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Concrete technology
- 2. TABLE OF CONTENTS Concrete Composition of concrete Making of Concrete
- 3. CONCRETE • A building material(mixture of broken stone or gravel, sand , cement and water) • Composite material • Can be spread or poured into moulds and forms
- 5. CONCRETE TYPES(STATE) Fresh concrete Hardened concrete
- 7. BATCHING Batching is the process of measuring concrete mix ingredients by either mass or volume and introducing them into the mixer . Volume batching Weight batching Volume batching • Adopted for small jobs . • Measures the fine and coarse aggregate.
- 9. WEiGH BATCHiNG Batching by weight Preferable to volume batching It’s equipment falls into 3 general categories : I.Manual, II.Semi automatic, III.Fully automatic.
- 10. MixiNG The mixing should ensure that the mass becomes Homogeneous , uniform in colour and consistency . Methods of Mixing : 1.Hands(using hand shovels) 2.Stationary Mixers 3.Ready mix concrete
- 11. Hand Mixing
- 12. Stationary MixerS Concrete is sometime mixed at jobsite in a These mixers may be of : 1.Tilting type , 2.Non-Tilting type ,
- 13. tilting type Mixer • Conical drum • Inclined one • Charging and discharging done by the opening
- 14. non tilting type Mixer Drum is cylindrical Opened on both sides
- 16. tranSporting 2) Wheelbarrows and Buggies : Short flat hauls
- 17. tranSporting 3) Belt Conveyors : Conveying concrete horizontally for higher/lower level.
- 18. tranSporting 4) Cranes and Buckets
- 19. tranSporting 5) Pumps : Conveying concrete from central discharge point to formwork.
- 20. tranSporting 6) Transit Mixer : used for transporting the concrete over long distance particularly in RMC plant .
- 21. PLACING • Placed in systematic manner • Within earth mould • In formwork • Steel shuttering • Underwater
- 22. ComPACtIoN of CoNCrete • Expelling the entrapped air from the concrete • In the process of mixing , transporting and placing of concrete air is likely to get entrapped in the concrete . • It has been found from the experimental studies that 1% air in the concrete approximately reduces the strength by 6%.
- 23. methods of CoNCrete ComPACtIoN 1) Hand Compaction Rodding Ramming Tamping 2) Compaction by Vibration Internal vibrator Formwork Vibrator Table Vibrator Platform vibrator Surface vibrator .
- 24. hANd ComPACtIoN Used for ordinary works Rodding Method of poking with 2m long, 16 mm dia. The thickness of layers for rodding should be 15 to 20 cm.
- 25. Ramming Compaction on ground in plain concrete. It is not used either in RCC or on upper floors. Tamping Top surface is beaten by wooden cross beam of cross section 10 cm x 10 cm.
- 26. ComPACtIoN by VIbrAtIoN By mechanical means Causes temporary liquefaction so that air bubbles come on to the top and expelled ultimately Internal Vibration It is most commonly used technique of concrete vibration. Vibration is achieved due to eccentric weights attached to the shaft.
- 28. exterNAL VIbrAtIoN This is adopted where internal vibration can’t be used due to either thin sections or heavy reinforcement.
- 29. tAbLe VIbrAtIoN It is mainly used for laboratories where concrete is put on the table
- 30. PLAtform VIbrAtIoN Similar to table vibrators-Large scale
- 31. CURING • Making satisfactory moisture content & favourable temperature in concrete • Hydration will continue Types: – Water curing – Membrane curing – Application of heat
- 32. WATER CURING • Slab-Immersion, water tank • Roof slab- Ponding, Filled with water • Concrete wall-Spraying,Water spray, gunny bags
- 33. MEMBRANE CURING • By plastic membrane • In less water availability conditions • Plastic sheets • Reduces evaporation
- 34. APPLICATION OF HEAT • Spraying of steam • Provides heat and moisture • Temperature- Accelerates hydration • Early strength • Only for precast structures • Speed construction
- 35. FINISHING • Last operation • Required in roads, airport, home floor • Formwork finishing • Surface treatment • Applied finishes
- 37. REFERENCES • Google.com • Concrete technology by M.S. Shetty. • www.civilblog.org • www.civilenggforall.com › theory
Editor's Notes
- Cement: Binding material Increases strength and durability Fills up the voids Good cement- IS specifications Fine Aggregate: Fills the voids existing in coarse aggregate It reduces shrinkage and cracking Coarse aggregate: It increases crushing strength of concrete Occupies major volume Water: Helps in playing, laying and setting Admixtures: Added during mixing of concrete Improve concrete quality, acceleration, retardation of setting time
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