What is fineness of cement?
WHAT IS FINENESS OF CEMENT? The fineness of cement is the property of cement that indicates particle size of cement and specific surface area. and indirectly effect heat of hydration. The fineness of cement affects hydration rate hence the rate of strength gain.
How does the fineness of cement affect hydration rate?
Fineness of cement affects hydration rate. The smaller the particle size,the more area available for water-cement interaction per unit volume. Therefore finer cement reacts faster with water and earlier strength gain. Bleeding can be reduced by increasing fineness. Shrinkage can be reduced by by increasing fineness.
How does the fineness of clinker affect the properties of cement?
How does the fineness to which the clinker is ground affect the properties of the cement? A. Increasing the fineness increases the rate of hydration of cement, which increases the rate of gain in strength and also the rate at which heat is liberated as in Type III compared with Type I cement (ASTM C150).
How can bleeding and shrinkage of cement be reduced?
Bleeding can be reduced by increasing fineness. Shrinkage can be reduced by by increasing fineness. Fineness test is used to check the proper grinding of cement. This answer was edited. As we know that the Bleeding phenomena reduce by increasing the fineness of the cement because of an increase in the surface area & adsorb water content.
How fineness affect the cement?
Increasing the fineness increases the rate of hydration of cement, which increases the rate of gain in strength and also the rate at which heat is liberated as in Type III compared with Type I cement (ASTM C150).
How does the fineness of cement affect the normal consistency of cement?
The Normal consistency of cement paste depends upon the factors such as temperature and fineness of cement. Higher the temperature and higher the fineness of cement results higher the normal consistency of cement and vice versa.
Is finer cement stronger?
If you took a cement and ground part of it to a greater fineness the finer portion would produce higher early strength than the other portion.
How fineness affects hydration rate?
The finer the cement particles and the greater its surface area, the faster is the rate of hydration and the greater is the proportion of the cement which reacts within the paste.
What is the effect of grinding on cement?
It improves the performance at young age (by formation of hemicarboaluminate), especially when the cement is well crushed. But a very fine grinding does not compensate for completely a significant presence of limestone.
What is fineness test of cement?
Fineness of cement is tested in two ways : (a) By sieving. (b) By determination of specific surface (total surface area of all the particles in one gram of cement) by air-permeability apparatus. Expressed as cm2/gm or m2/kg. Generally Blaine Air permeability apparatus is used.
What is the unit of fineness of cement?
cm2 / gramThe fineness of cement is represented as cm2 / gram i.e Area/mass. The fineness of cement is measured by sieving it on the standard sieve. The proportion of cement of which the grain sizes are larger than the specified mesh size is thus determined.
How the fineness of cement is obtained?
The required fineness of good cement is achieved through grinding the clinker in the last step of cement production process. As hydration rate of cement is directly related to the cement particle size, fineness of cement is very important.
What is the relation between compressive strength and fineness of cement?
It is seen in Table 6 that the % increase in strength is nearly twice the % increase in fineness for cements having fineness up to 2000 cm 2 /kg. For cements having a fineness greater than 2000 cm 2 /kg, increase in strength is the same as increase in fine- ness.
What is the normal consistency of cement?
The Standard or Normal consistency for Ordinary Portland cement varies between 25-35%. To prepare a mix of cement paste of Standard consistency 25-35% of water is added to cement. To explain in detail Let us assume a standard consistency is 30%. Take 400g of Cement for this quantity, Add 30% of Water.
What factors affect the consistency of concrete?
Factors which affect workability of concrete are:Cement content of concrete.Water content of concrete.Mix proportions of concrete.Size of aggregates.Shape of aggregates.Grading of aggregates.Surface texture of aggregates.Use of admixtures in concrete.More items...•
What are the 5 principal factors affecting the consistency of the cement?
The factors considered are water/cement ratio, cement/aggregate ratio with aggregate grade, the use of sodium hexametaphosphate powder as a deflocculant during mixing, compacting pressure in the mould, curing time under water after setting and testing age.
Why is normal consistency of cement important?
Finding out standard consistency of cement is essential because the amount of water added to cement affects the setting time of cement, Less water added than this standard consistency would not complete the chemical reaction thus resulting in the reduction concrete of strength and more water would increase water-cement ...
What does it mean when cement is fine?
Greater fineness of cement means the particles are finer and had more surface area. In case of very coarse cement, under some conditions it can cause a serious bleeding problem on some construction projects. There are already many research articles in journals and research papers that have discussed the effect of fineness ...
