FINENESS TEST OF CEMENT (IS:4031-1996)

Test for fineness of cement is carried out for proper grinding of cement and to measure the mean size of the grains in it. 

METHOD OF TESTING FINENESS OF CEMENT  : 

Sieve Analysis Method

Weighing a 100 g of cement with accuracy of 0.1 g as a sample and if any air-set lumps present in the sample are broken with finger. The sample is placed on a 90 micron sieve and continuously sieved for 15 minutes. 

The residue should not exceed the following limits :

• For Ordinary Portland Cement : The residue present in OPC cement should not exceed 10% by the dry weight of cement. The specific surface of this type of cement should not be less than 225 m2/kg.
• For Rapid Hardening Cement : The residue present in this rapid hardening cement should not exceed 5% by the dry weight of cement. The specific surface of this type of cement should not be less than 325 m2/kg.
• For Portland Puzzolana Cement : The residue present in PPC cement should not exceed 5% by the dry weight of cement. The specific surface of this type of cement should not be less than 300 m2/kg.

Test Procedure

Objective

To determine the fineness of cement by dry sieve method.

Apparatus

• Standard BIS Sieve No. 9 : With capacity of retaining particle size over 90 micron.

• Weighing Balance : Measures 10 g of cement with accuracy 0.01 mg.
• Glass rod, Stoppered Jar Pen, Lid other apparatus used.

Sample/Specimen

100 g of cement sample is taken and broken air-set lumps in the sample with fingers.

Procedure 

• Weigh approximately 10 g of cement to the nearest 0.01 g and place it on the sieve.
• Agitate the sieve by swirling, planetary and linear movements, until no more fine material passes through it.
• Weigh the residue and express its mass as a percentage R1,of the quantity first placed on the sieve to the nearest 0.1 percent
• Gently brush all the fine material off the base of the sieve.
• Repeat the whole procedure using a fresh 10g sample to obtain R2. Then calculate R as the mean of R1 and R2 as a percentage, expressed to the nearest 0.1 percent. When the results differ by more than 1 percent absolute, carry out a third sieving and calculate the mean of the three values.

Result

Read and report the value of R, to the nearest of 0.1 percent, as the residue on the 90 micron sieve.

OTHER METHODS

Air Permeability Method

In air permeability test, The fineness of cement is represented or calculated by specific surface, i.e. total surface area in cm2 per gram or m2 per kilogram of cement and is measured by permeability apparatus. 

This permeability apparatus essentially consists of :

• Permeability Test Cell : Place where cement is stored and air pressure is applied. 
• Flowmeter : Flowmeter help to determine the quantity of air passing per second through its capillary tube per unit difference of pressure.
• Manometer : Manometer help to measure the air pressure.

To determine the fineness, a cement sample of 2 cm height is placed on a perforated plate and air pressure is applied. The manometer is connected to the top of the permeability cell and the air is turned on. The lower end of the permeability cell is then slowly connected to the other end of the manometer. The rate of flow is so adjusted that the flowmeter shows a pressure difference (h2) of 30-50 cm. The reading (h1) in the manometer is recorded. The process is repeated till the ratio h1/h2 is constant.

The specific surface should not be less then following limits :

• For Ordinary Portland Cement : The specific surface of this type of cement should not be less than 225 m2/kg.
• For Rapid Hardening Cement : The specific surface of this type of cement should not be less than 325 m2/kg.
• For Portland Puzzolana Cement : The specific surface of this type of cement should not be less than 300 m2/kg.

The Sedimentation Method

The turbidometer is a apparatus used  to estimate the surface area of one gram of cement. The cement is  uniformly in a rectangular glass tank filled with kerosene. Then, parallel light rays are passed through the solution which strike the sensitivity plate of a photoelectric cell. The turbidity of the solution at a given instant is measured by taking readings of the current generated by the cell. By recording the readings at regular intervals while the particles are falling in the solution, it is possible to secure information regarding the grading in surface area and in size of particle. Readings are expressed in cm2/g.