Blocks that can be waterlogged will not convert concrete powder directly bordering the block into concrete when the block is waterlogged. I tested this with leaves, slabs, stairs, walls, fences, and fence gates.

How to recreate: 
1. Place down any block that can be waterlogged.
2. Place down concrete powder directly next to it.
3. Waterlog the waterloggable block.

Note: The concrete powder must be placed BEFORE the block is waterlogged or the concrete powder will convert into concrete.