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The field test for the quality of cement consists in putting a small quantity of cement in a bucket containing water. A good quality cement will
Following four field tests may be carried out to ascertain roughly the quality of cement:
(i) colour: Colour of cement should be uniform and greenish grey.
(ii) Physical Properties:
∙ Cement should feel smooth when touched or rubbed in between fingers. If it is felt rough, it indicates adulteration with sand.
∙ If hand is inserted in a bag or heap of cement, it should feel cool and not warm
∙ If a small quantity of cement is thrown in a bucket of water, it should float for some time before they sink.
∙ A thin paste of cement with water should feel sticky between the fingers.
∙ If the cement contains too much pounded clay and silt as an adulterant, the paste will give an earthy smell.
(iii) Presence of lumps: Cement should be free from any hard lumps. Such lumps are formed by the absorption of moisture from the atmosphere. Any bag of cement containing such lumps should be rejected.
A sample of cement is said to be sound when it does not contain free
The cement used in construction of docks and harbours is
A Portland cement with low C3A and C4A Fcontents is very effective against sulphate attack, such cement is called sulphate resisting cement. The use of sulphate resisting cement is recommended for concretes to be used in marine environment foundations in chemically aggressive soils.
For ordinary Portland cement the maximum expansion by Le Chatelier’s method should not exceed
If expansion is more than 10 mm, cement is said to be unsound.
In autoclave expansion should not be more than 0.8%
The initial setting time for ordinary Portland cement as per IS specifications should not be less than
The initial setting time for OPC should not be less than 30 minutes. The final salting time should not be greater than 10 hours.
As per IS specifications, the maximum final setting time for ordinary Portland cement should be
If p is the standard consistency of cement, the amount of water used in conducting the initial setting time test on cement is
The role of superplasticizer in a cement paste is to
Consider the following oxides
1. Al2O3
2. CaO
3. SiO2
The correct sequence in increasing order of their percentage in an ordinary Portland cement is
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