#GGBS
- 1. Changing the face of concrete Avinash Shaw Department of Civil Engineering NIT Durgapur Prof. A. K. Samanta
- 2. Ground-Granulated Blast-furnace Slag Sometimes, also referred to as GGBFS Obtained by quenching molten iron slag from a blast furnace in water or steam, dried and ground into a fine powder
- 3. Chemicals Present in GGBS CaO 30-50% SiO2 28-38% Al2O3 8-24% MgO 1-18% MnO 0.68% TiO2 0.58% K2O 0.37% N2O 0.27%
- 4. 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Portland Cement GBBS
- 5. What are its physical properties?... Particle size - 0.1 to 40 microns Specific Surface Area – 400-600 m2/kg Relative Density – 2.85-2.95 Bulk density –Loose - 1.0–1.1 tonnes/m3 Vibrated - 1.2–1.3 tonnes/m3 pH (T = 20 °C in water) – 9 to 11
- 6. Ma i n l y two u s e s Production of quality-improved slag cement, namely Portland Blast Furnace Cement (PBFC) and High-Slag Blast- Furnace Cement (HSBFC) Production of ready-mixed or site-batched durable concrete.
- 7. Durability • Provides protection against both sulphate attack and chloride attack. • Effectively replaced Sulfate-Resisting Portland Cement (SRPC) on the market for sulfate resistance because of its superior performance and greatly reduced cost • Useful against chloride attack in reinforced concrete in marine environments and in road bridges where the concrete is exposed to splashing from road de-icing salts.
- 8. Durability • use of GGBS in such instances will increase the life of the structure by up to 50% had only Portland cement been used, and precludes the need for more expensive stainless steel reinforcing. • also routinely used to limit the temperature rise in large concrete pours, which prevents the occurrence of micro cracking.
- 9. Durability
- 10. Appearance • The near-white color of GGBS cement permits architects to achieve a lighter colour for exposed fair-faced concrete finishes, at no extra cost. • Also produces a smoother, more defect free surface, due to the fineness of the GGBS particles. • GGBS cement prevents the occurrence of efflorescence, the staining of concrete surfaces by calcium carbonate deposits.
- 11. Appearance On the left-GGBS used On the right-Portland cement
- 12. Appearance Boyne Bridge M1 motorway(made of GGBS)
- 13. Powerfloating As GGBS concrete stays plastic for a longer time than Portland cement concrete, this enables the contractor to achieve a very flat finish.
- 14. Strength • GGBS cement has a higher ultimate strength than concrete made with Portland cement. • Higher proportion of the strength-enhancing calcium silicate hydrates (CSH) than concrete made with Portland cement only, and a reduced content of free lime, which does not contribute to concrete strength. • Doubles its 28-day strength over a period of 10 to 12 years.
- 15. Strength Typical strengths of 35 N concrete (N/mm2) GGBS % 7 day 28 day 56 day 0 32 42 43 20 30 43 45 35 27 43 47 50 23 40 44
- 16. Strength
- 17. Sustainability • GGBS is a by-product of steel manufacturing process, its use in concrete is recognized by LEED. • It significantly reduces the embodied CO2 of the structure.
- 18. Working with GGBS Concrete • Fresh concrete containing GGBS has better mobility characteristics, arising from the consistent fineness and particle shape of the GGBS powder, and from its slightly lower relative density. • The smoother surface texture and glassy surface of GGBS particles also helps to improve workability.
- 19. Placing, Compacting and Pumping • Easier to place the concrete into formwork and easier to compact by mechanical vibration. • Less liable to segregation during transport and handling. • Pumping is also easier, due to the slightly lower relative density and better flow characteristics.
- 20. Water Demand • Less of the mixing water(3–5% lower) is adsorbed onto the surface of the GGBS particles, as they are smoother and glassy.
- 21. The rate of early age strength gain of GGBS concrete is greatly improved by higher curing temperatures A temperature increase from 20 to 40°C is sufficient to increase the early strength GGBS concrete by a factor of two to four.
- 22. This graph illustrates that as the in-situ curing temperature increases, any delay in strength development that may arise as a result of increasing the % of GGBS may be negated by the increase in temperature.
- 23. Water in GGBS concrete takes slightly longer to combine chemically to form hydration products, thus making GGBS concrete a little more sensitive to poor curing. For GGBS contents of up to 60%, curing periods as recommended in IS 326 and BS 8110 for Portland cement concretes are sufficient. For higher GGBS contents, these periods may need to be extended.