Various cement types serve different construction needs. The main constituents of cement are limestone and clay. However, when you add certain constituents to it, the characteristics of cement can be enhanced. The most widely used Portland cement is categorised into three types, OPC, PPC and PSC. In this article, we will cover the fundamentals of PSC, how it’s made, its properties, its uses and benefits.
What is PSC in Cement?
The full form of PSC in cement is Portland Slag Cement. Portland cement is made by heating a mixture of limestone and clay in kilns at high temperatures to form pebble-sized materials known as clinker. The clinker is finely ground to form Portland Cement. Portland cement blended with blast furnace slag is known Portland Slag Cement.
What is Slag?
Slag is a non-metallic byproduct of smelting ores. When iron is produced, iron ore, iron scraps, limestone, coke, etc., are heated in a blast furnace. Coke is a type of fuel that burns to produce carbon monoxide, which converts solid iron ore into molten iron. The molten iron is cast into various iron products. When the iron ore is being combusted, it produces slag. Blast furnace slag consists of silicates, aluminosilicates and calcium-alumina-silicates. The molten slag comprises about 20% by mass of iron production.
The molten slag is cooled down to make it usable. In the case of PSC, manufacturers typically use granulated blast furnace slag. The molten slag is cooled by rapid water quenching to create a solidified structure with little to no crystallisation. This rapid cooling results in sand-size fragments, hence the term granulated Portland Cement.
How is PSC Made?
Portland Slag Cement is manufactured as follows:
- Materials comprising lime, silica, alumina and iron oxide are intimately grounded.
- This mix is heated at extremely high temperatures in a kiln to form Portland clinker.
- Portland cement clinker is ground with granulated slag with the addition of natural or chemical gypsum or calcium sulphate. Portland cement can be uniformly blended with finely ground granulated slag.
- No material other than gypsum should be added to the mix. Also, gypsum should be added in an amount that does not cause sulphur trioxide content to exceed 3%.
- The slag constituent should be in the range of 25% to 65% by mass of Portland Slag Cement.
- Natural or chemical gypsum may be added during the grinding process.
Applications of PSC
PPC can be used in the following constructions:
- Portland Slag Cement is suitable for general construction work including concrete mix, plasterwork and masonry.
- PSC is also suitable for hydraulic works like dams, retaining walls, etc.
- Mass concrete works like diaphragm walls, concrete roads, large foundations, etc., can also use PSC.
- PSC is especially preferred for marine construction like ports, harbours, or constructs near the coastal area.
- Industrial structures that are highly exposed to aggressive chemical environment can also be built using PSC.
- It is suitable for constructing parking lots, flooring, pathways, and basement constructions.
Properties of Portland Slag Cement2
Per the Bureau of Indian Standards (BIS), Portland Slag Cement has the following physical properties:
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Initial Setting Time
The initial setting time of cement is the time when it starts to lose its plasticity after being mixed with water. The initial setting time for Portland Slag Cement is 30 minutes (minimum).
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Final Setting Time
The time when cement loses its plasticity completely after it has been mixed water is the final setting time. The final setting time for PSC is 10 hours (maximum).
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Fineness
Fineness of cement is its particle size of cement which impacts the surface area and. The surface of PPC must not be less than 225m2/kg.
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Soundness
Soundness of cement is the change in the volume of cement when its set and hardened. Unaerated Portland Slag Cement shall not have an expansion of more than 10 mm and 0.8%, respectively.
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Compressive Strength
Compressive strength is to the capacity of concrete to withstand load without cracking or deflecting. The compressive strength of concrete at 72, 168 and 672 hours should be 16N/mm2, 22 N/mm2, and 33 N/mm2, respectively.
Benefits of Portland Slag Cement
Here are the advantages of Portland Slag Cement:
- Portland Slag Cement has resistance to sulphates and chloride. Hence, it is suitable in environments and soil where the content of sulphates and chlorides is high.
- Slag produced from smelting irons is repurposed and used to make cement. This makes PSC a sustainable construction material.
- PSC also facilitates reduced leaching of lime. Lime leaching is when excess water flows from cement.
- It provides better workability and application.
- Slag cement is also resistant to weathering attacks.
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| Feature | OPC | PPC | PSC |
| Main blended material | Primarily clinker and gypsum | Pozzolanic material such as fly ash | Granulated blast furnace slag |
| Strength development | Generally faster early strength development | Often slower early strength with strong long-term performance | Strong long-term strength and durability, depending on formulation and curing |
| Heat of hydration | Generally higher | Generally lower than OPC | Generally lower than OPC |
| Key durability benefit | General-purpose performance | Good durability in many applications | Strong resistance to chloride and sulphate ingress when properly designed and cured |
| Typical applications | General and specialised construction | Residential, masonry, plastering, and infrastructure | Marine works, mass concrete, foundations, roads, dams, and general construction |
The table should be reviewed by a technical expert before publication because performance varies by cement grade, mix design, curing, exposure conditions, and project specifications.
FAQs
What is the full form of PSC cement?
The full form of PSC cement is Portland Slag Cement. It is made by blending Portland cement clinker with granulated blast furnace slag and gypsum.
What is PSC cement used for?
PSC cement is used for general construction, foundations, masonry, plastering, roads, flyovers, dams, mass concrete, marine structures, basements, retaining walls, and water-retaining structures.
Is PSC cement good for house construction?
Yes, PSC cement can be used for house construction, including foundations, columns, beams, slabs, masonry, plastering, and flooring, provided the cement is suitable for the project and used according to the engineer’s specifications.
What are the advantages of PSC cement?
The main advantages of PSC cement include improved workability, lower heat of hydration, resistance to chloride and sulphate attack, reduced permeability, good long-term durability, and the use of an industrial by-product in cement production. [2] [3]
Is PSC cement suitable for coastal areas?
PSC cement is often considered suitable for coastal and marine environments because of its resistance to chloride ingress and sulphate exposure. The final choice should be based on the exposure class, mix design, curing practice, and professional project specifications.
What is the difference between PSC and PPC cement?
PSC uses granulated blast furnace slag as its supplementary cementitious material, while PPC uses a pozzolanic material such as fly ash. Both are blended cements, but their properties and suitability depend on the project conditions and product formulation.
