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    Effect of main and side chain length change of polycarboxylate-ether-based water-reducing admixtures on the fresh state and mechanical properties of cementitious systems
    (Ernst & Sohn, 2021) Özen, Süleyman; Altun, Muhammet Gokhan; Mardani-Aghabaglou, Ali; Ramyar, Kambiz
    In 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.
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    Effect of nonionic side chain length of polycarboxylate-ether-based high-range water-reducing admixture on properties of cementitious systems
    (Higher Education Press, 2020) Özen, Süleyman; Altun, Muhammet Gokhan; Mardani-Aghabaglou, Ali; Ramyar, Kambiz
    Despite 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.
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    Effects of anionic monomer type of water-reducing admixture on fresh properties, compressive strength and water adsorption of self-compacting concrete
    (Taylor & Francis Ltd, 2021) Özen, Süleyman; Altun, Muhammet Gokhan; Mardani-Aghabaglou, Ali; Unlu, Ayda; Ramyar, Kambiz
    In 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.
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    Silindirle sıkıştırılmış beton karışımlarının tasarım yöntemleri ve yapılan çalışmalar
    (2020) Mardanı-Aghabaglou, Ali; Bayqra, Sultan Husein; Özen, Süleyman; Altun, Muhammet Gökhan; Faqırı, Zia Ahmad; Ramyar, Kambiz
    Geleneksel 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.