Safe Procedure for Joining new concrete to old concrete Slab

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It is very critical o join new concrete with old concrete. If there is no proper joining of the old and new slab, then there may be leakage between the joining area.

Here I will show you the Safe Procedure for Joining new concrete to old concrete Slab as an example. The process remains the same for all types of concrete members like column, beam, and slab, etc.

Things to remember while Joining new concrete to old concrete

Safe Procedure for Joining new concrete to old concrete Slab
  • We should not join the new slab with an old slab only with the help of a cement slurry.
  • Clean the joining surface of the old slab with the help of a metallic brush completely.
  • Overlapping of reinforcement should be done.
  • The joining portion of the slab should be sloped (45 Degree).
  • Overlapping of steel should not be less than 50 D.
  • Lapping should be welded or bound with wire properly about 5 inches to six inches (5”-6”).
  • Casting should be done as soon as we apply chemicals on the old slab.
  • Concrete should be poured within 15 minutes after applying concrete patching compound on the old slab.

Safe Procedure for Joining new concrete to old concrete Slab

Safe Procedure for Joining new concrete to old concrete Slab
  • First of all clean the joining surface of the old slab.
  • Apply bonding agent i.e chemical (concrete patching compound) on the cleaned surface with the help of a brush.
  • Concrete patching compound may of the different company but procedures to apply are almost same. Example (Sikadoor-32, Dr. Fixit etc)

How to use concrete patching compound?

Taking the Example of Sikadoor-32 as a (concrete patching compound).

  • Sikadoor contains two chemicals let (A) White and (B) light black.
  • Mix both of them in a 1:2 ratio. It means if you take 1 kg of part (A) chemicals then take 2kg of part(B) chemicals.
  • Apply on concrete and pour concrete within max. 15 minute.
  • After pouring, a vibrator should be used to compact the concrete properly.

Checklist After pouring Concrete

  • Check whether the shuttering below the new slab is leakage or not.
  • Check if there is proper clear cover in the new slab or not.
  • Check whether proper compacting has been done or not.
  • Check whether the slope of the new slab matching with the old slab or not.

Watch video explanation to join new slab with old slab

I hope this article on “Joining new concrete to old concrete” remains helpful for you.

Happy Learning – Civil Concept

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