self leveling concrete minimum depth

A botched concrete pour by a contractor to extend a patio by 150 sq.ft. has resulted in an uneven surface. The outer region is the correct level but the surface level smoothly slopes down to a level about one inch lower near the center.
The contractor has suggested using a self leveling concrete pour to even everything out. This would fill in with depths ranging from about an inch near the center to essentially zero depth near the outer areas where the new concrete pour meets the original patio.
How well will the self leveling concrete adhere to the surface near the outer parts of the region where the fill depth would be essentially zero?
Should the outer regions be ground down to a minimum depth first?
Unfortunately ripping out the original pour is undesirable beacuase it was reinforced with rebar.
Thanks for any insight and advice.
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snipped-for-privacy@example.com wrote:

...
Depends on the product -- some manufacturers say theirs can be feathered out, others require minimum thickness of from 1- to 2/16". In general, the 2-part epoxy formulations are more likely (but not universal) to allow feathering out while the polymer-modified cementitous products require a minimum thickness. In short, follow manufacturer's instructions carefully and read the product specifications first.
I would recommend one of the epoxy formulations for the purpose outlined.
--
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snip

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Thanks for the advice. One more question...
Is self leveling concrete useless in matching levels with existing patio slabs that have the slight sloping grade away from the hosue to properly channel rain water away?
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