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Summary:Limestone Applied To Cement Production Line Limestone is the most readily available and cheapest blending material in cement plants. It can also improve a range of cement properties, including reducing the water consumption of cement …

Limestone Applied To Cement Production Line

Limestone is the most readily available and cheapest blending material in cement plants. It can also improve a range of cement properties, including reducing the water consumption of cement standard consistency, improving the compatibility of cement and water reducer, and improving the water retention of cement. Using natural and cheap resources, limestone is used as a mixture of cement production. Compared with slag, fly ash and volcanic ash, it has a huge guarantee for its resources, low price, convenient transportation and no drying. Economic value, so many cement plants want to add a lot of limestone in order to reduce costs. So how can we add as much limestone as possible without affecting the quality of the cement?

In the early 1980s, China began to use limestone as a mixed material and carried out practical engineering applications. Incorporating about 5% to 8% of limestone in the cement instead of clinker can increase the early strength of the cement without significantly reducing the late strength of the cement. However, when the amount of limestone is large, limestone will significantly reduce the cement strength in the later stage compared with slag and fly ash. One measure to improve the low strength of limestone in the late stage of cement is to add some chemical additives during cement production. Studies have shown that some organic alcohol amines have a late strength enhancement effect on high limestone cement.

The Role And Characteristics 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. Increased, more studies have shown that limestone participates in the reaction in the hydration slurry to form early-strength mineral calcium aluminosilicate, which promotes the development of strength, and the contribution of such inert or low-activity fine aggregate to the strength of cement paste. Even more than part of the pozzolanic active mixture.

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.

The Right Way To Use Limestone In Large Quantities

In this way, the main problem after the heavy use of limestone is the late strength reduction, 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, the late strength can be increased to 20%, this grinding agent has been out domestic for more than 10 years. 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%. (Adding grinding aid followed by blank compared with small grinding test cement 45um sieve residue decreased by 3.8% ~ 6.0%, 3 ~ 32um particle content increased by 3.11%, 28 days compressive strength increased by 8 ~ 25%).

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.

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