Fineness of cement has a great effect on the rate of hydration and subsequently the rate of gain of strength. Fineness of cement improves the rate of evolution of heat. Finer cement offers a more surface area for hydration and hence faster the development of strength. Increase in fineness of cement additionally increases the drying shrinkage of concrete and and so creates cracks in structures. Excessive fineness requirement increases expenses of grinding. Excessive fine cement requires more water for hydration, causing decreased strength and durability. Following article describes fineness test of cement by dry sieving. The reference Indian standard code : IS 4031 – Part 1
Apparatus required for fineness test of cement :
90 micron sieve, weigh balance, Pan, Lid, Glass Rod
Test Procedure for fineness test of cement :
- Agitate the sample of cement to be checked by shaking for 2 minutes in a stoppered jar to distribute agglomerates. Stir the finished powder lightly with fully clean dry rod in order to spread the fines all through the cement.
- Connect a pan below the sieve to accumulate the cement passing the sieve.
- Weigh roughly 10 g of cement to the closest 0.01 g and place it on the sieve. Fix the lid over the sieve.
- Prior to sieving, air set lumps of cement preferably should be broken.Agitate the sieve by swirling, planetary and linear motion till no longer fine material passes through it.
- Take out and weigh the deposit. Express its mass as a percentage (R1) of the quantity first placed in the sieve.
- Repeat the steps 3 to 5 with a fresh sample to obtain R2. Note : If variation between values of R1 and R2 is more than 1%, then carry out another set of sieving and obtain R3 value.Calculation
- Calculate the mean value (R) of residue of cement by taking average of R1 and R2 values. The fineness is express as % to nearest 0.1 %.