Tests on cement

• Tests conducted for Cement

a)Field test

• when hand is inserted into the cement bag after opening it, it gives a cool feeling.
• moreover it gives a smooth feel , when a pinch of cement taken & felt between fingers.
• Take handful of cement  & throw into bucket full of water, the cement particles starts floating & after sometime it starts to sink down .

B) Labortary tests

1) Fineness test

• Weigh 100g of cement & take onto the standard IS Sieve No.9 (90 microns).
• Break down the lumps present ,if any, with fingers.
• Sieve the sample  for about 12-15 minutes (mechanical sieving can also be done)
• Weigh the weight of the residue left on sieve.
• Weight of residue should be less than 10%

    Illustration Of Sieve Test: 

Weight of cement (before sieving)  in gram	Weight of sample (after sieving ) in gram	%difference in weight	Remarks
100	7.8	7.8 %	Less than 10%

2) Standard Consistency test (Normal Consistency test)

• This test is used to determine the initial setting time , final setting time & soundness of cement
•  This test is done by using “ Vicat Apparatus”

Procedure:

• Take 500 g cement & make paste by mixing it with water with different w/c ratios.Fill the sample in vicat mould within 3 -5 minutes i.e “gauging time. Attach a Standard plunger & allow it to dropdown by its self weight & penetrate into the cement paste.
• Repeat the  process with different percentage of water in the ccement paste
• The percentage of water by weight of cement at which the plunger penetrated for a depth of 33-35mm  from top is considered as the percentage of water required to make paste of standard consistency .it is denoted with “ P”
• Calculation of P

            P= w/c *100       

  (where, w= quantity of water used & c= quantity of cement used)

  (NOTE: Least count of balance =  1g & measuring cylinder =1 ml)

General value of P for OPC lies between 24 to 31%

3) Setting time test

     

a) Initial setting time

It is the time interval throughout which the cement remains in plastic condition required for mixing,placing & compacting.

Procedure:

• Take500g of cement  & gauge it with water (0.85P)
•  Fill the paste  in mould & place it under the needle of the vicat apparatus.
• The time elapsed from the adding of water to the point where the needle penetrates the   test block to a depth of 33-35 mm is noted.
• The time is the initial setting time. 
• The minimum initial setting time should be minimum 30 mins

b) Final setting time

• It is the time at which the concrete looses its plasticity & start gaining strength.
• When the vicat needle is unable to pierce through the test block more than 0.5 mm.it is considered, it has attained its final setting time
• The maximum final setting time should not be more than 10 hours 

4) Soundness test

• As presence of excess  lime , magnesia & sulphates causes unsoundness of cement as they lead to undesirable expansion of set & hardened mass.Thus soundness test is the remedial measure to prevent the cause.
• Autoclave Test is performed  for measuring soundness of cement, it indicates the presence of excess of both lime & magnesia ,unlike Le- Chatelier’s Test which indicates only presence of lime

Procedure:

• A cement specimen (25 x 25 mm) is placed in the standard autoclave & the steam pressure is raised to 21 kg/cm²  (gauge pressure) within 1 hour of turning on the heat.
• This pressure is maintained for next 3 hours.
• The autoclave is allowed to cooled & then the length of the specimen is measured again
• The % expansion of the specimen is found to be less than 0.8 %

Conclusion

Higher  the expansion of the specimen indicates the higher content of excess lime & magnesia

Physical Characteristics of Cement are mentioned in the Table: