The physical properties of fly ash

Fly ash is the fine ash collected from the smoke and dust after coal ignition. It is a key solid waste discharged from thermal power plants. The appearance of fly ash is similar to that of concrete, and the color tone changes from milky white to black gray. The color tone of fly ash is a key quality standard that reflects the amount and difference of carbon content. To a certain extent, it can also reflect the particle size of fly ash. The heavier the color tone, the denser the particle size distribution of fly ash, and the higher the carbon content.

Fly ash can be divided into high calcium fly ash and low calcium fly ash. In general, the color tone of high calcium fly ash is darker, while the color tone of low calcium fly ash is grayer. Fly ash particles have a porous honeycomb like structure with a large specific surface area and high adsorption specificity. The particle size range of particles is 0.5-300 μ m. Moreover, the bead wall is made of porous materials with a porosity of 50% to 80%, indicating strong water absorption ability.

The physical properties of fly ash include relative density, apparent density, particle size, specific surface area, water consumption, etc., which are macroeconomic manifestations of its composition and mineral composition. Because the composition of fly ash fluctuates greatly, which determines the significant differences in its physical properties. Among the physical properties of fly ash, particle size and particle size distribution are key new items. It immediately harms other characteristics of fly ash, the denser the fly ash, the larger the proportion of ultrafine powder, and the greater its specificity. The particle size of fly ash poses a risk to the early hydration reaction, while its composition poses a risk to the mid to late stage reaction.

From the perspective of physical properties, fly ash is a type of artificial carbon ash based thermoplastic resin. It has slight water hardening and cementitious properties, but when in powder form and water storage, it can undergo chemical changes with sodium carbonate or other alkali metal nickel hydroxide at room temperature, especially under water conditioning (steam maintenance) standards, and transform into a chemical substance with water hardening and cementitious properties, becoming a raw material for improving compressive strength and performance.