News Date:2016-06-23 14:18:45
People think that fly ash has a very fine, and how does the vertical roller mill machine grinding it? Practice has proved that particularly suitable for mechanical grinding coarse ash and fine ash effect was not significant. Even a long period of ultra-fine grinding, the pozzolanic activity is still low.
This is due to low activity of fly ash fundamental reason is that: 1, low CaO content, a high degree of polymerization (CaO / SIO2 about 0.8-1.2, oligomers less than 10%), soluble SIO2 and Al2O3 content is low, powder body surface along the grain off the little key, O2-, Ca2 +, Mg2 + and other less active site. Although the ultra-fine grinding can promote the dissolution of soluble reaction SIO2 and Al2O3, but the improvement of several other important factors insignificant and emblem, to improve the pozzolanic activity is limited.
The main chemical composition of fly ash as SiO2, Al2O3 and Fe2O3, the ash contains more calcium CaO. As early as 1914, Americans Anon issued a "study volcanic ash characteristics", the first found in fly ash oxides having pozzolanic properties. Because cement and concrete with fly ash in large quantities, and therefore its application China's cement industry has been the focus of the study.
According to data, the use of fly ash in concrete, it mainly produced three effects: the effect of active volcanic ash, Ca( OH2) that is produced by the hydration of cement fly ash will stimulate activity, so that the reaction to the CSH gel Lord gelling material; shape effect, namely fly ash particle morphology of the decision, when the content is more than 50% of the microbeads, improve liquidity, reduce water consumption of concrete, improve the concrete nature of the work; micro-aggregate effect, That is less than more than 45μm powder sieve pores can be filled with concrete, and Ca (OH2) gel produced by the reaction can also be filled with tiny pores of the concrete is more compact.
Now, with economic development, people's environmental awareness, fly ash recycling has become social concerns, Chaeng(Great Wall Machinery Co., Ltd). has developed a series of grinding mill to fly ash processing, after its fly ash fine grinding mill can not only speed up the rate of hydration of clinker particles can also damage ash dense spherical shell in advance, accelerate pozzolanic reaction of fly ash, thereby improving early strength cement . Fly ash or coarse ash after the original vertical fine grinding mill to a certain fineness, the ash formed after the incorporation of concrete admixtures, not only can replace part of the cement, coal, electricity, limestone consumption reduce the cost of concrete, protect the environment, but also improve the late strength of concrete to improve the workability of fresh concrete, improve the durability of concrete to produce high quality cement.
