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Öğe Effect of interlayer cold joint on mechanical properties and permeability of roller compacted concrete(Higher Education Press, 2025) Bayqra, Sultan Husein; Ozen, Suleyman; Mardani, Ali; Ramyar, KambizOne issue with layer application of roller compacted concrete (RCC) is the development of cold joints, which can cause damage to RCC structures. In this study, fly ash was used in place of 0%, 20%, 40%, and 60% of the cement or aggregate to examine the impact of interlayer cold joint formation on RCC mixtures. To promote cold joint formation, the second layer was placed and compacted with a delay of 0, 60, 120, or 180 min after the first layer. Three methods were tried for preventing cold joints from forming: one was to apply a bedding mortar to the interlayer, another was to add a set retarder admixture, and the third was to spray an adhesion-enhancing chemical additive on the surface of the first layer. Based on the 28 d specimens' compressive and splitting-tensile strengths as well as the depth of water penetration under pressure, the most effective method was found to be applying interlayer bedding mortar. Considering 180 min delayed layer castings, the splitting-tensile and compressive strengths of the control samples decreased by 31% and 17%, respectively, while the strengths of mixtures applying interlayer bedding mortar decreased by 9% and 10%. In addition, bedding mortar treatment decreased the water permeability by 59% compared to the control. Interlayer cold joint decreased all mixtures' moduli of elasticity, regardless of the age of the specimens. When the interlayer delay was 60 min, the modulus of elasticity decreased by 1%-4%. It was between 2% and 14%, and between 10% and 24% at 120 and 180 min for the interlayer delay. The longer the delay in placing the second RCC layer, the more detrimental the effect of the cold joint. This effect was most noticeable on mechanical and permeability properties tested with applied load or water pressure parallel to the cold joint, such as flexural and splitting tensile strengths and water penetration depth under pressure.Öğe Synthesis, characterization, and efficiency evaluation of next-generation grinding aids modified with organic acids(Elsevier Sci Ltd, 2025) Kaya, Yahya; Kobya, Veysel; Kaya, Yunus; Mardani, Ali; Ramyar, KambizGrinding aids (GAs) are continually modified to enhance grinding efficiency and cement's overall performance. Despite their widespread use in the industry, there is a lack of comprehensive research exploring GA modifications from a chemical standpoint. In this context, the present study focuses on the synthesis and performance evaluation of next-generation GAs achieved through chemical modification of commonly used compounds. To this end, nine modified GAs were synthesized by reacting carboxylic acids with varying carbon chain lengths (acetic, propanoic, and hexanoic acids) with triisopropanolamine (TIPA), diethanol isopropanolamine (DEIPA), and diethylene glycol (DEG). The chemical structures of the synthesized GAs were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 Nuclear Magnetic Resonance (13C NMR), and Gas Chromatography-Mass Spectrometry (GC-MS). Density functional theory (DFT) was also employed to analyze their molecular structures theoretically. Grinding efficiency was assessed through laboratory-scale experiments, while the adsorption potential of the modified GAs toward Ca2+ ions was examined via theoretical calculations. Zeta potential analysis of the obtained cements was conducted to corroborate experimentally the adsorption results derived from molecular modeling. The results indicated that chemical modifications enhanced both the milling efficiency and the adsorption performance of grinding aids, as confirmed by both experimental and modeling studies. These findings provide a valuable reference for developing energy-efficient and environmentally sustainable grinding aids.Öğe Başlıksız(Higher Education Press, 2020) Özen, Süleyman; Altun, Muhammet Gokhan; Mardani-Aghabaglou, Ali; Ramyar, KambizDespite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5 R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed.Öğe Başlıksız(Taylor & Francis Ltd, 2021) Özen, Süleyman; Altun, Muhammet Gokhan; Mardani-Aghabaglou, Ali; Unlu, Ayda; Ramyar, KambizIn this study, the effects of anionic monomer functional group type of the water-reducing admixture (WRA) on the fresh properties and compressive strength of self-compacting concrete (SCC) mixtures were investigated. Nine types of polycarboxylate ether-based high-range WRAs with the same main chains but different anionic monomers linked to the main chain were synthesized and used in different dosages to provide the desired slump-flow value in SSC mixtures. For this motivation, in addition to the control admixture consisted of 100% carboxylate functional group, 5, 10, 20 and 30% of carboxylate functional group was replaced by either phosphate or sulfonate group. Test results revealed that the admixtures containing sulfonate and phosphate anionic monomer improved the fresh properties of SCC mixtures compared to those of the control admixture. However, anionic monomer exchange in the structure of the WRA did not significantly affect the compressive strength and water absorption capacity of the SCC mixtures.Öğe Başlıksız(Ernst & Sohn, 2021) Özen, Süleyman; Altun, Muhammet Gokhan; Mardani-Aghabaglou, Ali; Ramyar, KambizIn this study, the effect of both main and side chain length changes of the admixtures on some properties of cementitious systems were investigated. Three different polycarboxylate-ether-based water-reducing admixtures (WRA) having constant molecular weights and different main and side chain lengths were synthesized. Single type of raw material and carboxylate functional group were used in all WRAs. The molecular weights, free nonionic contents, and anionic/nonionic ratios of the admixtures were kept constant. Test results showed that degree of fluidity was observed in cement paste and mortar mixtures in case the admixture main and side chain length is more or less than a critical value. This negative effect is thought to be due to the weakening of the adsorption ability by the chain length change of the admixtures, the being tendency of polymers to intertwine and the adsorbing of admixture on several cement particles simultaneous. Admixtures having excessive long or short main chain and side chain improved the time-dependent slump-flow retention of the mortar mixtures. The admixtures with short main and side chains had insufficient adsorption ability and the admixture with excessive long main and side chains had the interlacing risk of polymers. In both cases, time-dependent behavior improved because the amount of free admixture in solution increased. The change in the chain lengths of the WRAs affected the 1-day compressive strength of the mortar mixtures.Öğe Başlıksız(2020) Mardanı-Aghabaglou, Ali; Bayqra, Sultan Husein; Özen, Süleyman; Altun, Muhammet Gökhan; Faqırı, Zia Ahmad; Ramyar, KambizGeleneksel betonlara oranla hızlı üretimi, düşük maliyeti ve dayanıklılığının iyi olması silindirle sıkıştırılmış betonların (SSB) son zamanlarda dünyada yaygın olarak tercih edilmesine neden olmuştur. Söz konusu SSB, fabrikalar, petrol istasyonları, hava limanları, çeşitli endüstriyel zeminler, yollar ve barajlar gibi birçok alanda kullanılmaktadır. Normal betona kıyasla çok farklı üretim tekniğine sahip SSB’lerin karışım oranları çeşitli tasarım yöntemlerine göre belirlenmekte ve en çok tercih edilen yöntem olarak maksimum yoğunluk yöntemi dikkat çekmektedir. Bu çalışmada, SSB’lerin tasarım yöntemlerinden genel olarak bahsedilerek, maksimum yoğunluk yöntemi detaylı olarak açıklanmıştır. Ayrıca maksimum yoğunluk yöntemi ile tasarlanan SSB’ler ile ilgili çalışmalar özetlenerek bundan sonra yapılacak araştırmalar için önerilerde bulunulmuştur.
