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Compressive and Tensile Strength of Concrete

Testing of Cement

Initial and final Setting time of Cement- Click Here

Strength test-

 
Testing of Cement
 

A-compressive strength test-

This test is perform in order to check the compressive strength of the cement. In order to find compressive strength , mortar of cement and standard sand[ennore sand] is prepared in the proportion of [1:3]. Generally 555gm of ennore sand is considered. 

Water is added in the mortar in the proportion of [(P/4) +3] % & the paste is prepared is filled in the mould of size 70.6mm & is properly compacted & immersed in the water for curing. 

Sample is further being tested for the compression strength in UTM [universal testing machine] at the required age. Rate of loading 35N/mm2/minute. Where P is the % of water required to produce a paste of standard consistency.

B-Tensile strength test-

This test is performed to find Tensile strength of the cement. Method of preparation of the mortar in this case is same as above.

Water is added in the mortar in the proportion of [(P/5) +2.5]. Mortar is in filled in standard Briquettes [12 in numbers] in order to find its tensile strength. 12 number because the uncertainty involved in this test is more.
 
Tensile strength= ultimate load/6.45 cm2
Rate of loading= 3.5N/mm2/minute.

6-Chemical composition test-

The ratio of alumina to that of iron oxide should not be less than 0.66. The ratio of lime to that of silica, alumina & iron oxide should not be less than 0.66 & should not be greater than 1.02 [this ratio is referred as lime saturation factor] 

1- Total weight of insoluble Residue should not be more than 1.5%.
2- Total weight of magnesia should not be more than 5 %.
3- Total loss of ignition should not be greater than 4%.
4- Total sulphur contain should not be more than 2.75%.

2-Field test-

A-Physical property test-

A sample of cement to be tested should be uniform Gray in color. The sample should feel smooth when rubbed in between the fingers. The sample should be free from presence of air set lumps that are formed due to the absorption of moisture from the atmosphere.
 
If the small amount of cement is thrown in the bucket of the water it should sink & not float over the surface.

B-Strength test-

Prepare a block of 25x25x200 mm. from the given sample of cement to be tested & immersed in the water for 7 days. Place the block over the support spaced at 150 mm & subjected it to the loading of 340 N. The sample should not show no sign of failure under the given loading.

 

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