REACTIVE SILICA OF FLY ASHES IN RELATION TO THE BURNING CONDITIONS OF LIGNITES

A significant number of researchers have confirmed that the pozzolanic reactivity of fly ashes is depended, apart from their fineness, mainly on their reactive silica content, while the reactive calcium oxide content is also contributing to the total amount of calcium oxide that takes part in the hydration reactions. The present study includes the results of a series of laboratory tests, where the lignite burning kinetics is examined and in particular the effect of the burning conditions (temperature and retention time) of different originated lignites in the reactive silica content of the resultant fly ashes. A brief review on different methodologies for estimating the reactive silica content of fly ashes and the justification for the selection of the used methodology lies in the beginning of the paper.

The study concludes that, the reactive silica content of fly ashes is highly depended on their origin as well as on the burning conditions of the lignites. Regarding the burning temperature, an increase of the reactive silica content up to 1100 C, following the increase of the total silica content of the same fly ashes is observed. On the other hand, extended exposure of the lignites in the optimum temperature bears negative consequences on the reactive silica percentage of fly ashes. The aforementioned conclusions are testified by TGA and X-Ray Diffraction analyses.

• INTRODUCTION

• ACTIVE SILICA DETERMINATION METHODS REVIEW

• THE OBJECTIVES

• EXPERIMENTAL PROCEDURES

• RESULTS AND DISCUSSION

• CONCLUDING REMARKS

• REFERENCES