Metakaolin

simplified manner

1. METAKAOLIN PRESENTED BY: E.Vishnu vardahan(14-143) K.Ramakrishna Reddy(14-176)

2. Introduction Manufacturing process Physical properties Chemical composition Advantages Applications C onclusion CONTENTS

3. Meta +kaolin Metakaolin is an admixture used as an partial replacement of cement in HSC(high strength concrete). A concrete is said to be high strength concrete if its compressive strength is more than 40Mpa. Metakaolin is prepared by calcination of kaolin(clay mineral) at an temperature of 650-800ºC .It has pozzolanic properties. Chemical formula of Metakaolin is Al2O3·2SiO2·2H2O. I t reacts with Ca(OH)2 one of the by-products of hydration reaction of cement and results in additional C-S-H gel which results in increased strength. INTRODUCTION

4. Physical form-powder Fineness of metakaolin-700 to 900 m 2 /kg. Color of metakaolin – white/grey Specific gravity-2.50 Specific surface-8 to15m2/g. Physical properties

5. Some of components Chemical composition Chemical composition percentage (%) Silica (SiO 2 ) 54.3 Alumina (Al 2 O 3 ) 38.3 Ferric oxide (Fe 2 O 3 ) 4.28 Calcium oxide (CaO) 0.39 Magnesium oxide (MgO) 0.08 Sodium oxide (Na 2 O) 0.12 Potassium oxide (K 2 O) 0.50

6. When cement is partially replaced with Metakaolin, it reacts with calcium hydroxide and results in extra C-S-H gel. C-S-H gel is the sole cause for strength development in cement and cement based concrete Cement + Water = C-S-H gel + Ca (OH)2 Ca (OH)2 + Metakaolin = C-S-H gel It reduces the size of pores in cement paste by transforming finer particles into discontinous pores. It increases compressive and flexural strength. It reduces efflorosence in concrete. Use in high strength concrete

7. Strength and durability of concrete increases. Accelerates initial setting time of concrete Compressive strength of concrete increases@20% Cross section of structure can be reduced safely i.e. amount of concrete used can be reduced. Reduces shrinkage in concrete. Ecofriendly by reducing amount of co2 emission. Reduces heat of hydration leading to shrinkage and crack control Advantages

8. As it has various advantages it can be used in constructions of: dams Bridges Water retaining structures High rise buildings Off shore structures Mass concreting Nuclear power stations Applications

9. Compressive strength of concrete increases by 20%. Use of 15% metakaolin increases workability. Improves mechanical properties of concrete. uneconomical due to its high cost whereas it is economical in the aspects of durability and strength Conclusion