The effect of high-speed grinding technology on the properties of fly ash

Abstract

The aim of this work was to observe the impact of the milling technique employed by the DESI 11 disintegrator on the properties of fly ash. This type of mill is a high-speed pin mill with two counter rotors. The device selected for study allows the use of rotors with different working tools. In this case, two types of rotors were selected, identified as BR-AR and OR rotors. The OR rotor has cylindrical teeth, while the teeth on the AR-BR rotor can be described as rhomboidal. The fly ash was ground by 1, 2, 3, 5, and 10 passes through the mill. The Blaine specific surface area, particle size and particle size distribution were measured for each sample. The pozzolanic activity was also determined via a modified Chapelle test, and its influence on the shape of the grains was assessed by SEM. The results were compared together and with the original fly ash. There was a steep increase in the specific surface area and pozzolanic activity after the first pass through the mill. The second pass of ash through the mill did not increase the specific surface area due to strong aggregation, which gradually changes into agglomeration. However, the pozzolanic activity still increased during the aggregation phase. This phenomenon was clearly observable for both types of selected rotors. Based on the results, we can say that in the case of fly ash, a high-speed disintegrator can be a promising means of improving its properties via grinding and mechanical activation.