Document Type

Article

Abstract

The behavior of unprocessed calcareous fly ash in cement mortar mixtures is often questionable and unpredictable and that is one of the difficulties in confining these fly ashes within the limits of standards. This work aims at correlating the material characteristics with its behavior in mortar mixtures. An effort is made to understand how three of the reactive constituents; lime (CaO), silica (SiO2), and sulfates (SO3), affect strength and volume stability. Two raw calcareous fly ashes of different composition emanating from the Ptolemaida area, Greece, were systematically tested to define their profile as cementitious agents that could be incorporated in a cement mixture by replacing part of the cement. Apart from chemical analysis, a mineralogical analysis of their phases was carried out by x-ray diffraction and SEM microscopy. Fineness was measured by sieving and laser particle size analysis to identify the most prevalent grain size. In order to measure soundness and water demand of the pastes, the corresponding EN and ASTM standards were followed. A number of specimens were also prepared in order to determine the pozzolanicity index of the fly ashes. Furthermore, mortar mixtures with either calcareous fly ashes as the only binder or in combination with cement (50/50) were prepared both with and without superplasticizers (SPL) in order to monitor strength development. The early deformation of these mortars, stored at low relative humidity (less than 65%) and a temperature of 20 uC, was also measured. Evaluating all the results, some remarks are made about the performance of the existing standards. It is also obvious that the water/binder ratio is an important parameter which can be modified by using SPL and in this way it is possible to improve significantly strength and volume stability of cement-fly ash mortar mixtures.

First Page

9

Last Page

14

DOI

10.4177/CCGP-D-09-00012.1

Publication Date

1-1-2010

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