*What I expected to happen was...:

The nether brick was to stop a Ghast blast from hitting me. Also no energy from the blast was to go threw the Nether Brick.

What actually happened was...:

The Nether Brick was moving from the blast hit and fire was getting threw and set me on fire. The Ghast did fire many blast at the same area in a few seconds. Also the Ghast was not able to see me since I was digging a tunnel in Netherrack.