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civil engineering-->>Testing of Cement


Testing of Cement

Hand Test
Testing of Cement
There are many ways and methods for the testing of cement. Some of them need a proper laboratory setup while other can be conducted at field itself. For the sake of convenience we will divide the methods under following two categories as (i) Tests in Field and (ii) Tests in Laboratory.
Tests in Field
Field tests are convenient way of primary inspection of cement when it is used in small scale works or when decision has to be made during purchase process. These are some of the steps that can ensure you good quality cement while inspection at site-
a)      First cement bags should be open a little wide for visible inspection. There should not be any lumps formation inside the bag.
b)      Put your hand inside the bag and ensure additionally that there are not any hidden lumps. Also this activity should give u a feel of cool sensation on your hands.
c)       Take a sample of cement in your hand and rub it in between your fingers. It should be smooth in nature.
d)      Take another handful sample of cement and throw it in the bucket full of water. Particles of cement should float a while before sinking down.
Tests in Laboratory
Field tests only indicate that cement is not bad and can be used for small scale works. Thus Laboratory tests are necessary to confirm that cement is good in nature and can even be used for important works too. Following tests are necessary to be conducted on cement in laboratory-
a)      Fineness Test-The fineness of cement can be defined as the measure of size of particles of cement or in simple form “Specific Surface of Cement”. This test is usually carried out using IS sieve no.9 or 90 microns.
b)      Setting Time Test- Cement when mixed with water triggers a process which results in a hardened mass of mixture wherein hardness gradually increases with time. There are two setting times for cement- Initial Setting Time (IST) or Final Setting Time (FST).It is tested using Vicat’s Apparatus. Eg. For Portland Cement IST is around 30 mins and FST is around 600 mins.
c)       Strength Test- The strength of cement is defined in MPa or N/mm2. For grade 33 Portland cement, strength should be around 33MPa in 28 days. Compression test is carried out to check the strength of cement.
d)      Soundness Test- Soundness of cement can be defined as a process in which cement does not show any considerable change in volume after setting. Autoclave tests and Le Chateleir tests care carried out to check the soundness of cement.
e)      Heat of Hydration Test- The heat of hydration can be defined as heat from cement paste liberated as a reaction of water with cement. This test is usually carried out in thermos flask.
f)       Chemical Composition Test- A test is carried out on cement that tests the ratio of chemicals in the cement. Different standards and codes specify different value of such ratios. A standard oxide and chemical composition of Portland cement is as given below-
Chemical Compound
Percentage
Lime, Cao
60-66
Silica, Sio2
17-25
Alumina,Al2O3
3-8
Iron Oxide, Fe2O3
0.5-6
Magnesia, MgO
0.5-4
Sulphur trioxide, SO3
1-2
Alkalis
0.5-1.3
Four main compounds that are present in cement and percentage of which decides (one of the parameter) the quality of cement are as follows-
1.       Tricalcium Silcate
2.       Dicalcium Silicate
3.       Trialcium Aluminate
4.       Tetracalcium Alumino Ferrite

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