Silica fume concrete

This file describes that how the silica fume concrete works and its uses and defects in construction work.

1. SILICA FUME CONCRETE PRESENTED BY, D.SELVAGANESH, A.R.BAWA ABUL HASSAN, 3 rd YEAR, DEPARTMENT OF CIVIL, FATIMA MICHAEL COLLEGE OF ENGINEERING AND TECHNOLOGY, MADURAI – 20.

2. CONTENTS Introduction to silica fume concrete. Function of silica fume in concrete. Chemical composition. Physical characteristics. Available forms of silica fume. Properties of fresh concrete while using the silica fume. Properties of hardened concrete by the usage of silica fume. Applications of silica fume concrete. Advantages of silica fume material. Conclusion.

3. SILICA FUME CONCRETE Silica fume is an artificial pozzolona having high pozzolonic activity. It is a By- product from an electric arc furnace used in manufacture of silicon metal or silicon alloy. It has high silica content of more than 80%. It is an excellent for use as a portland cement supplement.

4. SILICA FUME CONCRETE

5. FUNCTION OF SILICA FUME Silica fume works on Two levels. The hydration of Portland cement produces many components, including silicate hydrates(CSH) and calcium hydroxide(CH). The silica fume is added to the CH for produce the additional CSH to obtain a very good compressive strength can exceed 15000 psi. The additional CSH produced by the silica fume is more resistant to attack from aggressive chemicals then the weaker CH.

6. CHEMICAL COMPOSITION Chemical composition depends on the product being made by the furnace. Composition is also influenced by the furnace design. It is mostly made of silica having percentage of more than 80. The other chemical composition include Fe2O3,Al2O3,Cao,Na2O,K2o in small percentages. Unlike the other By- products like Fly Ash, Silica fume from a single source has little or no variation in chemical composition from one day to another.

7. PHYSICAL CHARACTERISTICS It should be in premium white and standard grey colors. The specific gravity of the silica fume concrete is 2.2. Its specific surface area is to be 20,000 sq.meters / kg. Particle size is less than 1 micron with average diameter of 0.1 micron. The shape of the particle is spherical. It should be in Amorphous in nature.

8. AVAILABLE FORMS IN SILICA FUME CONCRETE Undensified forms with a bulk density 200 – 300 kg/m3. Densified forms with a bulk density 500 – 600 kg/m3. Pelletised forms with a bulk density 600 – 800 kg/m3. Slurry form.

9. PROPERTIES OF FRESH CONCRETE USING THE SILICA FUME WORKABILITY. BLEEDING AND SEGREGATION. SETTING TIME. PLASTIC SHRINKAGE. PROPERTIES OF HARDENED CONCRETE DRYING SHRINKAGE. CREEP. STRENGTH.

10. PROPERTIES OF FRESH CONCRETE USING SILIC FUME WORKABILITY: Workability is reduced Water demand increases in proportion to silica fume added. Water demand is 1% for every 1% of replacement of cement. Lower slump and & more cohesive mix .

11. BLEEDING AND SEGREGATION: Bleeding is reduced as silica fume particles find their way between two cement grains. Segregation is reduced as the concrete mix is more cohesive due to increase in number of solid to solid contact points. From the above two discussion we had cleared that the silica fume reduce the bleeding and segregation property of the fresh concrete.

12. SETTING TIME Time results have shown that the initial setting time and final setting time is not greatly influenced. This increase may be 30 minutes or so. PLASTIC SHRINKAGE Fresh concrete is subjected to surface cracking is known as plastic shrinkage. Since the silica fume concrete show no bleeding, fresh concrete is subjected to the plastic shrinkage. Precautions should be taken ass per normal concrete.

13. PROPERTIES OF HARDENED CONCRETE DRYING SHRINKAGE: Drying shrinkage test by different researcher show that the long time shrinkage of concrete is not affected significantly by the addition of silica fume to the concrete. CREEP: The creep of the concrete containing silica fume will be lower than the corresponding Portland cement concrete.

14. STRENGTH Concrete containing silica fume show outstanding performance in development of strength. Strength of 62 – 80 Mpa can be easily achieved. Silica fume forms backbone of high performance concrete due to early high strength properties.

15. APPLICATIONS It is used to construct a New TJ ORN Bridge in sweeden which having the high strength, workability, durability and free from any deformations and cracks. Girders using silica fume concrete. It is mostly used in high rise structures to increase the life time of the structure without any affects. It is most widely used in important structures which had a high strength when compared with another.

16. HIGHRISE BUILDINGS USING SILICA FUME Since 1990’s high rise structures or buildings uses the silica fume content to yield the high strength concrete , high compression strength, without affecting of wind forces , high abrasion resistance and high corrosion resistance.

17. GRIDERS REDUCED USING SILICA FUME CONCRETE

18. NEW TJ ORN BRIDGE IN SWEEDEN

19. ADVANTAGES OF SILICA FUME CONCRETE High early compressive strength. High tensile flexural strength and modulus of elasticity. Very low permeability to chloride and water intrusion. High bond strength. High electrical resistivity and low permeability.

20. CONCLUSION From the above discussions we have conclude the points about silica fume concrete. Silica fume can be used to manufacturing of concrete of very high strength at early age. Forms the backbone of modern day high performance. Strengths upto 200 Mpa can be achieved by using silica fume.