Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 8Citation - Scopus: 10Performance of Leonardite Humic Acid as a Novel Superplasticizer in Portland Cement Systems(Elsevier, 2021-10) 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.Article Citation - WoS: 130Citation - Scopus: 140Influence of Admixtures on the Properties of Alkali-Activated Slag Mortars Subjected to Different Curing Conditions(Elsevier Sci Ltd, 2013-02) Bilim, Cahit; Karahan, Okan; Atis, Cengiz Duran; Ilkentapar, SerhanThis paper presents the influence of shrinkage-reducing (SHR) and superplasticizing and set-retarding admixtures (SSRe) on the properties of slag pastes and mortars activated by liquid sodium silicate with different dosage and modulus ratio. Properties in the fresh and hardened state for these binders were investigated by means of measuring some properties including setting time, flowability, flexural strength, compressive strength, carbonation and shrinkage. In this study, fifteen pastes and mortars were prepared. Liquid sodium silicate was used to activate the slag at two sodium concentrations, 4% and 6% by mass of slag. Liquid sodium silicate and sodium hydroxide were blended to obtain 0.75 and 1 modulus ratio of SiO2/Na2O. Results showed that although the higher percentage of sodium in the activator produced a higher strength, workability and setting times rapidly decreased with the higher sodium concentration due to instantaneous reaction and quick hardening of slag activated by liquid sodium silicate. None of the admixtures generally had an impact on the setting times of alkali-activated slag (AAS) pastes. SSRe admixture increased the flow rate of AAS mortars while SHR admixture partially affected the flow values of AAS mortars. SHR admixture exhibited a slight decrease in the carbonation depths of AAS mortars. SSRe and particularly SHR chemical admixtures reduced the shrinkage of AAS mortars. However, the shrinkage values of AAS mortars still were higher than those of ordinary Portland cement (NPC) mortars. Curing conditions had a significant effect on the mechanical behavior in the hardened state of AAS mortars compared to NPC mortars. (C) 2012 Elsevier Ltd. All rights reserved.