Browsing by Author "Uzal, B."

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Citation - WoS: 47
Citation - Scopus: 49
Characteristics of Calcined Natural Zeolites for Use in High-Performance Pozzolan Blended Cements
(Elsevier Sci Ltd, 2014) Kucukyildirim, E.; Uzal, B.
Two natural zeolites with different characteristics were calcined at various temperatures in order to improve the benefits provided by their use in blended cements as cement replacement material. Natural zeolites were firstly characterized for their crystallinity by X-ray diffraction analysis, specific surface area by nitrogen absorption, and pozzolanic activity by electrical conductivity method, before and after the calcination. In order to assess the performance of calcined natural zeolite as cement replacement material, blended Portland cement pastes and mortars with raw and calcined zeolites were tested for their water requirement, free lime content, pore size distribution and compressive strength. The experimental results indicated that calcined zeolites are more desirable with lower water requirement and higher strength performance as cement replacement material than the raw zeolites. Blended cement with calcined natural zeolite showed higher compressive strength performance, when compared to that with the raw zeolite due to decreased porosity and refined pore structure of the hardened cementitious system. (C) 2014 Elsevier Ltd. All rights reserved.
Citation - WoS: 45
Citation - Scopus: 50
Enhancement of Pozzolanic Activity of Calcined Clays by Limestone Powder Addition
(Elsevier Sci Ltd, 2021) Argin, G.; Uzal, B.
The influence of limestone powder addition on pozzolanic reactivity of calcined clays were investigated. Two clays containing kaolinite and halloysite in their compositions were obtained from different deposits in Turkey and physical, mineralogical, and morphological properties of the raw and calcined clay were characterized. Pozzolanic reactivity of calcined clays with and without limestone powder addition was then examined by means of lime consumption in lime-calcined clay pastes and their isothermal calorimetry as well as strength activity index test. Limestone powder addition enhanced the pozzolanic reactivity of calcined clays by increasing lime consumption and presenting higher heat of reaction released during pozzolanic activity. Limestone addition also provided benefits of reduced water requirement and increased strength activity for calcined clays. Improvements in pozzolanic reactivity and strength activity of calcined clays with limestone powder addition were attributed to nucleation effect provided by limestone particles and also formation of carboaluminate phases during pozzolanic reaction. (C) 2021 Elsevier Ltd. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 10
Performance of Leonardite Humic Acid as a Novel Superplasticizer in Portland Cement Systems
(Elsevier, 2021) Ozuzun, S.; Uzal, B.
Significance of superplasticizers (SPs) in sustainable development of concrete industry is well known regarding to reduced water and Portland cement content of the mixtures. Development of eco-efficient alternative types of SPs is needed. A humic-acid based superplasticizer derived from leonardite (LHA) as a natural organic matter was examined in terms of its plasticizing performance and influence on hydration as well as properties of Portland cement (PC) in comparison with lignosulfonate- (LS) and naphthalene-based admixture (NA). The impact of LHA on hydration of Portland cement was investigated for various dosages of addition by isothermal calorimetry and thermo-gravimetric analysis of hardened pastes. In addition, effect of admixtures on setting time of PC pastes as well as flow and compressive strength of mortars were also studied. Experimental results indicated that LHA has similar impact on early hydration kinetics and setting time of PC when compared to NA. However, LS caused dramatic retardation on PC hydration. LHA addition was also increased the degree of hydration of PC both at 7 and 28 days, and this increasing was more pronounced at 7 days. LHA showed a comparable plasticizing performance to the other admixtures as measured by flow of mortars for 0.3% equivalent solid dosage. Compressive strength of mortars with LHA addition was higher than that of control PC mortar at 3, 7 and 28 days of age for all the dosages tested. LHA was found to have a considerable potential for use as superplasticizer in cementitious systems with its reasonable effects on hydration and properties of PC.
Citation - WoS: 3
Citation - Scopus: 3
Properties of Concrete With High-Volume Pozzolans
(Woodhead Publ Ltd, 2013) Uzal, B.
This chapter focuses on the materials and properties of high-volume natural pozzolan (HVNP) concrete. The characteristics of natural pozzolans used in high-volume pozzolan mixtures are discussed, together with the fresh and hardened properties of HVNP cementitious systems, their hydration characteristics and their microstructures.