characteristics of polycarboxylate-based water-reducing admixtures on behavior of cementitious systems: A review(Asce-amer Soc Civil Engineers, 2023-08-01) Felekoğlu, Burak; Ramyar, Kambiz; Kobya, Veysel; Karakuzu, Kemal; Mardani, Ali; MARDANİ, ALİ; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0002-1023-3962; 0000-0003-0326-5015; 0000-0002-7426-1698; C-7860-2015Polycarboxylate ether-based water-reducing admixtures (PCEs) have a significant impact on the workability of cementitious systems. The modifications of the chemical structures of the main and side chains can lead to the improvement of electrostatic repulsion and steric hindrance effect of PCEs, resulting in the superior performance of cementitious systems. In this study, the impact of main- and side-chain properties of PCEs on various characteristics, especially the rheology of cementitious systems, was examined in detail via prior studies in the literature. In addition, pH, adsorption conformation, and intercalation state, which affect the aforementioned properties of PCEs, also were studied. It was concluded that the geometric equilibrium between the main and side chains has a vital place in designing optimum molecular structures.Publication Improving the mechanical and durability performance of recycled concrete aggregate-bearing mortar mixtures by using binary and ternary cementitious systems(Elsevier Sci Ltd, 2019-02-05) Yüksel, Cihat; Beglarigale, Ahsanollah; Ramyar, Kambiz; Mardani-Aghabaglou, Ali; MARDANİ, ALİ; Mühendislik Fakültesi; İnşaat Mühendisliği Bölümü; 0000-0003-0326-5015; C-7860-2015Environmental concerns arising from the generation of huge amount of construction and demolition waste requires recycling this material, which would otherwise be sent to landfill. The mechanical and durability performance of mortar mixtures containing recycled concrete (RC) aggregate was investigated in this study. Although it is known that the adhered mortar creates a porous and a weak additional interfacial transition zone in recycled aggregate-bearing mixture, the dependence of the behavior on the type of new matrix should be searched in detail. For this purpose, compressive strength, ultrasound pulse velocity, water absorption, chloride ion penetration, freeze-thaw and sulfate resistance as well as drying shrinkage tests were conducted on mortar mixtures containing either natural aggregate (sand) or recycled concrete aggregate. Scanning electron micrographs and optical microscope images were obtained on specimens exposed to sulfate attack. The mineral admixtures used in the study included silica fume (SF), metakaolin (MK) and a Class C fly ash (FA). In addition to the control mixture including no mineral admixture (PC), silica fume- and metakaolin-incorporating binary systems (PC-SF and PC-MK) were prepared. Besides, two ternary systems, i.e., PC-SF-FA and PC-MK-FA were also designed. The results indicated a gradual strength gain beyond 28 days and reduction in initial shrinkage values in RC-bearing mixtures, compared to those of the sand-bearing mixtures. Besides, the porous character of RC helped reducing the internal pressure and resultant damage related with expanding water and swelling ettringite crystals in freeze-thaw and sulfate attack tests, respectively. The exact effect of recycled aggregate on mortar properties was found to be greatly dependent on the type of the cementitious system of the new mix.Publication Specimen size and shape effects on strength of concrete in the absence and presence of steel fibers(Pontificia Univ Catolica Chile, Escuela Construccion Civil, 2021-04-01) Nobakhtjoo, Amir; Mardani-Aghabaglou, Ali; MARDANİ, ALİ; Bayqra, Sultan Husein; Mühendislik Fakültesi; 0000-0003-0326-5015; AAJ-6415-2021; C-7860-2015In this research, the effects of size and shape on compressive and splitting tensile strength of fibrous and non-fibrous concrete specimens with different characteristic strength were investigated. With this aim, both fibrous and non-fibrous 10 different concrete mixtures with 0.3, 0.4, 0.5, 0.6 and 0. 