Testing of Cement
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Testing of cement- Testing of cement is done in order to check its performance when used for engineering Construction. Testing of cement is done in following two ways.
1- Laboratory test
2- field test
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| Cement |
Laboratory test-
1-Fineness test-
fineness of the cement is being tested to check the proper grinding of the cement which significantly influences the rate of hydration that in turn affects the rate of development of the strength & rate of evolution of heat. Fineness of the cement can be tested by any of the following method.
Note-Overgrinding is done then, rate of development of strength decreases so as rate of evolution of heat is also decreases.
A- Sieve method –
In this test 100 gm. of sample to be tested is placed over IS-Sieve no.9 [90µ] & sieving is done continuously for at least 15 minute along with the breaking of air set lumps, if formed in it. weight of the residue left over the sieve is noted after 15 minute. For OPC it should not exceed 10%.
Note- Sieve test is outdated now.
B-Air permeability test-
This method is used to find fineness of the cement represents in terms of specific surface area & expressed as surface area per unit weight. Generally Blaine’s air permeability apparatus is used to find fineness. The principle of this test depends upon the relationship between flow of the air through the bed of cement particles is forming the cement bed.
For OPC, specific surface area should not be less than 2250 Cm2/gm.
2-Consistency test-
In order to find initial setting time, final setting time, soundness, & strength characteristics of the cement a parameter referred as standard consistency is used. standard consistency is define as the consistency of cement paste that permits the Vicat’s plunger of dia 10mm & height 50 mm to penetrate into the mould up to the depth of 33 to 35 mm from the top[or 5 to 7mm from the bottom]. This test is performed to find moisture content which is required to produce the cement paste of standard consistency. This test is performed at the temp. Of 27±2 & relative humidity of 90%.
In order to perform this test take 500 gm. of cement & gauge it with 24% of the water in the first try & note the depth of penetration into the mould. Repeat the test at different water content up to an extent, penetration of 33 to 35mm from the top of the mould is observed. water content corresponding to this is noted & it is referred as “P”.
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