Tips for Laying RCC slab / roof

 In building construction the roof or slab for roof is very important constituents. For laying RCC slab following material is required such as Raw Materials for RCC Slab / Roof

• Cement 
• Coarse aggregate 
• Fine aggregate 
• M.S. Steel bar 
• Binding wire 
• Water 
• Shuttering materials such as wooden Ballies, Planks, and Iron Plates etc.            

According to 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 concrete. A.        Formwork or Centering and Shuttering                                          The 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 bars.         

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 distribution bars.

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.        After checking 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.                ;