Compaction of Concrete. Except for thin layer of plain concrete (for which tamping may be allowed), each layer of all grades / mixes of concrete shall be thoroughly compacted with approved mechanical vibrators of adequate power or as per IS 2505, IS 2506, IS 2514 supplemented by hand spreading, rodding and tamping as directed so that concrete works around the reinforcement, around entrapped fixtures and into corners of the formwork, embedded air is expelled, dense concrete is obtained and the exposed surfaces are free from air pockets, honey-combing and other defects. Type of vibrators (immersion vibrators, shutter vibrators, surface vibrators etc.) to be used shall depend on the type of structure for which concreting is done and shall have the approval of the Engineer-In-Charge. The size and number to be provided shall be such as to ensure proper consolidation. General precautions to be taken in vibration work shall be as follows- • Concrete once vibrated shall not be vibrated again. • Partially hardened concrete or mortar shall not be re-tamped. • Over-vibration, under-vibration or vibration of very wet mixes should be avoided. • Tapping or external vibration of forms by hand tools or immersion vibrators shall not be permitted. • Care shall be taken to prevent contact of immersion vibrators against reinforcement steel. These vibrators shall not be allowed to come in contact with the reinforcement steel after start of initial set. They shall also not be allowed to come in contact with forms or finished surfaces. • Whenever external vibrators are used, the design of formwork & the disposition of vibrators should be given special consideration to ensure sufficient compaction and surface blemishes.
Compaction of Concrete. The concrete shall be thoroughly compacted to the satisfaction of the Superintendent, whilst it is being placed in the works. Compaction shall be by means of continuous tamping, spading and vibration with approved vibrators. Care shall be taken to fill every part of the forms, to force the concrete under and around the reinforcement without displacing it, to work back coarse aggregate from the face and to remove all air bubbles and voids.
