PORTLAND SLAG CEMENT (PSC)
The blast furnace slag is a byproduct of Iron & Steel Industry. Iron ore, Coke and Lime stone are fed in to the furnace and the resulting molten slag floats over the molten iron at a temperature of 1500°C to 1600°C. The molten iron is tapped off, the remaining molten slag consist mainly Siliceous and aluminous residue is then water quenched rapidly resulting in the formation of Glassy granulates which is called Granulated Blast Furnace Slag. The molten Slag has a composition of 30 to 40% Sio2 and 40% CaO, about 14 to 18% alumina.
Ground Granulated Blast Furnace Slag (GGBS)
The Granulated slag if further grind in to fine powder to make Ground Granulated Blast Furnace Slag which is a supplementary cementations Material.
Portland Slag Cement (PSC)
Portland Slag cement is manufactured by either inter- grinding the Portland cement clinker, Gypsum and granulated slag or blending the ground granulated blast furnace slag (GGBS) with Ordinary Portland cement by means of mechanical blenders.
Slag cement is manufactured as per BIS specification IS 455 – 1989 and quantity of slag added shall be in the range of 25%to70%.
Concrete with Ground Granulated Blast Furnace Slag
Durable Concrete can be made by adding Ground granulated Blast furnace Slag as a mineral admixture at different dosages based on application and type of structure and exposure conditions.
Advantages of Portland Slag Cement
- Improved workability: The right designed concrete mixtures containing slag cement demonstrate improved workability and finishability when compared with 100% ordinary Portland cement concrete system due to its high fineness, as a result we can get segregation free and cohesive Mix.
- Reduced heat of hydration: Due to reduced heat of hydration, plastic shrinkage cracks can be minimised.
- High compressive and flexural strength: Concrete made with Slag Cement provides higher compressive and flexural strength compared with Ordinary Portland cement concrete due to additional calcium silicate hydrate(C-S-H) formation. Silicates in slag cement combine with the calcium hydroxide (CH), a byproduct of hydration and form C-S-H which enhances the both compressive and flexural strength.
- Reduced permeability: The inter connectivity of capillary pores will be discontinued and thus permeably will be reduced.
- Resistance to alkali- silica reaction (ASR): A chemical reaction between the alkalis in Portland cement and certain types of minerals present in aggregate. Use of Slag cement will reduce the potential of ASR occurring by reducing the amount of alkali available in the system that is available for reaction with the aggregate.
- Excellent resistance to sulphate attack: Sulphate attack occurs when concrete comes in contact with water or soil containing sulphates. These sulphates react with hydration products of the tri-calcium aluminate phase of Portland cement and with calcium hydroxide to form an expansive crystalline product called ettringite. Expansion due to ettringite formation causes tensile stress in concrete which leads the concrete begins to crack.Slag does not contain C3A, so its addition in concrete dilutes the total amount of C3A and also reduces the permeability due to which the sulphates do not penetrate in to concrete.
- Resistance to chloride attack: Due to reduced permeability and increased densification the diffusion of chloride ions will be greatly minimised in the concrete contains Slag cement.
- Lighter in colour: An Aesthetic appearance and low heat absorption due to its light colour.
- Reduced life cycle cost: Concrete produced by using slag cement can significantly improve the durability and extends the life of the structure and thus reduce the lifecycle cost of the structure.
- Fire resistance: Structures made with Slag cement resist the high temperature than the structures made with Ordinary Portland cement.
- Resistance to erosion: Concrete made with Slag cement demonstrated the resistance to erosion compared with Ordinary Portland slag cement.
The Engineering Consultants and Designers from all over the world are recommending Slag Cement due to its superior engineering properties.
Applications of Portland Slag Cement
- All Residential, commercial, Industrial Buildings,
- Marine and Irrigation structures, Airports
- Rigid pavements, Pre cast elements, Bridges,
- Pre stressed concrete, Pavement blocks,
- Masonry bricks, Sewage pipe line works,
- Effluent treatment plants etc.
Slag cement is a proven product world wide the following countries are extensively did the research on Slag cement and utilized in their infrastructural projects. Australia, Belgium, China, Canada, Denmark, France, Great Britain & Ireland, Germany, Japan, UK, Sweden, US, Netherlands, Malaysia, South Africa, India etc.
Some of the major structures made with slag cement at a glance
- Milwaukee’s Kilbourn tower(34 story skyscraper), Milwaukee, Wisconsin,
- Slag cement pavements beat ASR in Delaware,US
- 75-Four-Mile Test Section in Michigan,
- The Helena, Manhattan, New York,
- Air TrainJKF Project,
- Charenton canal Bridge in Louisiana,
- The Luas Taney Bridge comprises a 108.5m long cable-stayed bridge linking the LUAS line between Dublin city centre and Sandyford in South County Dublin
- King Fahad Causeway (Saudi Arabia-BahrainCauseway)
- Eastern Scheldt Barrier , built with blast furnace slag cement with a design service life of 200 years
- EURO Tunnel
- 3 Gorges Dam- China
- Thermal Powder Project , Chennai, India
- Library Building parliament of India
- Worli-Bandra sewage outlet pipeline, Mumbai, India
- Bandra Worli sea link, Mumbai, India
- Sardar Sarovar Narmada Nigam Dam/ Canal/ Powder House, Gujarat, India
- LNG Petronet- Dahej, Gujarat, India and Many More……
Conclusion: Use of Portland Slag Cement provides the following technical, commercial and environmental benefits along with sustainability.
- Reduction in CO2 emission, conservation of natural resources, to make durable structures.
- Reduced life cycle cost, enhanced engineering properties, cost economy, low energy consumption etc.