What is the effect of cement on concrete?
Effect of Fineness of Cement on Concrete Properties. Fineness of cement is a characteristic property of cement that signifies the particle size of cement and its specific surface area. Greater fineness of cement means the particles are finer and had more surface area. In case of very coarse cement, under some conditions it can cause ...
How does cement improve the workability of concrete?
Increasing the fineness of cement reduces the amount of bleeding in concrete by increasing the water requirement of concrete. The workability of non-air-entrained concrete is increased by increasing the cement fineness. The workability of non air-entrained concrete is increased by increasing the cement fineness.
Does air entrained concrete deteriorate?
The resistance of air-entrained concrete to deterioration caused by freezing and thawing decreases with an increase in cement fineness. The same trend is noted with non air-entrained concrete, but to a lesser degree.
Is air entrained concrete a reactive aggregate?
Both air-entrained and non air-entrained concrete containing 100 percent reactive aggregate are detrimentally affected by increased expansion at all ages by increases in the fineness of a high-alkali cement.
Does cement shrink when it is wet?
The fineness of cement influences the drying shrinkage of concrete. When the water content is increased because of fineness, the drying shrinkage is increased. However, if excessive bleeding due to coarseness of the cement takes place, a reduction in the drying shrinkage occurs.
What is the importance of fineness in 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.
What is the fineness of cement?
The fineness of cement is the property of cement which indicates particle size and specific surface area. Significance: 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.
How long does it take for cement to set?
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.
What is the purpose of fineness test?
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.
Why is the particle size distribution important in cement?
Smaller particles will react quicker than large particles. So the particle size distribution is more critical to attaining the final strength of cement.
How to measure cement fineness?
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.
What is the property of cement that indicates the particle size of cement and specific surface area?
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.
What does fineness of cement do to cement?
Increasing the fineness of a cement also increases the amount of mixing water required to achieve a given consistency and reduces the amount of bleeding by the concrete.
What does increasing the fineness of cement do?
A. Increasing the fineness increases the rate of hydration of cement, which increases the rate of gain in strength and also the rate at which heat is liberated as in Type III compared with Type I cement (ASTM C150). Increasing the fineness of a cement also increases the amount of mixing water required to achieve a given consistency and reduces ...
Why does cement increase in fineness?
An increase in fineness increases the amount of gypsum required for proper retardation because, in a finer cement, more C3A is available for early hydration. The water content of a paste of standard consistency is greater the finer the cement, but conversely an increase in fineness of cement slightly improves the workability of a concrete mix.
Why does fineness increase gypsum?
An increase in fineness increases the amount of gypsum required for proper retardation because, in a finer cement, more C3A is available for early hydration.
What is the last step in cement production?
One of the last steps in the manufacture of cement is the grinding of clinker mixed with gypsum. Because hydration starts at the surface of the cement particles, it is the total surface area of cement that represents the material available for hydration. Thus, the rate of hydration depends on the fineness of the.
What is the ASTM C 430-08?
The fraction of cement retained on a 45 μ m (No. 325 ASTM) test sieve can be determined using ASTM C 430-08. (For size of openings of different sieves .
What is the conversion factor of cement?
The actual range of the conversion factor varies between 6 and 2.2, depending on the fineness of the cement and its gypsum content.
What percentage of cement is good for concrete?
An even higher proportion of particles in the range of 3 to 30 μ m, up to 95 per cent, is believed to lead to an improved early strength and also to a good ultimate strength of concrete made with such a cement
How to determine the specific surface of cement?
The specific surface of cement can also be determined by the air permeability method, using an apparatus developed by Lea and Nurse.
Why is fineness important in cement?
However, increased fineness can also lead to the requirement of more water for workability, resulting in a higher possibility of dry shrinkage. Fineness test is used to check the proper grinding of cement and measures the surface area of the cement particles per unit mass.
What is the fineness of cement?
WHAT IS FINENESS OF CEMENT? The fineness of cement is the property of cement that indicates particle size of cement and specific surface area. and indirectly effect heat of hydration.
Does cement affect strength gain?
The fineness of cement affects hydration rate hence the rate of strength gain.
Does cement react faster with water?
Therefore finer cement reacts faster with water and the rate of development of strength and corresponding heat of hydration is high. Fineness is a measure of how even each granule is, leading to a greater surface area & greater the surface area more the adhesion. Bleeding can be reduced by increasing fineness.
