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Univerzitet u Zenici
  Doctoral theses defended at the University in Zenica

Date and place of thesis defense:
27.06.2008, Faculty of Metallurgy and Materials Science
Candidate:
mr. sc. Ilhan Bušatlić
Mentor:
prof. dr. Zijad Pašić

Thesis title:

Contribution to investigation of changes in reactivity and properties of cement with fly ash from the Kakanj Thermo-Electric Plant

Summary:
This research study investigates the effect of fly ash from the Kakanj Thermo-Electric Plant on the cement hydration process. Specifically, the study focuses on the physical and chemical characteristics of cement and its resistance to sulphate corrosion.
The hydration of Portland cement is a process, which mainly depends on the physical and chemical characteristics of the cement composite, whether plaster or concrete. The reaction mechanisms of the hydration of Portland cement minerals (C3S, C2S, C3A, and C4AF) have therefore been presented theoretically within the research framework. The effect of fly ash additives on cement hydration has been based on this theoretic data, as well as the detailed chemical charge of pozzolanic reactions between fly ash and cement. Within a framework of theoretic research on the reaction mechanisms of sulphate cement corrosion, and also the practical section of this research, the effect of fly ash additives on sulphate cement corrosion was also researched.
The practical section of this research examines the physical and chemical characteristics of fly ash from the Kakanj Thermo-Electric Plant, namely:
  • chemical composition (XRF method)
  • mineral composition (XRD method)
  • specific surface (Blen method)
  • specific density
  • distribution of particle dimensions (laser micro-sizer)
  • non-combusted carbon content (thermal TG/DTG-DTA method)
A preparation of fly ash and clinker derived from the Kakanj Thermo-Electric Plant was then ground using a laboratory ball-mill, resulting in six cement patterns with fly ash contents varying from 0% mass to 50% mass. All cements were ground to a specific surface of 3000 cm2/g.
The research examines the physical-chemical characteristics of these prepared cements and confirms that the inclusion of fly ash does influence the characteristics of cement, namely:
  • chemical composition
  • granulometric combination (sieve analysis)
  • specific density
  • normal consistency
  • start and end of cement linkage
  • cubage continuity
  • mechanical characteristics (load and force solidity) after 3, 7, 28, 56, 120 and 270 days
  • sulphate corrosion
In order to observe the impact of the inclusion of fly ash on the cement hydration process, the released hydration heat was examined, using a calorimetric method, and the specific conductance of the cement paste was examined, using an electro-conducting method under different water/cement factors (w/c = 0.5 and w/c = 1). The qualitative and quantitative compositions of cement hydration products were observed by restraining the cement hydration process following a period of hydration, an X-ray diffraction (XRD), and thermal analysis (TG/DTG-DTA) of the hydrated cement stone. It was established that the inclusion of fly ash does influence the cement hydration process, specifically the reactivity of cement.

Key words: fly ash, cement, cement hydration, pozzolanic reaction, solidity, sulphate corrosion, electro-conductance, calorimetric method, XRF, XRD, TG/DTG-DTA.

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