Evaluation of the increase fly ash reactivity through the sonochemistry method

ABSTRACT

The objective of this work was to evaluate the increase of fly ash reactivity (CV) through the sonochemistry method combined with the CV siphoning process, in order to separate constituent materials by phases, being amorphous and crystalline. After that, sonochemistry treatments were performed in two types of equipment as a way of comparison. The treated materials were characterized by the techniques of particle size, specific mass, surface area, chemical and mineralogical composition, and, finally, molded according to the norm NBR 5752: 2014. The modified Chapelle method was also applied to verify the consumption of calcium hydroxide. As a complementary study, microstructural analysis of CV was performed before and after the application of the sonochemistry method using scanning electron microscopy. The results of compressive strength proved that the method used contributed to an increase from 84 to 112.9% of the pozzolanicity index of the material associated with the application of ultrasound. The samples CV NAT, CV ULT SP and CV ULT UNI were able to fix higher amount of lime than CV SIF. However, the index of pozzolanic activity, through indirect hierarchization indicates a favorable behavior with the possibility, even, of declassifying the CV as pozzolanic material, if it is not submitted to a beneficiation process.. In microstructural images there was a reduction in particle size, probably caused by the breakdown of the CV pleospheres.

Keywords
Fly ash; ultrasound; activation sonochemistry; pozzolanicity activity