The color of the cement depends on the raw materials used to manufacture it. If the raw materials contain more iron the resulting cement will be darker. Colour has no significance on any properties of the cement. The strength of the cement is dependent only on the proportion of raw materials in the mix.
OPC Vs. Blended Cements
Blended cements (PPC & PSC) are better cements when compared to OPC cements with respect to DURABILITY OF CONCRETE STRUCTURES. They can be used for all normal construction purposes. Blended cements have certain added features that aid in the durability and longer life of concrete structures.
Advantage of blended cements:
- Continuous increase in strength with time
- Increased resistance against sulphate attack
- Improved workability
- Better cohesiveness of fresh concrete
- Reduced heat of hydration and thermal cracking
- Reduced corrosion of concrete
- Better water tightness
- Reduced Alkali – Silica reaction
- Better resistance to mild acidic water and aggressive environment
- Low drying shrinkage
- Environment friendly
High Early strengths cements have more heat of hydration which affects the concrete quality in the long run unless adequate initial curing procedures is not done at site. Use of Blended cements leads to reduced heat of hydration and hence less micro-cracks if not cured properly during initial stages. Hence use of Blended cements improves durability of the concrete structure.
It will be interesting to see how Cemex, the second largest ready-mixed concrete supplier and a major provider of aggregates, will play its cards. So far, it has traditionally bought cement from the French manufacturers, but will clearly only continue to do so if the price is right. On the other hand, if the French cement producers maintain their high-price policy, some local cement plants are likely to have to close.
Demand for cement is expected to shrink further in 2011 and, while a modest recovery looks possible in 2012, this will not be sufficient to offset the new independent grinding capacity coming online and all set to undercut current producer prices by a suitable margin to gain market share.