This civil engineering article sheds light on the points which should be considered before making ground beams design and plinth beam reinforcement details.
Prior to start concreting work for ground beams & plinth beams, proper examination should be carried out in the following two phases :-
Initially, test out formwork prior to arrange or bind reinforcement. It is important since specific formwork errors can’t be rectified or it becomes complicated to repair once the reinforcement is arranged in position.
Checking reinforcement.
01. Centering and shuttering / Formwork:
• P.C.C. of proper grade and thickness (least 50 mm and M5 or 1: 4:8 grade) should be provided prior to apply shuttering for ground beam and it should be perfectly leveled and remains in exact line.
• The P.C.C. should be expanded minimum 50 mm exceeding the width of beam on both faces. Verify all the level of ground beams.
It should be minimum 150 mm in natural ground, in order that the earth filled inside walls or a beam doesn’t get out throughout plinth filling. Also check that all ground beams are located on equivalent level.
• Verify that all the soil on which beam is placed is correctly compacted (specifically for freshly excavated foundation pits) so that the ground beam never sags throughout curing or watering due to settlement of loose soil.
• The bricks should not be used since it can’t retain exact level and line.
• Start formwork for ground beams or plinth beams after filling because providing props may lead to delay since time is required for detaching props and filling work can be resumed during that period causing delay of slab.
• Prior to apply mould release agent, the shuttering should be dry and shall be cleansed properly. During shuttering work, the similar type of release agent should be used for same shuttering materials.
• The surface of shuttering should be level and thin coating should be provided with mould release agent.
• The mould release agent should not get in touch with reinforcement or the solidified concrete.
• Shuttering should be set in such a way that the joints are sealed properly to resist leakage of cement slurry.
• Prior to binding or placing reinforcement, the size of beam should be examined properly.
• Make sure that the meeting point of beam & column is tight and no bulging should occur throughout concreting.
• Take out all the debris like dust, paper, leaves, chippings of woods, nails, reinforcement wastage, soil particles etc.
02. Reinforcement:
• Prior to set the concrete, verify the reinforcement details as per bar bending schedule and obtain the approval of structural consultant. • The reinforcement of beam should remain in exact alignment. If extent of beam exceeds 6 to 9 meter than camber should be arranged according to drawing. • Examine the laps of beam with detailed drawing. There should not be laps in middle of beams if they contain long span. The lap should be maintained at various positions at few different bars. • Verify the joints details according to detailed drawing- flexible or rigid. • Bent up bars should be provided based on detailed drawing. • Verify whenever the reinforcement of cantilever beam remains in top doubly anchored. • Also examine the counter balance of cantilever beam. • Stirrups should be placed at the intersection of beams and columns and in most cases it is generally overlooked.
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