How to add a lot of limestone to the vertical mill?Date: 2019-07-09 Views:
Limestone is a readily available and inexpensive blend of cement plants that also improves a range of cement properties. The use of natural and cheap resources, limestone, as a mixture of cement production, shows great economic value to the cement industry, so in order to reduce costs, many companies want to add a lot of limestone. So how can we add as much limestone as possible without affecting the quality of the cement? The Zhengyuan machine below analyzes how to add a large amount of limestone to the cement grinding.
First, the role and characteristics of the use of limestone in cement
Limestone is often simply mistaken for just a filler that reduces the amount of clinker in the cement to achieve the goal of reducing costs for cement manufacturers.
In fact, the impact of limestone and clinker grinding on cement strength has two main factors. On the one hand, the limestone can be compacted after reaching the appropriate ratio, so the early strength will increase; the limestone fine powder will play the role of “nucleation nucleus” in the process of cement hydration, promote the hydration of C3S, and lead to the densification of cement slurry. increase. On the other hand, limestone has limited hydration activity, and a large amount of limestone is used. The relative content of clinker is reduced, and the strength is reduced in the later stage.
The surface of the limestone fine powder particles is smooth, and the adhesion of moisture on the surface is small. Therefore, the limestone has a certain physical water reducing effect, and the incorporation of limestone does not affect the setting time of the cement.
Second, the correct way to use limestone in large quantities
The main problem after the heavy use of limestone is the late strength drop, so it should be supplemented with its late strength. Therefore, the correct application of a large number of limestone can be started from the following two aspects.
1. Adjustment of cement ratio: At present, many cement plants only add active materials in order to improve the strength, but these active materials are porous such as fly ash, slag, etc. These active materials have a slow hydration speed, so the early strength is relatively low. Therefore, proper limestone and fly ash, the effect of mixing slag is very obvious. It can be added to limestone by 18% without the aid of grinding aid.
2, the use of grinding aids: the current strong after-type grinding aids on the market has developed very mature, late strength can be increased to 20%. The use of grinding aids can completely compensate for the late strength problems caused by large amounts of limestone. After adding, the strong grinding aid is slightly lower than the strength of the early strength grinding aid for 3 days. We can compensate for the shortcomings of low strength by adding limestone with small soil, so that it can be used in cement. A lot of limestone is used. If fly ash or slag is properly incorporated, the amount of limestone can be increased to 26% or even 30%.
3. When the clinker strength is not high for 3 days (C3S content is less than 50%), the 3-day strength of adding 1~3% limestone is higher than that of adding clinker for 3 days.