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 Compatibility of Superplasticizers With Natural Pozzolan Blended Cement: Multi-Criteria Compatibility Index Through Rheology and Hydration Kinetics(Taylor & Francis Ltd, 2025-08-09) Argin, Gizem; Uzal, BurakAn effective technique to decrease carbon dioxide emissions in the cement industry is the partial replacement of clinker with supplemental cementitious materials (SCMs). Given the restricted supply of by-product SCMs such fly ash, blast furnace slag, and silica fume, natural pozzolans provide viable options in the manufacturing of blended cement. In cementitious systems with natural pozzolans, the use of superplasticizers is essential to compensate for the reduced workability caused by their higher water demand. This study investigates the compatibility of different superplasticizer types, administered at similar dosages, with Portland cement containing 40% natural pozzolan, focusing on paste rheology and hydration kinetics. A Multi-Criteria Compatibility Index (MCCI) was created to provide a comprehensive and quantitative evaluation of compatibility between natural pozzolans and different types of superplasticizers, utilizing rheological and hydration kinetics within a weighted scoring framework. The assessment findings indicated that PMS displayed the best overall compatibility, principally owing to its improved hydration properties, but PNS revealed enhanced performance in rheological characteristics. PCA demonstrated restricted compatibility in both categories. The MCCI framework delivered a balanced and thorough comparison unattainable by single-parameter studies, providing a solid methodological foundation for future study on SCM-admixture compatibility.