Please could someone tell me what's the purpose of the red bricks in this Raft Foundation?

That is not a raft foundation.. foundation are beneath or on ground..
That is a different type of slab..the benefits is just to reduce the volume of concrete and labour i.e cements, granite and sand.ppl now introduce hollow pot( either sandcrete or clay as in the picture). So far the structural requirements is still ment..no problems..

conceptbiz:
Please could someone tell me what's the purpose of the red bricks in this Raft Foundation?

That's not raft foundation, it's a type of slab/decking.

Thanks Guys,

Please could you tell me what would be the main benefit of this type of approach compare to mixed cements, granite and sand in this area of land.?

The land is at Ibeju / Lekki Iwerekun - Awoyaya