| Thu May 04, 2017 | Post #1 | S L Gupta (Civil Engg)
Join date: Mar 2008 | Dear Sir,
The size and MS Steel used in RCC column is designed on basis of load bear by the column.Up to 2 story building i.e. ground and first floor the steel bars given seems to be correct. Use cement concrete mix 1;1.5;3 in the column duly machine mixed and vibrated. See below
Cement concrete is strong in compressive strength but weak in tensile
strength. To increase tensile strength we use mild steel bars in cement
concrete. Steel bars used in cement concrete provide good strength to
the structure. A strong building structure is what all need for their
homes, offices and steel is the best option used with cement concrete.
1) Overlapping in Steel Bars in Reinforced Cement Concrete
There should be no joints in steel bars used for RCC work. If it is
necessary to use small length steel bars, proper overlap should be
given.
The joints of bars should be welded in case the diameter of
bars is more than 36 mm. Overlapping of bars should not touch each other
and they should be kept apart. Where it is not possible, overlapping
bars should be bound together at intervals not exceeding twice the
diameter of such bars with two strands of steel wires trusted tight. The
overlap should be staggered for different bars. The length of overlap
should not be less than 50 times the diameter of steel bar.
2) Precautions while Bending, Binding and Placing Steel Bars in RCC Work
- Steel bars are clear, free from loose mil scales, dust, loose rust and any oily materials.
- The bars used at site are manufactured from reputed brand and have a full length.
- Use full length steel bars in beams, slabs etc if not possible,
proper overlap should be given in steel bar and overlap should be
staggered.
- Tor, ribbed and twisted steel bars are used as they have more
tensile stress. Also they are economical and have more strength in
cement concrete.
- The bars must be in full length according to the design.
- Proper sizes/ height of crank bars are given in slab and beams etc.
- Proper support under crank bars of beams and slabs must be given.
- Steel bars are not disturbed while lying cement concrete.
- If steel bars are more in number in beams, the bars are placed in two layers by giving spacer between the layers.
3) Checklist/Points before Laying Cement Concrete
- Form work /shuttering should be checked for line, level and its strength.
- Steel bars and their placing should be checked.
- Proper cover to steel bars and adequate numbers of sports/chairs under crank bars must be checked.
- Proper planks or plates provided for walking over reinforcement are not disturbed during working.
- Raw materials should be proper and sufficient in quantity.
- Electrical pipes, fan box etc. should be laid before lying cement concrete.
- Gap in shuttering plates is sealed properly by jute bags /mortar /rubber etc.
- Shuttering plates are properly oiled.
- Curing arrangement must be checked in advance for smooth curing after laying RCC slab.
- Precautionary arrangements are taken in case of rains etc.
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