Rebar Hook different concrete strengths

[jreit]

Hello.
I had a question about rebar hooks with different concrete strengths at a joint.
Specifically, I have a precast prestressed concrete beam with f'c = 8.5 ksi and a continuity diaphragm with a f'c = 4 ksi to make the system continuous.
I am using rebar for the positive restraint continuity reinforcement, i.e. the bottom steel at the connection between the continuity diaphragm and the end of the beam.
When I hook a #6 bar, my development length into the beam is much smaller (~24") than if I develop into the diaphragm (~36").
Does the hook behave the same way regardless of which side of the joint it is developed and which side of the joint has the 12db dimension.

Sketch linked below.
Link

 

[KootK]

A hook developed in stronger concrete develops faster than a hook developed in weaker concrete. Performance of bars being developed is, in part, dependent on concrete splitting and therefore concrete tension (sqrt(f'c)). I would expect a hooked bar to be less impacted by concrete strength than a straight bar owing to the fact that some of the load transfer is via bearing at the knuckle. I don't really know what to do with that as far as quantifying the impact goes though. And ACI does not seem to afford any specific benefit for this phenomenon.