ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 54, (2) 144 - 151 (2010)


INFLUENCE OF THE COARSE FLY ASH ON THE MECHANICAL PROPERTIES OF THE CEMENT MORTARS
 
Jozic Dražan 1, Zelić Jelica 1, Janjatović Igor 2
 
1 University of Split, Faculty of Chemical Technology, Department of Inorganic Technology, Teslina 10/V, 21000 Split, Croatia
2 Nexe grupa d.d., Braće Radića 200, Našice, Croatia

Keywords: Waste materials, Fly ash, Cement, Compressive strength, Shrinkage
 

This study has examined the effect of fly ash used as replacement addition (in the quantities of 0-40 mass %) to the Ordinary Portland cement (OPC) (type CEM I 42,5R) on the setting time in the system of paste, compressive strength development (w/s = 0.475-0.5, t = 20°C) and on drying shrinkage of cement mortars (t = 20°C, RH ≥ 55 %). Enlarged addition of fly ash affects extension of setting time and also affects reducing of the water, needed to achieve normal consistency. The increased addition significantly improves resistance to drying shrinkage throughout the measurement period. On the other side, increased amount of added fly ash reduces early strengths of cement mortars. In the later hydration stages, when pozzolanic reaction takes place, the strength difference between samples made with and without addition of fly ash decreases. The effect of the pozzolanic reaction, determined by using TG/DTA, can be observed after 60 days of hydration. A detailed chemical (X-ray diffraction), thermogravimetric and morphological (scanning electron microscope (SEM)) analyses of the hydrated samples of mortars are presented.


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