This is a couple year old post, but just so it's not too confusing, the "expansion" joint actually has a more important job in this scenario, as a bond breaker. If the concrete is poured directly against the rough brick face, it can "lock" into it and create damage when the slab-on-grade moves...........
Not only are you almost always wrong, but you can't spell for chit either, Robpo.
Anytime hard materials meet hard materials in a cold joint it needs to be a soft joint with dimensions that exceed maximum expected movement of both members. Asphalt impregnated sugar cane fiber is the most common and cheapest with characteristics that make it almost ideal for this application:
It is more or less waterproof, it is cheap, it lasts a long time, and is able to rebound from normal expansion and contraction to maintain the seal. For critical applications, you can apply a backer rod and joint sealant over the expansion joint.
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