Browsing by Author "Kobya, Veysel"
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Publication Adsorption properties of polycarboxylate ether-based high range water reducing admixture on cementitious systems: A review(Elsevier, 2021-11-05) Karakuzu, Kemal; Kobya, Veysel; Mardani-Aghabağlou, Ali; Felekoğlu, Burak; Ramyar, Kambiz; Karakuzu, Kemal; Kobya, Veysel; MARDANİ, ALİ; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü; 0000-0002-1023-3962; 0000-0003-0326-5015; C-7860-2015; GBH-3020-2022; FEQ-9214-2022Adsorption of polycarboxylateether-based water-reducing admixtures (PCE) on the cement surface affects many properties of cementitious systems, especially fluidity. One of the most important parameters affecting the adsorption behavior of PCE is the anionic group properties. Therefore, understanding the anionic group properties of PCE is of great importance for cement-admixture compatibility. In this study, the effects of PCE's anionic group variation and cement properties on cement-admixture compatibility, especially adsorption, were reviewed based on the studies conducted in the literature. It was observed that phosphate and organo-silane substituted PCEs at certain rates have a positive influence on the fresh state properties of cementitious systems due to adsorption improvement and sulfate resistance. In addition, the fresh state properties of the cementitious system were negatively affected as the C3A content and the increment in fineness of the cement increased the admixture requirement. It was emphasized that the effect of pozzolan utilization on the adsorption properties of PCE in cementitious systems should be considered. Information was given about the properties of PCE recommended for use in the presence of pozzolan.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; Bursa Uludağ Üniversitesi/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 high temperature on polypropylene fiber-reinforced mortars containing colemanite wastes(Elsevier, 2021-11-23) Durgun, Muhammed Yasin; Özen, Süleyman; Karakuzu, Kemal; Kobya, Veysel; Bayqra, Sultan Hüsein; Mardani-Ağhabağlou, Ali; Karakuzu, Kemal; Kobya, Veysel; Bayqra, Sultan Husein; Mardani-Aghabaglou, Ali; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0003-0326-5015 ; 0000-0002-1023-3962; GBH-3020-2022 ; FEQ-9214-2022 ; CDR-7456-2022 ; C-7860-2015In this study, the effect of polypropylene (PP) fiber utilization ratio on the fresh and some hardened properties of mortar mixtures containing colemanite waste (CW), which mainly contains B2O3, SiO2 and CaO, containing mortar mixtures were investigated. The 17 mortar mixtures were prepared by replacing 0, 1, 3, 5, and 7 wt% of cement with CW and by adding 0, 0.5, 0.75, and 1% by volume of PP fibers to the control mixture. In all mixtures, water/binder ratio, sand/binder ratio and slump-flow values were kept constant as 0.485, 2.75 and 220 +/- 20 mm, respectively. Water reducing admixture requirement of each mixture was determined to provide the target slump-flow range in mortar mixtures. There was a change in the amount of admixture according to the amount of CW and fiber content in the mixture. The 28 and 56-day water absorption capacity, compressive strength and high temperature resistance of mortar mixtures were determined. Strength reduction of specimens exposed to 300 degrees C and 600 degrees C were compared. In addition, thermal and scanning electron microscopy (SEM) analyses were performed on the specimens. According to the test results, with the increase in the amount CW and PP fiber in the mixtures, the admixture demand to provide target flow value and the 28-day water absorption capacity of the mixtures increased, while the 28-day compressive strengths decreased. However, while there was no significant change in the 56-day water absorption capacity and compressive strength values of the specimens containing CW, the water absorption capacity increased and the compressive strength decreased upon the presence of fiber in the matrix. The specimens containing both of CW and PP fiber showed better performance in terms of high-temperature resistance.Item Su azaltıcı katkı zincir uzunluklarının farklı C3A içeriğine sahip çimentolu sistemlerin davranışına etkisi(Bursa Uludağ Üniversitesi, 2023-05-03) Kobya, Veysel; Mardani, Ali; Bursa Uludağ Üniversitesi/Fen Bilimleri Enstitüsü/İnşaat Mühendisliği Anabilim Dalı.; 0000-0002-1226-8405Bu tez çalışmasında, polikarboksilat esaslı su azaltıcı katkı (PCE) molekülü zincir uzunluk değişiminin, farklı oranda C₃A içeren çimentolarla ve farklı oranda uçucu kül ikameli çimentolu sistemlerle etkileşimi incelenmiştir. Tez çalışması üç aşamadan oluşmuştur. Birinci aşamada, sabit yan zincir uzunluğunda (2400 g/mol) PCE molekülü ana zincir uzunlukları ve molekül ağırlıkları değiştirilmiştir. İkinci aşamada sabit ana zincir uzunluğunda (21k) PCE molekülü yan zincir uzunlukları ve molekül ağırlıkları değiştirilmiştir. Üçüncü aşamada ise benzer molekül ağırlığında PCE molekülü ana ve yan zincir uzunlukları değiştirilmiştir. Sentezlenen PCE’lerden biri orta ana ve yan zincir uzunluğuna sahip katkı olup üç aşamada da orta değer olarak yer almaktadır. Bu sebeple toplamda 7 adet PCE sentezi yapılmıştır. Sentezlenen PCE’lerin çimento C₃A içeriği ile etkileşiminin incelenmesi için 5 farklı C₃A oranına sahip çimento ile hamur ve harç karışımları hazırlanmıştır. Buna ek olarak, söz konusu PCE’lerle, çimento ağırlığınca %15, %30 ve %45 oranında uçucu ikameli hamur ve harç karışımları hazırlanmıştır. Hazırlanan karışımların taze hal, reolojik ve bazı sertleşmiş hal özellikleri araştırılmıştır. Ayrıca, total organik karbon (TOC), dinamik ışık saçılımı (DLS) ve taramalı elektron mikroskobu (SEM) analizleri yapılarak PCE molekülü zincir uzunluk değişiminin çimento C₃A miktarı ve uçucu kül ile uyumu detaylıca incelenmiştir. Sonuçlara göre, belirli bir noktadan sonra ana zincir uzunluğu artışının (ana zincir uzunluğu 21k’dan büyük olduğunda) PCE’nin hidrodinamik çapını küçülttüğü, adsorbsiyon miktarını azalttığı ve performansını düşürdüğü tespit edilmiştir. Yan zincir uzunluğunun artışı (2400 g/mol’den büyük olması halinde) ise özellikle C₃A oranı yüksek çimento içeren karışımlarda reolojik özelliklerin olumsuz etkilenmesine yol açmıştır.