Properties of Cement
The properties of Cement entirely depends upon its composition, burning and grinding. The important properties of a good Cement are following :-
- Strength : The compressive strength of cubical blocks of ordinary Portland cement and sand (1:3) after 7 days should not less than 175 kg/cm2.
- Finess : The quality of Cement depends upon its fineness property. So good Cement should be fine. The fineness of Cement may be determined by sieve test. Also by touching the Cement, it may be checked and should be smooth.
- Soundness : All types of cement expand to some extent and it depends upon the composition, proper burning and grinding of Cement. A good quality Cement should not undergo large change in volume after setting. Also it should not crack or disintegrate after setting.
Some Following factors are also responsible for Properties of cement.
- Setting time
- Heat of hydration
- Loss of ignition
- Bulk density
- Specific gravity (Relative density)
The main causes if volumetric change or unsoundness are :-
- Excessive addition of gypsum
- Excess of lime
- Less burning
- Excess of magnesia content.
- Presence of Lumps : By absorbing the moisture from atmosphere the lumps are formed. A good Cement should be frame from lumps. These can be avoided by storing the Cement away from damp places.
- Colour : The colour of cement should be greenish grey. The colour indicates the degree of burning. e.g. A yellowish colour indicates poor burning.
- Resistance to moisture : The Cement should resist against moisture.
- Plasticity : A Cement should be plastic in nature.