Properties of Cement
The properties of Cement entirely depends upon its composition, burning and grinding. The important properties of good Cement are the 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 a 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 a 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 the atmosphere the lumps are formed. A good Cement should be a 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.