Cement is the glue in concrete, brickwork mortar and plaster. Every bag sold in India must meet an Indian Standard and carry the ISI mark, so the real choices are the type, the grade, and how fresh the bag is.
The main types
| Type | Standard | What it is | Where it suits |
|---|---|---|---|
| OPC (Ordinary Portland Cement) | IS 269 | Ground cement clinker with a little gypsum. Gains strength quickly. | RCC work where early strength matters; precast work |
| PPC (Portland Pozzolana Cement) | IS 1489 (Part 1) | OPC clinker blended with fly ash. Gains strength more slowly but keeps gaining it, with less heat. | Most house work: RCC, brickwork, plaster; damp and coastal areas |
| PSC (Portland Slag Cement) | IS 455 | OPC clinker blended with blast-furnace slag. | Foundations, coastal and sulphate-bearing soils |
OPC comes in grades 33, 43 and 53. The number is the minimum strength, in N/mm², that the cement must reach in the standard test at 28 days. Higher grade means faster, higher early strength; it does not mean the house is automatically stronger, because the strength of concrete depends far more on the mix and the water used.
Which cement for which job
- Foundation, columns, beams and slabs (RCC). Use what your structural engineer specifies: usually OPC 43, OPC 53 or PPC. Don't switch type or brand halfway through a pour.
- Brickwork and plaster. PPC or OPC 43. PPC's slower setting gives fewer shrinkage cracks in plaster.
- Coastal or damp sites, and water tanks. PPC or PSC are often preferred for durability. Ask your engineer.
- Urgent repairs or precast items that must be handled early: OPC 53.
How to read a cement bag
A genuine bag shows the brand and manufacturer, the type and grade (for example "PPC" or "OPC 53"), the IS number with the ISI mark and licence number, the net weight (50 kg), the MRP, and the week, month and year of packing.
The packing date is the one to check. Cement slowly absorbs moisture from the air and loses strength, so use bags within about three months of packing. Older stock should be used only for less important work, or tested before use.
Quick checks on site
- No hard lumps. Press the bag. Lumps that crumble between your fingers are fine; hard lumps mean the cement has started to set and should be rejected.
- Cool and smooth. Fresh cement feels cool and smooth when you put your hand into the bag.
- Bag intact. Torn or re-stitched bags may have been opened or topped up.
- Weigh one bag occasionally. It should be 50 kg.
Storing cement
Most cement is spoiled by moisture on site, not at the factory. Following IS 4082:
- Store in a dry, covered shed with a waterproof roof.
- Stack on a raised platform of planks or pallets, not directly on the floor, and keep the stack away from the walls.
- Keep stacks to no more than 10 bags high, so the bottom bags don't get compacted.
- Use first in, first out: the oldest bags first.
- In the monsoon, cover the stack with a polythene sheet.
How much cement will you need?
One bag holds 50 kg, about 0.035 m³ of loose cement. The quantity depends on the work: use the concrete calculator for slabs, beams and footings, the brick calculator for walls and the plaster calculator for plastering. Each shows the number of bags with the working.
