Investigation of different ways of activation of fly ash–cement mixtures: part 2—mechanical activation

Abstract

Introducing supplementary cementitious materials (SCM), e.g. fly ash, into cement composite results in ecological benefits. However, in the case of high amount of SCM used as a replacement of a part of cement, there are problems related to the development of the desired properties of the final composite. Such mixtures often require activation. In the first part of this series of publications, the results of chemical activation (using Na2SO4 and Ca(OH)2) of a mixture with a very high content of fly ash were discussed. The aim of this work was to investigate the influence of mechanical activation on hydration and microstructure of the binder composed of 80% of fly ash and 20% of cement. Mechanical activation was performed using a planetary ball mill. The following instrumental methods were used to investigate the activated fly ash-cement pastes: calorimetry, TG/DTG, FTIR spectroscopy, X-ray diffraction and scanning electron microscopy (SEM) coupled with EDS. It was shown that concomitant grinding of cement and fly ash is more effective compared to separate grinding. Mechanism of hydration/activation of such mixtures was discussed in detail.