Mechanical Activation Of Fly Ash Research Articles

The Mechanical Activation of Fly Ash

One of the main options in looking for the new building materials is using of wastes from an industry as a replacement of the existing ingredient. This way is used in the concrete production too. Basic effort is to find a suitable replacement for economically and ecologically unfavorable cement by another component or components. As one of these components can be used fly ash – by-product of coal-fired electric power stations. The using of the fly ash as an additive into concrete is quite old, nevertheless this component offers a lot of new possibilities today too. Mechanical activation is one of them. As mechanical activation is known sorting or grinding of fly ash. Activation by sorting brings some disadvantages as is not using of all production and the high price for rebuilding the plants. Much more effective option provides grinding of the fly ash. This practice also comes to Czech Republic and submitted publication summarizes existing knowledge and presents result from first tests done on Czech fly ashes.

Mechanical activation of fly ash: Effect on reaction, structure and properties of resulting geopolymer

Geopolymerisation of mechanically activated fly ash was studied at ambient (27 °C) and elevated (60 °C) temperatures by isothermal conduction calorimeter. Under both the conditions, mechanical activation enhanced the rate and decreased time of reaction. It was interesting to observe that in the samples milled for 45 min (median size ∼5 μm), a broad peak corresponding to geopolymerisation initiated at 27 °C after 32 h. The rate maxima at 60 °C, a measure of fly ash reactivity, showed a non-linear dependence on particle size and increased rapidly when the median size was reduced to less than 5–7 μm. Improvement in strength properties is correlated with median particle size, and reactivity of fly ash. The characterisation of the geopolymer samples by SEM-EDS, XRD and FTIR revealed that mechanical activation leads to microstructure and structural variations which can be invoked to explain the variation in the properties.

Effect of mechanical activation of fly ash on the properties of geopolymer cured at ambient temperature

The effect of the mechanical activation of fly ash on the properties of the geopolymers cured at ambient temperature has been studied. Mechanical activation of the fly ash results in particle size and morphology changes with concomitant increase in reactivity with alkaline liquid. Addition of free water in the reaction mix decreases mechanical properties of the geopolymer samples. After 28 days, compressive strength of the room temperature cured samples was 16 (2) MPa and 45 (8) MPa for unmilled and mechanically activated fly ash based samples, respectively.