Soundness Test of Cement
It is very important that the cement after setting shall not undergo any appreciable change of volume. Certain cements have been found to undergo a large expansion after setting causing disruption of the set and hardened mass.This will cause serious difficulties for the durability of structures when such cement is used.This test is to ensure that cement does not show any appreciable subsequent expansion is of prime importance.
The unsoundness in cement is due to the presence of excess of lime than that could be combined with acidic oxide at the kiln.This is also due to inadequate burning of insufficiency in fineness of grinding or through mixing of raw materials.It is also likely that too high a proportion of magnesium content or calcium sulphate content may cause unsoundness in cement. For this reason the magnesia content allowed in cement is limited to 6%.
APPARATUS i) The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 - 1969
ii) Balance, whose permissible variation at a load of 1000g should be +1.0g
iii) Water bath
ii) Balance, whose permissible variation at a load of 1000g should be +1.0g
iii) Water bath
PROCEDURE i) The mould is placed on a glass sheet and it is filled with the cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency.
ii) Then the mould is covered with another piece of glass sheet, a small weight is placed on its covering glass sheet and immediately the whole assembly is submerged in water at a temperature of 27 ± 2oC and kept it there for 24hrs.
iii) The distance separating the indicator points to the nearest 0.5mm is measured (say d l ).
iv) The mould is submerged again in water at the temperature prescribed above.The water is bought to boiling point in 25 to 30 minutes and it is boiled for 3hrs.
v) Then the mould is removed from the water, allowed to cool.The distance between the indicator points is measured (say d 2 ).
vi) (d 2 – d l) represents the expansion of cement.
ii) Then the mould is covered with another piece of glass sheet, a small weight is placed on its covering glass sheet and immediately the whole assembly is submerged in water at a temperature of 27 ± 2oC and kept it there for 24hrs.
iii) The distance separating the indicator points to the nearest 0.5mm is measured (say d l ).
iv) The mould is submerged again in water at the temperature prescribed above.The water is bought to boiling point in 25 to 30 minutes and it is boiled for 3hrs.
v) Then the mould is removed from the water, allowed to cool.The distance between the indicator points is measured (say d 2 ).
vi) (d 2 – d l) represents the expansion of cement.
REPORTING OF RESULTS The mean of the two values to the nearest 0.5mm to represents the expansion of cement.
Testing of Cement
Testing of Cement can be brought under two categories.
(a) Field Testing (b) Laboratory Testing
(a) Field Testing (b) Laboratory Testing
Field Testing
It is sufficient to subject the cement to field tests when it is trusted for minor works. The following are the field tests.
(a) Open and the bag and take a good look at the cement. There should not be any visible lumps. The colour of the cement should normally be greening grey.
(b) Thrust your hand into the cement bag. It must give a cool feeling. There should not be any lump inside.
(c) Take a pinch of cement and feel between fingers. It should give a smooth and not a gritty feeling.
(d) Take a handful of cement and through it in to a bucket full of water, the particles should float for some time before they sink.
(e) Take about 100 grams of cement and a small quantity of water and make a stiff paste. From the stiff paste , pat a cake with sharp edges. Put it on a glass plate and slowly take it under water with a bucket.See the shape of the cake is not disturbed while taking it down the bottom of the bucket. After 24 hours the cake should retain its original shape and at the same time it should also set and attain some strength.
If a sample of cement satisfies the above field tests it may be concluded that the cement is not bad.The above tests does not really indicates that the cement is really good for important works. For using cement in important and major works it is incumbent on the part of the user to test the cement in the laboratory to confirm the requirements of the Standard Specifications with respect to its physical and chemical properties.The tests which are usually conducted in the Lab to confirm those properties are …
1.Fineness Test 2.Initial and Final Setting Time Test
3.Shear Test 4.Soundness Test 5.Heat of Hydration Test 6.Chemical Composition Test
It is sufficient to subject the cement to field tests when it is trusted for minor works. The following are the field tests.
(a) Open and the bag and take a good look at the cement. There should not be any visible lumps. The colour of the cement should normally be greening grey.
(b) Thrust your hand into the cement bag. It must give a cool feeling. There should not be any lump inside.
(c) Take a pinch of cement and feel between fingers. It should give a smooth and not a gritty feeling.
(d) Take a handful of cement and through it in to a bucket full of water, the particles should float for some time before they sink.
(e) Take about 100 grams of cement and a small quantity of water and make a stiff paste. From the stiff paste , pat a cake with sharp edges. Put it on a glass plate and slowly take it under water with a bucket.See the shape of the cake is not disturbed while taking it down the bottom of the bucket. After 24 hours the cake should retain its original shape and at the same time it should also set and attain some strength.
If a sample of cement satisfies the above field tests it may be concluded that the cement is not bad.The above tests does not really indicates that the cement is really good for important works. For using cement in important and major works it is incumbent on the part of the user to test the cement in the laboratory to confirm the requirements of the Standard Specifications with respect to its physical and chemical properties.The tests which are usually conducted in the Lab to confirm those properties are …
1.Fineness Test 2.Initial and Final Setting Time Test
3.Shear Test 4.Soundness Test 5.Heat of Hydration Test 6.Chemical Composition Test
Thanks for this resourceful article. I have also posted an article about Field Test of Cement. you may find some extra test in my post. Thanks.
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Civil Engineering