What is the fineness of cement and what effect does the fineness of cement have on the properties of

In fact, the cement plant produces the same method of operation for the production of various grades of cement, but at the final grading, through screening, the smallest fineness is set as the highest grade, and the finest is set as the lowest. The fineness of 3-5 is determined, the fineness of 5-8 is determined, and the fineness less than 3 is set as special cement.

Anyone who has studied physics knows that the surface of any object has tension (gravitational force), and the smaller the particle of the object, the greater the gravitational force, that is, the stronger the ability to attract each other. Therefore, the grading of cement is also like this, the smaller the fineness, the higher the grade of cement.

Cement fineness refers to the thickness of cement particles, which is an indicator of the degree to which cement is ground or the degree of cement dispersion.

The effects of the fineness of cement on the properties of cement are:

1. The finer the cement particles, the larger the surface area that reacts with water, so the hydration reaction speed is faster, and it is more complete, and the early strength is higher, but the hardening and shrinkage in the air is larger;

2. The cement is too fine, which will significantly affect the performance of the cement mill, reduce the output and increase the power consumption. Therefore, the fineness of cement must be reasonably controlled in production, so that the cement has a reasonable particle gradation.

3. If the cement particles are too coarse, it is not conducive to the exertion of cement activity. It is generally considered that cement particles have high activity when they are less than 40 m, and when they are more than 100 m, they have very little activity.

Typically, cement is made up of many gradations of cement particles. The structure of cement particle gradation has a great influence on the hydration hardening rate, water demand, workability, exothermic rate, and especially on the strength of cement.

Particle gradation of cement fineness.

The particle gradation of cement produced by different grinding systems is quite different, and the overall particle distribution range of the open-circuit grinding system is relatively wide, the overall particle size of the particles is small, and the fine powder content is high. The distribution range of closed-circuit mill particles is narrow, the overall particle size of the particles is large, the fine powder content is less, and the coarse powder content is more.

The type and amount of mixed materials in cement will also affect the particle gradation of cement, and the content of fine particles in cement mixed with limestone and pozzolane with good grindability will increase. The content of fine particles in cement mixed with slag, phosphate slag and other mixed materials with poor grindability is less. For cement mixed with different mixtures and amounts, the required particle gradation is also different.

Cement fineness refers to the thickness of cement particles. Cement fineness is an important physical index that affects a series of architectural properties of cement. For cement of the same composition, the finer the particles, the larger the surface area in contact with water, the faster the hydration reaction, and the more fully the hydration reaction, the higher its strength, especially in the early stage of the market.

However, the cement particles are too fine, and the shrinkage is large when hardening, and cracks are easy to occur. It is generally believed that the cement particle size is less than 40um to have high activity. The cement particle size is greater than 90um, which is almost inert and only plays a filling role.

Therefore, cement must be controlled to a certain fineness of grinding to give full play to its gelatinity, but if the grinding is too fine, it will reduce the output of the mill, increase the consumption of electric energy, and increase the cost of cement. If it hardens in air, the shrinkage value will also increase, and the strength will decrease too quickly during storage.

If the cement is too coarse, the degree of hydration is not complete, if the hydration speed is too fast and the early strength of the concrete is too fast, there will be cracks or insufficient strength in the later stage.

Answer]: Qi suspicious a, b

This section examines cement, asphalt, and sand. Fineness refers to the coarseness of cement particles. The fineness of the mud directly affects the activity and strength of the cement.

Answer]: A cement performance indicators include fineness, setting time, volume stability, strength and heat of hydration. Fineness is one of the main indicators affecting the performance of cement, the finer the particle size of cement, the larger the surface area that reacts with water, the faster the hydration, and the higher the strength.

Internationally, Portland cement fineness is measured by the air-permeable specific surface area. Therefore, the answer is A.

Summary. The fineness of cement refers to the size of the cement particles, because the smaller the contact area with water, the faster the hydration. 1. The fineness of Portland cement and ordinary Portland cement is expressed by specific surface area.

The specific surface area is the total surface area of cement per unit mass m2 kg, the specific surface area of Portland cement should be greater than 300m2 kg, and the fineness of slag Portland cement, porosyl Portland cement, fly ash Portland cement and composite Portland cement is expressed by sieve residue, and its M80 square hole sieve sieve residue is not more than 10% or 45 m square hole sieve sieve residue is not more than 30%.

5.What is fineness, why should the fineness of cement be regulated, Portland cement and ordinary silicate.

The fineness of cement refers to the size of the cement particles, because the smaller the contact area with water, the faster the hydration. 1. The fineness of Portland cement and ordinary Portland cement is shown by the specific surface area surface culture. The specific surface area is the total surface area of cement per unit mass m2 kg, the specific surface area of Portland cement should be greater than 300m2 kg, the fineness of slag Portland cement, pozzolana Portland cement, fly ash Portland cement and composite Portland cement is expressed by sieve residue, and its m80 square hole sieve sieve residue is not large, and the slag is not more than 30% in 10% or 45 m square hole sieve with absolute destruction residue.

2. For cement of the same composition, the finer the particles, the larger the surface area in contact with the water, the faster the hydration reaction, and the hydration of the anti-nomadic slag should be more sufficient, but the cement particles are too fine, and the shrinkage is large when hardening, and cracks are easy to occur. Generally, Suiling believes that cement particles with a quiet size of less than 40um have high activity, and cement particles with a size greater than 90um are almost close to inert and only play a filling role.

3. The fineness of cement is expressed by the sieve analysis method, that is, the sieve allowance through the 0·08mm square hole sieve. If the sieve allowance is 5%, it means that the fineness of the cement is 5%, which is also expressed by the specific surface area. It is necessary to stipulate the simplicity and fineness of cement Portland cement and ordinary Portland The fineness of cement has an impact on the fluidity, slump, compactness, workability, durability and many other aspects of concrete, and the fineness of cement also has a certain impact on the strength. ()

Answer]: The fineness of cement refers to the thickness of cement. The finer the cement particles, the larger the surface area that reacts with water, and the more susceptible it is to moisture, the hydration is rapid and complete, and the early and later strength are higher.

However, in the empty air, the hardening shrinkage before the return of the year is larger, and the cost is also higher.