Simultaneous thermogravimetric and differential thermal analysis determination of products formed during hydration of bl
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Simultaneous thermogravimetric and differential thermal analysis determination of products formed during hydration of blended Portland cement doped with zinc Jiří Švec1 · Pavel Šiler1 · Jiří Másilko1 · Radoslav Novotný1 · Jan Koplík1 · Martin Janča1 · Jan Hajzler1 · Lukáš Matějka1 · Tomáš Opravil1 · Iva Kolářová1 Received: 11 January 2020 / Accepted: 14 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract With the increasing use of secondary raw materials and alternative fuels in the cement production industry, the amount of present trash elements rapidly increases. Most of these problematic elements affect the quality of produced clinker or blended cement. This study focuses on zinc and his influence on the hydration process and the formation of new hydration products. Zinc in percentage by mass of OPC 1% and 5% was added in the form of Zn(NO3)2, ZnCl2 and ZnO for modelling of the formation or modification of newly formed products. These new phases are present in mostly trace quantities, and quantification of even well-known phases such as Ca(OH)2 via X-ray diffraction method (XRD) is not suitable due to poor crystallinity and stoichiometry of some zinc compounds related phases. On the other hand, even smaller quantities of known phases could be precisely characterized via simultaneous thermogravimetric (TG) and differential thermal analysis (DTA). Special emphasis was given to mentioned Ca(OH)2 as one of the hydration degree indicators. With a very high content of chloride and nitrate anoint, the hydration, process was not only retarded by zinc but significantly altered causing creation of new phases mainly ettringite analogues with these anoints. In samples with a high dosage of Zn(NO3)2, ZnCl2 even Ca(OH)2 as hydration product cannot be identified by TG–dTG nor XRD. On the other hand with ZnO as zinc source, significant influence on hydration was proven. Initially as retarding agent for early stages of hydration, but also as the agent that increased final degree of hydration relatively to reference OPC. Keywords Ordinary Portland cement hydration · Zinc · Hydration retardation · Calcium zinc hydroxide
Introduction With the constant increase of ecological and economical demands of worldwide cement and concrete industry, the increasing amount of various secondary raw materials or even wastes are introduced into production, processing and technology of concrete based on ordinary Portland cement (OPC). A very important field of research and technology is also immobilization of toxic elements such as heavy metals from contaminated soils, wastewater or industrial wastes. The negative side of heavy metals immobilization via OPC
* Jiří Švec [email protected] 1
Faculty of Chemistry, Materials Research Centre, Brno University of Technology, Purkyňova 118, 61200 Brno, Czech Republic
use is changes in the hydration process and final mechanical properties of concretes caused by oxides or cations of these heavy metals. Heavy metals such as lead, chromium and zinc are among the most considered heavy me
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