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Right. But would that thin sliver section actually cause any issues once it's covered with a load of floor materials squashing it down? Just curious to understand more from folk with a bit of knowledge.
But good point on raising the whole thing up.
hugo7-
Any cementitious screed is a judicious mixture of cement and graded aggregates to get sufficient density and interlock to give adequate compressive strength and impact resistance.
A flowing grout, (Can be as thin a 'screed' as you can find), may 'work' down to just a couple of millimteres thick, but would be too expensive for filling thicker layers/voids where larger aggregates can be used within the thickness.
You also need to consider de-aerators within the screed to ensure that air is not incorporated during the mixing process leading to voids that can encourage water penetration, (and eventually carbonation of the concrete as CO2 dissolves into the water, forming weakly acidic hydrogen carbonate anions that slowly reduces the pH of the concrete and leads to conditions favourable to rust formation),
and,
shrinkage compensation, (standard cementitious materials shrink as they dry/cure).
And you want the screed layer to adhere to the existing slab to prevent a plane of weakness.
(This is why I suggested upthread a mechanical 'key' for any post-slab screed).
mespilus
The problem is that to make it level the new pour would be ~3cm thick at one end tapering down to nothing over a few meters.
If you were able to deal with the bonding issues it you might want to make it level by making the entire thing a minimum of 5cm higher (i.e. 8cm at the lower end).
Personally I'd be making it the problem of the person who was responsible for laying it. They need to fight it out between themselves and the pumping contractors (who are also partly responsible due to the problems they introduced.)