Application of isothermal and isoperibolic calorimetry to assess the effect of zinc on cement hydration
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The amount of zinc in the clinker or in the secondary raw materials has been increasing in recent years. Zinc can get to Portland cement from solid waste or tires which are widely used as a fuel for burning in a rotary kiln. The aim of this work was to determine the effect of zinc on Portland cement hydration. This effect was studied by isothermal and isoperibolic calorimetry. Both calorimetry methods are suitable for measurements during the first days of hydration. Isoperibolic calorimetry monitors hydration process in real-life conditions, while isothermal calorimetry does it at a defined chosen temperature. Zinc was added to the cement in the form of two soluble salts of Zn(NO3)2, ZnCl2 and a poorly soluble compound ZnO. The concentration of zinc added was chosen as 0.05, 0.1, 0.5 and 1 mass%. The results show that increasing amounts of zinc ions in cement pastes lead to hydration retardation and reduce both the maximum temperature and the maximum heat flow due to the retarding effect of zinc. The newly formed compounds during hydration were identified by X-ray diffraction method.
KeywordsPortland cement Zinc Isothermal calorimetry Solution calorimetry Hydration
This work was financially supported by the project Materials Research Centre at FCH BUT—Sustainability and Development. REG LO1211 with financial support from National Program for Sustainability I (Ministry of Education Youth and Sports).
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