This ceiling is underneath a bathroom. We let set new tiles in the bathroom above. 

 

But what is best advice to apply new cement to the now exposed steel?

 

 

as the rebar seems to already 50 pc  corroded    i would suggest    nothing apart from demolition   would be a safe repair    sure cement will stick to it   but you are just hiding the inevitable   demise of the structure   and hopefully not anybody that may be in its proximity   

holy ship, thats seriously bad work.................to be expected though

Thats a great photo to show why you need your 20mm of cover around reinforcement.

In your case they have just dropped the fabric meash directly onto to the ply shutters (ply? maybe I am being optimistic) and poured away.

 

Regardless of the condition of the reinforcement I would expect (hope) there to be 100mm depth of concrete so personally I wouldn't be unduly concerned unless you start inviting elephants around for a piss up.

 

The rebar is there as a secondary measure to reinforce the underside, the part thats in tension so only a catastrophic failure of each bar would put the connie at any risk.

 

Bad practice, hell yes, but why has it corroded. what room is that? another shower room thats had years of humidity? or was the floor above never ever tiled.

 

Simple enough task to protect the steel again.....can start with some primer red oxide just to stop the steel corroding further;  can even shove some ply back up to the underside;  can skim it,  but the easiest/best method is to gyproc it on battens or a metal grid in line with those concrete beams and it  will of course hide that blue pipework along the way.

 

I have to ask.....there's an old water feed pipe adjacent the sink waste, is it cut off? whats the story?

5 hours ago, Lamkyong said:

as the rebar seems to already 50 pc  corroded    i would suggest    nothing apart from demolition   would be a safe repair    sure cement will stick to it   but you are just hiding the inevitable   demise of the structure   and hopefully not anybody that may be in its proximity   

 

How did you reach the conclusion that the rebar is 50% corroded. I wonder if also you can see what diameter the rebar is?

2 hours ago, eyecatcher said:

 

How did you reach the conclusion that the rebar is 50% corroded. I wonder if also you can see what diameter the rebar is?

If you don't want to do anything about the steel then just mix some lanko 751 with the new motar and splash some on the existing cement to be covered and it will bond. Your floor may collapse in a few years when the rebar fails but the cement will stick on.

Thank you very much for everyone's input.

 

We will evaluate what to do and post the results in two or three months :-)

Don't forget to update us in 2 month

 

and the betting odds are as follows:

 

1/2 OP not yet got his finger out

2/1 OP bought red primer and left it a that.

3/1 OP heeded advice, protected the steel and installed a new ceiling.

10/1 OP about to post new thread "how to repair cracks in concrete floor

33/1 OP posts photos of collapsed floor

50/1 OP decided to "sod it" and moved out instead.

On 12/4/2016 at 7:34 PM, eyecatcher said:

Don't forget to update us in 2 month

 

and the betting odds are as follows:

 

1/2 OP not yet got his finger out

2/1 OP bought red primer and left it a that.

3/1 OP heeded advice, protected the steel and installed a new ceiling.

10/1 OP about to post new thread "how to repair cracks in concrete floor

33/1 OP posts photos of collapsed floor

50/1 OP decided to "sod it" and moved out instead.

100/1  op is  dead  crushed  by  falling  floor!

Rust itself forms a protective layer against more rust......in varying degrees depending on the conditions.

If you get a sturdy penknife or the like a try scraping into the rust it's possible you'll find the rebar has clean steel just below the surface.

The best way to remove damp source is to re-mortar the tile bed and coat well with two part epoxy, the lower grade stuff easily available.

Run the epoxy up the wall a couple of inches. to form a waterproof pan.

(The rust may also have come from condensation of steam filled bathroom over years.)

 

If repeat if you've removed the source of damp from above and there's shiny steel just below the rebar surface I'd do nothing. The underside of the concrete which came off or was never there has no strength function as it's the tension side, only to seal the rebar.