7 Water/Cement ratio were prepared. In the fibrous mixture specimens, the total amount of steel fibers to 1% by total volume. In the entire specimens, 42.5 R type Portland cement were used as bonding elements while crushed lime stones in 3 sizes were added to the mixtures. Furthermore, to evaluate the influence of size and shapes over specimens' strength, for each concrete mixtures two 10 cm and 15 cm cubic specimen beside two 10x20 cm and 15x30 cm cylindrical specimens were prepared as well. The prepared specimens were subjected to compressive and splitting tensile tests. The results showed that, regardless of the fiber amount and specimens' shapes, the decrease in specimens' size resulted in higher strength. But in the high ratio of Water/Cement and fibrous mixtures, the mentioned behavior was not observed.Publication Durability performance and dimensional stability of road concrete containing dry-shake surface hardener admixture(Elsevier, 2021-03-08) Mardani-Aghabaglou, Ali; Karakuzu, Kemal; Kobya, Veysel; Hatungimana, Daniel; MARDANİ, ALİ; Karakuzu, Kemal; Kobya, Veysel; Mühendislik Fakültesi; İnşaat Mühendisliği; 0000-0003-0326-5015; 0000-0002-1023-3962; FEQ-9214-2022; GBH-3020-2022; C-7860-2015Durability and dimensional stability problems are emerged in road concrete due to traffic loads and environmental factors. The concrete surface treatment is one of the preferred methods to solve these problems economically. As it is known, surface treatment is applied to the concrete surface as dry-shaking and liquid. It is understood from the literature that there are very limited studies about the use of dry-shake hardener admixture in concrete mixtures. In the present study, the effect of dry-shake surface hardener admixture application on mechanical, durability and dimensional stability properties of concrete mixtures having different w/b ratios were investigated. Totally ten series of concrete mixtures coated with and without dry-shake surface hardener admixture were prepared for this purpose. The slump value of concrete mixtures was determined as 85 +/- 5 mm. Vebe, slump and air content tests were performed for each mixture in fresh state and unit weights of mixtures were calculated. Also, compressive strength, modulus of elasticity, transport properties, abrasion resistance, freeze-thaw resistance and drying shrinkage behavior were investigated on the 7, 28 and 90-day specimens. In the light of the experiment results, compressive strength, modulus of elasticity, water sorptivity, abrasion resistance and drying shrinkage behavior of concrete mixtures were positively affected with adding of dry-shake surface hardener admixture. However, it was found that the dry-shake surface hardener admixture application had no significant effect on water absorption, depth of water penetration under pressure and freezing-thawing performances. (C) 2020 Elsevier Ltd. All rights reserved.Publication Effect of colemanite ore wastes utilization on fresh properties and compressive strength of cementitious systems(Springer Heidelberg, 2022-02-20) Özen, Süleyman; Durgun, Muhammed Yasin; Mardani-Aghabaglou, Ali; MARDANİ, ALİ; Kobya, Veysel; Karakuzu, Kemal; Mühendislik Fakültesi; İnşaat Mühendisliği Ana Bilim Dalı; 0000-0001-5522-427X; 0000-0003-4656-9430; 0000-0002-1023-3962; 0000-0003-0326-5015; C-7860-2015; P-9230-2015; AAJ-6415-2021In this study, the usability of colemanite wastes (CW), in mortar mixtures, was examined in terms of compressive strength, while at the same time it was aimed to evaluate the effects of this waste on the rheological properties of mortar and paste mixtures. Mortar and cement paste mixtures were produced by substituting 1, 3, 5, and 7% of the cement with the CW. Marsh-funnel flow times, mini-slump values, rheological parameters, and setting times of cement paste mixtures containing CW were determined. The time-dependent slump-flow and 1-, 7-, 28-, and 56-day compressive strength values of the mortar mixtures were determined. The microstructures of the specimens were evaluated by using SEM images, and phase analyses were examined with XRD analysis. The results showed that the use of CW negatively affected the fresh state properties and rheological parameters of cementitious systems. However, CW addition decreased the 1-, 7-, and 28-day compressive strength. Only a slight increase was observed in the strength of mixtures containing 5 and 7% CW at 56 days.
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