REACTIVE SILICA OF FLY ASH AS AN INDICATOR FOR THE MECHANICAL PERFORMANCE OF BLENDED CEMENTS

Abstract

Research on fly ash has currently shifted towards exploring the characteristics that determine its activity in the cement paste environment. Reactive silica is the principal parameter that determines the pozzolanic potential of a fly ash, its tendency, that is, to react with available calcium hydroxide to form hydration products with binding properties. Once reactive silica is accurately measured, there exists a good opportunity to relate it with the future strength development of a blended cementitious system. In the work presented herein such a correlation was developed. Its validity was tested for the case of several systems containing various kinds of fly ashes (of different lime content, multicomponent containing both types of fly ash and processed one). Results testify that the developed relationship can be applied to obtain a first approximation of the k-value of the respective blended cements, enabling an almost rapid prediction of the quantity and, most importantly, the quality of the ash used in the mix design.