How to join old and new concrete roof slab to avoid water leakage and proper bonding?

Question

i have to join flush a new rcc roof with the existing rcc roof resting on load bearing brick wall. the new rcc roof slab is supported by rc columns on other side

Answer 1

1) I would not recommend that you join them - as you would be unsure of the design of the old slab. You dont want the old to get some stress due to the new slab and fail.

2) To make sure that you dont have water thro them, the best option is to have the new slab have a hood to cover the gap with the old one so that no water can come to the gap.

Answer 2

if it is only for leakage you are planning to construct a new slab over old one, dear it is not safe and very expencive. here are some solutions u can try:
1. Lay terracing if not laid. before the terracing is laid, the surface of the slab should be thorouhly cleaned with RAG soaked in kerosene oil and treated with two coats of hot bitumen.
OR
2. wash the sufrace of exsiting slab with wire brush and little water. now paint the wet surface with neero (cement water paste). this will remove all the voids in the exsesting structure. you can also pump cement slurry into the cracks or cement grouting (mixed with some water proofing compund) over the suface. it will stop leakage.
OR
3. lay concrete paste 1 cement : 2 sand : 4 aggregate (Zeera) on the portion of slab you expect leakage from.
OR
4. Wash the slab with lime and water (Choona), it will make lime to occupy the free voids.
OR
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Answer 3

you can put a stopper on both side of the joint with one stopper having canopy at the top and extending over the other stopper.Treat this with good waterproofing coating.this is effective but not foolproof,one of my friend has devised a unique solution and a very effective one against dripping joint he simply put a drain(half cut pipe) under the joint and gave it a slope joining it into a down drain.

Answer 4

use a water stop between the two slabs and then cover with fiber glass sealant.

Answer 5

There are special epoxies made just to do this. They are very strong but will not cause the stress problems of concrete-to-concrete. Check out http://www.usanchor.com/Intro_Anchoring.shtml

Answer 6

look for "water proofing contractors" in the yellow pages of your area and consult them. a normal cement paste should help.