Fixing two slabs together

[flyingfifer64]

I have made the mistake of casting a new slab next to an existing one without joining them together with rebar. It's taken 12 months plus but the new slab has moved causing a crack in the floor (and new wall) of my shed / workshop.

What can I do to join the slabs together and prevent further movement? Would cutting slots at 90 deg to the joint and epoxying in lengths of rebar work?

I am also getting water ingress through the joint (occasionally we get very high water tables, flash floods stuff) If the rebar idea would work, could I open out the joint with a saw (about 5mmx10mm?) and fill with a Polysulphide joint sealer?

Ignorance is bliss, until you have to deal with the consequences....

The main slab is 2.5m x 5m with 12" deep trench around edges and 4" slab. The new slab is 2.5mx1.5m, tacked onto the end and is a straight 6" thick on clay soil. Loads are single skin thermalite block wall, foot traffic and perhaps a motorbike.

 

[Deluks]

On clay? Not much you can do really. Cast a new reinforced slab on top of the lot?

 

[Norcon]

If the 4" slab has the shed built on it, then how did movement of the 6" slab cause the the shed floor and wall to crack?

Which is only a few sq meters from your measurements.
And not connected with re bars or interlocked.

It's taken 12 months plus but the new slab has moved causing a crack in the floor (and new wall) of my shed / workshop

I would be off the opinion that the new slab has nothing to do with the cracks in your existing shed floor and walls.
But rather inferior foundations and inferior compaction techniquies.

Was the new slab some feeble attempt at shoring up the the crumbling shed?
I'm assuming the new slab is cast outside the perimeter of the shed.
Is that correct?

 

[^woody^]

Saw some slots across the joint, and install some bars with resin adhesive

 

[flyingfifer64]

The new 6" slab has no hardcore / compaction and is sitting on clay. It has moved relative to the original slab which is in good condition with no cracks. The shed extension was built across the two slabs.

As Deluks says, I guess without proper foundations the new slab will move as the clay dries out and shrinks.

Best I can do is epoxy in some Bars I guess and hope for the best. Any recommendations on product brand names, what do I need?