The Ramco Cements Limited answers your FAQs on cement & concrete

What is cement?
Cement is an adhesive material with principal constituent as lime capable of bonding together solid particles
Can you list the different types of cements ?
Portland Pozzolana Cement (Fly Ash based), Ordinary Portland Cement (33, 43, 53 grades), Portland Slag Cement, Composite Cement, Rapid Hardening Portland Cement, Sulphate Resisting Portland Cement
What are the types of cement commonly available in our Country ?
Portland Pozzolana Cement (Fly Ash based) and Portland Slag Cement
What is Ordinary Portland Cement?
Ordinary Portland Cement is an adhesive material containing lime, silica, alumina and iron oxide. It is manufactured by heating these ingredients together to a very high temperature and grinding the resultant hard mass called clinker with gypsum.
What are blended cements?
Cements derived by mixing together clinker with gypsum and mineral admixtures like Fly Ash and / or Slag are called blended cements.
What is PPC ( Portland Pozzolona Cement ) ?
PPC is Portland Pozzolana Cement manufactured using clinker, gypsum and fly ash.
What is PSC ( Portland Slag Cement ) ?
PSC is Portland Slag Cement manufactured using clinker, gypsum and slag.
What are the standards for blending materials like fly ash and slag?
Bureau of Indian Standards (BIS) has laid down the following standards for fly ash and slag
Fly Ash :: IS 3812
Slag :: IS 12089
What is concrete?
Concrete is the resultant hardened product obtained by mixing cement, sand, aggregates and water in specified proportions, capable of taking compressive stresses or loads. In some cases, chemical admixtures are also added.
Are there different grades of concrete?
Yes there are different grades of concrete based on required compressive strength. M20, M30 and M40 are the normally used grades of concrete. M20 means that the concrete can take on a minimum compressive strength of 20MPA (Newton/sq.mm) after 28 days.
What is workability of concrete and how can it be measured?
Workability is the ease with which concrete can be mixed, placed and compacted. The common method of measuring workability at site is through the slump cone test.
What are the factors to be kept in mind while executing concrete work at site?
1. Form work should be done in a rigid way so as to withstand all types of loads
2. It is highly recommended to design the mix for the required compressive strength
3. Proper monitoring with special emphasis on water:cement ratio and required workability is a must during concrete preparation
4. Adequate cover should be given to the reinforcement bars to prevent corrosion
5. Vibrators must be used for compaction
What are the tips for curing of concrete?
1. Concrete must be kept in moist condition for a minimum of 10 days.
2. Ponding with wet gunny bags or suitable curing compounds are necessary to control evaporation
What are the factors affecting durability of concrete?
1. Free lime in cement : Lime present in cement as Calcium Oxide on hydration becomes hydrated free lime. Higher free lime reduces the durability of concrete. This is generally higher in Ordinary Portland Cement (OPC) whereas in blended cements like PPC and PSC, secondary gel reactions take place between fly ash/slag and hydrated lime, densifying the cement paste thereby making the concrete impermeable
2. Heat of hydration : The heat generated during hydration of cement is called heat of hydration. If this is high, it can lead to thermal shrinkage thereby causing cracks. OPC has higher heat of hydration as compared to blended cements like PPC and PSC.

 

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