Three Effects of Fly Ash


Release time:

2021-01-08

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Three Effects of Fly Ash
 
Fly ash is the fine ash collected from the flue gas after coal combustion. Fly ash is the main solid waste discharged from coal-fired power plants. The main oxides of fly ash in thermal power plants in China are SiO2, Al2O3, FeO, Fe2O3, CaO, TiO2, etc. With the development of power industry, coal-fired power plant fly ash
 
Emissions are increasing year by year, becoming one of the largest industrial wastes in China. If a large amount of fly ash is not treated, it will produce dust and pollute the atmosphere; if it is discharged into the water system, it will cause river siltation, but the fly ash can be used as a resource, such as concrete admixture.
The fly ash is similar in appearance to cement and varies in color from milky to gray-black. The color of fly ash is an important quality index, which can reflect the amount and difference of carbon content. To a certain extent, it can also reflect the fineness of fly ash. The deeper the color, the finer the particle size of fly ash and the higher the carbon content. There is fly ash
 
Low calcium fly ash and high calcium fly ash. Usually the color of high calcium fly ash is yellow, and the color of low calcium fly ash is gray. The fly ash particles are porous honeycomb structure with large specific surface area and high adsorption activity. The particle size range is 0.5~300 μm. And the bead wall has a porous structure, pore
 
The rate is as high as 50%-80%, with strong water absorption. Inferior fly ash glass beads less, water demand, after use is easy to cause concrete bleeding or delayed bleeding, reduce the working performance of concrete, easy to lead to insufficient strength of concrete 28d, late strength growth is low, resulting in unqualified concrete engineering quality. So choose
 
Pay attention when buying.
 
Fly ash has three major effects:
 
(1) surface effect: fly ash surface can adsorb some ions in the slurry, which is beneficial to some harmful ions in fly ash solidified concrete and form hydration products as crystal nuclei.
(2) Filling effect: the difference in particle size between fly ash and cement can fill the pores of cement and aggregate, reduce the porosity of concrete and increase the compactness of concrete;
(3) The active effect of pozzolan: the active SiO2 in fly ash reacts with the cement hydration product CH twice to generate C- S-H gel to fill the pores of the aggregate-cement paste interface layer, improve the structure of the concrete interface, and improve the strength and durability.
 

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