What is the significance of Fineness of Cement?
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Fineness of Cement:
It is the property of cement that gives an idea about the size of particle in cement and thus surface area ratio.
1) Increase in fineness, increase in heat of hydration. This is due to an increase in surface area of cement requires more water content.
2) Bleeding reduces by increasing the fineness of the cement. This is due to an increase in surface area, adsorb water content.
3)By the increase in fineness, surface increases. Thus, it requires more water, and if calculation not done properly, dry shrinking possible to occur in concrete structures.
4)If particles are of small size. It’s surface area increase. This adhesion between them is increased.
Fineness test are performed to determine fineness of cement.
Reply, If you need clarity on any specific point.
The fineness of cement is property of cement which indicate the particle size of cement and specific surface area and thus indirectly effect heat of hydration.
Importance/effect of fineness of cement;
1. Fineness of cement affects hydration rate hence the rate of strength gain.
2. Bleeding can be reduced by increasing fineness. However, increased fineness can also lead to the requirement of more water for the workability, resulting in a higher possibility of dry shrinkage.
3. Fineness test is used to change the proper grinding of cement and measures the surface area of the cement particles per unit mass.
4. Therefore finer cement react faster with water and the rate of development of strength and corresponding heat of hydration is high.
It should not exceed following percentage by weight for different types of cement;
1. Ordinary portland cement = 10%
2. Rapid hardening cement = 5%
3. Low heat cement = 5%
The fineness of cement is a measure of the size of particles of cement and is expressed in terms of the specific surface area of cement. The fineness of cement is measured as the % weight retained on a 90µm IS sieve over the total weight of the sample. In the laboratory, the fineness of cement is tested by sieving and by the determination of a specific surface. For ordinary cement, the weight of residue left on the sieve shall not exceed 10%. The fineness of cement is the significant factor affecting the rate of hydration, rate of gain of strength, setting time, and rate of evolution of heat. The rate of strength development increases with fineness. Since the specific surface area is inversely proportional to the size of the particle, the surface area is more for finer cement than for a coarser cement. Therefore, the finer the cement, the higher the surface area for hydration and hence faster the development of strength.
Smaller cement particles react much quicker than the larger particles. A cement particle with a diameter of 1 µm will react entirely in 1 day, whereas the particle with a diameter of 10µm takes about 1 month. It is found that the particle size fraction below 3 microns affects one day’s strength and 3 to 25-micron fraction influence the 28 days’ strength. Setting time decreases with an increase in the fineness of the cement. Too much smaller particles in cement results in quick setting, thereby leaving no time for mixing, handling, and placing. Also, such cement is susceptible to air set and early deterioration. To increase the setting time of cement, it must be manufactured in a different range of particle sizes.
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Fineness is a property of cement that indicate particle size and surface area of cement particle.
Necessity of of fineness of cement:
Significance of Fineness of Cement:
Significance of fineness of cement
Fineness is an important factor in cement
Fineness has an important bearing on the rate of hydration and ultimately on the strength of cement. Finer cement has a greater surface area for hydration and hence faster and greater strength. The smallest particle
size is about 1.5 µ and the average size is about 10 (µ) microns. An increase in fineness increases the shrinkage of cement. In commercial cement, 25-30% of particles are of size less than 7 microns.
The fineness of cement is the property of cement which indicates particle size and specific surface area.
The cement hydrates with the presence of water. When cement is mixed with water, a layer is formed around the particles. The layer becomes bigger in size and makes the cement particles to separate. Due to the fineness of cement, hydration slows down. Smaller particles will react quicker than large particles. So the particle size distribution is more critical to attaining the final strength of cement.
The Fineness test of cement is done by sieving a cement sample through a standard IS sieve. The weight cement particle whose size greater than 90 microns is determined and the percentage of retained cement particle are calculated. This is known as the Fineness of cement.
Significance of Fineness of Cement
PROCEDURE OF FINENESS TEST OF CEMENT:
Fineness = (W2/W1) * 100
Fineness Test of Cement & Result:
Retained on 90µm Sieve (W2)
Result: The standard cement should have fineness less than 10 % as per IS Recommendations.