Is this saw blade faulty?
The filling is melted aluminum that galled/melted and filled the gullet and is covering one of the Tungsten Carbide teeth. You can pull it off with a pliers.

The negative rake angle of the blade is fine for cutting aluminum, it will push your workpiece away instead of tending to grab onto it. It will generate more heat and be more likely to melt the aluminum. You can feed the work harder to generate a thicker chip to carry the heat instead of rubbing/melting it off. 

A little spray of WD40 on your path can help immensely. 

The J Shape is supposed to be there.