In building construction the roof or slab for roof
is very important constituents. For laying RCC slab following material is
required such as
Materials for RCC Slab / Roof
- Coarse aggregate
- Fine aggregate
- M.S. Steel bar
- Binding wire
- Shuttering materials such as wooden Ballies, Planks, and Iron Plates
work arrangement laying of RCC slab can be done in 3 stages such as formwork or
centering and shuttering, bending and binding MS steel bars and laying of
Formwork or Centering and Shuttering
formwork should be as per ( I S : 14687-1999). To retain concrete, formwork or
centering and shuttering is required, which provides the support to the wet
concrete until it has gained sufficient strength to be self supporting. The
formwork or centering and shuttering used are from the material like timber,
plywood, metal or other as per site condition and requirement.
The shuttering / formwork should be so strong and rigid to prevent any
deflection and support the
load of concrete placed on it and it is water tight to
prevent the loss of cement mix water from concrete mix. For more detail see the
Article “Centering and
Shuttering / Form Work” Link given below Bending And Binding M S steel bars
The deformed steel bars should be
per (IS: 1786-1985)
At the time of designing the slab, it is consider that
concrete is strong in compressive strength but weak in tensile strength, so
make the structure safe against the tensile stress, steel bars are .provided.
Now a days use of TMT or Tor or Ribbed
or cold twisted deformed steel bars are in use instead of MS plain steel
bars because of their more bonding strength with cement concrete and have more compressive and tensile stress than that of mild steel plain
Spacing of steel bars
M S Steel bars
diameter and its spacing in the RCC slab is calculated by designing the slab
according to load and span of the slab. In general 12mm, 10mm and 8mm diameter
MS steel bars are used in RCC slab according to the length of span of the slab
and similarly spacing is from 4.5’’ to 6’’ in the main bars and 6’’ to 8’’ in
Try to keep steel bar used for RCC work without any joints.
If it is not possible due to long length of slab or to use small length steel
bars, proper overlap
should be given according to specification. To know more about steel bars see
the link below.
- Laying of
Cement Concrete Mix
After checking the formwork in line, level and strength than
check the MS steel bars bending, binding, overlap and spacing etc. After steel
bar bending and binding, lay the conduit pipe for electricity and fan hook etc
as per requirement.
the above points, place concrete or stone pieces having 12mm to 15 mm thickness
under the steel bars for providing the proper cover under steel bars. Make
walking way on steel bars by placing wooden plates to avoid disturbance in
steel bars. Now start to lay the cement concrete mix as per design but not
below the 1; 2; 4 ratio. The mix should be mechanically mixed and vibrated
after laying on the slab.
After laying the RCC
slab it should be cure for 28 days for getting full strength.
Fine sand should consist of natural sand or crushed stone sand. It should be hard, durable, clean and be free from organic matter etc. and should not contain any appreciable amount of clay balls and harmful impurities such as alkalis, salts, coal, decayed vegetation etc.