Finess Of Cement Test

Importance:
 This experiment is carried out to check the proper grinding of cement. The cement which is produced by an industry is checked for its quality, that either it is good for certain type of construction or it doesn’t posses that much strength. For example, for RCC and other heavy load bearing structures such as bridges it is essential that the cement which is being used in the concrete should have the ability to provide the required strength, while in the PCC structures it is not so much critical. The ability to provide strength of a certain type of cement is checked by finding the fineness of that cement, because the fineness of cement is responsible for the rate of hydration and hence the rate of gain of strength and also the rate of evolution of heat. If the cement is fine then greater is its cohisiveness, which is the property, required in the concrete because it gives compactness to the concrete. Usually cement loses 10% of its strength within one month of its manufacturing. Types of Sieves: There are different types of sieves such as # 10, # 100,# 200,# 300 etc. The number of the sieve indicates the number of holed present in a linear inch of that sieve. For finding the fineness of Wet or Dry cement, following number sieve is recommended by ASTM. Cement by wet process = # 300 sieve Cement by dry process = # 200 sieve

Apparatus:
Sieve # 200 Sample of cement Triple beam balance Brittle brush Empty plate Procedure: Take the triple beam balance and adjust the reading of the balance to zero. Take a pan and note its weight. Put some cement in the pan placed on the balance, so that the weight of cement becomes 100 grams. This will be weight w1 of the cement. Put the cement in the sieve carefully and close the sieve tightly. Start shaking the sieve horizontally, keep on shaking the sieve for 10 to 15 minutes regularly. After 15 minutes take the residue left in the sieve, put it in a pre-weighed plate and note the weight w2 of the residue with the help of triple beam balance. Then by using the following formula calculate the percentage fineness of cement: W1= Total weight of cement W2= Weight of residue Percentage of fineness= ((W1– W2 )x 100)/W1 ASTM-STANDARD: For 100 gram sample: IF Weight of w2< 10 gram: Cement is fresh. Weight of w2 > 10gram: Cement is not fresh. OR % age of fineness is ³ 90 %: Cement is fresh. % age of fineness is £ 90 %: Cement is not fresh. Readings of Experiment: Total weight of cement = w1 = 100 gram Total weight of residue = w2 = 13.4 gram % age of fineness = 86.6 %

 COMMENTS:
 “The fineness of cement is not according to the ASTM standard, so the cement is not perfectly fresh therefore it should not be used for making concrete where high strength is required but can be used for low load structures as fineness is not too bad”.